Summer 2016

Intelligent Glass Solutions

Summer

Summer 2016

HIGHLIGHTS FROM THE RECENT CHALLENGING GLASS 5 CONFERENCE

5

2016

GLASSCON GLOBAL IN BOSTON UNITED STATES – BRIDGING THE GAP MVRDV’S REMARKABLE GLASS BLOCK SYSTEM FOR CHANEL SMELLS REAL GOOD

An IPL magazine

GLASSTEC 2016 IN DÜSSELDORF IS ALMOST UPON US

INTELLIGENT GLASS SOLUTIONS

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Double glazed insulating glass, gas filled. Facade point fixed with crystal clear silicone adhesive.

Imagine Design Freedom ...

Crystal Clear Bonding for Point Fixed Construction New generation of structural adhesives Dow Corning® TSSA enabling: • Sleek, flush glass façade – invisible bonding • Improved durability – no glass drilling – no gaskets • Smaller point fixing connections*

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Dow Corning is a registered trademark of Dow Corning Corporation. © 2015 Dow Corning Corporation. All rights reserved.

Pictures courtesy of Cordeel AV18965, AV18966. Lit.-Nr. 62-1695C-01

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Publisher’s blurb

A

s I write this column (Friday 17th June) England have just won their first match in the European Championship Finals, they’ve just beaten their deadly rivals Wales 2-1 despite the overtures and sabre rattling of the worlds most expensive player Gareth Bale.

In fact, by virtue of Bale dissing England saying none of their players would get into the Welsh team he may very well have given the English the spur they needed to gain the victory. The competition is nicely up and running and the favoured teams, Germany, Spain, and the hosts France are flying through their respective groups, it would be a pretty safe bet to say the eventual winner will doubtless come from one of these three teams.

However before glasstec takes place in September, IGS, your favourite glass industry publication previews one or two of the other notable gatherings taking place in the industry. We have an exclusive expose from the oragnisers of GlassCon Global that happens in July in Boston US, this event takes place for the second time following on from the initial success in 2014 in Philadelphia.

It’s nice to see an international conference take place in the US that has representatives from outside of the US, GlassCon Global has quite an international feel to it with many of its presenters coming from outside of the US. The organisers are keen to promote the fact they are keen to “bridge the gap”. Read Anthony D’Arkangelo’s incredible editorial contribution starting on page 17.

The World Heavyweight Championship of glass industry events takes place this year as the one and only glasstec comes round once again in Dusseldorf, Germany from 20th to 23rd of September. This monster event with history dating back 46 years hosts all things visible and invisible for the best part of a week, all manner of products made from or with the wonderful see through material that is glass. You can read more about this starting on page 24 where we are given a sneak preview of some of this year’s expected highlights.

Essential to bring the recent Challenging Glass Conference that happened back in June to your attention, this is a sparkling event that, similar to glasstec and GlassCon Global happens on a biennial basis at academical institutions in and around Europe. Inside this issue of IGS we publish the words of Christian Louter one of the organisers of the Challenging Glass conference and we publish some of the papers from the evenet that we think you should be made aware of. IGS, it’s all good stuff

And while we’re on the subject of glass and glass industry events, please make a note that in March 2017 the Glass Supper goes walkabout. The inaugural Glass Supper Asia Pacific takes place on March 17th in Sky100, Hong Kong, you know you can trust me when I tell you that the line-up of Speakers is to die for, a small collection of demigods will address an expert group of glass industry leaders and chew the fat about all things glass in buildings. The fundamental theme, the cornerstone of the presentations will be Pollution - the Architects Role.

This theme of pollution kicks off in the London Glass Supper on Thursday 1st December in Gibson Hall, Bishopsgate and will continue in Hong Kong. Pollution is a menace to society on a grand global scale so we’ll be looking at this in enormous detail, what can the architectural glass industry do to make a real difference and reduce the dreadful pollution that engulfs the world? Pop along to the Glass Supper in London this December to find out what the experts say, then join us at the Glass Supper Asia Pacific next March where the problem of pollution is acute.

IGS, the most popular and beloved people powered glass industry publication

intelligent glass solutions

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Inside Why doesn’t the glass industry stop selling glass....and sell performance instead Bruce Nicol, Dow Corning Page 4

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The panel will also focus on the value of international collaboration between researchers, academia and industry stakeholders, and ways that collaboration can strengthen industry research and foster new innovations.

Anthony DarkAngelo Organiser, GlassCon Global Boston USA Page 17

The ceramic colours printed on the glass louvres also provides protection against the sun and the glare, the design of the ensemble blends harmoniously into the environment....

Klaus Lother Gartner GmbH Page 64

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e

this issue

Underneath the roof the building has a unique structural glass faรงade.

What makes this building unique is the west glass fins facades being tilted sideways 21 degrees.

Thomas Henriksen Mott McDonald Page 46

intelligent glass solutions

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The interaction of light with the electrons of the individual atoms of a glass determines the refractive index. If either electron density or polarizability are increased, the refractive index increases, too.

Lisa Rammig EOC Engineers Page 84

...all the conferences and exhibitions are addressing new challenges in respect of the term industry 4.0.

The glass processing industry and faรงade builders are no exception.

Paul Bastianen, The IGS Column Page 92

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Introduction

Why Doesn’t the Glass Industry

Stop Selling Glass?

Future City, LA - Blade Runner

An opinion piece by Bruce Nicol RIBA Architect

The glass industry stop selling glass? What’s that all about? How could an industry not sell anything? Well the question does not exclude selling. How about asking “Why doesn’t the glass industry stop selling glass……….and sell performance instead?”

We are finding more industries in today’s markets are involved in providing both a commodity and selling a service. In the ideal circular economy of things we would constantly use and re-use everything.

When I talk with architects about glass one question that often comes up is size. We all know, and are excited about, what Apple have done recently with pushing glass sizes. Of course this is not new. Large format glass has been produced in the past and definitely continues to be a trend. So what is the maximum size? Well most float lines are producing glass at 3.21m width. 3.3m is a possibility from any standard float line and there are some exceptions in China at 3.6m wide. Length ways will depend on cutting and handling capabilities. So in theory a piece of

glass is 3.21m x 15 year long, or however long the furnaces last these days and into the future. Of course this is not at all practical, but it does open the idea of time into the overall discussion about how we produce and sustain float glass.

Basically once the furnace is lit on a float line, then it is not turned off for 15-18 years or so. During that time there is a continuous moving ribbon of glass moving along at different speeds to produce the differing thickness required. It’s not unusual for around 25% of this ribbon of glass to be fed back into the furnace as cullet. This saves energy and makes the production more efficient.

Gas fired burners inside the furnace of a float line.

Pilkington Production 1950s

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Introduction

So what is to be done with the hundreds of tonnes of glass produced by a float line every single day for 15 years that is not returned as cullet?

Rough economies of scale suggest that to make a float line productive a required population of 10 million people is needed behind it. That is the market that drives the need for float glass, which after all is mainly for architectural and construction purposes.

To build one of these amazing pieces of kit known as a float line, requires in excess of £100 million. Not just on the equipment itself, furnace, float tank etc, but to acquire enough level land to facilitate the production. Don’t forget that moving ribbon of glass. Depending on glass thicknesses produced this ribbon of glass could be anything from 800m to several kilometres long before any cutting takes place!

So with all this effort and costs you might think glass is an expensive commodity. It is actually the cheapest it has ever been in history, and we, as a species, have been producing glass for many thousands of years.

We are at a point where some float lines will be turned off as the economies of scale are no longer viable. So are there any alternatives?

Current discussions in the façade design world are already talking about developers leasing facades. As facacde technologies develop then the façade industry would simply offer to the building owner an upgrade. As facades tend to have a high quantity of glass, and there are many arguments in place for increasing and decreasing the glass to wall ratio, then the glass industry could step into this leasing world far easier than the façade companies.

We have established that there is a constant supply of good quality float glass being produced on a daily basis. This commodity is very cheap. The glass industry makes money by ‘value adding’ work. That is to say all the downstream processing the glass needs to turn the commodity into a usable product. What determines this product? The performance of the façade. Hence it is not the glass which is important rather the performance. Don’t sell the glass….sell performance.

Performances requirements change and differ around the world. Performances can change around the façade of a building due to orientation. Energy efficiency codes and intelligent glass solutions

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regulations change also, so political influences can also come in to play.

Over the life span of a building it could be expected that the energy codes will change several times. These changes tend to be one directional. Ever more stringent. Striving for energy efficiency, and rightly so.

So within this principle idea to sell performance, would be a lease arrangement to up-hold the performance of the façade. As technologies, or codes change, then the glass industry could step in and upgrade the façade glazing. How would this work? Well on a very crude level you could say the industry ‘leases’ each glass surface to the building owner. Each surface contributing to the overall performance to varying degrees. So for example where a façade has an insulating glass unit made up of a monolithic outer and a laminated inner, we would have 6 surfaces.

car ownership and populations leasing time in cars rather than purchasing one outright. Better cars, better efficiency.

So, come on glass industry folk on all sides, start thinking about a circular economy and work towards what we are best at. PERFORMANCE related futures and all round energy efficiency through production, usage, upgrades and re-use.

Here’s the model then. Each surface is leased at £1.00/m2/year to the building owner. That’s £6.00/m2/year. Say for scale purposes only take a façade like London’s Cheesegrater, The Leadenhall Building, with around 70,000m2 of glass. The industry could generate £420,000.00 per year in leasing arrangements. Less than the initial glass contract but over the basic 10 year warranty offered from the glass industry, substantially more. We all expect buildings to survive longer than this warranty period.

So for the building owner they would get replacements when required, upgrades when necessary, and continued monitoring through out the lifetime of the building, not just the warranty period.

The glass producer would still own the glass.

Any defects would be the responsibility of the glass industry. All recycling of the product would be the responsibility of the producer.

Therefore quality control and re-use/recycling efficiencies would increase. Where BIM type modelling is used individual glass elements could be incorporated into that model with the future for the facades fullt documented for upgrade and recycle.

Sounds simple when I re-read this, so why not?

Well traditionally the industry is slow to react.

After all they have that 15 year long piece of glass to deal with. But in reality all it needs is a change in mind set in the same way that say the automobile industry is changing with less 5

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Connecting Global Competence

The future of building for China

The future of building

r e fo n: nlin hibitio o r e x t e r s i Reg ess and iste g e r r g con om/ the na.c

chi

bau

MMI Shanghai - bauchina@mmi-shanghai.com 6 Messe München GmbH - bauchina@messe-muenchen.de IGS.06.2016.001-008.indd 6 BAU17zitr+BCC16bam-210x284-intellglassol-E.indd 1

Messe München GmbH · info@bau-muenchen.com Tel. +49 89 949 -11308 · Fax +49intelligent 89 949 -11309 glass solutions 23/06/2016 13:44 29.01.16 09:32

C O N T E N T S Co nte nt s I GS Su m m e r I ssu e 2016

g

6 09:32

4

Introduction: Bruce Nicol The future of glass

Executive Boardroom Commentary

24

10 Christian Louter

Challenging Glass 5 Conference in Ghent

Celebrating Challenging Glass 17

Anthony DarkAngelo Project Director GlassCon Global Impacting the global market through technical education and innovation

24 Birgit Horn

Project Director glasstec 2016

Glass, the material of the future Amazing projects in glass

32 51 intelligent glass solutions

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32

F. Oikonomopoulou & F. A. Veer TU Delft, Faculty of Architecture T. Bristogianni & R. Nijsse TU Delft, Faculty of Civil Eng,& Geosciences Challenges in the construction of the Crystal House Facade

46 Thomas Henriksen

Mott McDonald

Etihad Museum – Structural glass wall 51

Lucio Blandini Werner Sobek, Stuttgart Transparent, complex, sustainable challenges for contemporary facades engineering

58

Marcin Brzezickia Wroclaw University of Technology, Poland See-through or not? Transparent architecture for non transparent intentions

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C O N T E N T S 68 Klaus Lother

Josef Gartner GmbH Glass facades with an inspiring light concept

76

Pierre Descamps, Jon Kimberlain, Jayrold Bautista & Patrick Vandereecken Dow Corning respectively, Belgium, US, Singapore, Belgium Structural glazing: Design under high wind load

84

Lisa Rammig EOC Engineers Residual stress as a result of heat impact in borosilicate glass components

The Paul Bastianen Column 92 The Paul Bastianen column

The most interesting training sessions this year 96 Authors Details

68 Intelligent Glass Solutions

Summer

Summer 2016

HIGHLIGHTS FROM THE RECENT CHALLENGING GLASS 5 CONFERENCE

5

2016

GLASSCON GLOBAL IN BOSTON UNITED STATES – BRIDGING THE GAP MVRDV’S REMARKABLE GLASS BLOCK SYSTEM FOR CHANEL SMELLS REAL GOOD

An IPL magazine

GLASSTEC 2016 IN DÜSSELDORF IS ALMOST UPON US

INTELLIGENT GLASS SOLUTIONS

Front Cover Photo: Inside the Ritz Carlton Hotel in Hong Kong Supplied courtesy of: Dr.Helmut Hohenstein Hohenstein Consultancy Photo by: Mary McArtney Published by: Intelligent Publications Limited (IPL) ISSN: 1742-2396 Intelligent Glass Solutions Publisher: Nick Beaumont Accounts: Richard Marks Editor: Sean Peters Production Manager: Kath James

Director of International Business Network Development: Roland Philip Manager of International Business Network Development: Maria Jasiewicz Design Director: Darren Cartwright Page Design Advisor: Arima Regis Lead Designer: Simon Smith Design and Layout in the UK by: CJ Media Telephone: +44(0)1299 861 484

Intelligent Glass Solutions is a quarterly Publication.The annual subscription rates are£59 in the UK, £70 in Ireland and mainland Europe and £96 for the rest of the world.

Email: nick@intelligentpublications.com Published by: Intelligent Publications Limited 3rd Floor, Omnibus House 39 - 41 North Road, London N7 9DP United Kingdom Tel: +44.207.607.9907 Email: nick@intelligentpublications.com Web: www.intelligentpublications.com

The entire content of this publication is protected by Copyright. All rights reserved. None of the content in this publication can be reproduced, stored or transmitted in any form, without permission, in writing, of the copyright owner. Every effort has been made to ensure the accuracy of the information in this publication, however the publisher does not accept any liability for omissions or inaccuracies. Authors views are not necessarily endorsed by the publisher.

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Executive Boardroom Commentary

Celebrating Challenging Glass!

Christian LOUTER

Jan BELIS

Freek BOS

Challenging Glass is proudly celebrating its 5th edition this summer 16 & 17 June in Ghent Belgium. This international conference, organized by Christian Louter, Freek Bos and Jan Belis, focuses on the architectural and structural application of glass. With participants from all over the world, more than 80 paper presentations, 4 keynote presentations and a special project session on the recently finished Crystal Houses in Amsterdam, the conference promises to be a great success.

glass, such as architects, engineers, scientists and industry partners. From the start, the organization has aimed at finding a balance between input from academia and practice.

Much of the innovations in glass applications in buildings come from practice. Getting those working in practice together with researchers provides valuable cross-fertilization which inspires new developments in both fields.

The conference got its title from the material characteristics of glass: it is a very challenging material to work with, both structurally and architecturally. The brittleness, caused by the absence of a crystalline structure, makes strength unpredictable and failure immediate and total. Its transparency and therefore privileged relation with light, gives glass its prominent role in architectural development since late medieval Gothic cathedrals. But Challenging Glass also refers to what engineers, architects and researchers should do with the material: stretch its possibilities, extent its limits, optimize its performance.

When initiating the first edition in 2008 to mark the end of their respective PhD studies, Freek Bos and Christian Louter had never suspected that Challenging Glass would evolve to its current importance within the international structural glass community. Challenging Glass has become one of the leading European scientific structural glass conferences, bringing together people from various disciplines with the architectural and structural application of intelligent glass solutions

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Challenging Glass is organized bi-annually, typically in collaboration with a leading structural glass research group at an internationally renowned university. As such, the conference was held at Delft University of Technology (TU Delft) in The Netherlands in 2008, 2010 & 2012, at the Ecole Polytechnique FĂŠdĂŠrale de Lausanne (EPFL) in Switzerland in 2014 and at Ghent University (UGent) for the upcoming 2016 edition. For the past two conferences Jan Belis has joined and strengthened the core organisational team.

Over the years, Challenging Glass has hosted several internationally renowned keynote speakers. An overview can be found in Table 1. At every edition Challenging Glass aims at a fine balance between architect, engineer and scientist keynote presenters so to initiate synergy between these disciplines. In 9

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Executive Boardroom Commentary

Zhangjiajie Foot Bridge. Design by Haim Dotan Architects.

addition, Challenging Glass typically strives for an out-of-the-box keynote presentation, such as the keynote presentation of material scientist Tanguy Rouxel (Université de Rennes) at Challenging Glass 1 (2008) that provided a remarkable view on the possibilities of glass, which was quite different from the one building professionals are used to. Another example is the keynote presentation at Challenging Glass 3 by Rogier van der Heide (Philips Lighting) that focused on the interaction between glass and lighting design.

For the upcoming edition of Challenging Glass, again a solid line-up of architects, (façade) engineers and scientist keynote speakers has been assembled. On Thursday, Israeli architect and professor Haim Dotan (Haim Dotan Architects) will show his spectacular glass works in China and across the globe. The Zhangjiajie foot bridge is a striking piece of design, daring visitors to cross a 300 m deep canyon of a cable stayed glass floor bridge.

Sven Plieninger of Schlaich Bergermann & Partner, a firm with a long time tradition in outstanding engineering will be discussing recent projects – such as the Dongguan Gymnasium in China – and future developments. The opening session will finish with a discussion by Agnes Koltay, façade engineer and founder of the successful Dubai-based consultancy Koltay Facades, of the facades of the Opus building (designed by Zaha Hadid and currently under construction).

The focus of this contribution will be on the

Dongguan Gymnasium, Dongguan, China, Design by gmp · Architekten von Gerkan, Marg und Partner (source: http://www.sbp.de/en/project/dongguan-gymnasium/)

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Executive Boardroom Commentary

particularities of double curved glass in the desert climate of the Arab peninsula.

On Friday afternoon, the program of the closing session is no less interesting. Dutch architect Willem-Jan Neutelings (Neutelings Riedijk Architects) explains how he treats the material glass in his buildings, showing among others the spectacular façade of the The Netherlands Institute for Sound and Vision.

Challenging Glass 5 will close with a special session on the Crystal Houses facade project, presented by architect Gijs Rikken (MVRDV) and researcher Faidra (TU Delft). This project was recently revealed in Amsterdam and forms an icon within the most prominent luxury shopping street of the Netherlands. By stacking and adhesively bonding solid glass bricks a stunning glass façade has been realised.

As for every edition, Challenging Glass 5 also hosts over 80 paper presentations, published by nearly 200 authors from 17 different

countries. These papers are divided over 11 subthemes, which address multiple scale levels ranging from glass material strength to high-end glass applications in structures and façades. Each of these papers has gone through a strict peer-review process for which Challenging Glass has installed a 15-person international scientific committee of leading experts in the field. On top of that, Challenging Glass has established collaboration with the recently launched journal Glass Structures & Engineering, thereby preselecting promising paper contributions for publication in the journal. These selected papers have gone through a double-blind journal paper review and correction process, thereby guaranteeing high quality final manuscripts. A copy of the first issue of Glass Structures & Engineering journal is kindly provided by publisher Springer to each participant of Challenging Glass 5.

The proceedings of the Challenging Glass Conferences provide an extensive overview of the developments in structural and

architectural glass research and engineering over the last decade. From a focus on bigbigger-biggest, with even increasing glass panel sizes being applied, attention now seems to shift to other developments providing added value. Minimalized structural adhesive connections based on foils and laminates are gaining more acceptance. Hot and cold bending of glass is applied ever more. Switchable glazing seems poised for a breakthrough as their performance improves.

Ultra thin glass has also become a popular subject for research. Its strength is fascinating, but it has still to find application opportunities.

On the other hand, fire performance and resistance of structural glass has received little attention in research, whereas it is a major issue in project applications. Further publicly available research is very much desirable.

Challenging Glass is grateful to all partners that contributed to the success of the Challenging Glass Conferences. With the input of paper authors, keynote speakers, local hosts, scientific

The Opus Building. Design by Zaha Hadid Architects.

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Executive Boardroom Commentary

Crystal Houses façade, Amsterdam. Design by MVRDV Architects.

committee members and the financial support from industry sponsors Challenging Glass has been able to realise high-quality conferences for a wide international audience. In addition, media partners such as IGS, have kindly supported Challenging Glass in announcing and reporting on the conferences, which is highly appreciated.

We are looking forward to a successful and inspiring 5th edition of Challenging Glass in Ghent!

More information on Challenging Glass can be found at www.challengingglass.com or obtained through CGC5@challengingglass.com.

The Netherlands Institute for Sound and Vision. Design by Neutelings Riedijk Architects. Photography scagliolabrakkee Š Neutelings Riedijk Architecten.

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Executive Boardroom Commentary

Challenging Glass 1, 2008, TU Delft (NL)

Luke Lowings - Carpenter Lowings Arch. & Des. (UK) Niccolo Baldassini - RFR (FR) James O’Callaghan - Eckersley O’Callaghan (UK) Tanguy Rouxel - Université de Rennes (FR)

Challenging Glass 2, 2010, TU Delft (NL)

James O’Callaghan - Eckersley O’Callaghan (UK) Werner Sobek - Werner Sobek / ILEK - Stuttgart (DE) Marc Simmons - Front Inc. (USA) Pascal Richet - IPGP (FR)

Challenging Glass 3, 2012, TU Delft (NL)

Tim Macfarlane - GLASS (UK) Erick van Egeraat - Des. by Erick van Egeraat (NL) Christoph Timm - SOM (USA) Rogier van der Heide - Philips Lighting (NL) Rob Nijsse - ABT / TU Delft (NL)

Challenging Glass 4, 2014, EPFL (CH)

Marilyne Andersen - EPFL (CH) Graham Dodd - ARUP (UK) Manfred Grohmann - Bollinger Grohmann Ing. (DE) Jacques Raynaud - RFR (FR) Paul Vincent - Renzo Piano Building Workshop (FR)

Challenging Glass 5, 2016, Ghent University (BE)

Agnes Koltay – Koltay Facades (UAE) Willem Jan Neutelings - Neutelings Riedijk Architects (NL) Haim Dotan - Haim Dotan Ltd. (IL) Sven Plieninger - Schlaich Bergermann Partner (DE) Gijs Rikken – MVRDV (NL) & Faidra Oikonomopoulou – TU Delft (NL)

Table 1: Keynote and plenary contributions to Challenging Glass.

Photograph made at Challenging Glass Conference 4, EPFL, Switzerland.

Photographer: Alain Herzog - EPFL

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Executive Boardroom Commentary

Apple Union Square revealed in San Francisco Foster + Partners

The opening of Apple Union Square in San Francisco marks an important step in Apple’s continuous evolution, its purpose and its role in the local community to bring a richer experience beyond opportunistic retail. Its innovative design enables new levels of transparency, openness and civic generosity, incorporating Apple’s new features and services.

Apple Union Square will be a model for future projects worldwide.

The design is the result of a close collaboration between Apple’s teams led by Jonathan Ive, chief design officer and Angela Ahrendts, senior vice president of Retail and Online Stores and Foster + Partners.

“This is an incredible site on Union Square and a chance to create a new public plaza. We have created the most inspiring and stimulating space imaginable, blurring the inside and 14

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outside”, said Stefan Behling, Architect, Foster + Partners. “It is possible to experience Apple’s extraordinary products and services while taking in the buzzing Union Square on one side and relaxing in the contemplative quiet of the new plaza on the other.”

A canopy of shading trees and a 65 foot (19.8 meters) by 50 foot (15.2 meters) ‘green wall’ planted with Ficus Repens (Creeping Fig) plants, bisected by a sheer waterfall at the western end of the plaza, creates a contrasting backdrop to the fountain.

Located on San Francisco’s famous and vibrant Union Square, the building’s vast glass sliding doors allow the store to connect the existing square to a new plaza to the north, creating unprecedented urban permeability.

Taking advantage of San Francisco’s moderate climate, the steel framed glass sliding doors, measuring 20.5 foot (6 meters) by 42 foot (12.8 meters) on the south side and 20.5 foot (6 meters) by 26.5 foot (8 meters) to the north, encourage natural ventilation throughout the store. Fresh air is drawn through the integrated structural spine before being expelled out through the roof. The store is powered by 100 percent renewable energy, including power produced by 130 photovoltaic panels integrated into the building’s roof.

As a foil to the lively activities of Union Square, the new art-filled plaza, featuring public Wi-Fi, is imagined as a tranquil garden of contemplation with tables and seating, creating a beautiful gathering place for the community. The Ruth Asawa fountain, an important heritage feature in San Francisco, has been given a new setting on the steps leading down to Stockton Street.

Apple has always been a pioneer in the use intelligent glass solutions

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Executive Boardroom Commentary

Glass stair and cantilever floor structure of the Forum space over looking Union Square Nigel Young / Foster + Partners

Open sliding doors to south side of store revealing the cantilever floor edge and the piano nobile Nigel Young / Foster + Partners

Top of east stair look towards the Forum and the Genius Grove Nigel Young / Foster + Partners

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Genius Grove looking out to the Plaza with 50’ high waterfeature and green wall Nigel Young / Foster + Partners

of glass. The treads of the glass staircases on either side of the store are held in place by precisely engineered metal lozenge shaped ‘pucks’ that are discreetly embedded into the glass tread and the stringer to give the impression of floating glass steps – an appearance of effortless simplicity, which belies the complexity of the engineering solution.

(30 centimetres) and extends 32 feet (10 meters) from the rear wall to create a 16 foot-high (4.9 meters) piano nobile. The extremely slim column-free floor structure is made possible by tuned mass dampers to eliminate vibration. The impression is of a floating stage in the centre of the space in dialogue with Union Square, creating a spectacular living room for the city.

The entire building is quietly supported by a giant steel truss structure that bridges over the neighbouring hotel basement ballroom.

In turn, this supports further trusses that create the tapered ceiling shape and integrate the network of services throughout the building.

Vertical bracing is neatly tucked away inside the spine and side-walls. Seismic engineering design principles guided every aspect of the structural design, setting the standard for innovation and performance. The generous 40 foot-high (12-meter) volume is divided horizontally by a dramatic cantilevered mezzanine floor which tapers to less than 1 foot

Pushing the boundaries of innovation, the luminous white ceiling, which appears as an opaque surface during the day, surprises visitors as it gradually turns on and dramatically illuminates the space at night. The custommade lighting panels emit a pure, even white glow, as well as having the capability to absorb ambient noise. The integrated grid that holds the ceiling panels in place has been designed so that all the services can be precisely located, while also making it flexible enough to accommodate any future technological advances.

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The Apple Union Square introduces five new features. ‘The Avenue’ is a specially designed area for the display of accessories incorporated into the central spine wall. The ‘Forum’, a new learning environment, where specialists from various fields come to entertain, inspire and teach, will occupy a prime central position on the mezzanine against a vast video wall which will also act as an animated backdrop for Union Square beyond. To the rear of the Forum is the ‘Genius Grove’ with a more relaxed setting amongst a small grove of trees, each within a single planter that doubles as a comfortable place to sit and rest while an Apple Genius answers any questions. The unique design of the tree planters was a collaboration between Foster + Partners and Apple’s Industrial Design Studio. The ‘Boardroom’ – a place for meetings, conversations and partnerships for local entrepreneurs and enterprises is discreetly placed behind the green wall.

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Executive Boardroom Commentary

GlassCon Global: Impacting the Global Market through Technical Education & Innovation

Anthony Darkangelo No matter where you go in the world, or what industry you are in, you will always hear about the importance of and need for innovation.

This is especially true in the architectural glass and glazing world. As the emphasis and need for sustainable and adaptive designs/ products increases, so too does the call for glass innovation. GlassCon Global was created to do just that: drive innovation in glass technology.

cutting-edge information on current and future products, trends and designs to all of the industry’s leading stakeholders.

GlassCon Global is a three-day, technical and educational conference that is held every other year in North America. This year, GlassCon Global 2016 is being held in Boston, MA from July 6-9. It brings together all facets of the architectural glass and glazing industry: from owners who commission projects, to the architects, engineers and specifiers who plan the projects, to contractors who enact the projects and to the manufacturers, academics and researchers whose ideas and products enrich the project. By bringing together the various segments, GlassCon Global is able to foster true industry collaboration and provide

The inaugural GlassCon Global conference was held in 2014, and it made waves throughout the industry. The agenda for the 2016 edition is loaded with even more information, innovation, collaboration and networking that will ultimately make the 2016 event more impactful than its predecessor. This year, the GlassCon Global agenda features more than 40 technical presentations that are tailored to provide participants up to 14 credit hours.

Each GlassCon Global educational track and plenary session is accredited by the AIA, and engineering credits will also be available.

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There is still time to attend GlassCon Global 2016. Registration is open at www. glassconglobal.com/registration and you can learn more about the conference at www. glassconglobal.com.

Education The agenda for the 2016 conference is posted online, and it contains panel discussions and educational tracks that will resonate within the industry for years to come. The educational tracks will feature more than 40 presenters covering topics such as high performance use of glass; scientific research; net zero, energy and sustainability; security, fire-rated and laminated glazing; case studies; market trends; and design considerations. The presenters in these tracks include esteemed names such as Christian Louter (speaking on fire testing of structural glass beams and initial experimental results), JĂźrgen Neugebaur (discussing thin glass), Jorma Vitkala (discussing worldwide glass market and trends), Valerie Block (speaking on designing safer glass railings with laminated glass), Werner Jager (discussing noise absorption and sound scattering of building envelopes) and many more!

In addition to the educational tracks, GlassCon Global will also feature several plenary session and panel discussions. GlassCon will kick off 17

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with comments from two of the world’s most influential architects: Jane Duncan, president of the RIBA will be presenting “the 2016 UK RIBA award-winning buildings and their global impact;” and Elizabeth Chu-Richter, the 2015 President of the AIA will be presenting “How we must be prepared to apply our talents anywhere and everywhere.”

The first GlassCon Global panel discussion will be “The Role of Glass in Adaptive Façades.”

Moderated by SOM’s Keith Boswell, and it will feature some of the industry’s brightest minds discussing the role glass plays in adaptive façades. Panelists Thomas Henriksen (Mott MacDonald), Stephen Selkowitz (Lawrence Berkely National Laboratory), Ulrich Knaack (Delft University of Technology) and Helen Sanders (Sage Glass) will share their insight on the three key challenges faced by glass in adaptive façades: 1) Light vs. Energy; 2) Reverse Innovation in Glass; 3) Static vs. Active Glass.

The second panel discussion will be the “Transatlantic Debate” (one of GlassCon Global 2014’s most talked-about panels). The Transatlantic Debate will be moderated by Dow 18

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Corning’s Bruce Nicol and will feature industry leaders sharing insights, expertise and trends from the various architectural glass and glazing markets. Panelists will cover why we have gaps that exist in design, technology and application and what we can do to fix those gaps. The Transatlantic Debate will also challenge manufacturers, architects and building owners

to leverage value and maximize usage of glass and glazing in construction.

The next panel discussion is “Stimulating Glass Innovaton through University Curriculum,” and it will be moderated by Façade Tectonics Institute’s Mic Patterson. Patterson and panelists Jürgen Neugebaur (University of Applied intelligent glass solutions

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Sciences FH-Joanneum), Doug Noble (the University of Southern California) and Christian Louter (Delft University of Technology) will discuss current university curriculum and changes that would stimulate innovation if implemented. The panel will also focus on the value of international collaboration and cooperation between researchers, academia and industry stakeholders, and ways that collaboration would strengthen industry research and foster new innovations.

The final panel discussion of GlassCon Global will be “XX(X)L Glass: Logistics, Quality & Assurance.” The panel will focus on the use of extra-oversized glass, which has become increasingly relevant in modern architecture.

Panelists will answer the questions on how the industry assures and controls that custom, manufactured oversized glass meets and exceeds clients’ quality standards. The panel will also examine the impact that logistics surrounding transportation of oversized glass has on project costs and the steps required to ensure the glass is boxed and safely transported.

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In addition to the panel discussions, GlassCon Global will also feature a presentation from renowned economist Anirban Basu. Titled, “The Economist Who Loved Me,� Basu will provide a global perspective on the economics that have an impact on our business and industry.

From the North American economies, to Asian and European, he will provide detailed, data-driven updates that are as entertaining as they are informative. Basu has a unique ability to provide information that can impact your business decisions on key aspects of economic life (trends characterizing financial, real estate, energy and labor markets) in an entertaining manner. He will provide the information attendees need to understand the current and future states of national and global economies that will help them prepare for the future.

Networking The relationships built and expanded during GlassCon Global are just as important as the great information shared. Networking is a key focus of GlassCon Global, because an industry that knows each other will generate more innovation. GlassCon Global 2016 will feature several networking events, including

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its grand welcome reception (on the evening of Wednesday, July 6) where attendees can enjoy a drink and catch up with colleagues old and new; a Cocktail Hour and Mystery Dinner (on the evening of Thursday, July 7) where attendees will go on a “mystery dinner” with delegates they may not have gotten to know otherwise; and GlassCon’s final evening networking event will be a closing celebration on the Spirit of Boston Sunset Dinner Cruise, where attendees will enjoy a unique mix of dining, dancing, entertainment and a remarkable view while solidifying new and existing relationships made during GlassCon Global 2016. GlassCon Global also has several networking breaks and meals built into its program.

Partners and Sponsors GlassCon Global would not be successful without the support of some of the glass industry’s leading manufacturers, suppliers and organizations. Platinum Partners Dow Corning, Eastman, the LMCI and Tecnoglass have recognized the impact of GlassCon Global and offered their support. Bronze Partners Kuraray and North Glass, along with Supporting 22

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Partners GANA and USGlass Magazine are also contributing to GlassCon Global’s success.

Several other companies have recognized GlassCon’s value and signed on to become sponsors, including: AGNORA, AkzoNobel, Mott MacDonald, Quanex, SAFTI FIRST, SageGlass, Sapa Extrusions, Sedak, Tremco, Vidaris and W&W Glass.

The support and involvement of these leading companies are helping ensure GlassCon Global 2016 will have a positive impact on the industry.

Exhibitors While GlassCon Global is a technical conference (and not a tradeshow) there will be 15 exhibitors at the event so attendees can see some of the latest and greatest products during networking breaks and meals. GlassCon Global 2016’s exhibitors are: 3M, AGNORA, AkzoNobel, Dow Corning, Eastman, Kuraray, Momentive Performance Materials, Next Energy Technologies, North Glass, Quanex, Roschmann Group, SAFTI FIRST, SageGlass, Sedak and Tecnoglass.

Boston GlassCon Global is being held at the Boston Renaissance Waterfront Hotel from July 6-9.

Attendees can come in early to experience the Fourth of July celebrations in one of the United States’ most historic cities. Boston is constantly ranked among the most innovative cities in America and has a slew of museums, theaters, parks, sports, dining options and much more.

To get some ideas on things to do while you’re in Boston for GlassCon Global, visit www. glassconglobal.com/things-to-do-in-boston.

Registration While spots are quickly filling up, registration is still open for GlassCon Global. You can register at www.glassconglobal.com/registration.

Groups of three or more are eligible for a discount, and you should contact the registration office directly at +1 855-5GLASS5 (+1 855-545-2775) for registration or +44 2033185635.

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20–23 September 2016

Is glass intelligent?

Forget everything you ever knew about glass. What glass can do today is revolutionary. Wafer-thin sheets bend and hold electronic wires. Ultra-thin glass opens up visions of smartphones which can be wrapped around your wrist. Solar façades can be individually designed with the click of a mouse.

You can find out how intelligent glass really is at glasstec, the world’s leading trade fair. The best way to prepare for your show visit is to use the sector guide on the glasstec portal.

For further information contact: International Trade Shows Link Ltd. Ramsay House, Marchmont Farm _ Link Road Hemel Hempstead _ Hertfordshire HP2 6JH Tel. +44 (0)1442 23 00 33 _ Fax +44 (0)1442 23 00 12 info@itsluk.com

www.glasstec.de/industryguide

www.itsluk.com

SUBSCRIPTIONS

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glasstec 2016: Glass – the material of the future

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A

s before, Düsseldorf will be the international meeting point of the glass industry from 20 to 23 September 2016. Again, glasstec 2016 will present a comprehensive bandwidth of all innovations, trends and solutions, combined with a sound professional support programme, featuring practical and scientific insights. “glasstec is the world’s leading trade fair in the glass industry,” says Joachim Schäfer, Managing Director at Messe Düsseldorf, “and we will see again this year that this material is set to assume an even greater role in a wide variety of working and home environments – whether in architecture, engineering or the automotive industry. Glass and innovation go hand-in-hand.”

About 1,200 exhibitors are expected to be there, so that glasstec covers the entire value chain associated with glass as a material.

The previous event in 2014 attracted over 43,000 visitors (from 87 countries) from mechanical engineering, glass manufacturing, processing and finishing, the trade sector, architecture and construction, windows and façades and solar. The internationalism of these experts – of whom 63 per cent came from outside Germany last time – is globally unparalleled in the glass industry. Moreover, 85 per cent of visitors said they were directly involved in decisionmaking processes at their companies.

The support programme will revolve around a special show entitled “glass technology live” with an industry symposium. This year’s motto will be “Future – Glass – Performance”.

Directly next to glass technology live, visitors will find the Glass & Façade Competence Center.

As before, the Craft Center with the stand of the Federal Association of the German Glazier

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Trades (BIV) will be present at the trade fair and will have a special action space called Craft LIVE where visitors can acquire expertise and engage in practical exercises. It will also feature the Auto Glazing Competition and the Glass Art Exhibition.

The glasstec conference programme will include a scientific conference on structural glass engineering, called engineered transparency, the International Architecture Congress with visions for modern glass structures and a new conference entitled “Function Meets Glass” which will be about high-precision manufacturing processes for thin glass.

Again, visitors from mechanical engineering, industry, crafts, architecture/construction, windows/façades, general engineering and solar engineering can look forward to an extensive programme with specialist information geared towards various target groups.

“

About 1,200 exhibitors are expected to be there, so that glasstec covers the entire value chain associated with glass as a material

”

Glass Technology Live: a highly topical and practical trendsetter Running under the motto “Future – Glass – Performance”, Hall 11 will again put a special focus on spectacular exhibits, innovative products and forward-looking solutions which we can expect to be relevant for the next 3 to 5 years. This year, too, the special show will be held under the patronage of Prof. Stefan Behling, Senior Executive Partner at Foster & Partners in London, and will be organised by the IBK 2 team from the University of Stuttgart.

The focus will be above all on free-form, ultrathin and solid glass. The special show will offer inspiration to architects and planners seeking new application options, but it will also showcase the full range of new applications of further developments in glass products. “glass technology live” will feature a highcalibre industrial symposium as part of the gtl exhibition space, with a variety of talks on highly topical subjects. gtl will be free of charge for all trade fair visitors. Numerous international representatives in architecture, industry and science will present their use of glass in various projects. The special show and trade symposium will put a clear focus on the future of the glass industry. The programme of the gtl symposium will be dedicated to a different focal topic on each of the trade fair days. Content will be presented by different partners: the Colloquium of the Research Association of the German Glass Industry (HVG) and the Technical Glass Society of Germany (DGG) on glass melting and moulding (Tuesday), the German Machinery & Plant Manufacturers’ Association (VDMA) on glass processing and finishing technologies and on Glass Industry 4.0 (Wednesday), the University of Stuttgart on architecture and digital planning processes (Thursday), and the German Federal Flat Glass Manufacturers’ Association on glass in windows and on façades (Friday).

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Everything you want to know about building envelopes Directly next to “glass technology live”, visitors will find the Glass & Façade Competence Center. The thematic focus of the Center will be on glass for façade planners, construction engineers and architects, supplemented by suitable exhibitors’ presentations in Halls 9, 10 and 11. Moreover, a wide range of information will be on offer from various institutes and associations.

They will include the German Federal Flat Glass Manufacturers’ Association (BF), ift Rosenheim GmbH, the German Association of Independent Advisers in Façade Engineering (UBF), the University of Augsburg (Institute of Construction and Real Estate), Dortmund University of Applied Sciences and Arts (Department of Architecture), the Technical 26

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University of Darmstadt (Institute of Materials and Mechanical Engineering in Construction) and the Insulated Multiple-Glazing Quality Association.

Division of the North Rhine Westphalian Chamber of Engineering (4 time units).

The attendance fee is EUR 49 and includes admission to the trade fair for two days.

International Architecture Congress – inspiring visions On the Wednesday several speakers from wellknown architectural offices will present their visions of architectural glass under the title “Contrasts/Glass in Architecture”. The international Architecture Congress will be held in collaboration with the North Rhine Westphalian Chamber of Architects and the University of Stuttgart.

Scientific conference: engineered transparency On the Tuesday and Wednesday international scientists will discuss developments in structural glass engineering (CCD Süd). The focus will be on energy, façades and glass. As before, the event will be held in partnership with the Technical Universities of Dresden and Darmstadt.

The Architecture Congress is officially recognised as CPD by the Chamber of Architects (4 teaching sessions in architecture and interior design) and by the Architectural

2016 will be the first time that engineered transparency includes special sessions with the Research Association of the German Glass Industry (HVG), the Technical Glass Society of Germany (DGG), the German Trade Association intelligent glass solutions

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Craft Center with Craft LIVE – special interactive show The Craft Center will cover a wide range of products and services for the glass-processing trade sector. The main focal point will be the stand of the Federal Association of the German Glazier Trades (BIV) in Hall 9 which summarizes the numerous offerings for the glazier trade and crafts and the glass finishing arena.

The same hall will also accommodate the special show Craft LIVE on the subject of “Measuring and Testing Glass”. of Structural Glass Engineering (FKG) and the German Federal Flat Glass Manufacturers’ Association (BF).

The presentation sessions will be on the topic of “embedded functions”. Some of the projects and research activities featured at the Conference will be presented at Glass Technology Live. engineered transparency is a conference with a technical and scientific orientation, aimed, in particular, at target groups in research and development and in construction and implementation. It is intended for scientists, construction engineers, planners, architects, designers, experts in the construction industry, building authority staff and interested building owners. It will be held at the beginning of glasstec, on 20 and 21 September. intelligent glass solutions

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A number of practically focused stations and a demonstration space will illustrate the entire process chain, showing visitors from the glassprocessing trade the conditions, procedures and areas of liability which are associated with the issue of glass stability. Anyone from the glass-processing industry is welcome to have a go at using the tools and material themselves.

It starts with the storage of material, followed by the dimensioning of glass, then processing, finishing and mounting, and finally the testing of oscillation performance.

The Auto Glass Competition – culminating in an award for the 2016 Automotive Glass Champion – will be held in a central space in Hall 9, so that the support programme for the glazing trade will also include the area of automotive glass. This

domain, which requires so much precision, will focus on the latest techniques. Again, the event 6 of 8 is primarily being organised by the Federal Association of the German Glazier Trades (BIV).

Another major feature at the Craft Center will be a special show entitled “glass art”. The spectrum of exhibiting artists from internationally renowned galleries will range from glassware through sculptural objects to glass painting.

As before, BIV will give the Glass Finishers’ Award and the Glaziers’ Award to the most successful national companies in this segment.

Function Meets Glass – The future belongs to thin glass Display, touch, smart and solar glass involve the manufacturing and processing of highprecision thin glass. The conference “Function Meets Glass” on 19 and 20 September 2016 will look at ways of making such products at the highest level of quality, under short cycles and with maximum output. The new conference will show what kind of applications are already feasible today, using special processes and technologies in the manufacturing and processing of functional glass. High-calibre presentations will be given by representatives of research and industry, each time followed by an international 27

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dialogue. The conference will be held as part ofglasstec and in cooperation with the VDMA Glass Technology Forum, the VDMA Photovoltaic Equipment Workgroup and the East Bavarian Institute of Technology Transfer (OTTI).

Extremely well prepared and superbly informed – Industry Guide and Trend Compass As before, to help visitors maintain an overview of the wide range of features and facilities offered at glasstec, there will be a special overview for each target group at www. glasstec.de. The Industry 28

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Guide will contain all the facts, figures and offers of exhibitors as well as details of the support programme, arranged according to target groups. The main target groups are structured as follows: “Mechanical Engineering”, “Manufacturing, Processing and Finishing”, “Crafts”, “Architecture and Construction”, “Windows and Façades” and “Solar”.

Thanks to the Trend Compass, information about the innovative products and services is readily available at the click of a mouse button. This is where, in the run-up to glasstec, visitors can numerous innovations, presented

under the following trend categories: Reduction of costs and emissions in the glass production process Glass Industry 4.0 – smart integration of products and processes Innovative technologies for thin-glass production and processing Intelligent glass for building envelopes, display and smart glasses, interiors and vehicles Lightweight and tough hollow and packaging glass Innovative products for processing in the glazier trade

• • • • • •

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All the relevant glasstec details are available online, both in the exhibitors’ database under “Companies & Products” and under supplementary services, allowing each visitor to prepare for the trade fair in depth.

Trade fair preparations made easy Additional services include, for instance,

information about hotels and how to travel, customisable site maps and tips for visiting the City of Düsseldorf. Discounted tickets can be purchased in advance, on good presale terms, at www.glasstec.de. E-tickets are available at EUR 33 (1 day, EUR 46 at ticket office), EUR 50 (2 days, EUR 66 at ticket office) and EUR 78 (all

4 days, EUR 96 at ticket office) and can also be used for travelling to and from the exhibition centre on local public transport (VRR trains, trams and buses).

Furthermore, our glasstec site is available in a responsive design, suitable for mobile access, and as an app for iOS and Android. glasstec 2016 press contacts Daniel Krauss and Brigitte Küppers Tel.: +49(0)211 4560-598 or -929 Fax: +49(0)211 4560-87 or 598 Email: KraussD@messe-duesseldorf.de KueppersB@messe-duesseldorf.de

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The Whole World in one Window

To encourage interaction and collaboration among students was the goal when the Blavatnik School of Government (University of Oxford, England) decided to make one building out of three. The architectural design by Herzog & de Meuron reflects the open communication concept. It has its architectural culmination point in the “Window to the World” – a gigantic glass pane giving a remarkable view from one of the shared areas. sedak realized the pane with dimensions of 10.7m x 3.2m. The glass manufacturer produced the double insulating glass unit with an area of 34 square meters and an overall weight of 3.5 tons. The transportation of the oversize glass pane was organized by sedak as well.

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The Blavatnik School of Government is part of the University of Oxford and has been educating young people since 2012. Until 2015, the institute in the Jericho neighborhood was located across three separate sites. To encourage interaction and collaboration among the 120 students, the Swiss architecture firm Herzog & de Meuron was awarded to create a building with an open design. The result is a five-floor complex with an oversize glazing that makes it an open building cubature. The core - a glass pane in 10.7m x 3.2m – is particularly impressive.

Window to the World For oversize glass units, a special knowhow is

Above: The core of the glass façade of the Blavatnik School of Government in Oxford is the “Window to the World” fabricated by the German glass manufacturer sedak. With an area of around 34 square meters, it offers an unobstructed view from one of the shared areas at Walton Street.

as indispensable as exceptional capabilities in production and logistics. The „Window to the World“, fabricated by sedak, consists one laminate made of two 10 millimeter low-iron glass panes. The glass units are laminated with a 1.52 mm thick PVB interlayer, processed into a double insulating glass and coated against glare and solar heat gains. To facilitate the installation

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in Oxford, a stainless steel frame provided by the client had been bonded to the insulating glass unit in sedak’s production hall.

With an area of around 34 square meters, the “Window to the World” offers an unobstructed view from the shared area at the opposite side of Walton Street where Oxford University Press, the world’s largest university press, is located.

The Transportation: as Individual as the Product Exceptional products demand for exceptional logistics. For a safe transportation, all glass panes fabricated by sedak are packed in special wooden crates. The 3 tons heavy “Window to the World” was packed in a wooden crate with an inclined frame structure and then shipped overland. Thus, the height of the truck was not exceeded and the glass was not damaged on its 1,200 kilometer long way from Gersthofen to Oxford.

Special Installation Technique for Special Purpose Since the glass pane had to be installed under a building ledge, not only the logistics but also the installation technique presented a challenge. The usage of a common crane was impossible due to the overhanging façade.

A special construction was fabricated to lift the glass pane from below into the building envelope. It was connected to the frame of the “Window to the World” during the installation.

“With sedak, we have an outstanding glass manufacturer. Besides the exceptional production capabilities, we appreciate the quality and the adherence to schedules as well as their support during the planning process”, says Michael Schlinz, sales representative at Waagner-Biro.

Above, right: The stainless steel frame installed at sedak’s production hall facilitated the installation of the 3.2m x 10.7m glass pane in the overhanging façade.

Right: The building of the Blavatnik School of Government was designed by the architects at Herzog & de Meuron. The complex in Jericho, Oxford stands out due to its height: With 22m it exceeds the height usually allowed around Carfax Tower by 3.8m.

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Amazing projects in glass

Challenges in the Construction of

the Crystal Houses Façade F. Oikonomopoulou & F. A. Veer TU Delft, Faculty of Architecture, The Netherlands T. Bristogianni & R. Nijsse TU Delft, Faculty of Civil Engineering and Geosciences, The Netherlands

1. Introduction A novel glass brick façade has been designed and engineered for the purposes of a high-end store in Amsterdam. At the time of writing the façade has been completed and the store is expected to open within early 2016. The new façade is an accurate yet completely transparent reproduction of the building’s previous 19th century elevation, entirely made of adhesively bonded solid glass bricks, reinterpreting the traditional brickwork and the typical architraves above the doors and windows. Even the elaborated original wooden frames of the openings are reproduced by massive cast glass elements. As the façade ascends conventional clay bricks intermingle in between the glass ones to create a gradual transition to standard brickwork on the top, residential floor. The standard brickwork of the last floor is structurally independent from the façade below, supported by a steel beam spanning the length of the façade. Based on the structure of the former masonry façade, the elevation of 10 by 12 metres employs more than 6000 solid glass bricks, each 210 mm thick and 65 mm high. The width of the bricks is either 105mm or 210mm to reproduce the pattern of the Dutch bond brickwork.

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Fig. 1. Illustration by MVRDV Architekten of the concept behind the glass brick façade. intelligent glass solutions

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Fig. 2a. 3-D impression by MVRDV Architekten of the glass block façade

Fig. 2b. Photograph of the façade during construction.

The desire of the architects for pure transparency did not allow for the use of any metal supporting structure. Thus, the glass façade had to be selfsupporting. In principle this is plausible owing to the high compressive strength of glass and the considerable thickness of the masonry wall that enhances the construction’s resistance against buckling. The lateral stability of the façade is further reinforced by four buttresses. Formed by interlocking bricks in the interior of the glass wall they create a continuous relief of increased rigidity. Figure 3b shows an illustration of the structural scheme followed in order to maximize transparency. To achieve a completely transparent glass structural system the bricks are glued together by a clear adhesive. Extended research and testing of various types concluded to the choice of a UV-curing, one-component transparent acrylate designed for high strength bonding of glass to glass.

Due to the low viscosity of the selected adhesive, it was determined that only the horizontal joints of the blocks are bonded; a solution that rendered optimum visual result as well. Series of four-point bending tests demonstrated that the selected adhesive leads to a monolithic behavior of the glass-adhesive assembly and to a homogeneous load distribution under loading when applied uniformly in a layer of the optimum thickness (Oikonomopoulou et al. 2015). In specific, the selected

adhesive reaches its maximum bonding strength when applied in a layer of 0.3 mm. Figure 3a illustrates how a relatively thinner or thicker layer can critically affect the adhesive’s strength and consequently the structural behavior and carrying capacity of the glass system. The low viscosity and ideal thickness of the adhesive in combination with the inelastic nature of glass require various implications regarding its homogeneous application as well as the allowable tolerances in the overall façade. Not only the geometry of each brick but even the layered construction of the glass wall have to be confined within a tight dimensional precision of a quarter of a millimeter. Any accumulated deviation larger than that could lead to inhomogeneous and improper bonding of the glass components, compromising not only the visual quality, due to visible flaws in the adhesive layer, but also the structural performance, due to the initiation of local peak stresses. This particularly high level of precision has never been realized before in such a large building scale.

The demand of extreme accuracy and transparency generated many challenges in the engineering of the Crystal Houses façade that required innovative solutions so that the glass masonry wall can meet both visual and structural prerequisites. These challenges and their corresponding solutions are presented in this article.

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Fig. 3a. Schematic depiction of the relation between an adhesive’s optimum strength and thickness.

Fig. 3b. Principle of the proposed adhesively bonded glass brick system.

2. Fabrication and controlling of the bricks In previous realized examples of façades employing solid glass bricks, such as the Atocha Memorial (Christoph,Knut 2008) and the Optical House (Hiroshi,NAP 2013), borosilicate glass was opted for the fabrication of the bricks. Due to its low thermal expansion coefficient, borosilicate presents a much higher resistance in rapid temperature changes; as well as much less shrinkage and thus, higher dimensional accuracy during the annealing of the blocks. In contrast, in this project soda-lime glass was chosen for the fabrication of the bricks(Oikonomopoulou et al.

2015), which is characterized by a higher thermal expansion coefficient 34

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than borosilicate, and consequently larger volume changes due to temperature variations. As the required Âą0.25 mm tolerance necessitates the postcasting processing of the blocks regardless if they are made out of borosilicate or soda-lime glass, the latter was preferred due to its considerably lower raw material cost.

The fabrication of the approximately 6000 solid glass bricks was assigned to the Italian company Poesia specialized in cast glass components. Each brick is manually cast by pouring molten glass in high precision open steel moulds. A low-iron glass recipe is used in order to obtain completely colorless bricks. To acquire the desired smooth intelligent glass solutions

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surface texture the moulds are preheated to a constant temperature.

If a mould is too cold, then the hot glass coming into contact with the cold metal surface freezes instantly, creating a rough, wavy surface. On the other hand, if a mould is too warm, the glass tends to stick to the walls of the mould. After the glass is poured into the mould it is left to cool by air temperature to 700 °C before it is removed and placed into an annealing autoclave. There, a long and meticulously controlled cooling process prevents the development of internal residual stresses.

In specific, every brick with 65 mm by 105 mm by 210 mm dimensions requires approximately 8 hours of cooling, while a brick of double volume requires 36-38 hours respectively. During the annealing process, natural, inevitable shrinkage occurs to the glass volume. This mainly appears on the top face basically due to gravity force. This top layer is trimmed by a CNC machine which processes the block to the precise height. Finally, the two horizontal faces of each block are polished to a smooth flat surface to minimize any local projections.

The final glass bricks are then subjected to two controls to verify if they meet the desired dimensional precision. First, a cut-out metal plate is used

as a jig to control the bricks’ total length and width (see Figure 4a). Only if a brick can go through the cut-out, it can be used in the façade. The accepted bricks are then controlled by a specially developed measuring system that evaluates if they meet the 0.25 mm precision in height and flatness. Five LVDT sensors with 1 micrometer (0.001 mm) measuring accuracy, fixed on an aluminium frame, take height measurements at the edges and center of each brick (see Figure 4b). If not all five points are within the desired 0.25 mm tolerance in height the brick has to be re-polished or discarded. Besides the measuring control, the glass bricks are also submitted to a visual inspection in-situ for minute cracks and defects on their bonding surfaces, commonly caused by the handling and transportation processes. Bricks with even minor cracks have to be discarded, as the almost 10% shrinkage of the adhesive during its curing triggers the propagation of cracks even less than one millimeter deep due to introduced tension, resulting to visible cracking of the brick (see Figure 4c).. Only the glass components that pass both the measuring and visual controls are used for the construction of the façade.

Fig. 4b. Measurement controls of the final bricks.

Fig. 4a. Measurement controls of the final bricks. intelligent glass solutions

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Fig. 4c. Propagation of a minor crack after the curing of the adhesive.

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3. Construction of the glass brick wall 3.1. Levelling the starting surface The construction of the glass masonry wall started above a 0.60 m high by 0.20 m wide reinforced concrete zone. The concrete base guarantees the impact resistance of the lower part of the façade against hard objects and has been calculated to withstand a car impact with 50km/h speed.

To match the texture and color of the glass wall, the plinth is coated along its height with a stainless steel sheet laminated with SentryGlasÂŽ to a hardened glass pane. A 30 mm thick stainless steel plate bolted on the top of the concrete plinth forms the base of the glass masonry wall.

The extreme accuracy of the developed system necessitates a starting building surface with a flatness of matching precision. Consequently, the stainless steel plate had to meet a 0.25 mm height precision over a total length of 12 meters. This measurement accuracy is much higher than the one achieved even by high precision survey methods and called for the development of an innovative measuring and calibrating system in order to obtain the desired flatness on the starting surface.

In specific, bolts set every 275 mm support and allow for the levelling of the stainless steel plate in consecutive steps. By using conventional

levelling equipment the plate is initially levelled above the concrete to an accuracy of a few millimeters. Figures 5a, 5b and 5c show the measuring laser system developed to further level the stainless steel plate to a flatness of less than 0.25 mm. A continuous plastic open conduit with both ends sealed is elevated from points fixed on the concrete surface essentially parallel to the stainless steel plate. The conduit is then filled with a nontransparent liquid. At its balance state, the liquid will achieve nearly absolute horizontal flatness, establishing the reference level for calibrating the stainless steel plate. A laser machine with a precision of one micrometer, fixed on an aluminium frame with three legs stepping on the stainless steel plate (see Fig. 5c) takes measurements on the liquid’s surface, mapping the plate along its complete length. Then, by tightening or loosening the counternuts of the bolts the plate is levelled according to the reference liquid surface to the desired accuracy. When the stainless steel plate is successfully levelled, the gap between the concrete base and the stainless steel plate is filled with nonshrinking concrete and left to cure. By using this method, the stainless steel starting surface was successfully levelled to a maximum total height deviation of 0.24 mm.

Fig. 5a. 5b. 5c. Images of the stainless steel base and the measuring system developed for its levelling.

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3.2. Bonding The special characteristics of the adhesive required the construction of the façade inside a UV-filtering tent to provide protection against sunradiation, the weather elements and dust. To ensure controlled levels of temperature and humidity, heating equipment was installed inside the tent so that the adhesive is maintained in workable temperatures during winter. During the summer, when the ambient temperature exceeded 30°C the construction was stopped.

Structural and visual tests suggested that the complete contact surface between blocks had to be bonded. The uniform application of the adhesive not only ensures the homogeneous load distribution, but it is also essential for maximizing transparency in the connections. Indeed, the high transparency of the solid glass bricks reveals any small defect in the adhesive layer. Air bubbles and gaps in the spread of the adhesive, overflow, as well as capillary action of the liquid along the vertical faces of the bricks can disturb the optical result. Therefore, a customized bonding method was developed in order to minimize the occurrence of these defects.

Initially, the surfaces to be bonded have to be cleaned with 2-propanol.

Special PURE® (self-reinforced polypropylene) moulds are used to distribute the adhesive in an X shape, leading to a controllable and uniform spreading and the minimization of air bubbles and overflow when pressed by the weight of the block (see Figure 6a). To avoid any capillary effect between adjacent bricks each brick is placed in such a way so that the excessive adhesive is directed towards the free sides. This is achieved when the first side of the brick to touch the bonding surface is the one corresponding to the adjacent, already fixed, brick. Once the adhesive is evenly distributed an initial 5 seconds UV exposure in low intensity stabilizes the brick in position but still allows for the easy removal of any overflow of adhesive. After cleaning, the adhesive is further exposed to UV radiation in an intensity between 20-60 mW/cm2 for 60 - 120 seconds depending on the brick size. Once a complete brick layer is bonded all horizontal and vertical joints are sealed so that the façade becomes water- and moisture- tight. For the sealing, a more elastic, clear UV-curing adhesive of the same family, specially designed for outdoor applications is selected.

Fig. 6a. Mould used for the bonding of the bricks.

Fig. 6b. End result after bonding.

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The virtually zero thickness of the adhesive layer, essential for the desired structural performance, meant that the façade had to maintain a tight height precision per layer of construction as the adhesive itself cannot compensate for any dimensional intolerances. Even the allowed ¹0.25 mm tolerance per block can accumulate to an offset of a few centimeters in the total dimensions of the construction. This reveals the level of complexity of the manual bonding process and called for a highly skilled building crew and a strictly controlled construction process, as follows.

To avoid accumulated deviations along the height of the construction, before starting to bond a complete row of bricks, all of its glass elements are laid down. The occurring horizontal seam between the laid brick and the bonded ones below is checked with a feeler gauge. If the seam is larger than 0.25 mm, a brick that achieves better contact is chosen for the specific location. The final selection of the bricks is then numbered in order for the correct sequence to be kept. Every two meters of elevation, the levelling along the total length of the façade is recorded using a high accuracy total station. In the case of accumulated deviations, bricks with

a 0.5mm or a 1 mm smaller height were manufactured to be used for levelling the wall. These bricks were specifically employed to level the elevation of the wall before the architraves bridging the wall segments were installed.

3.3. Construction and installation of the architraves The architraves, placed above the window and door openings, were pre-manufactured in the TU Delft Glass and Transparency Lab into one single component each. They comprised special tapered glass bricks that were bonded together by the same adhesive system along their vertical surfaces. Due to the low viscosity of the selected adhesive the architraves had to be assembled in a special rotating steel mould, shown in Figure 7a. The rotating mould ensures that the adhesive is always horizontally applied and that the final architrave would have the desired arch geometry, with a straight top line, complying with the maximum 0.25 mm deviation rule. The finished components were transferred on site and installed in situ by a crane, as shown in Figure 7b.

Fig. 7a. Bonding one of the architraves in a special rotating table at the TU Delft.

Fig. 7b. Installing the architraves of the ground floor.

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3.4. Transition layer between standard and glass masonry The desire of the architects was to create a transition zone of glass and normal clay bricks towards the top of the faรงade, in order to create a smooth, gradual connection to the standard brickwork of the final, residential floor of the building. Nevertheless, the combination of the two different materials proved to have various practical implications.

Apart from their different mechanical properties that would result in an inhomogeneous structure in the transition zone, there is a great difference in the size of acceptable tolerances between the two types of bricks. But most importantly their bonding together necessitates the use of various adhesives, involving the risk of their intermixing when they came in contact with each other. Moreover, the strongly alkaline character of most mortars used for the bonding of standard ceramic bricks attacks the glass surface and must be avoided. For these reasons an innovative solution was applied: glass bricks, 40 mm narrower covered with an 18 mm thick ceramic tile at each visible side would be placed instead of standard bricks at the specific locations. The cladded glass block does not differentiate from a standard masonry brick even if one looks at it from an angle. Although one can see completely through the horizontal

bonded surfaces, the air trapped in the non-bonded vertical sides of the glass bricks creates a mirror surface that does not reveal what lies behind.

The result provides a monolithic glass structure, and simultaneously gives the impression of a ceramic and glass masonry intermix zone. Shear tests on various different adhesives were conducted to evaluate their bonding degree to ceramic and glass and their load-bearing capacity before failure.

Tests included specimens left into water for two hours and specimens wetted and then frozen prior to testing to observe if increased moisture and frost can decrease the bonding strength. From the tests it was concluded that the adhesive with the optimal combination of carrying capacity and visual performance was a brown colored modified silane polymer, as shown in Figure 8a. After their bonding, the seams around the ceramic tiles are sealed using a special acrylic-based mortar of less than 3% volume shrinkage after curing and with similar texture and color to the mortar used for the standard masonry on top (see Figure 8b). The ceramic tiles were applied on the faรงade after all the glass blocks had been bonded in place (see Figure 9), to avoid adhesive stains on the exterior surface of the ceramic tiles. The end result of the intermixing, gradient zone can be seen in Figure 10.

Fig. 8 a. & b.

Bonding and sealing of the ceramic tiles

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Fig. 9. Completed glass brick wall with the 40 mm narrower bricks bonded on location.

Fig. 10. The faรงade after the bonding and sealing of the ceramic tiles

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3.5. Installation and bonding of the glass window and door frames The traditional, wooden window and door frames of the previous 19th century faรงade were also reinterpreted entirely in glass by massive cast components (see Fig. 15). The frames comprised various components that had to be connected via completely transparent connections to each other as well as to the glass masonry wall. The challenge in this case was achieving a completely flawless vertical adhesive connection of maximum transparency and at the same time of the desired structural capacity. In this case, the adhesive should also account for horizontal deviations in the glass masonry wall as well as for small dimensional variations in the cast frame components. A clear silyl-terminated semielastic polymer was chosen due to its relatively high viscosity, colorless nature and easy application. Shear tests were conducted on a series of prototypes, bonded by an 8 mm thick polymer layer on a surface of 130 mm x 157.5 mm to test the structural performance of the selected adhesive. The experimental set-up is illustrated in Figures 11, 12 and a graph with the results is presented in Figure 13. The chosen adhesive provided consistent results. All specimens failed when reaching a load of approximately 4 kN and a deformation of 11 mm.

At these values, the force started to drop gradually while the polymer layer started to tear in the exterior, while visible delamination was occurring in the interior. It should be noted that the shear tests were

conducted one month after the production of the specimens. At that point only an exterior peripheral adhesive zone of circa 20 mm had been fully cured, as this product cures in reaction to atmospheric moisture and thus the curing of the interior core is a prolonged process. Therefore the resulting strength values are considered conservative, as a higher shear strength of the adhesive on the actual window frames is expected after a curing period of a few months. Even so, the deducted values were considered satisfactory by the structural engineers against the accounted windload case. The window and door frames were installed after the glass masonry wall had been completed and all ceramic tiles had been bonded and sealed. Special temporary aluminum frames were made to place and hold the glass frame components on their exact location. First, the various components were bonded together along their horizontal surfaces by a more elastic UV-curing adhesive of the same family as the one used for the masonry to form the complete frame. Then, the polymer was applied along the vertical connections. To achieve a completely uniform distribution of the polymer without any trapped air gaps, the polymer was applied simultaneously from both sides of a glass frame. The polymer connections were left to cure for several days to reach a satisfactory strength before the supporting aluminium frames were removed. Finally, the glass panes were adhesively bonded to the frames by the same transparent elastic polymer, completing the faรงade.

Fig. 11. Experimental set-up of the shear tests of the window frame connection

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Fig. 12. Experimental set-up of the shear test

Fig. 13. Force to deformation graphs of the specimens tested in shear

4. Conclusions and discussion An innovative, completely transparent adhesively bonded glass masonry wall has been realized in Amsterdam, setting a new example on the structural potential of glass and stretching the level of transparency that can be achieved in a wall construction. By bonding cast glass elements with a clear adhesive of high stiffness, the 10 m by 12 m faรงade is an entirely transparent masonry wall that can carry its own weight and support wind loads without the need of any supportive substructure. This is only plausible when the adhesive-glass assembly functions as one rigid unit against loading. Testing of various different adhesives pointed out that the desired monolithic behavior under loading was achieved only by a UV-curing one-component acrylate. However, the optimum thickness of the selected adhesive is a mere 0.3 mm, introducing new challenges in the engineering of the faรงade from the manufacturing of the bricks to the bonding method. The fundamental difference between a conventional brickwork and the developed glass masonry system is that a standard mortar layer can compensate for deviations in the size of the bricks, while the selected adhesive cannot. This lead to an allowable tolerance of a quarter of a millimetre in the glass bricks. Due to the inevitable natural shrinkage of molten glass, such dimensional accuracy could only be achieved by CNC-trimming the bricks to the desired height after casting. Each brick was subjected to meticulous measuring controls by specially developed jigs and equipment to verify that they meet the dimensional prerequisites.

Still, even this virtually zero allowable tolerance per glass brick can accumulate to a considerable offset in the total height of the faรงade.

This reveals the level of complexity of the manual bonding and the importance of a strictly controlled and precise construction process from the levelling of the starting supporting surface to the installation of the window and door frames. A completely transparent wall bears yet another challenge: any defect on the masonry system is visible.

Therefore, besides a visual inspection of each brick for surface defects, a new bonding method had to be developed in order to allow for the completely homogeneous distribution of the adhesive, without any visible gaps, bubbles or overflow. The end result is a completely transparent, self-supporting glass masonry skin with virtually invisible connections.

Overall, the adhesively bonded glass masonry system presented in this paper can set the base for new architectural applications where structural transparency is desired. Owing to the experience gained through the realization of the Crystal Houses project, the engineering of the system can be further developed to simplify its application and reduce the involved challenges in future designs. Most of the engineering challenges presented in this paper can be confronted if a thicker adhesive that accounts for larger tolerances could be used as the bonding media or if a new casting method is found that can result to bricks with acceptable tolerances without further processing. By improving the geometry of the wall, the faรงade can obtain the desired rigidity even by a more elastic, thicker adhesive. In the same context, by using bricks of smaller dimensions, the shrinkage during the cooling down process would be within acceptable limits, rendering post-processing unnecessary.

Fig. 14. Transparency level of the wall.

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Fig. 15. Close up of glass masonry wall, the architraves and the cast glass window frames.

5. Acknowledgements The project was done as research for Ashendene-Leeuwenstein BV whose permission to publish the results is gratefully acknowledged.

MVRDV and Gietermans & Van Dijk are responsible for the architectural design and Poesia Company for the manufacturing of the bricks and cast window frames. We thank Ashendene-Leeuwenstein BV and MVRDV for the 3-D impressions of the case study. We also thank Rob Janssen from Siko BV for his valuable advice and assistance. The authors gratefully acknowledge Kees Baardolf and Kees Van Beek for their invaluable technical assistance and insight throughout the project.

6. References Christoph, P., Knut, G.: Innovative Glass Joints - The 11 March Memorial in Madrid. In: Bas, F., Louter, C., Veer, F. (eds.) Challenging Glass: Conference on Architectural and Structural Applications of Glass, Delft, the Netherlands 2008, p. 113/668. IOS Press, The Netherlands Hiroshi, N., NAP: Residence in Hiroshima. In: DETAIL: Translucent and Transparent, vol. 2. vol. 01-02/2013, p. 157. Institut fur international Architektur, Munich, (2013) Oikonomopoulou, F., Veer, F., Nijsse, R., Baardolf, K.: A completely transparent, adhesively bonded soda-lime glass block masonry system. Journal of Facade Design and Engineering 2(3-4), 21 (2015)

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Fig. 16. The glass masonry faรงade.

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Structural Thomas Henriksen

T

he new Etihad museum in Dubai is being build for the 2016 celebration of the union of the Arab Emirates in 1971. The new museum is placed next to the existing Union house at the Dubai water front. The new museum has a state-of-theart complex structural glass faรงade which has been designed by the architects Moriyama and Teshima. The new building is shown in figure 1.

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glass wall

Figure 1: Etihad Museum with the complex geometry roof and the tilted structural glass fin facade

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Figure 2 Tilted structural glass fin view from the inside

The building comprise of a complex geometry roof clad with glass fibre reinforced plastic (GFRP) panels with panel sizes of 3m x 3m.

Underneath the roof the building has a unique structural glass façade. What makes this building unique is the west glass fins facades being tilted sideways 21 degrees. To allow the tilted glass fin façade to stand up the double glazed units in the façade has to be engaged in a structural system to support the tilted glass fin and at the same time support the self-weight of the glass fins and the double glazed units.

A view from the inside of the tilted glass fin façade is shown in figure 2.

Because of the big roof cantilevers the inplane movement of the roof structure are so significant that the structural glass fin façade has to be constructed in a way so the structural roof system and the structural façade system moves independently form each other. The structural glass fin façade has to be structurally

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detached to avoid breakage of the glass fins.

This adds a lot of constraints to the west glass fin façade because the glass fins are tilted sideways. The longest glass fin is approximately 13m, the double glazed units are segmented to glass lengths of maximum 6m to allow standard sized glass to be used.

Structural system for the glass fin façade.

The initial conceptual structural system was based on a coupled system which relied on tie-rods positioned at every second glass joint, concealed in the joint. The idea behind the coupling system is to transfer the resulting force from the overturning moment to the tie-rod and thus stabilizing the glass against rotation, the overturning moment of the glass arise because the tilted glass fins. However because of the narrow space between the glass elements the coupling system was deemed difficult to construct without having a great impact on the architectural intend. Therefore

alternative solutions to a loading bearing system for the glass wall were investigated.

The different solutions comprised of: A. Cantilever, 2bay, integrated coupled tie rod system (Architects proposal) B. Single span beam (Coupled to the roof structure) C. Glass supported in plane (Corner stone solution) D. Continuous DGU E. Cantilever, 1bay, integrated coupled tie rod system F. Cantilever, 2bay, integrated coupled tie rod system, with horizontal ties G. Vertical glass fin solution To be able to assess the 7 different proposed options it were necessary to find a number of themes where the options could be compared against. 10 different points was proposed : 1. Structural system 2. Structural Analysis (Time)

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Figure 3 Evaluation of the proposed 7 options to a structural system for the tilted glass fin façade.

3. Connection to Roof 4. Joint between Glass Panes 5. Corner Connection 6. Installation Strategy 7. Replacement Strategy 8. Architectural Intent 9. Material Cost 10. Robustness For each points an evaluations were made and given a color; green, yellow or red. The decision for the color was based on initial structural calculations and design and installation experience. The result of the evaluation is shown in figure 3.

Based on the finished evaluation 3 options was initially eliminated; Option B, option D and option G. They were disregarded because of the red colors in the evaluation matrix. Option B was disregarded because of the issues to connect the structural glass fin façade to the roof without introducing forces in the glass fin

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system which would break the glass fin, due to the large movements in the roof. Option D being one of the options with most advantages was disregarded because of the price of the continuous DGU of almost 13m being 7 times more expensive than the segmented DGUs of only 6m. Option G is a proposal to change the tilted glass fin façade into a glass fin façade with vertical glass fin; this would have eliminated the problem with the overturning moment of the glass, and simplified the required structural system for the glass façade, so that the double gazed units only had to be stacked on top of each other. However this option was deemed to significant a change to the architectural intend and it was disregarded. Option A, option E and option F all rely on tie rods being integrated into the joint lines of the glass.

Option A and option F both relied on a 2 bay tie rod system which is very difficult to achieve without having to laminate small shear keys into the glass laminate and increasing the glass build-up from 2 to 3 glass ply’s. The system

was then disregarded based on it challenging buildability. Option E is a simplified tie-rod system relying on a single bay, which means bigger forces in the tie-rod. This system was disregarded based on the same constraints as option A and F. The remaining solution is option C. Option C structural system relies on transferring all the self-weight of the glass wall to the most right-hand glass unit in the west façade (the corner stone). This panels then transfers the all the in-plane load from the glass wall to the bottom steel superstructure.

This option was chosen because it kept the architectural intend and at the same time did not have to utilize expensive non standard double glazed units. The corner stone panel, has a bespoke build-up compared to the rest of the panels. The inner lite of the double glazed unit consist of 4 x 10mm heat strengthened glass. This is to give the panel sufficient redundancy in case of glass breakage. The glass wall is being installed in the summer 2016.

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Still Plenty More to Come!

Immediately following on from this page, Lucio Blandini of Werner Sobek discusses, in detail, the complexities and high demands required of glass facades and glass in buildings today, this demand is not just from the architectural fraternity, these are the necessities of global society in general. An excellent paper and one of many published by kind permission of the organisers of the Challenging glass 5 conference that recently took place in Ghent, Belgium. Do not skip this article!

Following on from Lucio’s paper is Marcin Brzezicki.

I’ll leave you to pronounce that name properly. Marcin’s paper goes deep into the meaning of transparency and looks at if and how the meaning changed from what it originally stood for. Light from light my friends, get enlightenment and knowledge starting with this article on page 58. I’d just like to bring one more paper to your attention and that is the editorial contribution from Lisa Rammig of Eckersley O’Callaghan. In her paper Lisa analyses the heat impact on glass and the resulting residual stress caused by heat bonding of two glass components. You’ll no doubt pass your glass engineering degree after reading this particular article that begins on page 84.

Oh yes, there are so many great reasons to keep reading this magazine.

Subscription information is on Page 23. Step lively now!

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Transparent, Complex, Sustainable Challenges

for Contemporary

Façade Engineering Lucio Blandini Werner Sobek Stuttgart (WSS), Germany, www.wernersobek.com

1. Introduction The tasks a façade has to fulfill in contemporary high-end architecture have become more and more complex and challenging. An innovative skin has to block a considerable amount of sun radiation in summer, while it has to prevent heating energy from getting lost in winter. On the other side the iconic character of “signature” architecture pushes for glass façades to become almost dematerialized, a development further reinforced by recent advances in modern glass technology.

Contemporary façades have to reach high transparency rates and have to follow extremely complex geometries - while still fulfilling requirements with regard to energy consumption and user comfort.

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Enzo Ferrari Museum, Italy (WSS)

Some question whether the extensive use of glass in facades is sustainable. We believe that even fully glazed facades can be sustainable, provided they are designed and engineered accordingly. A sustainable façade has to allow for (controlled) natural lighting and (controlled) natural ventilation and reduce energy consumption to a minimum, allowing the latter to be offset by the use of renewable energy sources, such as solar or geothermal energy. Moreover, materials used should be kept to a minimum and be recyclable. A proper combination of transparent and opaque parts may become fundamental in the search for a synthesis of transparency and sustainability – while keeping in mind that glass is a building material that can also be used for opaque buildings skins. In certain cases the client and the architect call not only for transparent and sustainable skins, but also strive for extreme geometrical complexity.

The engineering work is then even more challenging, because of the increased difficulty in detailing, producing, and erecting such kind of facades.

A selection of recent projects show the different approaches and solutions developed by Werner Sobek for skins that not only fulfill the formal and aesthetical demands of contemporary architecture, but which are also sustainable – both with regard to their resource consumption and their influence on the overall energy consumption of the building.

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2. Transparent and sustainable skins 2.1. Doha Convention Center, Quatar The recently opened Doha Convention Center in Qatar aims at strengthening the role of Doha as a business hub in the Middle East. A special feature of the building is the transparent cable-stayed facade at the entrance areas along the southern and western sides of the building.

How can such highly transparent facades be sustainable in a Middle Eastern climate? The answer lies in a combination of different solutions such as a cantilevering roof, a 10° façade inclination and the use of coated insulated glass units. Sun shading elements and partially opaque sections at the eastern and northern sides of the building allow for the overall energetic balance of the building to be further optimized.

The entrance facades have been engineered by prestressing stainless steel cables horizontally over max 180 m between two bow-strings.

A more traditional vertical layout of the cables was not possible, since the long-span roof could not be used for vertically prestressed cables.

The south façade (which is 297 m long) was therefore divided into two segments, thus matching the movement joints of the main structure.

Each facade segment is subdivided into modules by hinged steel columns. These columns are 20 m high and stand at a distance of 18 m to each other. They reduce the free span of the cables under horizontal loads and also act as tie-backs for the roof structure.

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Doha Convention Center, Qatar (HG Esch)

The insulated glass units measure 3.0 m by 1.4 m. Their dead load is hung from the top by tension rods which are placed at every vertical joint. The glass clamps are placed at a distance of 300 mm from the vertical joints.

The free span could thus be reduced and the glass thickness optimized.

The cable clamps transfer wind loads to the cables just by contact; therefore their size could be kept to a minimum. Given the long spans

to be dealt with, keeping control of horizontal deflections and of the resulting warping in the insulated glass panes was a particular challenge.

Steel fins with different heights were therefore planned at the top and the bottom. Their specific stiffness against wind loading allows for an optimized and gradual deflection shape, thus reducing the amount of warping at the corner glass units. All the details and particular solutions

View of the south facade (HG Esch)

View of the east-end of the south faรงade (HG Esch).

View of the north-west faรงade edge with sun shading fins (HG Esch).

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developed for the Doha Convention Center help to increase the level of transparency to an astonishing level. The coherent approach towards minimizing the loadbearing structure not only confers a very elegant appearance to the façade, but is also an important contribution towards making the structure sustainable with regard to the use of natural resources.

2.2. Maison de l’Histoire Européenne, Brussells The ‚House of European History‘ will soon offer visitors the opportunity to learn about the history of Europe and to take a critical look at the questions facing Europe today. The project was planned and designed

by Paris-based architects Chaix & Morel and JSWD Architects from Cologne. The museum is housed in a former dental clinic, which had to be comprehensively refurbished and extended to be able to fulfill the requirements of a modern museum. The conversion plans include an extension on the courtyard, which is enclosed on three sides, as well as the addition of three stories.

The new facade has been conceived as a double skin façade: The outer skin consists of an energetically sustainable mix of opaque and transparent glass elements; the former are placed in front of concrete cantilevering boxes, the latter are stiffened by glass fins and set in front of a triple-glazed thermal skin. Openings in the outer skin have been optimized to allow for natural ventilation of the cavity between inner and outer skin, so that cavity overheating can be prevented. The façade offers a high degree of transparency in combination with excellent user comfort and an efficient energy system. The transparence is enhanced by the use of glass fins and by the bracing effect of the skin laminated glass panes.

Competition Rendering (Chaix & Morel).

Site view of the outer glass fin skin (WSS).

View of the façade cable clamps (HG Esch).

The height of the fins varies and reaches up to 14 m at the two western corners. Both the transparent and the opaque elements forming the outer skin have a custom designed line pattern printed on them: this optimizes the amount of solar energy passing through the outer skin and at the same time gives a uniform appearance to the whole facade.

View of the base details (HG Esch).

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3. Iconic and complex skins 3.1. Enzo Ferrari Museum, Modena The museum dedicated to Enzo Ferrari in Modena plays with the duality between the renovated historical building where Ferrari was born in

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Enzo Ferrari Museum (Studio 129).

1898 and a futuristic exhibition gallery designed by the late Jan Kaplicky (Future Systems, London). The gallery embraces the masonry building, whereas its sculptural form is clearly inspired by sport car design. From the gallery the view converges through the transparent curved façade to Ferrari’s birth house - it is as if you were looking through an oversized car windshield. The glass façade is made of insulated glass units with argon filling; this helps to reduce heat losses in winter. Horizontal sun shading elements and solar control coatings reduce the cooling loads in summer, still allowing for a high degree of natural lighting for the exhibition area.

The overall energy balance is optimized through the high performing metal skin. Below the yellow coated aluminum profiles, thermal bridges have been avoided by using a foamglas insulation layer with a custom developed adjustable point support system. Cooling and heating are provided by a special geothermal type of heat pumps with thermal exchange elements placed underground at a depth of 130 m.

Given the geometrical complexity of the building envelope, the engineering philosophy chosen for the façade of the Enzo Ferrari Museum in Modena was to maintain a relative simple geometry for the facade panels. These were adapted to the different geometrical situations by means of complex customized detailing. The geometry of the 11 m high cable-stayed glass façade is defined by two intersecting conical surfaces, which inclined towards the interior by 12.5°. The sinuous form of the façade was accomplished using 32 mm stainless steel cables and mainly regular planar glass units. A curved hollow steel girder constitutes a top-side support for the cables and outlines the complexity of the edge, which results from the intersection between the roof surface and the conical façade surfaces. The girder has a length of 62 m and a diameter of 1,000 mm and is made of 13 single-curved segments which were fully welded on site. Special attention was paid to controlling the deflections of the whole façade as well as the warping of the most critical insulated glass units by optimizing every single cable pretension force.

The façade engineering of the Enzo Ferrari Museum was a considerable challenge, due to the required transparency and the geometrical

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complexity in conjunction with the energy and comfort requirements that had to be met. Such complex freeform skins call for a change in the planning process from 2D drawings to 3D digital models. Despite the computational progresses in approaching such complex skins, the detailing, production and erection of such envelopes remains a very demanding task.

3.2. Fraunhofer Institute, Würzburg The competition for the extension of the Fraunhofer Institute for Silicate Research in Würzburg has been won by Zaha Hadid Architects with the idea of using glass only as skin material for both the transparent and opaque areas, as a reference to the silica research objective of the institute.

View of the glass fixing and cable clamp (Studio 129).

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View of the faรงade with sun shading elements (Studio 129).

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View of the Fraunhofer Institute (Christoph Seelbach).

This also leads to a sustainable approach to the energetic balance of the building. Geometrically the five-storey building follow the course of the ‚Luitpoldstraße‘ before swinging around towards the existing buildings and leads to a very complex three-dimensional external envelope.

Due to the architectural wish to exclude any visible fixings, Werner Sobek developed an innovative solution and tested it on a full-scale prototype.

Monolithic glass panes were curved by using special molds and backpainted with polyurethane to allow for a residual safety mechanism in case of glass breakage. In general, the glass cladding is fixed to a steel truss substructure by means of aluminum adapter frames, with screws inserted through the joints between the panels. The frames are bonded with structural silicone at the back of the panels.

Façade partial view (Christoph Seelbach).

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4. Conclusions Werner Sobek has designed many iconic skins. The individual solutions presented in this paper show some possible answers on how to address the challenge of achieving facades that are transparent, complex and sustainable at the same time. The innovative character of certain solutions requires that all the involved parties from the clients up to the contractors share the will to push the boundaries within a reasonable extent. Therefore good teamwork has been essential for the success of the projects shown above: especially the early involvement of the manufacturing companies, as well as the late involvement of the designers during the construction phase has allowed for the intended design to be translated into built reality.

Method of fixing of the cladding glass panels (WSS).

Monolithic curved glass panes with aluminium adapter frames and polyurethane white backpainting as safety layer (WSS).

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T

ransparency has become a new division of architectural theory and practice and has created a new kind of aesthetic sensibility, opening up a wealth of possibilities for visual expression The growing importance of the visual aspects in architecture is obvious, especially with respect to façades. Transparency is no longer limited to specific functional purposes (e.g. illumination of the building’s interior), but becomes a tool of formal expression itself.

This raises questions regarding the theoretical/ideal/institutional background for the application of architectural glass and impacts the perception of architecture by observers. The paper presents a general outline of ideological/institutional inspiration for architectural practice in the perspective of new types of architectural transparency.

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See-through

or not.

Transparent architecture for non-transparent intentions Marcin Brzezickia Wroclaw University of Technology, Poland. marcin.brzezicki@pwr.edu.pl Introduction The transparent trend that has been developing in architecture for more than 120 years is now in the stage of dynamic prosperity, although a distinct change can be seen. The “ideal” transparency that can currently be achieved in architecture is the result of a long process involving the development of material production technology and the methods of its installation (mounting and fastening).

Contemporary architectural transparency (optical property of the material) is constantly

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being redefined, and over the last decade, new trends have begun to emerge.

A question arises whether there is any connection between optical transparency and the institutional meaning of the term transparency, which is usually associated with government policies and corporation governance. Despite the recent shift towards picturesque surroundings, it is the optical properties of transparent materials which have “suffered” the most. What might seem as merely a linguistic/semantic trick of modifying

the meaning of the word is in fact greatly affecting the real architecture, its relationship with people, and the way society perceives it.

Convoluted paths of transparency Since glass was first developed, its optical parameters have changed considerably.

The manufacturing technology has greatly improved and what once was a foggy bulb of glass mass is now a smooth and flawless pane. Originally, the modernist glass was supposed to flood the interiors with light and

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“

Even early modernists knew that the light-transmitting envelope is optically transparent only in certain lighting conditions, while in the other conditions, the virtual image dominates over the real (transmitted) one

”

free the people from the sad and dull reality of 19th century architecture, as “…modernist architecture used the agency of transparent glass to erode the distinction between interior and exterior space” (Shimmel 2013). I believe this – in those days – innovative attitude can be labeled as honest use of glass, despite the naivety of the predecessors of the modern movement. Visually, glass makes a building more volatile than a solid masonry wall with sculpted details. The application of glass, especially in the form of flat sheets, creates a deliberate optical effect, which results from the physical properties of all smooth surfaces. A pane that is smooth enough to transmit light without scattering can also create a virtual image (i.e. the reflection in the glass pane).

This is the reason why Mies van der Rohe in his garden photographed a model of a famous glass skyscraper (Colomina 2007) to judge the prevailing optical effects that would create the image of the building.

The original honest transparency became a subject of theoretical considerations. Changes came in the 1940s and 1950s and culminated in the famous essay by Rowe and Slutzky titled “Transparency: literal and phenomenal”. Public found out that apart from “literal” (optical) transparency, there also exists “phenomenal” transparency (Rowe, Slutzky 1963). Although the paper did describe interesting figure-ground phenomenon it did not contribute anything new to the field of optical transparency of light-transmitting materials, but instead caused some confusion, which was then multiplied by numerous interpretations by other authors. As Haag-Blatter concludes her critique “literal and

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phenomenal transparency in no way provide us with a new general definition” (Haag-Blatter, 1978). The first part of the paper by Rowe and Slutzky became very sound and started the career of the notion of “transparency”, which is disassociated from its original optical meaning.

As Shimmer writes, that papers by Rowe and Slutzky were “…influential in shifting the interpretation of transparency“ (Shimmel 2013) towards new post-modern meanings of blurred translucency and vagueness. This moved the new meaning towards more metaphorical, but still deeply thought-through visual design proposals. This happened to coincide with the development of material technology that allowed for new types of transparency.

Does smooth always mean transparent?

Even early modernists knew that the lighttransmitting envelope is optically transparent only in certain lighting conditions, while in the other conditions, the virtual image dominates over the real (transmitted) one.

Optical transparency is a fragile property that is determined by many aspects of the surrounding environment. Basic glass simply does not guarantee optical transparency for all viewing angles. The phenomenon of overlapping real and virtual images was initially considered valuable, but soon – with the increased use of glass – the phenomenon became ubiquitous and common. The transmissive qualities of glass had also a negative impact on the microclimate due to the greenhouse effect. The ideology that was born out of the need for illuminated interiors suddenly turned to advanced technologies to reduce this illumination. At the time, excessive

heat gain was defied by placing a microscopic layer of metal on the glass pane (i.e. a thin metal coating). It did temporarily solve the problem of overheating but it also permanently blocked the view into the building. Mirrored glass became eminent, especially in corporate architecture, where efficiency counts.

This visual change notably moves the public attention, and the honesty of the architectural glass application in buildings and its semantic meaning is questioned. The first associations are obvious and simple: optical transparency means that the building has nothing to hide, just as the company/government that occupies it. Transparency was a handy feature to consider: it was visually appealing and politically very sound. PR managers quickly realized that companies do not need to create a bona fide institutional transparency if they can simply give people the mere optical transparency to serve as a symbol. As Vidler rightly points “…the politics of the moment insisted, and still insist, on the illusion that light and enlightenment, transparency and openness, permeability and social democracy are not only symbolized but also effected by glass” (Vidler 1993). This strong yet unfortunate misconception is confirmed in many completed buildings. To name the two: the Foster’s renovation of the Reichstag’s Building (Fig. 1a) and Petzinka, Pink and Partner’s CDU political party headquarters (Fig. 1b). CDU building is encased in a transparent envelope that allows people to see the glazed hall, but not to penetrate into the office rooms, where the real politics happens.

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Fig. 1a. Reichstag’s Building (Architect: Foster and Partners, 1999), Photo by author.

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Fig. 1b. CDU headquarters in Berlin (Architect: Petzinka, Pink and Partners, 2000). Photo by author.

The strive to achieve institutional transparency turns out to be a very dangerous path, as it allows the public to scrutinize the processes that were previously hidden. It might be speculated here that as contemporary institutions and corporations are becoming more and more transparent visually, they still remain inaccessible and vague as far as institutional transparency is concerned. This direct and simple glass equals honesty attitude to transparency was thoughtfully criticized and questioned. The extensive use of glass does not improve democracy, it rather raises more the questions than it actually answers. Optical transparency is considered “… a convenient marketing gimmick in sales pitches rather than a thought-through functional concept to be taken seriously” (Zinnbauer, 2015).

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Transparency deliberately interrupted Gradually shallower ideological convictions have replaced the original honest meaning of transparent architecture. The visual aspect of architecture has a new interpretation. It is not that glazed architecture was not visual before, but the pressures are distributed a bit differently. In 1995 Terence Riley in a catalogue of famous “Light Construction” exhibition claimed that “the facade becomes an interposed veil (…) distancing the viewer of the building from the space or forms within and isolating the viewer within from the outside world.” (Riley 1995). This trend of gradual erosion of transparency is widely seen, especially in the way the glazing technology develops towards the obscuring of transparency: printing, fritting, tinting the glass. This results in interesting

formal and visual effects, where glass becomes a bearer of a completely new content.

Previously, the obstruction of transparency resulted from the unfavorable lighting conditions or because of poorly performed installation job. Nowadays transparency is deliberately questioned with the designer fully aware and with the obvious reference to the ideas of the Popea’s veil covering the face of the Neron’s lover or lace lingerie (see Fig 2a and 2b).

Interrupted transparency is also used to soften boundaries between the inside and outside thus the building is gradually dissolved in the surrounding landscape.

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Fig. 2a. Interrupted transparency: Clinique du Parc, Lyon (arch. Xandau, 2007). Photo by author.

Fig. 2b. Interrupted transparency: HĂ´pital Jean Mermoz, Lyon (arch. F.-H. Jourda , Jean 2008). Photo by author.

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Fig. 3a. Redundant transparency – Institut Jacques Monod in Paris, France (arch: François Chochon and Laurent Pierre, 2009). Large panes of clear and green-tinted glass are point mounted to the concrete facade. Photo by author.

A surprisingly smooth transition from transparency to translucency comes at the end of 1980’s with the famous Très Grande Bibliothèque in Paris competition entry by Rem Koolhaas of the Office for Metropolitan Architecture (OMA). Perrault’s transparent and Koolhass’es translucent proposal clearly discriminate the separation of new trends.

New postmodern transparency becomes translucency. This change in optical properties of the architectural envelope results from the intention to invite the observer of architecture to participate in the “game of guessing”. The visual information reaching the observer is only partial, leaving a great scope for individual interpretation. The connection between translucency and institutional transparency is less obvious, but still can be observed. While the optically transparent architecture is still in fashion, I perceive its blurred/translucent type to be much more honest. Blurred transmission in many cases is conditioned by the functional need of scattered illumination in the building, to name only the Bloch building, Nelson-Atkins

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Museum of Art in Kansas (arch. S. Holl, 2007), Kunstmuseum Dieselkraftwerk in Cottbus (arch.

Anderhalten Architekten, 2007) or Kunsthaus in Bregenz (arch. P. Zumthor, 1997). The postmodern translucency introduces not only a less literal, but a more phenomenal approach to material. Paradoxically, this new contemporary blurred transparency corresponds to the condition and the social and political structure of the world much more accurately than before: the lack of rules, the vagueness of ideas, the out-of-focus human perspectives.

Illumination no longer required Due to their high durability and resistance against climatic conditions, transparent materials are becoming a popular cladding material, not only designed to illuminate the building’s interior, but also because of their ability to change the appearance of the building. This unique feature of glazed envelopes pushed architects towards extensive use of glass, not only on light-permitting/ illuminating sections of the façade, but on

the whole surface (including spandrel, slab and ceiling). In these regions, light-permeable envelopes functioned more as a cover than a fenestration. Thus, light-permeable materials are also used as elements contributing to the overall formal expression of the building by light-activating those parts of the façade that were previously neglected (Fig. 3a and 3b).

Transparency thus became “a redundant feature of the material”. Light-permeable materials are “used for their chemical and climatic durability, rather than for their optical properties” (Brzezicki 2014). The image-transmitting quality of the fenestration diminishes, becomes a seethough cladding, or even a redundant feature of the light-permeable envelope.

New transparency – the conclusion Two trends that I labeled transparent and translucent/blurred/interrupted are now coexisting. Optically transparent architecture is build/raised to convince the public of the investors’ clean intentions (regardless of their actual goals). A reflection – an immanent

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Fig. 3b. Translucent envelope – Silesian Museum in Katowice, Poland (arch: Riegler Riewe Architekten, 2002). Photo by author.

feature of the smooth glazed envelope – is perceived as a tool of destabilizing this picture.

While transparent architecture is facing a wave of criticism, the same objections could be raised against translucent envelopes, which are designed to achieve numerous visual effects.

The process of gradual erosion of transparency has led not only to the devaluation of the initial meaning of the term on the semantic level (both optical optical phenomena which scatter, hide and block the light wins over a message that directly communicates the intentions to the viewer – the clear glass and its honesty. Instead of facades, architects create multilayered envelope structures designed to obstruct the view in both directions and to allow view only to a certain predefined depth of the envelope. As a result, despite the extensive use of glass, it is the optical transparency, the visual connection and the spatial continuity, that has suffered the most.

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Acknowledgements This paper was funded by the Polish National Science Centre grant entitled: “New trends in architecture of transparent facades – formal experiments, technological innovations ”, ref. no. 2014/15/B/ST8/00191.

References Brzezicki, M.: Redundant Transparency: The Building’s Light-Permeable Disguise. Journal of Architectural and Planning Research. 34 (Winter, 2014), 299–321 (2014) Colomina, B.: Unclear Vision: Architectures of Surveillance. In: Bell, M., Kim, J. (eds.) Engineering Transparency: The Technical, Visual, and Spatial Effects of Glass, pp. 78–87, Princeton Architectural Press, New York (2008) Haag-Bletter, R.: The opaque transparency. In: Kipnis, J., Gannon, T. (eds.) The Light Construction Reader, pp. 115–120. Monacelli Press, New York (2002) Riley, T.: Light Construction, The Museum Of Modern Art, New York (1995) Rowe, C., Slutzky, R.: Transparency: literal and phenomenal, Perspecta, 8, 45–54 (1963) Rowe, C., Slutzky, R.: Transparency: literal and phenomenal. Part II, Perspecta, 13/14, 287–301 (1971) Shimmel, D.P.: Transparency in theory, discourse, and practice of Landscape Architecture. The Ohio State University (2013) Vidler, A.: Books in space: Tradition and Transparency in the Bibliothèque de france, Representations. 42, 115–134 (1993) Zinnbauer, D.: Architecting transparency, Back to the roots – and forward to the future? Transparency International, Global Conference on Transparency Research, Lugano, June 4-6 (2015)

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Kurt Schwitters:

Merz, exhibition designed by

Zaha Hadid Galerie Gmurzynska,

Zurich, Switzerland

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K

urt Schwitters: Merz, is a major retrospective exhibition that builds and expands on Galerie Gmurzynska’s five decade long exhibition history with the artist, bringing together a unique selection of seventy works across all media.

Key works of each period are presented in a fully transformed gallery space designed by Zaha Hadid. This collaboration results from the idea of an architectural homage by Zaha Hadid to the famous Merzbau of Kurt Schwitters.

Having successfully realised a similar project seven years ago, where Hadid transformed Galerie Gmurzynska, Zurich into a Suprematist space in reference to Kasimir Malevich, this collaborative project pays tribute to the second important artistic influence on Hadid’s work – Kurt Schwitters.

All images: Courtesy of Galerie Gmurzynska

Schwitters’ Merzbau has been described as a living, inhabited collage, ever-shifting and expanding, and this was the starting point for Hadid’s exhibition design which pushes beyond mere random collage to embrace the unpredictable richness and the complex variegated order found in nature. Seminal paintings and sculptures by Schwitters are married with Zaha Hadid’s works to define an evolving ecology within the gallery; a process of mutual adaptation facilitated by a mediating connective tissue that morphs between the aggregated objects, receives them, embeds them and thereby connects them into a complex, unitary spatial construct.

“This design process is capable of delivering an intricate order, open ended and unpredictable, but at any time highly articulate.

It is full of contingencies, but forges a unique, path-dependent identity,” explains Patrik Schumacher, Zaha Hadid’s collaborator of three decades.

“The project was only possible through our extraordinary partnership with the late Zaha Hadid and Zaha Hadid Architects. A partnership that has formed over a decade. One of our most memorable collaborations was Zaha’s selection of Suprematist works by the Russian avant-garde juxtaposed with her architecture at Galerie Gmurzynska. The current Schwitters exhibition with Zaha Hadid’s exhibition design, is the logical complement to the Suprematism exhibition and takes place in the same space.

Zaha’s spirit is ingrained in the DNA of Zaha

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Hadid Architects and this exhibition is a testimony both to her and to the continuous creative powers of Zaha Hadid Architects under the leadership of Patrik Schumacher,” said Mathias Rastorfer, CEO and co-owner of the Gmurzynska Galleries.

As Galerie Gmurzynska, Zurich, is within the same building complex that once housed the famous Galerie Dada run by artists Tristan Tzara and Hugo Ball, and with the city celebrating 100 years of DADA this year, this retrospective is both overdue and extremely timely.

The exhibition will be realized in curatorial collaboration with Adrian Notz, the director of Cabaret Voltaire where the DADA movement originated in 1916 and one of the main locations of this year’s centennial festivities.

Adrian Notz will create sections devoted to archival documents covering Schwitters’s important ventures into poetry, theatre, stage design and sound which complement and further contextualize his unique visual praxis.

The retrospective will also shine a light on Kurt Schwitters’s significant influence on a whole range of artistic generations succeeding him – from David Bowie to Damien Hirst – or as the renowned curator Norman Rosenthal put it: “there is no artist working today that has not been influenced by Kurt Schwitters”.

Kurt Schwitters: Merz will be accompanied by an extensive in-depth publication of more than 250 pages with previously unpublished archival material and newly commissioned writings by the former Museum Ludwig director Siegfried Gohr; Patrik Schumacher of Zaha Hadid Architects; Peter Bissegger, who recreated the Merzbau for Szeemann’s Gesamtkunstwerk show; Cabaret Voltaire director Adrian Notz; art historian Jonathan Fineberg, University of California – Irvine; and Norman Rosenthal.

The gallery actively supports the conservation and legacy of Schwitters’s art as a major donor to the Littoral Arts Trust’s effort in restoring the artist’s damaged Merzbarn in Elterwater, England.

Kurt Schwitters: Merz exhibition at Galerie Gmursynska Paradeplatz 2 8001 Zurich, Switzerland www.gmurzynska.com 67

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Glass Façades with an inspiring light concept New Ludgate in London forming a lively new quarter near St. Paul´s Cathedral

Klaus Lother, Josef Gartner GmbH

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solidity to the building. With a unique interplay of colours in the façade Two New Ludgate provides special accents in the city of London.

The coloured louvres can be closed manually in fixed positions and therefore offer a wide range of views. These Gartner façades are playing a substantial role to create stimulating office areas in this sustainable building and to improve the value of the building.

Dialogue between two striking and complementary new buildings The site of New Ludgate is redolent with history.

From here the Belle Sauvage coaching inn welcomed or saw off numerous fictional and real travellers; Pocahontas and London’s first live rhinoceros paid visits. Later came railway engineers who put an iron viaduct across Ludgate Hill, and World War II, which left the site in ruins.

N

ew Ludgate is the transformation of a London City block into a lively new quarter near St. Paul´s Cathedral. At this historic site the new buildings One and Two New Ludgate offer flexibly designed office space with contemplative zones of loggias and terraces. Office workers will benefit from façades with an inspiring light concept. In 2016 One New Ludgate won the Royal Institute of

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Chartered Surveyors’ top prize for Commercial Office Buildings.

Floor-to-ceiling low-iron glazing offers spectacular views to St. Pauls Cathedral and the city and reduces the need for artificial light.

The masonry grid of One New Ludgate keeps direct sunlight off the glass and throws light into the floorplates and, when viewed obliquely from the street’s wide pavements, gives a

The site on the old city wall of Ludgate Hill was formerly home to some outdated 1980s office buildings, the tallest element of which breached Primrose Hill viewing corridor height restrictions, and which offered little in the way of public amenity, with a dull sunken arcade at its lower levels. London Architect Fletcher Priest was asked to masterplan the site by Land Securities, separating it into two headquartersized office buildings – 30 Old Bailey to the north, designed by Sauerbruch Hutton with Fletcher Priest as executive architect, and 60 Ludgate Hill, designed by Fletcher Priest.

So a dialogue between two striking and complementary new buildings was set up. A new pedestrian route through the site was created that leads to an urban square or piazza to the east. Both landmark buildings were completed in spring 2015.

Prime office space of 349,555 sq. ft. with stimulating outside areas One New Ludgate comprises nine storeys with retail shops and bars under glass awnings on the ground floor. The building boasts extensive external private space accessible from intelligent glass solutions

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every office floor. This includes a loggia and a substantial south-facing terrace that provides uninterrupted views towards St Paul’s Cathedral.

Two New Ludgate offers high-quality, up-todate office space with a restaurant and retail areas. A generously glazed double-height entrance hall continues the space of the street into the building. The upper floors offer flexible office space, and there is a roof terrace with sweeping views of St Paul’s Cathedral. intelligent glass solutions

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Both buildings offering prime office space of 349,555 sq. ft. with varied and stimulating outside areas. Offices offer accessibility to open space like a busy public piazetta or more contemplative zones of loggias and terraces.

Integration between floors should improve the staff interaction. One New Ludgate has 154,856 sq. ft. office space and 24,960 sq. ft. retail space.

Two new Ludgate has 195,239 sq. ft. office space and 5,880 sq. ft. retail space.

One New Ludgate with white precast concrete frames At a height of 39m One New Ludgate building is animated by bars and retail outlets under fixed white glass canopies. A masonry grid keeps direct sunlight off the glass and throws light into the floorplates. White precast concrete frames, simply detailed, respect their neighbours and set off the floor-to-ceiling lowion glazing, while vivid amber ‘Kathedral’ glass 71

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fins are used on the piazzetta façade in the new public space, where a mature tree provides shade. Retail and restaurants line the ground floor, and come together in this new piazzetta.

One New Ludgate also boasts extensive private external space, accessible from every office floor. This includes a set-back loggia and balconies and a substantial south-facing terrace at the fifth floor set-back level with uninterrupted views of St Paul’s which is capable of accommodating 300 people, landscaped by Gustafson Porter.

13,150 sqm façade with a storey-high glazing and curved elements The façade of One New Ludgate with a total area of 13,150 sqm consists of 3,675 mm x 1,500 72

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“

Offices offer accessibility to open space like a busy public piazetta or more contemplative zones of loggias and terraces

mm large elements with a storey-high glazing.

The curved elements were manufactured with three different radii measuring 1 m, 6 m and 13 m. Sliding doors are installed on 1st, 5th and 7th floor. Rectangular louvres of stone and glass with a depth of 615 mm and a width of 125 mm frame the individual elements and provide of sun and glare protection.

”

Life load deflections after the construction phase, axial reductions of columns and vertical thermal building movements cause an opening and closing of the horizontal joint in the façade of up to 12 mm. In order to take up the external vertical stone and glass louvres the joints had to be increased to maximum 30 mm. The horizontal overhanging and projecting louvres intelligent glass solutions

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are supported by similar vertical louvres and are not anchored to the faรงade system.

Double glazing of laminated safety glass The faรงade was provided with double glazing consisting of laminated safety glass (VSG) on the inside and on the outside in order to increase safety and burglary protection.

The double glazing consists of 2 x 5 mm laminated glass VSG, float low-iron glass with ipasol 50/27, 16 mm cavity with argon filling, laminated glass VSG consisting of 2 x 5 mm float low-iron glass.

The alternating installation of glass and stone elements in particular required a complex logistic planning. Installation was carried out intelligent glass solutions

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exclusively in one direction. A glass element was always followed by a stone element.

In addition, the storage area was severely restricted.

The glass louvres consist of an aluminium base frame on which the laminated glass was adhered to. These laminated glass units consist of 4 mm single Kathedral glass, four-colour interlayer, 8 mm heat strengthened low iron glass and an amber edge screen printing. The four differently coloured interlayers and the screen printing give the glass its unique colour.

The small canopies on the ground floor form another special feature. These transparent roofs are partly three-dimensionally curved and span over 4.5 m between large columns.

Two New Ludgate with a unique interplay of colours, cranked and curved faรงades With a unique interplay of colours in the faรงade Two New Ludgate differs from the architecturally connected One New Ludgate with its white louvres. The coloured louvres can be closed manually in fixed positions and therefore offer a wide range of views. Each of the storey high glazed elements of the 52 m high building has been provided with a GRC ledge on top and on bottom. 24 different colours in always other constellations make the curved faรงade elements unique in their appearance. The ceramic colours printed on the glass louvres also provide protection against the sun and glare. The design of the ensemble blends harmoniously into the environment along Limeburner Lane and Old Bailey.

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Gartner provided the cladding for Two New Ludgate with a total façade area of 7,746 sqm. The elements of the cranked façade are 3,700 mm high and 3,000 mm wide; the elements of the curved façade are 3,700 mm high and 1,500 mm wide. Top and bottom areas have always been provided with GRC ledges. The corner elements have different sizes and angles. The elements themselves are flat but segmented and therefore have an arch-shaped arrangement. Life load deflections after the construction phase, axial shortening of the columns and vertical thermal building movements cause an opening and closing of the horizontal joint in the curved façade of up to 15 mm.

Glass louvres in 24 different colours The façade was provided with a double glazing consisting of laminated safety glass (VSG) on the inside and on the outside in order to increase safety and burglary protection. The double glazing consists of 2 x 5 mm laminated glass VSG, low-iron glass with ipasol 50/27, 16 mm cavity with argon filling, laminated glass VSG consisting of 2 x 5 mm float low-iron glass. intelligent glass solutions

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A special feature are the coloured glass louvres which can be adjusted manually via the façade access equipment in a variety of positions.

Future users will be able to decide which areas should be hidden.

A steel façade with sharp steel edges was realized on the ground floor. In order to achieve this all mullions and transoms made of steel sheets were welded together to the required steel profile. For architectural reasons the outer and inner edges were designed with sharp edges.

The glazing of the steel façade consists of 2 x 6 mm laminated safety glass (VSG), float low iron glass with ipasol 70/39 and a dark-grey edge screen printing, 24 mm cavity with argon filling, VSG 2 x 6 mm float, size: 1.5 x 4.2 m.

The coloured glass louvres are made of 2 x 12 mm thermally toughened glass panes which are connected to one laminated VSG glass pane by means of a structural silicone bonding on top and bottom of the aluminium profiles.

There are no aluminium profiles on the vertical sides.

The façade design of the entrance area is completely round. For this reason the handcrafted steel transoms had to be curved.

The curved double glazing is 3 x 4.2 m large and consists of 2 x 8 mm laminated safety glass (VSG), float low iron glass with ipasol 70/39 edge screen printing, 16 mm cavity with argon filling, VSG 2 x 8 mm float.

BREEAM Excellent rating and convinced tenants One and Two New Ludgate have been awarded with a BREEAM Excellent rating.

The sustainability of the building was mainly influenced by a façade with a high amount of daylighting to reduce the need for artificial light on the office floors. The interesting architectural and façade concept also attracted the property market. Land Securities as owner has sealed a trio of lettings at One New Ludgate to the Commonwealth Bank of Austria, law firm Ropes & Gray and the marketing consultancy ZK Associates with a total area of 115,000 sq. ft. Also the 18,140 sqm high quality office space and the 550 sqm large retail of Two New Ludgate area have already been fully rented to Japanese bank Mizuho.

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Structural Glazing:

Design under high windload Pierre Descamps Dow Corning Corporation, Belgium Jon Kimberlain Dow Corning Corporation, Midland (United States) Jayrold Bautista Dow Corning Corporation, Singapore Patrick Vandereecken Dow Corning Corporation, Belgium (Patrick.vandereecken@dowcorning.com)

Introduction Structural silicone glazing has a long history of proven performance on building facades. The engineering practice of glass bonding dates back to the mid 1960’s evolving into being the sole means of retention for glass on the face of buildings in the early 1970’s, with the original project still in service. Evolution of the practice has continued with improvements such as sealant chemistry which facilitates rapid manufacturing following the commercialization of two part sealants in the early 1980’s. New trends including the use of large glass sizes, sophisticated engineering analysis using finite element analysis and stronger engineering performance for high windloads have recently challenged the conventional methods of design to continue this evolution. Answering these challenges should result in enhanced long term performance in challenging environments for a proven technology. The article outlines the use of finite element analysis to better understand the impact of design geometry, windloads and sealant performance to understand the challenges in this continued evolution.

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Fig 1. Harpa Concert Hall ReykjavĂ­k: Photo copyright Nic Lehoux

1 New trends The use of large glass panes in places under high windloads is one of the new trends in commercial buildings (figure 1). Today it is not uncommon to design systems assuming a windload above 5kPa or glasses bigger than 3m x 2m.

Current standards for structural glazing (ASTM C1401, ETAG002, GB16776) consider trapezoidal glass deformation with homogeneous stress distribution within the sealant bite. This means that the sealant bite is proportional to the glass size (small dimension) and to the windload, and inversely proportional to the sealant design strength as shown in equation 1 where b is the sealant structural bite, a is the shortest lite dimension, WL is windload and Ďƒdes is the allowable design stress.

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b = 0.5 * a * WL / Ďƒ des

(1)

Using sealants with a design stress of 140 kPa, bites become rapidly unacceptable (>30mm) for large glasses and projects under high windloads. These large bites lead to the need to increase aluminium profile widths, thereby increasing the costs and decreasing building energy performance. Increasing the sealant design strength would be an option to decrease the sealant bite but increasing the sealant modulus leads to increased stresses due to daily thermal deformation (figure 2) of glass and aluminum frame. Increasing sealant stiffness also increases potential stresses taking place due to building settlement or earthquakes, where stresses occur due to sealant deformation.

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In Finite Element Analysis, “true” stresses are considered and not “engineering” stresses. In H-bars, FEA shows two regions of high local stresses (figure 3): 1) The surface area in the center decreases with elongation due to material incompressibility (Poisson ratio close to 0,5), leading to a local stress higher than the engineering stress. At 100% elongation, the middle section is reduced by half, leading to a local stress which is two times as high as the engineering stress.

Fig 2. Stress in function of elongation for sealants of different modulus (stiffness) due to differential thermal deformation

In projects with large glass sizes and high windloads, glass deflection is usually above 1% (L/d > 60) as maintaining the glass deflection below 1% would lead to an increase in glass thickness, thereby again increasing project costs. However, under high glass deflection, the assumption of homogeneous stress distribution along the sealant bite is no longer valid.

This was already briefly mentioned in an annex of an ETAG002 report [1].

In this report, an additional term accounts for effect of glass deflection on the sealant stress (equation 2). This additional term is a function of sealant rigidity (ER), glass deflection (α) and sealant thickness (e) and also sealant bite.

2) At the metal to sealant interface, the sealant deformation is restricted by the interface, leading at the interface, to a higher rigidity modulus [2], and therefore a local stress which is much higher than the engineering stress (figure 3). The calculated local stress can vary considerably depending on the model used for FEA analysis (Neo-Hookean, Mooney-Rivlin,…) and the parameters used for the simulations ( mesh size, poisson ratio,…).

Therefore local stresses are always higher than engineering (or average) stresses. For this reason, local stresses calculated in structural glazing systems should always be compared to local stresses simulated from H-bars where failure is known, and not to sealant design strengths derived from engineering stresses. For instance, using our model, FEA simulations of 12x12x50mm, TA joints show a maximum principal stress around 6 MPa when applying an engineering stress of 1MPa.

σ = 0.5 * a * WL / b + ((b * α * ER)/ (2*e)) (2) This equation already indicated that increasing the sealant bite and/or sealant stiffness can have a negative effect on the sealant stress. Finite Element Analysis (FEA) software is now available and should allow us to have a better insight into the stress distribution of a sealant bead. The next paragraph discusses an FEA sealant stress distribution study for cases where glass deflection is between 1 and 2%. This study shows the effect of increasing sealant bite and sealant modulus on stress distribution.

2 FEA simulations Sealant design strengths in the different global standards for structural glazing (ETAG002, ASTM C1401, GB16776) are obtained from “maximum characteristic strengths” measured before and after accelerating ageing, and application of a safety factor. A design strength of 140 kPa is usually considered for silicone-based sealants. The maximum characteristic strength is obtained from standardized H-bar configurations by dividing the maximum force by the initial surface area (here 12mm x 50mm). This is usually considered as an engineering stress.

Figure 3: increased local stress at the edges of the sealant/glass interface on a 12mm thick TA joint

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Fig 4. Maximum value of first principal stress in function of joint bite, joint thickness and glass deflection

In this study, a Neo-Hookean model was considered with a Poisson ratio of 0.49. Mesh was optimized for calculation. Different models were also assessed which came to the same conclusions but different “true� stress values.

A. 2D simulation of a structurally bonded system In this first study, a 2D system made of a 1.9m wide glass pane glued at each side to an infinitely rigid frame using a silicone joint is considered.

The thickness of the glass pane is adjusted to obtain a maximum deflection at glass center of respectively 1% and 2% for a wind load of 4920Pa 1) Effect of sealant bite on local stress build-up.

Calculations are carried-out for 3 joint thicknesses ( 6, 7.5 and 9mm); for each joint thickness, joint bite is varied between 15 and 40mm. For each joint configuration, the maximum value of the first principal stress is plotted (figure 4). The stress in function of sealant bite is also plotted, assuming a homogeneous stress distribution (equation 1).

As expected, the stress calculated using the assumptions made in equation (1) shows a continuous decrease when increasing joint bite because the stress is assumed homogenously distributed and decreases with the sealant bite. If we consider glass deformation, we observe, using FEA, a decrease of the maximum local stress when increasing joint bite up to 20mm. But, for a bite around 25mm, we observe a saddle point where the trend reverses and maximum local stress starts to increase with joint bite. It is interesting to observe that when increasing joint bite, a fraction of the joint works in compression and does not contribute in sustaining the wind load ~ orthogonal to the glass pane (figure 5).

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Fig 5. joint displacement along Y axis, zero displacement corresponding to frame surface – a) for a joint bite of 15mm, displacement is everywhere negative meaning all joint works in traction b) case of a 40mm joint bite, the outer part of the joint (red color) works in compression

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Fig 6. Evolution of the maximum value of first principal stress in function of joint bite and sealant modulus, for a joint thickness of 6mm. Calculation was carried-out with different values of Îź and k corresponding to a material half stiff or two times more stiff compared to standard DC993 material.

2) Effect of sealant elastic modulus on local stress build-up

2D simulation of the frame system is replicated assuming one sealant thickness equal to 6mm but considering three sealants of different elastic modulus. Effect of sealant bite on stress build-up is calculated on varying bites between 15 and 40mm (figure 6).

The graph shows that increasing the sealant modulus also increases the local stress. The joint bite corresponding to the minimum stress is also displaced to smaller bites. This result is intuitive because a low modulus sealant shows a larger total joint elongation limiting joint compression.

On the contrary, a more rigid sealant shows already compression for a relatively small joint bite of 15mm. This calculation demonstrates that using a very rigid material is not suitable when significant glass deformations are considered. From two materials showing the same tensile strength at break measured on test piece, the less rigid material should be preferred. Of course, movement of glass pane with respect to the frame must also be minimized to prevent the glass pane from sliding out of the setting block sustaining the dead load. Therefore selection of material rigidity will necessarily be the result of a tradeoff.

calculated for a 20mm joint bite. The stress is calculated in a parallel plane (In Plane) located close to the interface between the sealant joint and the glass.

Fig 7. First principal stress distribution close to the adhesion plane, sealant joint bite of 20mm and thickness of 6mm.

B. Modelling a 3D geometry The 2D model has been extended to 3D (figure 7), incorporating the learning acquired from the 2D simulation effort. The glass pane has 1.9 x 1.4 m2. Glass thickness is 8 mm and glass deflection at center is 20.8 mm (1.5%) for a wind load equal to 5000Pa. Using symmetry, a quarter of the glass pane is modelled. Figures 6 represents the first principal stress

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Fig 8. Distribution of first principal stress close to the interface between the sealant joint and the glass pane. Joint bite is respectively 15, 20 and 30mm. The red dotted line represents the transition from traction to joint compression.

As expected, we observe that the stress is maximum in the middle of the frame profile; in the corner, the first principal stress has a negative value, which indicates a local compression of the joint. Changing the joint bite from 15mm to 40mm, we obtain results that are very consistent with 2D simulation, with the existence of a saddle point after which the maximum local stress increases with joint bite. As for the 2D simulation, increasing the joint bite is also characterized by a displacement of the point at which compression takes place in the joint (figure 8).

principal stresses and (maximum) Von Mises stresses for a 2D structural glazing case, were compared, varying the sealant bite. Results are shown in figure 9.

Figure 9 confirms, for glass deflections around 1%, the existence of a saddle point in the sealant bite from which the sealant stress increases with increasing bite, when using Von Mises stresses, in contradiction with the simplified equation generally used in structural glazing.

As this exercise indicated that Von Mises stresses would affect the results on sealant stress distribution within the sealant bite, the maximum

Fig 9. Maximum Von Mises stresses compared to first principal stress in a 2D structural glazing example with 1% glass deflection.

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Fig 10. Flame Towers, Baku, Kazakhstan: Photography by Farid Khayrulin, Design HOK

CONCLUSIONS The study demonstrates the importance of considering glass sheet deformation in the calculation of stress built up in sealant joints of large aspect ratio (Bite to thickness ratio >2). Stress distribution is very inhomogeneous and results from both the local joint rotation associated with glass pane deflection and to the shear stress induced in the joint due to the lateral displacement of the glass pane associated with deflection. Both principal stresses and Von Mises stresses show that above a 25mm bite, those local stresses may increase with sealant bite and sealant stiffness (Young Modulus), a conclusion which is not in agreement with global standards for structural glazing.

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The study also shows that for large glass and high windloads, local stresses can sometimes be reduced by applying smaller sealant bites, sealants with lower modulus or by increasing the sealant thickness, thereby decreasing the sealant aspect ratio (bite/thickness). Therefore, careful sealant joint analysis can help improve the performance of structural glazing frame designs by sometimes preventing the use of large sealant bites, thereby enabling the use of reduced frame widths leading to improved energy performance of the façade. Such an approach has been taken for the structural bonding of glass at the Baku Flame Towers where a 7kPa windload was considered

(figure 10) and is considered on a regular basis through collaboration between Dow Corning and façade consultants.

References 1. Charts and graphs referenced in figures 2 – 9 are the property of Dow Corning Corporation 2. Figure 1 - Harpa Concert Hall Reykjavík: Photograph is the copyright of Nic Lehoux 3. Figure 10 - Flame Towers, Baku, Kazakhstan: Photograph is the copyright of Farid Khayrulin, Design HOK

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The next issue of IGS will be in September The Glasstec 2016 Special Edition, featuring award winning articles exclusively written for this magazine and therefore difficult to obtain elsewhere.

The usual features will continue: Executive Boardroom Commentary The Paul Bastianen Column Watch out for the BIG IGS interview September 2016, make a note in your diary.

To ensure you never miss a copy, why not subscribe? See page 45 for details.

For inclusion in the Glasstec Special Edition of IGS contact: nick@intelligentpublications.com

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Residual stress as a result of heat impact in

borosilicate glass

components Lisa Rammig Eckersley O’Callaghan, United Kingdom, lisa@eocengineers.com Delft University of Technology, Faculty of Architecture and the Built Environment, Architectural Engineering + Technology

Architectural trends have tended towards curved glass envelopes and maximised transparency by reducing solid fixing areas. One approach towards transparent glass connections is a heat bonding process based on the principles of welding. This paper investigates the level of residual stress in soda lime silica and borosilicate glass caused by a heat-based connection or forming process. Nominal levels of residual stress prior to heat impact, directly after heat impact and after annealing will be measured on small-scale samples, utilizing a scattered light polariscope (SCALP). Material properties in the large temperature range required for the heat bonding process have been identified to allow subsequent numerical modelling to verify the results obtained in this study.

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1. Introduction During the past decades a vast development in structural glass envelopes and enclosures could be observed, aiming to achieve a maximum amount of transparency.

The development from an infill material to a structural material enabled designers to develop buildings that are based on using a large amount of glass i.e. atriums skylights and structural glass enclosures.

These Glass structures feature the ability to merge with their surroundings and become invisible, nearly dematerialised if the connections are kept to a minimum. This requires a large amount of structural engineering, detailed analysis and precise detailing to achieve safe sufficient structures.

Although significant amount of research in transparent bonding materials and bonded connections has been undertaken in recent years, solid metal connections are still commonly used to form structural glass connections.

With the development that can be observed in structural glass, tending to an optimisation of connections and production capabilities, leading to a reduction of the amount of fittings and an increase in the transparency of glass structures, however, to overcome the necessity of opaque connections, further research is required to innovate in this respect as opposed to improve existing technology. One experimental proposal is the heat bonding (welding) of borosilicate components to achieve monomaterial transparent connections. Borosilicate is chosen in this case, due to its low coefficient of linear thermal expansion (3.3 for Borofloat 33, 8.4 for soda lime silica). The welded connections themselves shall not be discussed in this paper, the focus shall in fact be on the analysis of the heat impact itself on the glass and resulting residual stress from heat impact caused by heat bonding of two glass components.

2. Material Properties To study the behaviour of a material in temperature range, it is essential to understand the material properties in relation to temperature. Commonly, material properties are established for a small temperature range only, however, to understand the behaviour of the material when heat bonded, larger temperature ranges need to be considered. Key thermal and mechanical properties have been obtained from manufacturer’s literature [Schott Borofloat 33, 2013] and will be introduced in this chapter. Material properties are highly dependent on the chemical composition of the material, and even relatively small variations in composition might result in significantly different behaviour. The chemical composition of the investigated glass [Schott Borofloat 33, 2013] is shown in Figure 1.

Fig. 1: Chemical composition of Borofloat 33

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1.1. Borosilicate Borosilicate glass is primarily used in chemical and pharmaceutical industries due to its high chemical resistance and low coefficient of linear thermal expansion, which is essential when substances are to be heated in test tubes.

For the same reason, borosilicate is commonly used as fire resistant glazing. However, due to a smaller production it is more expensive than soda lime. Until Schott developed a Microfloat process for borosilicate in 1993, it was produced in a drawing process resulting in larger surface deviations. Maximum available standard sizes here are smaller than for soda lime, however building relevant sizes can be achieved.

Thermal tempering of borosilicate is extensively more sophisticated than the thermal tempering of soda lime. However, by rapid quenching and a decrease of the quenching temperature, Schott have developed a process to overcome the problematic caused by the low thermal expansion and can produce thermally tempered borosilicate.

1.2. Material Properties Comparison at Ambient Temperature

Properties Density [kg/m3] Scratch hardness on the Mohs hardness scale Coefficient of mean linear expansion α10-6 [K-] (20-300 °C) Thermal conductivity [W/m2K] Softening point [°C] Processing temperature [°C] Modulus of elasticity E [N/mm2] Poisson Ratio μ Bending Strength [N/mm2] Compressive Strength [N/mm2] Tensile strength [N/mm2] (at constant load) Maximal thermal shock resistance ΔTmax [K]

Soda lime Glass 2490 6-7 8.4

Borosilicate Glass 2230 4.5 3.3

450 x 30 710-735 1015-1045 70000 0.2 30 700-900 30-80 7 68.02

4500 825 1260 63000 0.2 30 700-900 70 7 192.4

Table 1: Material properties for soda lime silicate and borosilicate as obtained from [Petzold et al., 1990]

1.3. Thermal Material Properties Thermal Shock Whenever glass is rapidly cooled, thermal shock is one of the immediately resulting issues causing a high breakage potential. During the process of tempering the cooling rate creates differing temperatures on the surface and in the core of the glass, leading to a stress differential, however, also temporary stress is induced in the glass though a temperature gradient.

Although the stress formed during cooling is temporary, failure can occur caused by the differential of surface and core temperature. The maximum possible stress will occur if the surface is instantaneously cooled while the core remains at the higher temperature. Under these conditions stress is given by [Shelby, 2005]: σ=EαΔT/(1-�) ΔT: difference between surface and core temperature α: thermal expansion coefficient of the material 85

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Specific heat capacity The heat capacity of a material is the amount of energy required to alter (increase or decrease) the temperature of an object by one Kelvin. The specific heat capacity for the borosilicate used in the tests described in this paper is shown in Figure 2 as obtained from manufacturer’s literature [Schott Borofloat 33, 2013] up to 500 °C.

Fig. 2 specific heat capacity of Borofloat 33

1.4.

The thermal elongation data provided was utilised to calculate the coefficient of linear thermal expansion for a temperature range up to approximately 600 °C (Figure 4). Unfortunately values above these temperatures could not be obtained, although these would be required to verify test results with a viscoelastic numerical model.

Fig. 4 Coefficient of linear thermal expansion over a temperature range up to 600°C

Mechanical Material Properties

Thermal Expansion (Linear or volumetric), is the tendency of the material to change the volume due to the temperature increase. Typical measurements of the thermal elongations are up to the transition temperature as shown in Figure 3 provided by Schott [Schott Borofloat 33, 2013].

1.5. Optical properties Glass is a solid that transmits light in the visible spectrum, which has not only made it to be a great building material as it transmits light into the building while forming a protecting layer, but this also allows to measure stress in the material with the help of a visual light polariscope.

To describe the thermal expansion of a glass, three main factors are to be considered: the thermal expansion coefficient, the glass transformation temperature and the softening temperature. While the thermal expansion coefficient indicates the relation between the volume of the glass and its temperature, the glass transformation temperature indicates the begin of the viscoelastic behaviour and the softening temperature (dilatometric) indicates the begin of flow under modest load [Shelby, 2005].

Refractive Index The interaction of light with the electrons of the individual atoms of a glass determines the refractive index. If either electron density or polarizability are increased, the refractive index increases, too. The RI of the borosilicate measured in this study is 1.473 according to data provided by the manufacturer, compared to 1.51 for soda lime glass.

3. Test setup

The thermal elongation as provided by the glass manufacturer [Schott ,2013] is shown in Figure 3 comparing the utilised Borofloat 33 with Pyrex borosilicate 3.3 and pure Silicon.

Fig. 3 Thermal elongation as obtained from [Schott ,2013]

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1.6. Heat impact on material structure and residual stress after heat bonding (welding) To understand the local heat impact of a welding process on borosilicate components, a physical test has been carried out. Although connections between two glass components have been established, these shall not be discussed in this paper, as the focus shall be on the influence of the temperature on the residual stress of the glass component irrespective of the geometry. To represent the heat bonding process while achieving a neutral geometry that would not influence residual stress measurements, flat specimen with a size of 100mm x100mm have been heated locally to working temperature and then undergone a controlled cooling process. Residual stress measurements have been carried out on these borosilicate specimens that have undergone a local heat treatment using temperatures high enough to achieve a chemical bond between two specimens. Temperatures required to achieve a chemical bond have been established in previous experimental tests (Rammig, Direct Glass intelligent glass solutions

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Fabrication, 2010) where specimens where heat bonded and underwent fracture mechanical testing to proof that the bond is stronger than the parent material. These tests were established on an experimental basis and further mechanical testing will be required to obtain significant results, however the results suggest, that chemical bonds can be achieved in a heat bonding process.

To achieve a heat bond between two borosilicate specimens, the glass requires local heating to working temperature. This is only possible if the entire specimen requires heating to Tg to avoid thermal shock related breakage. To minimise visual distortion locally, where the specimens have been heated to working temperature, it has been experimented with temperature exposure prior to the manufacture of the specimens that were used for the stress measurements. For these experimental trials two components were bonded to understand temperature ranges required to achieve an atomic bond. Insufficient heating of the entire specimen easily leads to breakage, while the local temperature impact could be optimised for a short duration, reducing visual distortion and still achieving sufficient bond between two specimens.

10 specimens of 50mm x 50mm and 4mm thickness have been tested, 5 of which have undergone the heat treatment and 5 of have been measured untreated. Residual stress has been measured on 5 points on the specimen as shown in Figure 5. Each point has been measured in two directions, x and y at 90 degrees to each other and perpendicular to the edges of the specimen. Initial measurements were taken prior to the heat treatment to monitor residua stress levels of the fabricated glass, the second measurements were taken directly after the welding process, when the specimen had only undergone a controlled cooling process, but have not been annealed, and the final measurements were obtained after the annealing process, to understand whether the stress induced can be fully released.

The specimens have been heated with a burner utilising earth gas and oxygen in adjustable quantities. The air –gas mixture was adjusted manually, to gradually increase the temperature of the flame and heat up the specimen. Two different nozzles have been used, a larger opening for a big, low temperature flame (up to 600-800°C) and a smaller nozzle to achieve a slim focused flame with temperatures up to 1500 °C to locally heat a small are of the glass ( 10mm). As no heat gauge could be fitted on the nozzle of the burner or the specimen, a thermal camera (FLIR-T 640) has been used in the heat range mode of 300°C-3000°C to monitor temperatures of the specimens. The camera offers three temperature ranges for operation; -40-100°C, 150°-600°C and 330°-2000°C. Given that required temperatures are significantly larger than 600°C, the highest temperature range was chosen for the measurements, despite the expectation of inaccuracies of measurements in the temperature range below 300°C. To assure that the heating process is repeatable in the most similar way despite using a manual process, the specimens were retained in position in a welding jig (Fig. 8). Two steel clamps keep the glass in position allowing expansion as a non-combustible tape with low friction is used to separate the glass from the steel clamp and allow expansion while retaining the specimen in position.

A fracture mechanical evaluation of the influence of the temperature on the strength of the material is anticipated through ring-on ring tests, however this paper only discusses the impact of the process on residual stress.

Fig.6 Specimen in welding jig

Fig. 5 Test specimen with measuring points

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exact adherence to maximum temperature and different heating and cooling rates during the annealing cycle is of high importance to achieve a continuous annealing result with a homogeneous stress distribution in the component [Greil, E., 1964].

To avoid breakage due to thermal shock during the process of temperature impact, the entire specimen requires heating up to temperatures 600-700°C prior to local heating of the specimen centres to working temperature (~1200°C). After the heat impact that typically was held for 35 seconds. Temperatures have been monitored with a thermal camera to understand heat impact over time and max temperatures are shown in Figure 11. After the heat impact in the centre of the specimen, the entire specimen requires controlled cooling to room temperature before the glass needs to be annealed in a full annealing cycle over 20 hours (Fig 9) to remove locked in residual stress from the temperature impact.

The relaxation temperature of the annealing cycle is defined by the glass composition. Fig 7 shows annealing temperatures for several glass compositions, including the Borofloat 33 utilised in the tests.

To achieve a relaxation of stresses, the glass requires a homogeneous heating of the entire component so that stress can be released through the plastic behaviour of the heated material. The cooling through the transformation phase of the glass has to be slow enough to avoid further stress being locked in. This means that the cooling rate is the crucial factor in the annealing process. It is dependant on the thickness of the material as well as the composition, which cooling rate is chosen. The annealing cycle used for the specimens tested is shown in Figure 15 and is based on material properties obtained from literature [Schott Borofloat 33, 2013] and [Greil, E., 1964].

Annealing The annealing of glass is a method to ‘relax’ stresses that have been locked in through a heat impact i.e. in this case a bonding process.

Annealing is equally important to commonly used glass processing techniques such as heat gravity bending (‘slumping’). After the heat impact the glass requires an additional cooling process in which controlled temperature drop leads to a relaxation of locked-in stress. The Glass type Schott, Mainz: DURAN 50 Geraeteglas 20

Relaxation Temp.°C 575 575

Therm Gl 16 Therm. Gl 2954 Supremax 56

544 596 750

Supremax Supremax Fiolax clear

722 573 571

Fiolax brown Bleiglas Uvioglas Fernsehkolbenglas Glaswerk Wertheim Geraeteglas Roehrenglas fuer Automaten Resistenzglas Sterilisatiosglas Bleiglas Molybdaen-and Kovar Glas

566 429 452 445 538 530 582 566 550 428 512

Glass type Kolbenglas Leuchstoffroehrenglas Leuchtstoffroehren-Farbglas Ruhrglas Apparateglas Roehrenglas

Relaxation Temp.°C 562 530 510 520 496

Ampullenglas Leuchtroehrenglas Osram:

538 506

Bleiglas-M Bleiglas Roehren-Normalglas Magnesiaglas Wolframglas Hartglas Thueringer Glaeser:

435 425 505 515 528 743

Rasotherm Gerateglas G52 Geraeteglas 399

570 605 540

Gegeef

560

Fischer Prima

530

Glass type Quickfit: Laborglas Philips: Gluehlampenglas 01 Gluehlampenglas 03 Fernsehkolbenglas 162 Sovirel: Pyrex Borosilikatglas 73201 Borosilikatglas 74001 Borosilikatglas 74644 et al Borosilikatglas 75001 Bleiglas Tschecjische Glaeser SIMAX Glas SIAL Glas Ampullen Neutral Glas ThermometerGlas PN Einfaches Fenster und Behaelterglas

Relaxation Temp.°C 565 435 510 465 545 562 550 480 508 438 536 562 581 550 530

Fig. 7 Annealing temperatures for several glass compositions [Greil, E., 1964]

Fig.8 Annealing cycle for borosilicate specimen

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4. Test results It was expected that residual stress would be relatively consistent on small specimens prior to the heat treatment and deviations and measurement errors were predicted to be low. Similarly it was expected that residual stress levels on the annealed specimens would be low, however deviations were expected to be larger. Directly after the heat impact, larger variation on residual stress within the specimens was predicted as well as significant stress in the glass due to the high temperatures applied.

1.7. Visual assessment of residual stress Residual stress was visually monitored under a polarisation filter prior to heat impact, just after heat impact and after annealing. All visual assessments were carried out at a consistent room temperature of 24°C. Residual stress at the three stages mentioned is shown in Fig 9.

Prior to the heat impact, no stress could be observed under the polarisation filter, the specimen appears to be evenly annealed with residual stress levels to small to be visible under a polarisation filter. Figure 14b shows the distribution of residual stress immediately after the heat impact. The glass has been cooled to room temperature in a controlled way (Figure 10), however, the fast cooling process leads to stress being locked in. With the centre of the specimen having been heated, the stress distribution appears relatively evenly in the opposite corners of the specimen, with slight non-uniformities in the areas the specimen was clamped to the jig.

After the annealing process, again, no visual stress could be observed in the visual assessment through polarised light (Fig 9b).

1.8. Residual stress measurements Non-destructive testing on the surface stress has been carried out using a scattered light polariscope (SCALP 5) to understand the impact of heat induction and annealing on the residual stress of the glass.

The SCALP operates by sending a polarised laser through the thickness of the glass. The laser beam scatters on the particles of the glass and the intensity of this scattering is recorded through the thickness of the glass, the device obtains the absolute optical retardation at every point of the beam, which is then converted to stress values [GlasStress, 2013].

Residual stress measurements on the heat treated specimen have first been carried out immediately after the heat treatment, just allowing the specimen to cool down to room temperature (24°C) and have then been repeated after the annealing process.

The annealing cycle used is optimised for the borosilicate used (Borofloat 33) and is shown in Figure 8.

Ideally residual stress levels prior to heat induction and after annealing should be identical, however, previous tests carried out on slumped annealed glass showed that this might not be the case and the annealing process might not release locked- in stress evenly. The general effects of thermal history on thermal and mechanical properties are well understood and as such should be taken into consideration.

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Fig 9 a, b and c Residual stress under polarisation filter before and after welding and after annealing

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Fig. 10 Temperature at 45, 405, and 675 seconds

1.9. SCALP calibration As the refractive index (RI) of borosilicates differs from the RI of soda lime silicates, the polariscope requires adjustment to be able to measure borosilicates accurately. The RI of the borosilicates used is 1.48 as previously described, which according to the polariscope manufacturer requires a laser angle <75°.

Pixels not sufficiently reliable for stress calculation are referred to as excluded pixels. Parasitic scattering of the light beam saturates the sensor and leads to an exclusion. Aproximately 5 to 15% of the data is lost due to parasitic scattering preliminary at entrance and exit points of the laser [GlasStress, 2013].

Readings with a fit error >10% and excluded pixels of >20% were not considered in the data processing.

Results were separated based on the direction of stress measurement, average stress values were calculated for each direction and finally overall results were transferred in Excel format.

5 points were measured for each specimen in x and y direction. Then principal stress was calculated to: σ1,σ2= (σx+σy)/2 ± √((σx-σy)2/2 + 4 tau,xy 2) assuming that the shear stress = 0. The SCALP is not capable of measuring shear stress; hence this assumption has been made, as shear stress could not be verified.

Fig.11 Temperature profile for 5 tested specimen

5. Measurement results To understand the impact of heat on the glass through a heat bonding or -deforming process, the same three conditions have been analysed: prior to heat impact, directly after a local heat impact and after annealing of the specimen. The specimens were measured on 5 points (Figure 5) in x and y direction.

6.1 Data analysis The data was analysed using the manufacturer’s software (GlasStress SCALP Software version 5.8.1.4). Processing of the results was based on the fit error and the amount of pixels that were excluded from the measurement. The fit error refers to the root-mean-square error of the fitting curve that is used to smoothen retardation results and allow stress calculation. Large values indicate that measurement data is invalid. The manufacturer suggests that acceptable values are between 5 and 15% [GlasStress, 2013].

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Results are shown in Table 2. Measurements of residual stress prior to heat treatment are very consistently in the acceptable range for annealed glass [Haldimann et al, 2008].

Measurement point

1 2 3 4 5

Prior to heat impact Mean principal SD (MPa) residual stress (MPa) -3.51 0.68 -3.24 0.14 -3.27 0.31 -3.39 0.45 -3.35 0.51

After heat impact Mean principal SD (MPa) residual stress (MPa) 5.39 1.30 -0.6 0.58 -0.08 1.76 2.51 1.96 1.34 0.97

After annealing Mean principal SD (MPa) residual stress (MPa) -1.72 1.52 -1.10 0.50 -1.45 0.96 -0.90 1.09 -0.86 0.58

Table 2. Principle residual stress on specimen

While the distribution of residual stress prior to heat impact is very even throughout the specimens (Fig. 12), after welding larger differentials can be observed, with compressive values in the corners of the specimen, surrounding the centre point that was exposed to localised heat impact.

This matches results previously described under a polarisation filter shown in Fig. 9 although distribution of stress after welding appears to be not as homogeneous as indicated in the polarisation image. However, intelligent glass solutions

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Fig 12. Principle residual stress on specimen prior to welding, after welding at 24° C and after annealing at 20° C

stresses measured are much lower than expected; The significance of the results obtained is questionable though, as the measurement device has a tolerance of +/- 4 MPa for measurements <20 MPa [Aben, H., Anton, J., et al., 2010], which, given the small values measured, might have a significant influence on the results and suggests that the device is not reliable for measurements of the pre-annealed and annealed glass. After annealing, the stress distribution is more homogeneous again, with a higher standard deviation in results. Deviation in results directly after heat impact is comparably high. The experimental results shall be verified in a numerical model, which will, however require reliable material properties over the large temperature range the glass is exposed to. After annealing, the stress distribution is more homogeneous again, with a higher standard deviation in results. Deviation in results directly after heat impact is comparably high.

6. Conclusion Temperature impact on the residual stress of glass specimen is shown in the results obtained through experimental testing of borosilicate specimen. The importance of an additional annealing process can be observed, as residual stress is clearly reduced. However, measurement results obtained in areas of large heat impact, where surface deformation of the specimen can be observed, show larger deviations and error rates, so further testing might be required to verify the results obtained in this study. Residual stress levels measured after the heat impact were significantly lower than expected and might not be reliable, as stress is below the threshold where the scattered light polariscope used (SCALP 5) can obtain reliable measurements. Through the process however, it could be verified that a controlled process needs to be followed to heat the glass to Tg, as thermal shock breakages where observed when specimen were heated too quickly. This will require further studies to explore optimised exposure temperatures. The visual assessment of stress shows, that a controlled annealing process, reduces stress induced through a welding process/ heat impact can be relaxed and components do not show significant residual stress or stress differentials that would make the glass unemployable as an annealed glass component for a building application. It is assumed that stress is sufficiently eased out for the glass to undergo further thermal treatment processes, however, this shall be verified in further tests. For application in an industrial process, controlled heating, temperature exposure at Tmax and controlled cooling would require further optimisation and study.

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Advanced numerical analysis utilizing viscoelastic material models will have to be carried out to verify the current results. These rely on the availability of material properties in the temperature range explored, which could not be obtained for this study; hence further research is required. In practice, apart from the use shown in this study, the analysis methodology as well as material properties obtained for large temperatures have a wide variety of applications, including the study of fire resistant glazing or gravity curved glass. The latter is commonly in use, however stress levels are not very well understood so further studies on residual stress of gravity formed glass shall be carried out.

7. Acknowledgements The author gratefully appreciates the provision of material property data

by Schott and would specifically like to thank Dr. Lutz Klippe and Dr. Folker Steden for their availability to discuss the data provided. The tests have been carried out at the Glass and Facade Technology Group at the University of Cambridge and the author would like to thank Dr. Mauro Overend for the support with carrying out the tests. Information on calibration and measurement optimisation for the use of the polariscope (SCALP 5) for borosilicate glass has been gratefully received by Dr. Johan Anton from GlasStress.

8. References [1] Aben, H., Anton, J., et al., On non-destructive residual stress measurement in glass panels, in Estonian Journal of Engineering, 2010, 16, 2, p150–156 [2] Choudhery, M.K., Potter, R. M., 2005, Heat Transfer in Glass-Forming Melts, Chapter 9, In: Properties of Glass- Formation Melts, Eds: Pye, D.L., Montenaro, A., Joseph, I., CRC Press, Boca Raton, USA, 2005 [3] Fluegel, A., 2007, Glass Viscosity Calculation Based on a Global Statistic Modelling Approach, In: Europ. J. Glass Sci Technol. A, vol. 48, 2007 no.1, p.13-30 [4] Fluegel, A., et al., 2005, Statistical Analysis of Glass Melt Properties for High Accuracy Prediction: Density and Thermal Expansion of Silicate Glass Melts. In 79.Glastechnische Tagung der DGG, Wuerzburg, Germany, May 23-25, 2005 [6] Haldimann, M., Luible, A., Overend, M, Structural use of glass, Structural Engineering Document no. 10, International Association for Bridge and Structural Engineering (IABSE),2008 [7] Petzold, H. Marusch, B. Schramm, Der Baustoff Glas, Verlag für Bauwesen Berlin, 1990 [8] Scattered Light Polariscope SCALP Instruction Manual, Ver. 5.5, GlasStress Ltd. [9] Schott Borofloat 33, 2013, The Versatile Floated Borosilicate Glass - With an Infinite Number of Applications, Product Specification Material, Schott 2013, www.schott.com/ borofloat, accessed December 2015 [10]Shelby, J.E., 2005 Introduction to Glass Science and Technology [11]Stanworth, J.E., 1950, Physical Properties of Glass, Clarendon Press, Oxford, UK, 1950 [12]Wigginton, M,; Glass in Architecture, Phaidon, 1996 91

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The most interesting training sessions to follow this year The IGS Column of Paul Bastianen 2016 is the year of several interesting congresses and exhibitions for the glass sector. I am putting the main ones in chronological order so we can focus on them: The 11th International conference on coatings on glass and plastics, ICCG11, June 12-16 in Braunschweig/ Germany The Challenging Glass Conference, 5th edition, at Ghent University, Ghent/ Belgium, June 16-17 The engineered-transparency Conference, during the glasstec trade fair in Düsseldorf/ Germany, September 20-21.

I may have missed some very important events in other parts of the world but I want to focus only on these three, particularly significant to Europe, they stand high with their respective programmes. Below is a summary of the programmes and topics that will be discussed in order to arouse your interest and justify the need to attend one or more of them.

ICCG11; THE 11TH INTERNATIONAL CONFERENCE ON COATINGS ON GLASS AND PLASTICS; Introductory Session – Market and Business in the Field of Coatings on Glass and Plastics; Challenges for Automotive Glazing (Prof. Dr. 92

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Jürgen Leohold, Volkswagen AG, Germany); Architect’s Dream List (Christoph Timm, SOM, USA); Ultra-thin Glass (G-Leaf™) and its Applications (Akihisha Saeki, Nippon Electric Glass Co.,Ltd., Japan); Advanced R2R Manufacturing of Printed, Organic, Flexible Electronics (Dr. Sorin G. Stan, VDL Enabling Technology Group, The Netherlands); Organic Solar Films from Vacuum Roll-toRoll Manufacturing for Building-integrated Photovoltaics (Dr. Martin Pfeiffer, Heliatek GmbH, Germany); Market and Business Prospects on Batteries (Dr. Isotta Cerri, Toyota Motor Europe, Belgium); High-Performance Wet Coatings on Glass and Plastics: History and New Developments (Prof. Dr. Helmut Schmidt, HSM TechConsult, Germany); Plasma Medical Science Innovation towards a Future Therapy (Prof. Dr. Masaru Hori, Nagoya University, Japan); Worldwide Glass Market and Trends – Executive Summary from GDP 2015 (Jorma Vitkala, Glaston, Finland) Session 1 – Advanced Vacuum Processes Future of Sputtering (Prof. Dr. Hana Barankova, Uppsala University, Sweden) Session 2 – Wet-chemical and Hybrid Processes Large Area Organic Optoelectronic Devices Containing Vacuum and Solution Processed Layers (Prof. Dr. Uli Lemmer, Karlsruhe Institute of Technology, Germany)

Session 3 – ALD, CVD, and Atmospheric Plasma Processes Large Area Atmospheric ALD / MLD on Flexible Substrates (Stephan Klotz, BASF Schweiz AG, Basel, Switzerland) Session 4 – Processes for Flexible Substrates Roll-to-Roll Processing for Flexible Devices and Components Utilized in Wearable and Mobile Electronics and the Coming IoT Era (Dr. Neil Morrison, Applied Materials Web Coating GmbH, Alzenau, Germany) Session 5 – Film Growth, Process Control, and Model Based Concepts Modelling of Titania Growth by DC Magnetron Sputtering (Prof. Dr. Stephane Lucas, University of Namur, Belgium) Session 6 – Energy Conversion, Saving, and Storage Switchable Mirrors Based on Metal Hydrides for Smart Windows (Dr. Yasusei Yamada, National Institute of Advanced Industrial Science and Technology, Japan) Session 7 – Optics, Consumer Electronics, and Communication Recent Developments in the Field of Precision Optical Coatings (Dr. Marcus Frank, Optics Balzers AG, Liechtenstein)

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Session 8 – Medical, food, and environmental applications Food Packaging in the Future (Prof. Dr. HorstChristian Langowski, Fraunhofer Institute for Process Engineering and Packaging IVV, Freising, Germany) CHALLENGING GLASS CONFERENCE, 5TH EDITION Conference themes: • Projects & Case studies • Joints & Fixings & Adhesives • Strength & Stability • Laminated Glass & Interlayer Properties • Hybrid & Composite Glass Components • Numerical Modeling & Experimental Validation • Curved & Bended Glass • Architectural Design, Geometries & Lighting • Structural Glass Design Philosophy & Structural Safety • Insulating Glass Units • Glass in Facades

Exhabition Glasstec Düsseldorf

Keynote speakers: Agnes Koltay Director at Koltay Facades Dubai, United Arab Emirates Willem Jan Neutelings Partner at Neutelings Riedijk Architects Rotterdam, The Netherlands Haim Dotan CEO at Haim Dotan Ltd. Tel Aviv, Israel Sven Plieninger Partner and Managing Director at Schlaich Bergermann Partner Stuttgart, Germany ENGINEERED-TRANSPARENCY The conference »engineered transparency« that was first introduced at glasstec in 2010, will shine for the fourth time in Düsseldorf. Its main focus this year will be on the dissemination of information related to several aspects of glass in buildings. Due to the fact that the saving of natural resources becomes more and more important, the building envelope and its materials are in the spotlight of future interest both in energy saving and economic efficiency.

The use of glass in facades due to its transparency enables the utilization of natural daylight to light the buildings. It is a tendency to optimally dematerialize the building envelope to profit from the natural lighting at a highest rate as possible and from the solar radiation for heating the building in cold seasons. Such intelligent glass solutions

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developments lead to applications of glass as structural elements in facades beyond its traditional application as window or room enclosure.

Glass is only a single component of a facade.

But a facade is more than a mere enclosing element and requires more complex consideration with regard to economy, feasibility, environment and sustainability during its entire life cycle. Built in applications and latest trends in planning and research of facades shall present new ways in a comprehensive and overarching approach for

an economical, environmental and sustainable design.

The application of photovoltaic modules as a type of cladding in facades shifts these with regard to their function from a mere enclosure to the power generating force. The facade turns into an element with doubled function in terms of energy. The building envelope not only saves the energy and resources but becomes also a power station itself.

The conference addresses mainly engineers and architects in exchanging mutual needs 93

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and requirements relevant to projects and showing in many case studies the issues regarding the energy and sustainability, design and construction as well as presenting the new research and the developments in structural use of glass. The participation of glass producers and processors as well as the interested clients will complete the global facets of this event.

The »engineered transparency« provides a platform for building professionals to share information and knowledge in and around the use of glass in buildings. Such an exchange will contribute to future research, developments and innovations for the structural use of glass in building applications.

Special Mini-Symposia At this year´s »engineered transparency« there are two special mini-symposia planned.

One organized by the “Hüttentechnischen Vereinigung der Glasindustrie” (HVG) and “Deutschen Glastechnischen Gesellschaft” (DGG) will address the main topic on “Glass with integrated functions and embedded sensors”.

The second symposium will overview the glazing technologies and will be presented in cooperation with “Fachverband Konstruktiver Glasbau” (FKG) and “Bundesverband Flachglas” (BF).

Sessions are dedicated to: • Façade-architectural design • Special symposium “glass technologies” and “embedded functions” • Structural glass • Structural design • Glass composites and coatings • Glass projects • Solar technologies

everyone is talking about the renewable energy and fossil-free energy production. Construction sector will not escape this challenge and has to come up with good integrated systems this is the reason that the aforementioned conferences and congresses are indeed tackling those themes.

Another challenge is the demographic development of the population. Today, 70% of the world population lives in cities, this leads to the creation of megacities. According to the United Nations statistics, between 2014 and 2030 the top 10 megacities will accommodate millions and millions of people. This is shown below.

The cities to grow at the fastest rate are: New Delhi, Mumbai, Beijing, Dhaka, Karachi and Cairo. All of them outside Europe and the USA where no dramatic further growth is expected.

Europe is not any more the continent with the largest population, it lost this role during the last centenary as the population in Europe dropped from 25.5% of the total population to less than 11% and is still decreasing compared with other continents. The population in the USA however maintains its 5.5% stake in the overall picture.

You will find that all the conferences and exhibitions are addressing new challenges in respect of the term industry 4.0. The glass processing industry and façade builders are no exception.

Everything is about the fourth industrial revolution. The manufacturers are now at a new stage of organizing and controlling of the entire value chain and the entire life cycle of production and products.

Targeting industrial 4.0 is the holistic approach to optimize the production flow from the order position through the entire production process to delivery and installation; that includes all steps between the order up to recycling.

This requires that all production data including mechanical work are held together. This permanent information exchange can only be done in real-time via software, glass fabricators have to be extremely efficient in networking of data and specification of conditions of production, especially of products requiring high qualitative art to manufacture and also for special products. This creates the step to truly individualized production and products, to high specification of individual properties of the manufactured products. Industry 4.0 is quickly becoming the standard because the construction is individualized to the highest specifications with 3D printing and special designs.

If you can imagine that in Dubai (again) a new tower is being built which will be the tallest building in the world, its height surpassing that of the Burj Khalifa, the challenges in production methods are really crucial.

Emaar’s tower in Dubai harbor arear taller than the Burj Khalifa

With the Keynote speakers: Werner Sobek, Werner Sobek Group, Stuttgart Tom Minderhoud, UNStudio, Amsterdam Juan Lucas Young, Sauerbruch Hutton, Berlin Johann Sischka, Waagner-Biro, Wien.

As we live very fast now, with many changes occurring so quickly that we are struggling to keep up with them, the developments of today must be followed properly.

After the climate conference in Paris last year, 94

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T h e I G S c o l u m n o f PCaausle BSatsutdi ai en se n

You will find everything that is new in the world of the glass market at glasstec 2016, then it is highly recommended to go to this major world exhibition in DĂźsseldorf on 20-23 September 2016 .

Glasstec is the leading trade fair for the global glass industry and its suppliers. It takes place every two years in DĂźsseldorf and offers to inform and teach about the properties of glass as the material from its manufacturing to processing and about its various applications and recycling. Glasstec delivers innovations in the glass industry, glass engineering, glazier craft, gives new impetus to the architecture and discusses trends concerning solar and photovoltaics. There is no better place to showcase product innovations, forwardlooking processing techniques and new glass applications to trade visitors from all over the world.

If you would like to comment on this column or on other topics, I would be pleased to hear from you by phone +31 643 888 728 or email p.bastianen@planet.nl

So there is no business like glasstec business..â&#x20AC;Ś in the world of glass.

Trade fair grounds in Dusseldorf

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AUTHORS DETAILS Case Studies

Main Header Dr. ir. Christian Louter Chair of Structural Design Department of Architectural Engineering & Technology (AE&T) Faculty of Architecture and the Built Environment (A+BE) Delft University of Technology (TU Delft) Julianalaan 134 2628 BL Delft The Netherlands +31(0)628241871 Christian.Louter@TUDelft.nl Anthony (Tony) Darkangelo Finishing Contractors Association 1 Parkview Plaza | Suite 610 | Oakbrook Terrace, IL 60181 United States of America P: (866) 322-3477 F: (630) 590-5272 | www.finishingcontractors.org

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Ms.Birgit Horn Glasstec Messe Dusseldorf GmbH P.O. Box 10 10 06, 40001 Düsseldorf Messeplatz, Stockumer Kirchstrasse 61, 40474 Düsseldorf Germany Telephone: +49 (0)211 4560-01 Fax: +49 (0)211 4560-668 E-Mail: info@messe-duesseldorf.de http://www.glasstec-online.com/ Internet: http://www.messe-duesseldorf.de/ F.Oikonomopoulou & F. A. Veer TU Delft, Faculty of Architecture, The Netherlands, Julianalaan 134 2628 BL Delft The Netherlands T. Bristogianni & R. Nijsse TU Delft, Faculty of Civil Engineering and Geosciences, Stevinweg 1 2628 CN Delft The Netherlands Tel: +31 (0)15 27 89802

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Thomas Henriksen Mott McDonald 10 Fleet Place London EC4M 7RB United Kingdom T +44 (0)20 7651 0300 E:Thomas.Henriksen@mottmac.com www.mottmac.com Lucio Blandini Werner Sobek Stuttgart AG Albstr. 14 70597 Stuttgart / Germany Tel.: +49.711.76750-0 Fax: +49.711.76750-44 stuttgart@wernersobek.com www.wernersobek.com

Marcin Brzezicki, PhD marcin.brzezicki@pwr.wroc.pl Wroclaw University of Technology Faculty of Architecture ul. Prusa 53/55 50-317 Wroclaw Poland www.arch.pwr.wroc.pl Klaus Lother Josef Gartner GmbH Gartnerstraße 20 89423 Gundelfingen Germany Tel: +49 9073 84-0

Tel:+49 9073 84-2100 E: info@josef-gartner.de

www.josef-gartner.permasteelisagroup.com

www.permasteelisagroup.com Patrick Vandereecken Dow Corning Parc Industriel de Seneffe 1, 7180 Seneffe, Belgium

Phone:+32 64 88 80 00 E: patrick.vandereecken@dowcorning.com www.dowcorning.com Lisa Rammig Eckersley O’Callaghan 9th Floor 236 Gray’s Inn Road London WC1X 8HB Tel: +44 (0) 20 7354 5402 E: london@eocengineers.com www.eocengineers.com

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The OPUS Project, Dubai, UAE Client: Omniyat Properties Architect: Zaha Hadid Architects: Images courtesy of Zaha Hadid Architects:

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