Multi-Story Timber Structures In Denmark

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MULTI‐STORY TIMBER STRUCTURES IN DENMARK

OCTOBER, 7 2016

ABSTRACT This paper demonstrates the feasibility of multi‐story timber construction from a legal and technical perspective in Denmark. The main objectives of the investigation are to determine the primary benefits of timber, analyse the legislation and technical issues including the consideration of the challenges of recent high‐rise timber constructions from other countries, as well as to offer solutions of a more wide‐ spread building with wood. The answers have been obtained through the analysis of theoretical research, and qualitative data through interviews with experts in the field. The general finding of the research is that multi‐story timber structures are certainly feasible in Denmark and have quite a positive outlook for the near future.

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ACKNOWLEDGMENTS I would like to express gratitude to my supervisor, Peter John Andersen, whose professional knowledge has helped me to complete this dissertation and who provided me with valuable materials, while guiding me along the entire time of writing.

I would like to also thank Finn Larsen, senior fire safety and structure engineer of Rambøll, who I interviewed, for his valuable time, professional expertise, materials and information provided.

Likewise, I would like to thank Jonas Sangberg, creative architect of Sangberg Architects, as well as Minik Lange Peder, graduate student of Danish Technical University, who I also interviewed, for their time, valuable information and educational expertise.

KEYWORDS 

multi‐story structure;



high‐rise construction;



tall building;



timber structure;



tall wood;



heavy timber;



mass timber;



structural systems;



timber benefit;



regulations;



timber challenges;



Denmark.

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TABLE OF CONTENTS ABSTRACT ................................................................................................................................................... ii ACKNOWLEDGMENTS ............................................................................................................................... iii KEYWORDS ................................................................................................................................................ iii TABLE OF CONTENTS ................................................................................................................................ iv LIST OF FIGURES ........................................................................................................................................ vi 1.

2.

3.

INTRODUCTION .................................................................................................................................. 1 1.1

BACKGROUND INFORMATION AND PROBLEM FORMULATION ............................................... 1

1.2

PRIMARY RESEARCH QUESTION ................................................................................................ 2

1.3

SECONDARY RESEARCH QUESTIONS ......................................................................................... 2

1.4

RESEARCH OBJECTIVES .............................................................................................................. 3

1.5

DELIMITATION OF WORK ........................................................................................................... 3

METHODOLOGY ................................................................................................................................. 4 2.1

CHOICE OF THEORETICAL BASIS AND RESEARCH METHODOLOGY .......................................... 4

2.2

CHOICE OF WORKING METHOD ................................................................................................ 5

THEORETICAL BASIS ........................................................................................................................... 6 3.1

EVOLUTION OF HIGH‐RISE TIMBER STRUCTURES ..................................................................... 6

CONCLUSION OF THE CHAPTER ......................................................................................................... 9 3.2

BENEFITS OF TIMBER USE IN CONSTRUCTION .......................................................................... 9

CONCLUTION OF THE CHAPTER ....................................................................................................... 11 3.3

BUILDING REGULATIONS ......................................................................................................... 12

3.3.1

BUILDING REGULATIONS IN DENMARK ........................................................................... 13

3.3.2

BUILDING REGULATIONS AROUND THE GLOBE .............................................................. 15

CONCLUTION OF THE CHAPTER ....................................................................................................... 16 3.4

WOOD AS A STRUCTURAL MATERIAL ...................................................................................... 16

3.4.1

CHARACTERISTICS OF WOOD .......................................................................................... 17

3.4.2

TIMBER STRUCTURAL SYSTEMS AND PRODUCTS ........................................................... 18

CONCLUSION OF THE CHAPTER ....................................................................................................... 22 3.5

OTHER PARAMETERS REGARDING MULTI‐STORY TIMBER CONSTRUCTION .......................... 23

3.5.1

FIRE PROTECTION METHODS .......................................................................................... 23

3.5.2

MOISTURE CONTENT AND SHRINKAGE ........................................................................... 25

CONCLUTION OF THE CHAPETER ..................................................................................................... 26 3.6

CURRENT MULTI‐STORY TIMBER STRUCTURES AND THEIR CHALLENGES ............................. 26

3.6.1

“TREET” IN BERGEN, NORWAY ........................................................................................ 27

3.6.2

CHALLENGES OF USING A WOODEN STRUCTURE IN “TREET” ........................................ 29

3.6.3

“FORTE” IN MELBOURNE, AUSTRALIA ............................................................................. 29 iv

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3.6.4

CHALLENGES OF USING A WOODEN STRUCTURE IN “FORTE” ....................................... 31

3.6.5

“WOOD INNOVATION AND DESIGN CENTER” IN BRITISH COLUMBIA, CANADA ........... 31

3.6.6 CHALLENGES OF USING A WOODEN STRUCTURE IN THE “WOOD INNOVATION AND DEISGN CENTER” .............................................................................................................................. 35 3.6.7

“LIFECYCLE TOWER ONE” IN DORNBIRN, AUSTRIA ......................................................... 35

3.6.8

CHALLENGES OF USING A WOODEN STRUCTURE IN “LCT ONE” .................................... 38

CONCLUTION OF THE CHAPTER ....................................................................................................... 39 4.

5.

EMPIRICAL DATA .............................................................................................................................. 40 4.1

INTERVIEW ANALYSIS PROCEDURE ......................................................................................... 40

4.2

INTERVIEW DATA ANALYSIS ..................................................................................................... 40

4.2.1

ESSENTIAL BENEFIT .......................................................................................................... 40

4.2.2

LEGAL CONSIDERATIONS AND TECHNICAL ISSUES ......................................................... 41

4.2.3

POSSIBLE IMPROVEMENTS .............................................................................................. 45

CONCLUSION .................................................................................................................................... 47 5.1

FUTURE PERSPECTIVES ............................................................................................................ 48

5.2

CONTEXTUALIZATION .............................................................................................................. 49

BIBLIOGRAPHY .......................................................................................................................................... 50 APPENDICES ............................................................................................................................................. 54

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LIST OF FIGURES Figure 1 (left): One of the longhouses from 4500 BC. (right): Reconstruction of a longhouse from 3000 BC.4 ............................................................................................................................................................. 6 Figure 2 (left): Pagoda from the 7th century in Japan. (right): Pagoda from the 11th century in China.5 6 Figure 3 : (left) Urnes stave church and (right) Borgund stave church from the 12th century in Norway.6 ..................................................................................................................................................... 7 Figure 4 (left): Leckie Building of 6 stories in Vancouver, Canada. (right): Perry House of 7 stories in Brisbane, Australia.8 ................................................................................................................................... 7 Figure 5 (left): “Tall Wood Residence” in Vancouver, Canada(right): “HoHo Wien” in Vienna, Austria.13 .................................................................................................................................................................... 9 Figure 6 : Approximate energy per volume unit consumed during production of various materials. .. 10 Figure 7 (left): The quantity of CO2 released into the atmosphere during the manufacturing process of materials along with CO2 stored on the left. (right): Net emissions of CO2 from the graph on the left.15 .................................................................................................................................................................. 10 Figure 8 : Process of CO2 storage during a forest´s life.18 ........................................................................ 11 Figure 9 (left): Maximum height of a building entirely made of combustible materials. (right): Maximum height of a building made of combustible materials either with a sprinkling system or fire resistance cladding. .................................................................................................................................. 13 Figure 10 : A building with the top floor between 12 and 22 m above ground.22 .................................. 13 Figure 11 : Maximum building heights of timber frame structures around the globe according to local regulations.27 ............................................................................................................................................ 15 Figure 12 (left): The structure of a tree. (right): Softwood´s microstructure consists of early‐wood (EW) and latewood (LW).30 ............................................................................................................................... 17 Figure 13 : Three directions of a flawless tree – L: Longitudinal (Vertical), R: radial and T: tangential (horizontal). .............................................................................................................................................. 18 Figure 14 : A configuration of a panelised (CLT) timber system. ............................................................. 19 Figure 15 : Locations of CLT producers around the world. (Interview presentation) ............................. 20 Figure 16 : The composition of columns‐beams structural system.39 ..................................................... 21 Figure 17 : The structure of a hybrid system under development.41 ...................................................... 22 Figure 18 : The charring diagram of mass timber under the fire exposure.42 ......................................... 23 Figure 19 : Diagrams of the measured char rates of the horizontal (left) and vertical (right) elements.43 .................................................................................................................................................................. 24 Figure 20 : The test of a panelised system made of CLT elements under a pressure load. (Interview presentation) ............................................................................................................................................ 25 Figure 21 : The diagrams of calculated cumulative shrinkage for a 12‐story structural comparison.46 . 26 Figure 22 : The structural system with “power floors” on the left and a completed building with envelope protection on the right. ........................................................................................................... 27 Figure 23 : Connection composed of slotted steel plates with dowels. ................................................. 28 Figure 24 : Currently the second tallest timber building in the world, “FORTE”. ................................... 29 Figure 25 : Panelised structural system consisting of CLT panels and prefabricated modules. ............. 30 Figure 26 : Stabilization of CLT panels by angled steel plates and brackets with screws. ...................... 30 Figure 27 : Wood innovative and design centre building on the left. Exposed timber element inside of building on the right. ................................................................................................................................ 32 Figure 28 : The construction process of a columns‐beams system. ....................................................... 33 Figure 29 : The overall structural section of used building materials. .................................................... 33 Figure 30 : The connection of the column and the beam by the hidden steel connectors. ................... 34

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Figure 31 : Lifecycle tower one building on the left. The plan’s drawing shows the core using a black thick line in the middle. Building configuration on the right. .................................................................. 36 Figure 32 (left): Prefabricated façade panels consisting of glulam. (middle): Installation of hybrid timber slab. (right): Mechanical services build between glulam beams. ................................................ 37 Figure 33 (left): The process of connecting the hybrid slab to the concrete core by steel brackets with pins. (right): The process of inserting the hybrid slab into the tubes on a prefabricated façade element. ................................................................................................................................................... 37 Figure 34 : Overview of the setup of the prefabricated façade element with the hybrid slab.66 ........... 38

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1. INTRODUCTION 1.1 BACKGROUND INFORMATION AND PROBLEM FORMULATION At the moment, half of the population on earth is living in cities and the future percentage of urbanization is predicted to dramatically grow up to 75% by 2050. Recently, considerable attention has been paid to approximately 3 billion extra inhabitants that will demand housing in the next two decades, which will be result of 40% rise in the world population. Moreover, the global construction industry has been an important issue in recent years, accounting for over 40% of total energy use on the planet and approximately 45% of global CO2 emissions.1 Statistical predictions play an important role in the construction industry, forecasting that the urban densities will grow, thus demanding the buildings to be bigger and taller. To put it shortly, the challenge for the construction industry is to accommodate the significant increase in population, especially in the cities, while significantly decreasing the carbon emission footprint.

Previous studies have shown that one of the methods for change can be utilizing the wood in the structural system of constructions. In the last decade, as a structural material, timber has attracted much attention from researchers around the globe. Their focus has been on studying the major advantages and issues of using wood compares to typical materials, such as steel and concrete. The studies have demonstrated that the significant benefits of wood are sustainability and environmental aspects. Another research from Yale University has found that the CO2 emissions in construction industry can be decreased in the range of 14 to 31 per cent by using engineering wood as a sustainable alternative to steel and concrete.2 The most interesting approach to this issue has been proposed by a leading Canadian wood architect Michael Green et al., who state that "The 19th century was the age of steel, the 20th of concrete. This century is the new age of timber."3 However, Denmark has a roots in traditional clay architecture and wooden structures are not commonly seen around the country. Technically, the typical building structure in Denmark is usually constructed either by a combination of concrete – bricks in residential buildings or steel – glass in the commercial constructions. Compared to other countries or cities, the trend of mid‐ and high‐rise timber building in recent years has had a significant upward direction. The world record for the tallest wooden building has changed various times in the past 5 years and it is likely to be broken even more often in the near future. The most recent one, a 14‐storey timber building, has been constructed in Norway. The notion of the highest timber building in the industry will surely only be a temporary one, because there are a

1

(Green Michael, Why we should build wood skyscrapers, 2013) (Alter Lloyd, 2014) 3 (Green Michael, 2016) 2

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number of other taller timber buildings under construction or in the projecting phase. Naturally, multi‐ story timber structures have also been built in other countries, for instance in Sweden, England, Germany, Austria, Canada, Australia and many others.

The first research question for this dissertation came up during the Q&A session at an international exhibition called Architectural@Work, which took place on 16‐17th of May, 2016 in Copenhagen. The primary focus of the exhibition was on wood in architecture, wooden products and architectural services. The presentation topics ranged from the reintroduction of engineering wood in housing to wooden architectural monuments in nature.

The problem involves an extensive spectrum of competent figures in our society who have effective influence on construction projects, starting from the client and/or developer, design team, up to the authorities and public community. Each area of professionals must have a certain degree of construction expertise. The problem statement of this dissertation is directed mostly towards architects, constructing architects, engineers and authorities, who have the highest impact on structural design as well as execution.

1.2 PRIMARY RESEARCH QUESTION The main goal of this paper is to investigate the key considerations of legislation and technical issues related to high‐rise timber structures in Denmark as well as the exploration of existing timber cases from abroad in order to carry out multi‐story timber construction in Denmark in compliance with its legislation and technical perspectives.

Can using timber structure for multi‐story building in Denmark be feasible in terms of legal and technical aspects while achieving economical construction at the present time?

1.3 SECONDARY RESEARCH QUESTIONS 1. What are the major benefits using timber as a structural material compared to steel and concrete?

2. What are the legal and technical issues that prevent the construction of the multi‐story timber structures in Denmark and, at the same time, what are the common challenges in the construction of high‐rise timber structures in other countries?

3. What are the areas that need to be changed and/or improved in the Danish construction industry in order to construct multi‐story buildings using timber as a sustainable alternative?

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1.4 RESEARCH OBJECTIVES The primary objective of this dissertation is to describe and analyze the benefits of timber, the current legislation and technical challenges related to using timber as a structural material for multi‐story buildings in Denmark. In this research paper, we explore the following points: 

The background establishment of multi‐story timber structures in general and the evolution of building regulations.



Comparison and evaluation of beneficial characteristics of timber in relation to conventional materials of steel and concrete.



Assessing whether the building regulations regarding the multi‐story timber structures of more than 4 stories are appropriate/ready or not.



Identification of the primary aspects of timber as a structural material in relation to multi‐story buildings.



Finding out whether tradition, legislation or construction are the main obstacles preventing the building of multi‐story timber structures in Denmark.



Investigation of recent major issues of multi‐story timber structures in other countries.

1.5 DELIMITATION OF WORK Unfortunately, in following pages, only two primary benefits of timber are explored while others are only touched upon, however, all of them will be considered for final conclusions. The key limitation of this research is that it is primarily focused on Danish construction industry with regards to the timber structural solutions of tall buildings in other countries. All existing timber structures that have been constructed until now will be considered. The major restriction will be that only timber structures higher than 4 stories will be analyzed, while also only the current building legislation of Denmark will be followed.

However, studies on high‐rise timber structures in Denmark as well as abroad, are still lacking. To the author´s best knowledge, very few publications can be found that discuss the issues of using wood as a structural system in Denmark, whereas more literature is available for the countries abroad.

The reader´s expectation should be to gain new perspectives about the evolution of timber structure, the benefits of timber compared to steel and concrete materials, the regulation regarding the high‐rise timber constructions, the technical principles in multi‐story timber structures and the major challenges in constructing multi‐story timber buildings abroad.

The paper has been written from a constructing architect´s point of view with the highest emphasis on material and feasibility research.

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2. METHODOLOGY 2.1 CHOICE OF THEORETICAL BASIS AND RESEARCH METHODOLOGY The dissertation research is conducted as an investigatory and descriptive study and a primary analytical research. The data consists of primary sources of other relevant dissertations about high‐rise timber structures; and secondary sources: building regulations and guidelines, case studies, reports, journals, articles and books, all related to the subject. The mentioned sources provide overall knowledge and understanding of what the timber´s use benefits are in building structures, what the challenges regarding high‐rise timber structures are and how the challenges of high‐rise timber construction can be addressed in Denmark as well as in general.

For the empirical part, the data was collected in the form of interviews with selected specialists in the field of building industry whose expertise is relevant to timber structures, but each with different specialization.

The author chose to interview an architect from Sangberg Architects, who was also the presenter of reintroduction of timber in housing during the international exhibition event in Copenhagen, which served as the inspirational starting point for this research paper; followed by the Senior Engineer of Fire Safety and Structure from Rambøll, who leads an initiative to build more constructions using wood in Denmark; and a DTU student, who wrote a recent master dissertation about multi‐story timber structures. Secondly, based on their knowledge and experience with designing timber constructions related to Danish construction, the interview data was evaluated in a qualitative research manner in order to gain current information and insight in the field towards formulating the primary data.

Moreover, it was possible to utilize the empirical data in combination and comparison to the theoretical data to answer the secondary questions of the research and eventually the primary one. Throughout the whole process, the supervisor´s guidance and counselling was of great help in undertaking and structuring of this academic research paper.

Additionally, at the beginning of the research, it has been considered to be undertake this paper using a case‐study method, however, during the research process, it has changed to a typical procedure.

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2.2 CHOICE OF WORKING METHOD The dissertation is divided into 5 main chapters: 1. Introduction: involves selection of the topic, problem formulation, research question with secondary research questions, research objectives and delimitation of work 2. Methodology: includes choice of theoretical basis and research methodology, and choice of working method 3. Theoretical Basis: describes, evaluates and interprets the evolution of timber structures and regulations, the major benefits of timber, the regulation of multi‐story timber structures, timber as a structural material, structural systems and wooden products and analyses the common challenges of multi‐story timber construction from abroad.

4. Empirical Data: involves evaluation of the qualitative data acquired through interviews in a descriptive, discussion and comparative manner, to answer the secondary research questions and ultimately the primary one using a combination of secondary data and personal experience.

5. Conclusion: includes subjective final conclusion, future perspectives and conceptualization towards the next phase – the bachelor project.

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3. THEORETICAL BASIS 3.1 EVOLUTION OF HIGH‐RISE TIMBER STRUCTURES In order to understand the importance of timber structures and some of the issues confronted in applying it nowadays, it is important to simultaneously have a look at the historical evolution of timber structures and regulations in the construction industry.

Throughout the history of humanity, wood has always been used to build the roof above people´s heads. Wood as a construction material reaches deep into the history, considered as one of the oldest and most widely used construction material. Wood has also been the material used to create certain necessary tools. Through the rich history of wood, the first timber shelters/buildings, called longhouses, can be dated back to 4500 – 3000 BC. Typically, longhouses were erected for agricultural purposes by farmers, however, they did not have a long life time and reconstruction was required every twenty years, as shown in Fig. 1.4

Figure 1 (left): One of the longhouses from 4500 BC. (right): Reconstruction of a longhouse from 3000 BC.4

Some the of historical multi‐story timber structures from around 800 to 1400 years ago can still be found in Japan, China or Norway and these days, the temples, also called pagodas, are the most traditional multi‐story timber structures in history. Those pagodas have already been constructed in Asia for centuries while they have also endured the natural phenomena like wind, humidity, earthquakes, etc. One of the oldest wooden pagodas from the 7th century that is 32 meters tall at 5 stories still exists in Japan. The 32 metres pagoda is strengthened with a centrally located column, as depicted in Fig. 2. Furthermore, the world´s tallest wooden pagoda comes from 11th century and it is located in China’s earthquake zone, having 9 stories that reaching 67 metres with an additional 11 metre spire on top.5 The pagoda is built entirely from wood with circular shape and wooden structure supporting the five visible stories and four hidden floors by a central column, as can be seen in Fig. 2.

Figure 2 (left): Pagoda from the 7th century in Japan. (right): Pagoda from the 11th century in China.5

4 5

(Leonardo da Vinci, Pivotal Project, 2008) (Gerard Robert, Victoria Valencia, and Jen Kinney, 2014)

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Other known historical multi‐story timber structures, also called stave churches, can be found in Norway. Both of the oldest Scandinavian churches are made entirely from wood and in addition, they were built by a technologically advanced type of timber construction, which includes large columns, beams and arches, as illustrated in Fig. 3. The churches are two of the 40 remaining timber churches in the world. Even though the churches were built in the 12th century, they still stand even after being exposed to the natural forces for so long.6 Figure 3 : (left) Urnes stave church and (right) Borgund stave church from the 12th century in Norway.6

Moving closer to the present times, more contemporary high‐rise timber structures were built a century ago in Canada and Australia. In Vancouver, Canada, a 6‐storey office and industrial building “Leckie Building” was constructed in 1908, while 15 years later, a 7‐storey business building called Perry House was erected in Brisbane, Australia. Both of the buildings can be seen in Fig. 4. A building technique known as brick‐and‐beam construction was used back in the early 20th century, where the building structure consists of columns and a beams from mass timber, supporting the external façades made of brick. The brick‐timber method allowed the creation of large open rooms, utilizing the great span of timber. Both of the mentioned buildings were constructed before the introduction of regulations for timber construction regarding fire limitation. In terms of regulations, the height of the buildings,

story

numbers and/or wide areas had not been specified yet.7 Figure 4 (left): Leckie Building of 6 stories in Vancouver, Canada. (right): Perry House of 7 stories in Brisbane, Australia.8

The history of timber construction was marked by several large fires that occurred in urban areas around the world from early 1700´s until the middle of the 20th century, which motivated the introduction of regulations regarding combustible materials. Due to uncontrolled and undivided wooden constructions (design of fire safety), one fire happened in the Danish capital city, too. The

6 7

(Brooke Bob, 2002)

(Wood Skyscrapers – Organization, 2013)

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largest fire in the history of Copenhagen began in 1728 and lasted for 3 days. It destroyed around 28% of the city and another 20% of population was left with no home. The reconstruction works took 9 years.8 That was the reason behind the specified strict limitations in building regulations for combustible constructions, such as the presence of automatic sprinkling system, passive fire protections, building height, size of rooms and building distance from the street. It was a decisive time when timber was officially replaced in multi‐story buildings by non‐combustible materials – steel and concrete.

One of the first contemporary regulations in Denmark was implemented in 1961. Additionally, mass timber elements such as glued laminated timber came to be utilized in sport halls during the dry climate condition of that period.9 Performance‐based regulations as a new approach began to be introduced to the market in second half of the 20th century, firstly in United Kingdom. They were adjusted in 1985 and again revised 6 years later. Following United Kingdom, New Zealand implemented performance‐based regulations in 1992, with Norway in the late 1990´s. In the past 2 decades, a number of other countries also introduced amendments to their regulations, including Denmark.10 Nevertheless, first part of performance oriented regulations in Denmark was implemented in 1982, with the final one created in 2005.11 The integration of performance‐based regulations has resulted in a dramatic growth of multi‐story timber buildings during the last decade. The multi‐story timber buildings are nowadays becoming increasingly popular, also in consideration of related new regulations with combination of CO2 reduction and prefabrication improvement of mass timber products. Additionally, the highest number of multi‐story timber buildings has been constructed in the last 10 years and in the same time, the tallest timber structure record has been broken several times. At the moment, “Tree” is the holder of the world record for the tallest timber building at 49 metres in Bergen, Norway. The runner‐up for the global record with 32.2 metres is “Forte” in Melbourne, Australia. More detailed information regarding both buildings will be presented in chapter 3.6.1.

The world record is surely going to continually change due to other buildings which are either already being constructed or in the planning phase. One of such projects is the “Tall Wood Residence” in Vancouver, which will be completed in 2017.12 It will be a residential dormitory for students consisting of 18 stories at 53 metres, as depicted by Fig. 5. The dormitory will not remain the tallest timber building

8

(Copenhagen Portal, regularly updates) (Global Buildings Performance Network (GBPN), 2010) 10 (Minik Lange Pedersen, 2016) 11 (Global Buildings Performance Network (GBPN), 2010) 12 (McLean Steve, 2016) 9

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for a long time, because in the same year, a new such building is expected to be completed in Vienna.

As illustrated in Fig. 5, the structure called “HoHo Wien” with 24 stories and the height of 84 metres will be the tallest timber building ever built. Furthermore, HoHo Wien will be constructed using composite elements ‐ timber‐concrete, also named as hybrid structure whereas the dormitory in Vancouver is proposed to be constructed entirely from mass timber elements that are a combination of a panelised structural system with a columns‐ beams system.13 Figure 5 (left): “Tall Wood Residence” in Vancouver, Canada14 (right): “HoHo Wien” in Vienna, Austria.13

CONCLUSION OF THE CHAPTER To summarize, the evolution of using timber in constructions has been slowed down by huge conflagrations that led to the limitations in ensuing regulations. These continued to influence the Danish as well as many other states’ construction industry. Nonetheless, in the last 20 years, the performance‐based regulations and development of heavy and mass timber products have brought new possibilities to use timber in building even taller structures.

It is also notable that the evolution of using timber as structural material will continuously be promoted by new buildings in the near future and, personally, it will be extremely exciting to see how impressive the next high‐rise timber structures will come to be. The evolution of timber in tall constructions is sure to continue.

3.2 BENEFITS OF TIMBER USE IN CONSTRUCTION The construction of buildings around the world typically consists of the most common structural materials; steel, concrete and timber. Each material has its pros and cons. For instance, steel contributes with its high off‐site production, reducing noise and dust on construction site, and in the same way as concrete enhances strength, which also provides great versatility and limitlessness of aesthetic possibilities.

With the huge advantages of steel and concrete in mind, there are two worthy considerations of using timber in construction that steel and concrete do not provide. They are the low consumption of energy

13 14

(Arnaud‐Goddet Nicolas, 2016) (McLean Steve, 2016)

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and the potential of carbon emissions reduction. The purpose of this chapter is to explore both of these beneficial aspects as well as pinpoint some additional advantages.

The energy demand for building materials is based on life cycle assessments (LCA). Various research assessments show that to produce timber, less energy is consumed when compared to other materials such as concrete and steel. The proposition is that timber’s manufacturing process requires much less work. The Fig. 6 outlines the amount of energy consumed in kWh/m³ to manufacture the rough sawn timber, concrete and steel. As can be

APPROXIMATE ENERGY DEMAND FOR MATERIAL PRODUCTION (kWh/m³)

seen,

the

energy

demanded

for

manufacturing steel is approximately

80000

74000 kWh/m³, while the production of

60000

74000

40000

200

20000

concrete requires around 1300 kWh for

1300

the same amount, and rough sawn timber

0

ROUGH SAWN TIMBER

CONCRETE

just around 200 kWh/m³.

STEEL

Figure 6 : Approximate energy per volume unit consumed during production of various materials. 15

The energy used in manufacturing the building materials comes mostly from non‐renewable energy sources, meaning that more CO2 emitted into the atmosphere, contributing to the global warming. The amount of CO2 released and stored during manufacturing process of building materials and the net CO2 emissions can be found in Fig. 7. A closer look at the data indicates that net emissions of CO2 are only released in the manufacturing of steel at 5320 kg/m³ and concrete at 120 kg/m³, while timber results in a negative level of ‐235 kg/m³.

CO2 RELEASED AND STORED IN THE MATERIAL'S MANUFACTURING (kg/m³) 6000

5320

5000

5320

4000

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‐250

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‐235

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Figure 7 (left): The quantity of CO2 released into the atmosphere during the manufacturing process of materials along with CO2 stored on the left. (right): Net emissions of CO2 from the graph on the left.15

15

Numbers in bars figure based (Forest and Wood Products Research and Development Corporation, 2004)

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In order to utilize the potential of carbon emission reduction, the forest resources have to be used in a practical manner. Forests are a primary carbon storage for our planet and when plantation of a new forest is well managed, it can remarkably add to carbon reduction in the atmosphere. The photosynthesis process of tree emits oxygen to the atmosphere while in the same time absorb carbon dioxide. The CO2 is accumulated in tree’s tissue during its lifetime, and thus, every form of timber is considered as a great “carbon storage”.16 Wood has amazing capacity to store carbon dioxide and provide the reduction. Specifically, one cubic meter of wood is able to accumulate one tonne of CO2.17 However, the tree´s growth as well as the ability of releasing O2 and storing CO2 continuously slows down, as illustrated in Fig. 8. More importantly, unless the wood enters

the

process

of

decomposing, dying or burning, carbon dioxide stays in the trees after they are cut down.18 Figure 8 : Process of CO2 storage during a forest´s life.18

Wood is a material, which is capable of significantly contributing to both of the parameters –less embodied energy and simultaneous storage of the CO2. There are additional benefits of timber, outlined in the following points: 19       

Shorter construction time due to prefabrication off‐site leading to a more accurate, higher quality building; Good thermal and fire performance properties; Wood is strong and light due to the cellular structure of the material resembling a bone; Lightness of timber allows for easier transportation and smaller size foundation; Easy manageability on the building site and much less ensuing noise; Made of natural and renewable source – trees; Visual quality, healthy and comfortable indoor climate.

CONCLUTION OF THE CHAPTER It is important to note that different publications provide different values about the required energy used in manufacturing of the building materials. In the case of concrete, the numbers approximately range from 1700 to 2100 kWh/m³, from 82000 to 124000 kWh/m³ for steel, compared with numbers presented in Fig. 6. This is due to the fact that manufactures have different approaches and also use

16

(Kremer, P. D., and Symmons, M. A, 2015) (Chadwick Dearing Oliver, Nedal T.Nassar, Bruce R. Lippke, James B. McCarter, 2013) 18 (Minik Lange Pedersen, 2016) 19 (Arup, 2015) & (White Gavin, Dowdall Alan, Neve Oliver, 2015) 17

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different measurement methodology. Additionally, some sources state that the values for concrete include reinforced steel, whereas others do not. Moreover, Fig. 6 indicates the energy demands for rough sawn timber, while CLT or glulam are required further fabrication, demanding more energy. For comparison, processed timber needs around 300 kWh/m³ and glulam demands proximately 1200 kWh/m³. The most of the required energy to produce the mass timber elements is consumed during the drying process up to a certain moisture content. However, no matter how the life cycle assessment (LCA) is calculated, timber comes out as a clear winner compared to concrete or steel. A similar scenario is performed in Fig. 7, where different sources provide various numbers. Nonetheless, they are in relevant scope.

Although steel and concrete have great material performance, they are also materials with very high contribution of greenhouse gas emissions. Overall, steel makes up about 3% of greenhouse gas emissions and concrete over 5%. Both are materials of the last century. Therefore, the global goal is to reduce the carbon footprint, and the engineering wood is a desirable material for the construction industry. Trees are known as a natural material within our ecosystem that filters the atmospheric air by absorbing carbon dioxide, while releasing oxygen. In this sense, the wood is a fantastic storage material too. It would store even more carbon dioxide if a higher amount of timber was stored in the building, as furniture or other fixtures.

3.3 BUILDING REGULATIONS In the following few pages, with global comparison, the building regulations regarding high‐rise timber structures in Denmark will be investigated. This chapter discusses regulations relevant only to combustible materials and applicable to tall buildings.

One of the primary rules of building regulations in Denmark is to regulate the height and area and also put forth demands on fire‐resistance ratings of combustible as well as non‐combustible constructions.

While the combustible constructions have been significantly limited, the non‐combustible constructions have been categorized separately. Simultaneously, in the same way as the development of building regulations in other countries, Danish norms are incorporating new methods, materials and technologies that are to be utilized during the design and construction process.

Today´s height and area regulations are based on the historical evolution of the construction industry.

They used to be even more severe in terms of fire protection standards than is the case nowadays. For example, the maximum building height had always been linked to the highest point that firefighters could reach using ladders and it depended on water hose pressures as well. At the moment, the limitation of the height is not that important in terms of firefighting because of dramatic improvements in firefighting technology in the last 3 decades, such as the automatic sprinkling system. In addition, the

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legislation regarding combustible constructions and fire safety has continuously developed since the 1990s and still has the tendency to gradually improve.20

3.3.1

BUILDING REGULATIONS IN DENMARK

The required building height for combustible constructions has not significantly changed over time in Denmark. The maximum height of the top‐level floor for a combustible structure is not allowed to exceed 5.1 meters without an applied active measure (automatic sprinkling system) which roughly equals to a 2‐story building, as illustrated in Fig. 9. With active or passive measures such as a sprinkling system or sufficient cladding class K2 60 A2 s1, d0 [a 60‐minute fire protection system], the uppermost floor is not allowed to exceed 12 meters, which is equivalent to a 4‐story building, as shown in Fig. 9.21

Figure 9 (left): Maximum height of a building entirely made of combustible materials. (right): Maximum height of a building made of combustible materials either with a sprinkling system or fire resistance cladding.22

In Denmark, every other building, with the uppermost story being between 12 and 22 m above the ground, the structural elements are required to comply with the rating of R 120 A2‐ s1,d0 [120 minutes], as illustrated in Fig. 10.

Figure 10 : A building with the top floor between 12 and 22 m above ground.22

The supplement in Danish guidelines for a building where the uppermost story is between 12 and 22 m above the ground and beyond 22 m states that, “the load carrying constructions in a building are considered to have sufficient fire resistance if it can be documented that the building will maintain stability throughout a 120‐minute standard fire test. This means that key elements and the anchoring of such elements have a fire resistance of minimum 120 minutes. The construction may include building

20

(MGB Architecture + Design, Green Michael, 2012) Based on (Danish Energy Agency, 2nd version, 2016, “Collated examples of fire safety measures in buildings 2012.”)

In addition, the same requirements are also confirmed by other two guiding manuals: (Danish Enterprise and Construction Authority, 2004, “Information on structural fire safety.”) as well as (Bjarne Lund Johansen, Anders Bach Vestergaard, translated by Peter John Andersen, 1st version, 2011, “WOOD 66 guidelines for educational purposes.”)

22 (Danish Energy Agency, 2nd version, 2016) 21

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components with a fire resistance of less than 120 minutes if it can be documented, for example by use of the codes of practice, Eurocodes etc., that the building will maintain its stability regardless the collapses and possible fall of parts of the construction. Further it shall be documented that the fire sections of the building remain intact throughout the necessary time span. With regard to fire compartments and fire divisions this time span is normally 60 minutes. Key elements are such elements whose function is vital to the overall stability of the building. The fact that these elements may be able to withstand a 120 minutes standard fire test is not considered sufficient as such.” 23 Moreover, a building height of over 22m is evaluated separately in terms of fire strategy and as is well‐ known, height brings further challenges in terms of mechanical installations. In one of Danish guidelines, a building height of over 22m is separated into divisions of buildings with the uppermost story between 22 and 30‐40m above ground; less than 60m; and in the range of 60 to 100m. The main reasons behind the specific division to the 30‐40m level are to ensure appropriate water pressure, longer evacuation time, firefighter elevator, access to the roof, automatic sprinkling and alarm system, and certain corridor width including stairs. The next division of less than 60 m is due to higher demands on action preparation and primary escape of people by lift, which are secured by additional aspects, such as water‐boosted pumps, pressurised ventilation system and secondary power supply. Buildings with height of up to 100m further require two firefighter elevators, special strategy for water‐filled hoses as well as different demands on core elements.24 Furthermore, the fire section areas range from 600 m² to 2000 m² depending on the usage category for buildings protected by passive measures, whereas fire section area protected by active measures varies from 2000 m² to 10 000 m², also depending on the usage category. The sizes of fire sections apply for both non‐combustible as well as combustible constructions.25 In addition, the latest building regulations and supporting policy in Denmark involve contemporary and productive implications. Regulations demand mandatory computer modelling as well as ecological design considerations. Primarily in terms of energy, regulations require blow‐door and HVAC testing for all types of buildings; renewable energy sources included in energy calculations, such as thermal pumps

23

Based on (Danish Energy Agency, 2nd version, 2016, “Collated examples of fire safety measures in buildings 2012.”)

In addition, the same requirements are also confirmed by other two guiding manuals: (Danish Enterprise and Construction Authority, 2004, “Information on structural fire safety.”) as well as (Bjarne Lund Johansen, Anders Bach Vestergaard, translated by Peter John Andersen, 1st version, 2011, “WOOD 66 guidelines for educational purposes.”)

24 (Aalborg, Odense, Aarhus, Copenhagen fire and building authorities, 2013) 25 Based on (Danish Energy Agency, 2nd version, 2016, “Collated examples of fire safety measures in buildings 2012.”)

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or solar panels; voluntary low energy categories; and a national goal of just 25% of energy used in the buildings from 2020.26

3.3.2

BUILDING REGULATIONS AROUND THE GLOBE

The regulation of building heights for combustible constructions across the world differs substantially.

Russia holds the strictest regulations with the maximum limit of 3 stories. Countries that have no exact height limit are United Kingdom, Norway, New Zealand and Australia. These countries regulate the minimum level of safety performance and evaluate each project individually, which allows the adoption of alternative solutions. They are utilizing the advantage of performance‐based building regulations more than any other countries.

Besides the above‐mentioned countries with alternative solutions instead of regulations, there are countries such as Austria and North America. In Austria, one of its architects in 2008 came to the conclusion that under the then‐current building regulations a twenty‐story wooden building was already allowed. In North America, British Columbia (BC) has been the leader in the implementation of building regulations in 2009 that permit a greater utilization of wood construction in taller buildings.

The BC Building Codes were amended to allow wood construction of up to 6 stories for residential function. Elsewhere in North America, several other provinces and states have been conducting their own research, based on British Columbia´s lead.27 The maximum limits of building heights for timber construction around the planet are shown in Fig. 11.

Figure 11 : Maximum building heights of timber frame structures around the globe according to local regulations.27

26 27

(Global Buildings Performance Network (GBPN), 2010) (MGB Architecture + Design, Green Michael, 2012)

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CONCLUTION OF THE CHAPTER To conclude, the legal realities regarding tall combustible structures in Denmark and the height limit of high‐rise timber structures originally come from Collated examples of fire safety measures in buildings as well as other similar guiding manuals, which should, however, only be used as a guiding tool for designers in the building sector. Therefore, the most common misunderstanding in the Danish timber construction sector stems from the fire guidelines, that is, a timber structure is prohibited to be built above four stories. It is one of reasons why Denmark is partially behind some other countries in terms of timber construction. Legally, there are no barriers, because the Danish fire regulations are designed as performance‐based, meaning that any type of building is allowed as long as the building can be well‐ documented. Nonetheless, the above‐cited supplement, taken from the fire guide manual, only confirms that the regulations function as performance‐based. Still, using performance‐based building regulations requires a more collaborative process among all project parties than building traditionally.

“As explained by the fire safety technology advisor Anders B. Vestergaard from DBI during the presentation debate at the School of Architecture in Copenhagen earlier this year, timber construction is relatively rare in Denmark, though it is rather a manifestation of tradition than of engineering problems.” 28 It has been the case that regulations have been implemented in various countries, seeing mostly 2‐ story wooden houses or “low‐rise” commercial buildings made of timber. Regulations are especially persisting in countries less open to innovation and invention. On the other hand, unlimited building regulations have brought new possibilities in some countries that have already given rise to prominent timber constructions.

3.4 WOOD AS A STRUCTURAL MATERIAL To achieve technically proper performance of high‐rise timber structures, it is important to understand the theory of wood aspects and structural behaviour of systems. In this chapter, we will focus on some key characteristics of wood and production of main mass timber products and structural systems that we could use to develop high‐rise timber constructions to maintain the stabilizing system. The chapter is divided into two sub‐chapters; in the first one, we explain the types of tree and their structure, and how three different directions of tree influences the sawing patterns; while the second sub‐chapter describes mass timber products with their manufacturing and transportation, along with different structural systems.

28

(DBI – Danish Institude of Fire and Security Technology, 2016)

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3.4.1

OCTOBER, 7 2016

CHARACTERISTICS OF WOOD

Timber is a natural and ecological material, which comes from forests. Botanical trees are categorized into softwood and hardwood for solid timber. Under hardwood trees, we categorize broad‐leaved trees that change their leaves each growing season once, whereas evergreen trees are grouped under softwood and are cone‐bearing trees with needles. Softwood has lower density and strength as well as less durability than hardwood, and therefore it is cheaper. In Denmark, softwood is used to produce engineering timber, such as glulam. Additionally, cross‐laminated timber (CLT) panels are also primarily made of softwood.29 As illustrated in Fig. 12, the basic structure of a tree is composed of a pith in the middle, heartwood, sapwood, cambium and inner and outer barks. The annual rings are indicated by two different colours, due to the fact that grains grow with different density during the growing seasons, spring and autumn.

During spring, the cell wall is thinner in grains than during autumn, which are categorized into early‐ wood (EW) and latewood (LW). This means that latewood is denser and stronger than cell walls of early‐ wood. Latewood can be 3 times denser than early‐wood. 30 Figure 12 (left): The structure of a tree. (right): Softwood´s microstructure consists of early‐wood (EW) and latewood (LW).30

A flawless tree is measured by three different approaches that are – longitudinal (L), tangential (T) and radial (R) directions, as shown in Fig. 13.

The physical structure of a tree is considered to be an orthotropic material, because of dissimilar properties in each direction. Even though a tree has three primary directions, strength, stiffness and other properties are significantly unequal only in two main directions – vertical (longitudinal) and horizontal (tangential) directions to the grain of a tree. The strength and stiffness is much larger in the vertical direction to the grain than the horizontal one.31

29

(Leonardo da Vinci, Pivotal Project, 2008) (Minik Lange Pedersen, 2016) 31 (Leonardo da Vinci, Pivotal Project, 2008) 30

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Figure 13 : Three directions of a flawless tree – L: Longitudinal (Vertical), R: radial and T: tangential (horizontal).32

In order to get the highest strength and stiffness of timber, trees are sawn along the grain in the shape of various sawing patterns. After timber fabrication, timber has to be classified according to its strength. The grading process is done either by a certified grader or an appropriate machine according to specified standards. A grader manually evaluates the timber depending on the size, technical properties and blemishes. A machine is able to examine the deflection and standard compliance among another technical abilities of machine grading.33

3.4.2

TIMBER STRUCTURAL SYSTEMS AND PRODUCTS

Timber products ranging from “lightweight” to “heavyweight” and production and building methods have made significant progress over time. Generally, timber structures are ordinarily classified to low‐ and rarely high‐ rise buildings. Low‐scale timber buildings typically use a lightweight framing system, which leads to size and scope limits compared to a heavyweight structural system. Conversely, a heavyweight structural system mainly increases the flexibility to construct high‐rise buildings. Both structural systems are utilized for different applications while they differ in the thickness of the cross‐ section. Still, there is no threshold level that defines exactly which one is “lightweight” or “heavyweight”. Commonly, each piece of solid timber with thickness over 80 mm is considered “heavy”.

Normally, lightweight construction consists of small‐size studs that are formed with cladding to the walls or floors elements. On the other hand, heavyweight construction is made of numerous pieces of timber and large‐size prefabricated elements that connect into a superstructure. Under Heavy Timber, we understand the column and beam elements, while Mass Timber is known as solid‐wood panels that together allow the building to be more spacious and taller. In following pages, the combination of both systems will be referred to as Heavy Timber system.

Mass Timber structural system is one of the framing styles in timber construction, called Panelised system, and consists of entirely cross‐laminated timber (CLT) panels. Another framing system, called Columns‐Beams system, is a Heavy Timber structural system consisting of numerous large elements of wood‐based products from glue‐laminated timber, also named glulam (GLT); laminated veneer lumber (LVL) and laminated strand lumber (LSL), among others. In addition, a Heavy Timber structural system usually involves CLT panels within other products. Each one of the products has their own individual

32 33

(Minik Lange Pedersen, 2016) (Leonardo da Vinci, Pivotal Project, 2008)

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properties, and therefore, it has to be applied correctly according to its purpose (load or non‐load bearing).34 Overall, a multi‐story timber building can be constructed utilizing two types of Heavy Timber structural systems; the panelised system and the columns‐beams (post‐beam) system; and also one type of a hybrid system, which uses the combination of materials.

PANELISED STRUCTURAL SYSTEM A contemporary panelised system consists entirely of solid cross‐laminated timber (CLT) panels. A whole load‐bearing system is made of CLT panels that can be oriented vertically as walls and horizontally as floors and roofs. Normally the wall panel is composed of 3 to 5 layers of timber, while the floor and roof elements are manufactured from 5 to 7 layers to ensure greater stability. CLT panels are stacked on top of each other, creating internal and external partitions. The primary advantage of CLT panels is the off‐site prefabrication that can already come as pre‐cut with holes and tolerances. The panels are typically stabilized either by brackets or fasteners while using a lot of screws, nails or bolts. This type of structural system can also be manufactured into modules. The off‐site prefabrication leads to a fast construction process, reduces the working cost, and at the same time increases the precision of the elements while avoiding potential mistakes on the site.35 Figure 14 : A configuration of a panelised (CLT) timber system.36

Even though the cross‐laminated timber (CLT) panel was invented in Austria more than 20 years ago, it is still relatively new on the market. The CLT is a solid based panel of boards stacked crosswise on top of each other consisting of several layers, sometimes also called “jumbo plywood”. The layers are glued together on wide faces of lumber and sometimes they are also glued on the narrow faces. The CLT panels have at the least 3 layers in an orthogonally alternating orientation to the neighbouring layers.

The build‐up of panels is mainly determined by the load‐bearing performance which results in a specific thickness. A usual cross‐section of panels has odd number of layers which vary between 3 and 7. In some special cases, the conservative layers may be orientated in the same direction in order to increase

34

(Bejder, Anne Kirkegaard, 2016) (Minik Lange Pedersen, 2016) 36 (Grondahl Mika, 2010) 35

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the structural capacity. Structural installation of CLT refers to the outer skin orientation corresponding to the primary direction of the load‐bearing capacity.37 The market offers CLT panels of up to 500 mm in thickness and length of up to 24 m, however, the transportation and the crane lifting capacities are limited. CLT panels are rather new products on the market and as of now there are not many manufacturing sites. 90% of panel producers are located in Europe, specifically more likely in the area around Austria and the south of Germany. The remaining 10% of producers are located in Canada and one in New Zealand, as seen from Fig. 15. The number of mass timber producers is visibly expanding following the growth of timber buildings around the globe.

Figure 15 : Locations of CLT producers around the world. (Interview presentation)

Furthermore, the transportation of mass timber products, especially CLT, is able to deliver 3 to 4 times the number of elements by one truck compared to prefabricated concrete elements.38 It is due to the fact that timber is a much lighter material than conventional materials. The estimated average density of timber is around 450 kg/m³, whereas for concrete it is approximately 2400/m³ and for steel 7800 kg/m³.

COLUMNS‐BEAMS STRUCTURAL SYSTEM As opposed to the panelised system, the columns‐beams system utilizes a wider spectrum of engineering timber products. It is composed of CLT and glulam or LVL and LSL elements.

A product made of dimensional lumber, which is especially utilized in columns‐beams structural system, is called Glulam (GLT). GLT consists of no fewer than 4 lumbers that are glued together parallelly with structural adhesives. The dimensional lumber is cut along the grain in order to reach high stiffness and strength in one direction. Therefore, the final product – glulam can be found in various sizes and

37 38

(KLH Massivholz GmbH, 2012) (Cross Timber Systems, 2016)

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strengths across the timber industry. Glulams are used as columns or beams and they are an appropriate product for large constructions where long‐spans are required.

Figure 16 : The composition of columns‐beams structural system.39

Contrary to CLT and glulam, Laminated Veneer Lumber (LVL) is made of thin laminated layers of wood veneers glued together by waterproof structural adhesives. The veneers are produced by rotary peeling of logs that are afterwards dried and sorted depending on their stiffness and strength. Then, +/‐ 3mm layers of veneers are coated with structural adhesives and are put into a hot press. The hot press produces a compressed board that is sawn into reasonable lumbers.

Another product made of veneers is Laminated Strand Lumber (LSL), sometimes also called Parallel Strand Lumber (PSL). LSL is a structural composite lumber made of the same veneer, but in a smaller size than LVL. The veneer sheets are cut into small, long pieces that have knots or other blemishes, and are used to fabricate the laminated strand lumber. In fact, LSL is a by‐product of LVL and produced by the same technique using steam injected compression. Normally, LVL and LSL can be utilized for a secondary structure in multi‐story timber buildings as mullions in a glazed façade system as well as columns and beams of smaller sizes when compared to glulam.

“If you are going to make more money by cutting down your trees to grow crops, you are going to do that. But if you are incentivized to re‐grow trees and turn them into laminated‐strand lumber you are really talking about farming building. We grow our food; the earth has got to grow our homes as well, as explained by Canadian wood leading architect Michael Green.”39 Mass Timber products require improvements in the approach of how we manage and harvest the forest and how we manufacture the products from raw wood to the value‐added product. The products such as LVL and LSL can provide the benefit of a lower mark lumber, while in another respect it would not be used for structural purposes. After the wood is harvested, the logs are transported to a sawmill where they are cut into the required dimensional lumber. Then, the wooden chips are broken down or planed into veneers. While it might have been considered as a rubbish, it is actually either used as cellulose to heat‐up the dryer during lowering the moisture content or as structural composition. The

39

(Green Michael, 2013)

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LVL and LSL´s advantage is just one of the examples that show the potential of Mass Timber products and how they could contribute to the construction and the timber industry.40 HYBRID STRUCTURAL SYSTEM AND COMPOSITE ELEMENT Besides the panelised system and columns‐beams system made entirely of mass timber, a hybrid system is a composite system consisting of a combination of timber‐concrete or timber‐steel. Nowadays, the timber‐ concrete combination is using a concrete core of a building with mass timber columns and composite floor elements. A usual composite floor element is composed of a concrete topping slab, which is supported by CLT panels or glulam beams. A second combination under development right now – timber‐steel, similarly to columns‐beams system, consists of steel beams.41 Figure 17 : The structure of a hybrid system under development.41

The reason to develop a hybrid system is to utilize the beneficial attributes of each material and eliminate the weaker parameters of the other one. Timber can benefit from the concrete’s stiffer structure, higher fire resistance and higher acoustic rating, whereas steel can offer big‐size resistance products.

CONCLUSION OF THE CHAPTER To conclude the chapter, by exploring wood´s characteristics we are able to see why timber products are the way they are now. Due to two various strengths in vertical and horizontal directions, it is much harder to design a timber structure, whereas a typical building is made of steel or concrete. However, diverse large‐scale timber construction design is manageable either by each of the system separately or by a variant combination of panelised system and columns‐beams system that makes multi‐story timber construction possible.

Moreover, there is some scepticism about connecting timber with concrete, how a natural material as wood can be joint together with rigid concrete. Therefore, a hybrid system requires a lot of testing and modelling before the execution in order to achieve buildability from a technical point of view. Currently, different structural hybrid systems are under development in the construction field by Austrian and American experts. It is going to be interesting to see if concrete can work together with timber.

40 41

(MGB Architecture + Design, Green Michael, 2012) (Skidmore, Owings, Merrill, LPP, 2013)

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3.5 OTHER PARAMETERS REGARDING MULTI‐STORY TIMBER CONSTRUCTION Except for structural matters, there are technical aspects behind high‐rise construction such as fire safety and shrinkage and moisture of a natural material. A good design plan of high‐rise timber construction also considers the mixture of fire resistance safety measures, obtainable humidity in construction as well as maintaining possible shrinkage in connections. It is important for architects, engineers, constructing architects as well as other professionals in the construction industry working at a high‐rise timber project, to understand the importance of all the aspects that can further mutually influence each other.

In this chapter, we will focus on the methods of protecting the timber constructions against fire, what the normal moisture content is and how shrinkage influences the connections.

3.5.1

FIRE PROTECTION METHODS

In addition to the active measures such as the sprinkler system, fire and detection alarms, there are two commonly‐known passive methods; the so‐called charring method and the encapsulation method.

CHARRING METHOD In terms of fire‐resistance performance, mass timber structures behave significantly differently than a lightweight framing system. Due to the dense solid panels of timber and the ability to withstand fire, mass timber can also be considered a fire‐resistance material.

Even though wood is known as a combustible material, by International standards, mass timber structures (panelised system; columns‐beams system) are considered to perform well under exposure to fire. When the timber structure is made of mass timber products, it performs under fire conditions excellently. It is because a certain mass of wood is created and formed by the char layer that simultaneously insulates the remaining part of wood from the penetrating heat, as illustrated in Fig. 18. Due to the capability of wood to create a resistant char layer during the process of burning, the fire rating of mass timber elements can be calculated based on the smallest thickness for structural purposes and the rest of the available thickness for charring. The charring method is commonly used by authorities around the globe.42 Figure 18 : The charring diagram of mass timber under the fire exposure.42

42

(MGB Architecture + Design, Green Michael, 2012)

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CHARRING RATES The measured char rate of horizontal elements (ceiling and roof) is calculated by 0.65 mm/min, if only the first layer is affected by expose to fire. The value of 1.3 mm/min is for an additional layer affected by fire until the 25 mm‐thick char layer is reached. Hence, the rate of 0.65 mm/min can be implemented until the joint of the next timber layer, as presented in Fig. 19.

Figure 19 : Diagrams of the measured char rates of the horizontal (left) and vertical (right) elements.43

As is depicted in Fig. 19, the calculated char rate of the vertical element (wall and column) is 0.63 mm/min for only the first layer, while every additional layer is measured by 0.86 mm/min. 43 Additionally, every testing facility can provide the rates with slightly varying values, depending on the technical properties of the particular element.

ENCAPSULATION METHOD The alternative and more passive approach towards fire protection of a mass timber structure is the encapsulation method. Encapsulation is similar to the standard construction approach of obtaining the fire rated elements (walls, floors, roofs) in combustible as well as non‐combustible buildings. Mass timber elements are covered either by fire‐resistant layers of plasterboard or fire‐resistant paint that is directly applied on the timber elements. For instance, timber or steel structural systems are able to withstand 2 hours of exposure to fire using a two‐layer plasterboards protection.

Normally, the encapsulation method is used to maintain the fire‐protection of either a timber structure or a steel structure, however, the charring method also achieves safe and reliable performance in a combustion process and is progressively more allowed around the world.

43

(Stora Enso Wood Products, 2016)

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3.5.2

OCTOBER, 7 2016

MOISTURE CONTENT AND SHRINKAGE

The density of timber in terms of moisture content is measured by water substance in a given volume.

Density depends on the amount of void area in and between cellular walls that the water can fill up.

Constant cell density of all species is in the range of 1400‐1500 kg/m³. Therefore, the factors influencing timber density are the cell size and the quantity and the distribution between the cellular walls.

Generally, timber´s density affects all major properties as well as the manufacturing process in the physical characteristics such as strength, stiffness, hardness, fire resistance, easy machinery, etc. The performance of timber can consequently be affected by moisture content in the cellular walls.44 Different moisture content after production has shown large differences in performance between the light wood and mass timber systems. Whereas the typical amount of moisture in light wood construction ranges from 15% to 19% and over time stabilizes at 8‐10%, the mass products are already manufactured with 10 ±2 amount of moisture. Due to this, mass timber elements of panelised system are more easily manufactured and produce extremely little shrinkage in the vertical/longitudinal direction. A slightly higher shrinkage of CLT and glulam than LVL or LSL products can be seen in the horizontal/perpendicular direction due to its composition.45 This results in accumulative shrinkage over the height of the panelised structural system that may demand additional consideration in the connections, whereas the columns‐beams system does not require extra care of the shrinkage. Fig. 20 shows the behaviour of different physical properties in the two directions of the CLT composite panels (wood) under the cumulative loads during the test performed for the "Dalston Lane" project, which is a 9‐story panelised building under construction in London, UK. Therefore, the solution was to insert pieces of timber in the vertical direction into the floor element. The test result was recommended to be shared in this paper during the interview with the Senior Engineer from Rambøll.

Figure 20 : The test of a panelised system made of CLT elements under a pressure load.

(Interview presentation)

44 45

(National Association of Forest Industries, 2004) (MGB Architecture + Design, Green Michael, 2012)

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Another example of cumulative shrinkage is illustrated in Fig. 21. A 12‐story panelised system (right) has a calculated cumulative shrinkage of 31.2mm, whereas no cumulative shrinkage is in the columns‐ beams system (left).46 Figure 21 : The diagrams of calculated cumulative shrinkage for a 12‐story structural comparison.46

The volume of moisture in wood is a simple function – when moisture increases in volume, the volume of wood increases as well and the same is true in the opposite direction. The mechanical properties and quality of timber elements are substantially influenced by the moisture content, meaning that a mass timber system must not be exposed to weather phenomena (water, snow/ice, solar radiation) and ground (humidity and heat movements).

CONCLUTION OF THE CHAPETER The important observation is that the contemporary active and passive fire strategies have been found to provide fire safety of the timber structures without encapsulation, using only charring methods.

Charring methods allow for the reduction of weight and the cost of construction, and in the same way maintains the beauty of timber. Even though the encapsulation method is required to protect the timber elements, which leads to covering the beauty of timber, it is still the case that the timber structure fulfils the function of storing emissions as opposed to concrete or steel ones.

As mentioned earlier when talking about shrinkage, wood is an orthotropic material that may cause issues in long‐run. However, this should not pose problems if mass timber is dried down to certain amount of moisture and if it does not get wet during the construction process. As seen above, the durability can also be one of the reasons why multi‐story buildings are typically constructed using only concrete.

To conclude, all challenging aspects considering high‐rise timber structures are surmountable up to the same technical qualities than any other concrete construction.

3.6 CURRENT MULTI‐STORY TIMBER STRUCTURES AND THEIR CHALLENGES To construct a high‐rise timber building in Denmark, it is necessary to investigate the cases that have already been built in other countries, in all important respects that are unknown or unclear for the

46

(MGB Architecture + Design, Green Michael, 2012)

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Danish construction industry. Several of the mass timber systems and hybrid mass systems are currently under development at different places around the world. From Austria, Germany, Norway, England, Australia to North America, standards are intended to be set for timber designers, contractors as well as producers in order to deliver economical, safe and durable structural systems, primarily consisting of timber. In this chapter, we will analyse the characteristics of the current timber cases that already exist.

3.6.1

“TREET” IN BERGEN, NORWAY

BRIEF DESCRIPTION AND FACTS Currently, the world’s tallest multi‐story timber building is located in Bergen, Norway, and it is called “Treet” which is Norwegian for “The Tree”. The building is utilized for residential purposes and consists of 62 apartments with 14 stories. The design process took 3 years from 2010 to 2013 and the construction process started in April 2014 with finish in autumn 2015.

THE DESIGN AND STRUCTURAL SYSTEM “The Tree” is 49 metres tall, consists of basement garages made of concrete and the rest of the building – the 13 stories are constructed entirely from mass timber elements. The main timber structure is formed by GLT and it is similar to contemporary timber bridge systems. The core of the building is assembled by prefabricated CLT modules which are already equipped with necessary apartment fixtures and mechanical installations such as kitchen and bathroom cabinets, sprinkles, electricity, water pipes, etc. (see Fig. 22). In this case, the modules have ensured shorter construction time along with mitigating

the

challenge

with

moisture.

Figure 22 : The structural system with “power floors” on the left and a completed building with envelope protection on the right.47

The timber structure is built on a concrete ground floor which functions as the building’s foundation.

The GLT trusses secure the overall stiffness of the building on the facades, since the CLT modules

47

(Abrahamsen Rune B, Malo Kjell Arne, 2014)

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contribute only insignificantly and therefore, prefabricated modules are independent of the main load‐ bearing structure. The CLT modules behave as “pieces of LEGO” on top of each other. The first four floors rest on the slab of ground floor that is above the underground concrete garage. The building’s stories 6 and 11 are denoted as “power stories”. They consist of concrete slabs connected to the strengthened GLT trusses and the GLT trusses on the facades. The concrete slabs form the foundation for the stories above, but they are not a part of the main structural system. The roof is also made of prefabricated concrete slabs as a 3rd layer of concrete in the timber part of building. The slabs’ purpose is to increase the building’s mass in order to obtain better response to the dynamic activities, in this case the activity of the wind.48 The building’s performance is energy efficient and meets the passive house demands of European building regulations. Every module is well insulated and almost air tight, including the proper joint connections.

CONNECTIONS The engineering team for “The Tree” has chosen to use the already verified connection technology in timber bridges as well as large timber buildings. The lengthy GLT structural trusses are connected by the slotted‐in steel plates and dowels. This type of connection is able to withstand large forces. An example is shown in Fig. 23.

Figure 23 : Connection composed of slotted steel plates with dowels.49

FIRE‐SAFETY DESIGN The structural fire‐safety design for the building is in accordance with the Eurocode 5 (CEN 1995‐1‐2 2004). The main load‐bearing structure is designed to withstand 90 minutes of fire exposure, while the secondary bearing structure must withstand 60 minutes. In addition, the fire safety of the building is secured by sprinklers, pressurized in the escape stair shaft and all the surfaces in the escape routes are improved with flame‐retardant paint. The GLT truss elements are projected with a filling that can burn and do not require extra fire‐proofing. All the steel connections are hidden inside the glulam trusses at a minimum 70‐mm distance from the outer surface and therefore do not fall within the 90‐minute fire

48 49

(Bjertnaes Magne Aanstad, Malo Kjell Arne, 2014) (Abrahamsen Rune B, Malo Kjell Arne, Bjertnaes Magne Aanstad, 2015)

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resistance requirement. The joints are filled with a fire‐resistant filler between every column and beam.50

3.6.2

CHALLENGES OF USING A WOODEN STRUCTURE IN “TREET”

During the designing of “The Tree” residential building, two main challenges came up. The first one was to respond to a dynamical behaviour by increasing the mass of the building and incorporating the glulam trusses in the façades. Even though the building’s mass was higher with the glulam truss stiffness, the wind action still caused problems with the maximum dynamic response of the building.

The values of the wind action were a higher than recommended. They had been re‐evaluated in order to avoid discomfort for the building’s residents.

The second challenge was to protect the timber elements from permanent weather conditions to eliminate their maintenance. It was solved by additional layers of glass on the north and south façades, and of metal cladding on the east and west facades. 51

3.6.3

“FORTE” IN MELBOURNE, AUSTRALIA

BRIEF DESCRIPTION AND FACTS The runner‐up for tallest multi‐story timber building is called “FORTE”, and is located in Melbourne, Australia. It is a 10‐story residential building, consisting of retail businesses on the ground floor and apartments on the remaining stories. It can be seen in Fig. 25. The highest point of “FORTE” is 32.2 metres, which makes it the world’s tallest apartment building made entirely of CLT panels. All CLT panels were manufactured in Austria and then shipped to Australia in 25 containers. It was calculated that the building would store approximately 761 tonnes of carbon dioxide. If the building had been built from concrete or steel, it would have increased the CO2 emotions by 1451 tonnes.

Figure 24 : Currently the second tallest timber building in the world, “FORTE”.52

DESIGN AND STRUCTURAL SYSTEM The structural system of “FORTE” is entirely made of CLT panels which stand on top of the pile foundation with ground floor made of geopolymer concrete, in the same way as in the above‐ mentioned “Treet”. It is due to the required larger spans for retail businesses and keeping the timber

50

(Abrahamsen Rune B, Malo Kjell Arne, 2014) (Abrahamsen Rune B, Malo Kjell Arne, Bjertnaes Magne Aanstad, 2015) 52 (Forte Living, 2012) 51

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protected from wet ground. The vertical CLT panels for stair and lift cores were erected first. Once they were in place, the rest of the internal and external panels could be installed in their respective positions.

The panels are one‐story high. The building process was repeated one by one for each story until the whole structure was completed. The entire building uses 759 custom CLT panels with each consisting of

5

layers.

bathrooms

The were

mounted

as

prefabricated modules, as shown in Fig. 25.53 Figure 25 : Panelised structural system consisting of CLT panels and prefabricated modules.54

The whole CLT skeleton of the building simultaneously supports both the vertical and horizontal loads.

The durability of timber structure was achieved by rain cladding of recycled aluminium panels and a damp‐proof membrane placed in the cavity. The facades are monitored with strategically located the moisture sensors. The CLT panels of the roof and balconies are protected by a water‐proof membrane.

Moreover, the acoustic performance was a priority in the building’s design, and this has been achieved by going beyond the recent building norms. The non‐structural screed of 70mm in the thickness of the floor secures low frequency in order to increase the vibration performance.

CONNECTIONS The CLT panels are connected using 90‐ degree‐angled steel connectors fastened together with screws, as shown in Fig. 26.

Figure 26 : Stabilization of CLT panels by angled steel plates and brackets with screws.55

FIRE‐SAFETY DESIGN Numerous tests were required to ensure proper design solutions in terms of fire safety. The structural system of the building required fulfilling the 90‐ and 120‐minute regulations of fire exposure. The design

53

(Survey of International Tall Wood buildings ‐ Forte, 2012) (Wood Solutions, design and build ‐ Forte, 2012) 55 (Minik Lange Pedersen, 2016) 54

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team had decided to protect the building by the encapsulation method – plasterboard protection.

Therefore, two procedures have been undertaken within the encapsulation method: firstly, the 128mm walls have been covered by 13mm fire‐grade plasterboard with direct fixation and with a documented ability to withstand a fire exposure of 90 minutes. Secondly, the 146mm floors have been protected by 2 layers of 16mm fire‐grade plasterboard with direct fixation and fulfil the fire‐exposure requirement of 120 minutes. All connections have also been covered with plasterboards. Moreover, the bare walls of 158mm are able to withstand a fire exposure of 90 minutes.56

3.6.4

CHALLENGES OF USING A WOODEN STRUCTURE IN “FORTE”

One of the main challenges for the “FORTE” building was handling the CLT panels as a new structural system. It has been quite a new approach of designing and constructing by timber, compared to steel or concrete. Secondly, it was the documentation of the fire safety capacity of the timber elements which are protected by plasterboards and the expansion of the wall’s cross section. The verification of elements has been established by undertaking various fire tests. Ultimately, the third main challenge was ensuring the highest possible durability of timber products in relation to weather conditions. The durability has been achieved by wrapping a damp‐proof membrane around the timber envelope, the installing of moisture sensors into the façades and using aluminium screening on the façades.57

3.6.5

“WOOD INNOVATION AND DESIGN CENTER” IN BRITISH COLUMBIA, CANADA

BRIEF DESCRIPTION AND FACTS The Wood Innovation and Design Centre (WIDC) is currently the tallest modern timber building in North America with a height of 29.5 metres, located in northern British Columbia. The WIDC was realized as a showcase for local wood products and demonstration of increasing expertise in the design and construction of large timber buildings. The structure is used for academic purposes and functions as a learning resource centre that supports the design, fabrication and testing of timber products in contemporary research and teaching labs. The design process began in early 2013, with the construction of concrete foundation and deck starting in August of the same and the building was virtually completed by the end of October 2014. A detailed design of the substructure was still under development when the construction began. The WIDC building utilized a variety of locally manufactured engineering wood products, and is illustrates in Fig. 27. In addition, the WIDC incorporates numerous other sustainable design strategies and fulfils the LEED Gold certification.58

56

(Wood Solutions, design and build ‐ Forte, 2012) (Survey of International Tall Wood buildings, Forte, 2012) 58 (RDH Making Buildings Better, 2016) 57

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Figure 27 : Wood innovative and design centre building on the left. Exposed timber element inside of building on the right.59

THE DESIGN AND STRUCTURAL SYSTEM The building’s envelope is enclosed by a concrete deck from the bottom and a concrete slab from the top in order to protect the wood structure from the wet ground and to seal off from weather conditions.

Except for the ground floor deck and the floor of the penthouse mechanical room, the mass timbers are used entirely for the structural system, consisting of GLT, CLT and LVL. The structural system is an innovative combination of a glulam column and a beam frame construction, including customized CLT floor panels with a CLT core in the centre. The core of the building ensures lateral stability and it features a staircase, elevator and mechanical shafts. At the same time, the CLT core, together with the CLT floor panels, guarantee vertical stability and the vertical loads are transferred to the glulam beams, followed by the glulam columns. The same scenario is repeated at each of the 7 stories from the top to the bottom of the building. The inside wood elements were left exposed wherever it was possible. The external façades consist of triple‐glazed curtain wall system with vertically laminated veneer lumber (LVL) mullions. The LVL mullions function as vertical columns against the wind and are protected by aluminium veneer. In addition, the rest of the facades are supplemented by structural insulated panels that are clad with natural or charred wooden cladding. Both of the wood claddings have been coated with a fine finish to increase the durability by providing resistant coating from insects and moisture.

The specially charred wood cladding results in quite a unique and pleasing‐to‐the‐eye architectural appearance. When it comes to the acoustic comfort, the sound transmission of the walls achieved the required rating by single and double layers of drywall, double‐stud walls and insulated and resilient channels. The sound transmission over the CLT floors was reduced by installing acoustic mats and

59

(Canada Wood Council, Wood Works, 2016)

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carpets.60 Some of the rooms have dropped noise‐barrier ceilings consisting of double‐layered plasterboards. Constructional composition is presented in the overview in Fig. 28 below.

Figure 28 : The construction process of a columns‐beams system.61

The building’s structure is called a balloon frame and it means that the columns are positioned one above the other and the loads are freely transferred from end‐grain‐to‐end‐grain of the columns. The horizontal beams are assembled into the columns sides so there is no intersection with the vertical section of the building. This system minimizes the growth of the vertical shrinkage, which is one of the critical strategies towards successful design of high‐rise timber structures. The reason is because the crushing strength of wood is significantly different between the parallel‐to‐grain and the perpendicular‐ to‐grain directions. This building system is expandable to the other building systems and scalable to higher buildings. It has been confirmed by a total of 4 prototypes consisting of 12, 20, and 30‐story buildings which were developed as part of a feasibility study. Moreover, the building is equipped with sensors which monitor the shrinkage, deflection, vibration and moisture during the whole life‐time of the building. The recorded data is used to help design teams with future high‐rise timber buildings.62

Figure 29 : The overall structural section of used building materials.63

60

(Canada Wood Council, Wood Works, 2016) (Minik Lange Pedersen, 2016) 62 (Canada Wood Council, Wood Works, 2016) 63 (Danzig Ilana, 2013) 61

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CONNECTIONS The concrete‐ reinforced raft deck varies in thickness from 400 to 600mm and the steel baseplates for the core walls and columns were positioned and cast into the concrete deck. The core walls elements are connected to the baseplate anchors by shear wall brackets using self‐tapping screws in order to create continual shear walls. The columns elements are connected to the baseplate anchors by bolted and welded thick plates that are pre‐installed at the bottom of each column. In Fig. 30, the connections of the column and beam balloon‐framed system can be seen. As described in the chapter before, the columns are continuously connected from end‐grain‐to‐end‐grain of columns with vertical steel plates inserted between the columns. The threaded rods are connected to stabilize the glulam columns with the sleeve inserted into the lower part of the upper column before the lower column. The nuts are used throughout the sleeve to tighten the columns after the column is in its place. The installation of the column connection is completed after the sleeve is concealed. The glulam beams are connected by hidden, so‐called, Pitzl connectors inside the beam which are inserted into the pre‐installed opposite shape of the Pitzl connector on the side of the column, and then on the beam.

Figure 30 : The connection of the column and the beam by the hidden steel connectors.64

FIRE‐SAFETY DESIGN The fire‐safety design of WIDC is based on the British Columbia (BC) Building Code in combination

with

site‐specific regulations. Due to the lack of legislation regarding timber structures, the building was designed based on the combination of the 2012 BC Building Code, research and testing to develop the regulations for equivalent safety levels.

The building was designed to use the reduced cross‐section method to estimate the capacity of structural timber elements after a certain duration of fire exposure. Therefore, the cross‐sections of structural timber elements were chosen with a certain thickness for expansion. All CLT‐walls are able to withstand fire for 1.5 hours while the 3rd and 6th CLT‐floors are fire resistant for 1 hour, with other floors with same rating. The escape stairwells, escape corridors and elevator shafts were required to

64

(Canada Wood Council, Wood Works, 2016)

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be treated with fire‐retardant coating and intumescent paints. Furthermore, these paths were constructed to prevent the smoke mitigation from one compartment to another. In addition, the steel Pitzl connections are prevented against fire by glulam columns and beams due to using the concealed approach.65

3.6.6

CHALLENGES OF USING A WOODEN STRUCTURE IN THE “WOOD INNOVATION AND DEISGN CENTER”

The WISC is the highest timber building at the moment and it was built as a “front runner” in North America where the new legislation and building techniques had never been applied before. The main challenge was to meet the fire safety design of the building regulations while trying to keep the timber elements exposed at as many places as possible for aesthetic purposes. Therefore, the fire safety strategy was achieved by hidden functional steel connections, sealed mass timber elements and holes, and using fire‐resistant coating in the exit paths. In addition, the charring method was used for the load‐ carrying timber elements, meaning elements oversizing. Additional lessons learned were that the full advance of off‐site prefabrication, full building information modelling (BIM) and an integrated project delivery (IPD) system should be involved in the timber building project from early beginning in order to ensure a comparatively economical project.66

3.6.7

“LIFECYCLE TOWER ONE” IN DORNBIRN, AUSTRIA

BRIEF DESCRIPTION AND FACTS The LifeCycle Tower ONE (LCT ONE) is a 27‐meter commercial office tower of 8 stories. The building was erected within just 9 months in September 2012 and is located in Dornbirn, Austria. LCT ONE was developed as a prototype research project into using mass timber in a structural system, with a new prefabricated design and construction approach. The building’s purpose is to transfer the gained knowledge about the advantages of mass timber buildings as an educational laboratory. This pilot project is a central building for testing and marketing, because the construction system should achieve feasibility and international marketability. It reduces the material weight by 42% compared to similar‐ sized conventional constructions, while the type of the building system resists destruction by fire and earthquake without losing its stability. Due to the maximized R‐value and avoided thermal bridges of the curtain façades, the building was able to meet the Passive House standards.

65 66

(Danzig Ilana, 2013) (RDH Making Buildings Better, 2016) & (Danzig Ilana, 2013)

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Figure 31 : Lifecycle tower one building on the left. The plan’s drawing shows the core using a black thick line in the middle.

Building configuration on the right.67

THE DESIGN AND STRUCTURAL SYSTEM LCT ONE has been built using a hybrid construction system, consisting of composite elements made of two or more materials combined. In this case, the primary material is timber, combined with a secondary material ‐ concrete. The reinforced concrete core, glulam columns and timber‐concrete composite slabs buttress the building’s structural system. The concrete core secures the lateral loads and the combination of concrete core, hybrid timber slabs and glulam columns secure the vertical loads.

The CLT panels have not been used in this building and instead have been replaced with concrete, as opposed to the other cases mentioned above. Firstly, the concrete core was casted on‐site all the way to the top and secondly, all prefabricated elements were installed on top of each other. Due to preventing the contact of timber with the wet ground, the designers have decided to build the entire ground floor with concrete and the rest of the hybrid timber elements stand on top of the concrete ground floor. One floor was built per day, meaning that dry prefabrication is an efficiently precise building method, qualitative and time‐wise. In addition, the timber elements on the facades have been protected by metal cladding. The LCT ONE building, structural plan and the composition of elements are illustrated in Fig. 31 above.68

67 68

(Minik Lange Pedersen, 2016) (Wood Solutions, design and build – Lifecycle Tower One, 2012)

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The glulam columns had already been pre‐installed with windows in the façade elements and the hybrid slabs consisted of glulam beams coved with concrete slabs, as presented in Fig. 32 (right, middle). This type of hybrid slab has two main advantages: it has a long span of up to 9.5m and the place between the glulam beams can be utilized for mechanical services, which reduce the floor’s thickness, as illustrates in Fig. 32 (left).

Figure 32 (left): Prefabricated façade panels consisting of glulam. (middle): Installation of hybrid timber slab. (right): Mechanical services build between glulam beams.69

Over the last 15 years, in the Austrian region of Land Vorarlberg, wood has become the primary structural and building material. The regulations are increasingly becoming localised, which also left its mark on this project in that the prefabricated elements were assembled within a short distance from the building’s construction site.

CONNECTIONS So called mortise and tenon joints have been implemented in the LTC ONE building. The hybrid slabs have been attached to the concrete core by angled brackets including pins, while the other side of hybrid slabs have been connected by tubes which are sticking out from the glulam columns in the façade elements. The hybrid slabs have been moved through the holes in every corner of the elements and then inserted into the pins and tubes on both sides, as shown in Fig. 33 below.

Figure 33 (left): The process of connecting the hybrid slab to the concrete core by steel brackets with pins. (right): The process of inserting the hybrid slab into the tubes on a prefabricated façade element.70

69 70

(Kaufmann Hermann, Steiner Martina Pfeifer, 2012) (Kaufmann Hermann, Steiner Martina Pfeifer, 2012)

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The benefit of this connection method is a fast installation of prefabricated elements, however, the connectors are not able to ensure the lateral loads of the whole structure. Therefore, the horizontal loads are simultaneously transferred to the concrete core which takes care of them. The installation process of the prefabricated façade and slab elements is illustrated in Fig. 34.

Figure 34 : Overview of the setup of the prefabricated façade element with the hybrid slab.66

FIRE‐SAFETY DESIGN The structural connections are designed protectively with no wood‐to‐wood connecting method. The steel brackets and pins are protected against fire by the concrete part of the hybrid slabs. By this approach, the fire penetration through the slab elements is eliminated and every floor becomes a separate fire compartment. Moreover, several fire tests have been undertaken to determine the acceptable solution and a 2‐hour fire performance has been achieved for the hybrid slabs. The 90 minutes required for the rest of the structural system were met by expanding the exposed columns and beams. The quality and simplicity of the building structure consequently lead the fire authority to allowing the requirement for sprinkling system to be removed. As in this case of the other timber buildings, the collaboration between the design team and fire department has been key in terms of finding a suitable solution.71

3.6.8

CHALLENGES OF USING A WOODEN STRUCTURE IN “LCT ONE”

The major challenge during the design and construction period was predicting and understanding the structural behaviour of a wood‐concrete hybrid structure. Several fire and acoustic tests had to be performed to meet the required regulations. The first fire test of the hybrid slab lead to failure after 30 minutes under direct fire exposure. Lots of adjustments and improvements into the hybrid slab had to

71

(Survey of International Tall Wood buildings ‐ Lifecycle Tower One, 2012)

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be done in order to meet the requirement of 2 hours of fire exposure. Another challenge was to determine the various tolerances between the concrete and timber elements.72

CONCLUTION OF THE CHAPTER To summarize, we have described and analysed recently constructed timber buildings with different types of structural systems while observing the following common things: 



 

 

All projects were executed under a close collaboration of the client, design team, authority, contractor and element producer. The procurement procedure of all timber constructions were undertaken either by partnering or integrated design delivery.

All presented buildings have been built on a concrete base. Three of the buildings have ground floors entirely made of concrete, while one of them has a reinforced concrete desk.

All of the timber constructions have a designed durable external envelope.

In terms of fire resistance, the buildings have been protected with the combination of charring and encapsulation methods. Dependent of height, two of the buildings have been equipped with automatic sprinkling system.

Steel connections in each of the buildings have been used with fire protection either by timber element itself or fire‐resistance plasterboard.

Main cores of the buildings have been made of CLT panels in 3 cases, whereas in one case – Lifecycle Tower One, it has been constructed using concrete.

The results of analysing different cases from abroad show that legally as well as technically, we are able to develop multi‐story timber buildings, which the Danish construction industry can draw inspiration from.

72

(Wood Solutions, design and build – Lifecycle Tower One, 2012)

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4. EMPIRICAL DATA 4.1 INTERVIEW ANALYSIS PROCEDURE The approach to analyse the qualitative data from the interviews has been the connection of the inductive and deductive approaches.73 The basis behind this combination has been given by some of the questions that required specific experience from the interviewee´s field, and the author thus did not expect the interviewees to perform any kind of pre‐study or scrutinizing the theory. Moreover, the primary target of the interviews was to obtain different perspectives and observations of the presented problem, and the theory that may help come to certain conclusions with future perspectives.

Each of the interviews consisted of 12 questions, including the same 11 questions with one specific question to each interviewee. The complete transcripts can be found in Appendix 2. The questions have been processed in a discussion manner using quotes and practical notes, because the interviews themselves were quite long. Certain questions have been asked that pertained to information not found in the literature or experience from the field. Investigative information regarding Danish construction tradition and new technical methods of building have been considered. The interviewees are addressed by their professional titles. The analysis of the questions has been conducted one by one or have been separated into areas towards answering the secondary research questions.

4.2 INTERVIEW DATA ANALYSIS Interviewees Architect: Jonas Sangberg

4.2.1

Senior Engineer: Finn Larsen

DTU student: Minik Lange Peder

ESSENTIAL BENEFIT

This chapter answers the first secondary question by analytical and discussion manner: What are the major benefits of using timber as a structural material compared to steel and concrete?

Question 1: The interview started with the question considering whether the primary focus of the Danish construction industry should be towards multi‐story timber buildings. The answers were as expected, each one of the interviewees reckons that the construction industry should definitely move in this direction, helping reduce the CO2 emissions, since “90% of Danish buildings are built by concrete” and “wood is the most sustainable alternative and mainly in terms of reducing CO2”. Moreover, the Senior Engineer explained some other reasons for introducing wood – sustainable way of manufacturing and the potential of using wood in the construction industry instead of the paper industry, because lower production of paper is expected in the future. Furthermore, they pointed out

73

(Burnard P., Gill P., Stewart K., Treasure E., Chadwick B.,2008)

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that “there are issues that have to be solved in the near future” and that “tall timber building should be explored and researched more” in order to establish them in the Danish society.

As illustrated by the comparative numbers in the theoretical part, the interviewees’ opinions regarding the use of timber before concrete or steel are in line with the life‐cycle assessment.

Conclusion: Apart from other benefits, the essential one behind using timber in construction has been unequivocally agreed on, and that is timber being capable of reducing the CO2 emissions when compared to concrete. To conclude, timber structures should be the primary focus of the Danish construction industry, important also in achieving the country´s target of carbon neutrality, shorter construction time and healthier indoor comfort for the final user, among others.

Most importantly, mass timber has to be able of competing with steel and concrete, otherwise nobody would build using timber on a large scale, regardless of how much the emissions would be reduced.

4.2.2

LEGAL CONSIDERATIONS AND TECHNICAL ISSUES

This chapter answers the second secondary question by analytical and discussion manner: What are the legal and technical issues that prevent the construction of the multi‐story timber structures in Denmark and, at the same time, what are the common challenges in the construction of high‐rise timber structures in other countries?

Question 2: The question whether tradition or regulations are the main obstacles to developing high‐ rise timber structures in Denmark was asked. All three of the interviewees thought that tradition had a large impact on evolution of timber structures in Denmark. The Architect mentioned it was because Denmark did not have so much raw material such as Norway or Sweden, whereas the Senior Engineer and the DTU student pointed out the huge conflagration that occurred in Copenhagen, which lead to using non‐combustible materials such as clay and concrete, while especially prefabricated concrete became the main material until now. In their opinion, this tradition of non‐combustible materials resulted in regulations in the Danish system towards combustible materials, and they agreed that regulations were the reason why timber buildings had not yet become so popular in the country.

Moreover, the Senior Engineer confirmed that current Danish regulations allowed construction of up to 12m using combustible material, while every other building above that limit had to be built with non‐ combustible materials. He also mentioned that “if the building solution is documented with the same safety procedures as with combustible materials, then it will be allowed to be built.”

Reflecting upon the answers, it is obvious that tradition has an enormous influence on timber structures in Denmark and even though country is not rich with raw materials – timber, the performance‐based

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regulations allow for the opportunity to construct timber buildings of more than 12m for the uppermost floor in Denmark.

Question 3 and 4: The following questions were related to the main technical issues in timber construction – fire safety, shrinkage and moisture. The answers indicate that high‐rise timber buildings cannot be built at a height of around 20 stories using only timber, the limit being in the range of 12 to 15 stories, due to the fact that wood is an orthotropic material, which has 3 different degrees of stiffness and 6 various degrees of strength in each direction. The Senior Engineer said that cities in general would not require having many buildings above 10 stories, bringing additional problems with installations. He explained using an example of a proposed 34‐story timber building with a concrete core from Stockholm that “engineers of the project have calculated a 0.5m shrinkage over a certain period of time”, as well as using other cases, especially panelized systems. He also pinpointed that the industry had not have enough experience with Hybrid structures and “it would be interesting if wood and concrete could work together”. The DTU student added that “lightness of wood causes dynamical issues for high‐rises”. The Senior Engineer mentioned that “CLT elements do not need to be used for everything.” It means that they also have some limits and are a relatively new material in the market, however, by a combination of a panelized system and a columns‐beams system, it would be possible to build a more flexible multi‐story timber building. Even though wood is a complex material to work with, it is manageable to continuously improve and develop the systems so that more timber buildings will come to be constructed.

All three interviewees confirmed that fire was the biggest issue with regard to multi‐story timber constructions. In terms of material comparison in relation to fire, the Architect and the Senior Engineer clarified that “compared to steel, wood is controllable under fire exposure by charring rates”. In fact, it is one of its benefits, because wood does not expand when it is heated, whereas steel does, therefore, char layers of wood can be calculated using charring rates. Moreover, the DTU student believed that passive fire resistance approach of using the charring method would be more expensive than the encapsulation method, while the Senior Engineer said that “it would be more or less the same”. This economical topic is subjective, while substantially dependent on the specific project’s demands and fire‐design strategy.

Question 5: The interviews pointed to the fact that lack of knowledge about mass timber elements as well as lack of manufacturers is still present in the construction field in Denmark. It is natural that we want to invent new building methods, but it requires performing lots of tests that not many companies are willing to undertake. From the Architect’s perspective, it is notable that the Danish government is putting an emphasis on innovation and “companies are able to get the funding”. Furthermore, the DTU

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student noted that “the construction industry is in the process of undertaking timber structures right now and maybe there will be one in 4‐5 years” while he recommended expanding knowledge by collaborating with countries that had already constructed high‐rise timber buildings.

The Senior Engineer highlighted that the transportation of wood elements demanded less space and the elements are more accurately produced than ones made of concrete. Long transport of CLT elements from places where the CLT producers are located, such as Austria or Germany, will thus not be a major problem. The Senior Engineer also pointed out that “Denmark will not have any CLT producers unless we have more volumes of wood.”

To sum up, the discussions and progress in the Danish construction field in relation to timber structures is certainly under way and it is only a question of sharing knowledge to reach a faster construction of the first multi‐story timber building. Additionally, it is clear that the construction industry will introduce new producers in the market only when it economically beneficial, and transportation is not a big issue because of the ability to fit comparably more elements into a single truck.

Question 6 and 7: These questions related to the very important element of this paper – durability and moisture content/shrinkage. The interviews showed that moisture is one of the key considerations when it comes to timber buildings. In order to avoid moisture in timber elements, “proper construction and protection during construction period” is necessary. In addition, the Architect and the Senior Engineer added that durability of the wood structure is achievable by either an additional protection layer or a damp‐proof membrane on the outside of the structure. It is obvious that the design team and the contractor must carefully secure the timber structure from being exposed to outside conditions and consequently mould. Moreover, the advantage of mass timber products is that they dry out fast and the contractor is able to work on them the day after the floor elements were raised, as opposed to concrete, where the period is not certain.

As is known, wood has a moisture ratio of 10±2% and depending on different degrees of strength in various directions, the CLT connections shrink by 5% in the horizontal way while only 1% in the vertical direction. The Senior engineer prefers to use steel nail connections or a bracket system, whereas the DTU student inclines to using sensors to monitor the moisture in a panelised system during the building’s life‐time. These subjective perspectives depend on a variety of options and the specific situation.

Question 8: Maintenance and long term perspectives are necessary issues to discuss regarding sustainability in the comparison of steel, concrete and timber structures. The DTU student noted that timber structures would require more maintenance, because of the steel bolt connections, whereas

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the Senior Engineer believed that timber structures would not demand any extra maintenance as long as they were correctly constructed and the Architect reckoned that choice of low maintenance products should be mandatory and should be one of the first design parameters. Due to the fact that each one of the interviewees responded to the question from a different point of view, it is possible to agree with all of them.

Furthermore, the Senior Engineer added that we had a wrong debate about the long term duration of buildings, because “they are outdated rather fast and we should look on the building as a product, similar to a car.” In addition, he defended that “we keep certain buildings to maintain tradition, however, most of the buildings will be demolished.” It is a good point, because design requirements change quite fast and perspectives of living adjust every decade, so there is no reason to design buildings for the long‐term, but rather with shorter and recyclable approaches in mind. This approach of thinking only supports the rise of timber structures as ecological and recyclable alternative.

First part of Question 9: The first half of following question discussed the main obstacles in the industry regarding multi‐story timber structures in Denmark. The Senior Engineer and the DTU student both answered that regulations were the major issue and that it would be desirable if the economy would be supported to perform tests, whereas the Architect thought the main issues were tradition and “a dinosaur business of concrete elements that is hard to break”. My perspective is that regulations and tradition are simultaneously going together, due to the reason that tradition has long been directed by regulations.

A specific question for the Architect and the DTU student: The following question was about the challenges that they had experienced during the designing of timber structures. The Architect explained certain fire issues regarding one of the projects where additional complications occurred, while the DTU student experienced that the lightness of the wood caused issues with dynamic actions in the height.

Conclusion: Summing up the legal issues, it can be concluded that it is a common misconception in the Danish construction industry that it is prohibited to construct a higher than four‐story building using combustible materials. This height limit comes from the guidelines for designers such as collated examples of fire safety measures in buildings, however, fire regulations are no formal barrier being only performance‐based regulations in compliance with the supplement specified in the guiding manuals.

It has been found that tall timber structural systems have two major technical issues that are fire safety and shrinkage in structural system. The designers do not have enough experience regarding fire exposure of combustible structures and wood is an orthotropic material having different degrees of

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strength in different directions that cause shrinkage in certain heights. Although timber structures have technical issues that depend on the specifics of the project, they surmountable by innovative fire strategies and connections that need to be further explored.

4.2.3

POSSIBLE IMPROVEMENTS

This chapter answers the third secondary question by analytical and discussion manner: What are the areas that need to be changed and/or improved in the Danish construction industry in order to construct multi‐story buildings using timber as a sustainable alternative?

The last three questions of the interviews were directed towards recognizing how can the respective areas can be improved to help construct more multi‐story timber buildings in Denmark. After understanding the obstacles in the Danish construction industry, this chapter includes recommendations towards an improvement of certain areas. The aim of the research was not only to highlight the problematic points, but also propose new approaches.

Second part of question 9, and Questions 10 and 11: Upon being asked the questions on how to solve the obstacles, the Senior Engineer and the DTU student suggested that regulations should be more flexible towards the choice of the structural material and they should be directed towards performance‐ based regulations. Nevertheless, it is obvious that fire safety should remain the priority. The Senior Engineer proposed to take a look on cases from abroad and to transfer them into Danish practice. He pointed out “The Tree” case in Bergen and that “the sprinkling system is a very good solution in terms of timber’s exposure to fire.”

Apart from that, the Architect suggested that the regulations should specified how much CO2 footprint is allowed for a building and they should be directed towards alternative choices of materials. He commented that there are people interested to build with wood, although, there is not yet enough them. He also expected that experimental timber building would occur in the near future and from that point on, “people will start to understand that it is not dangerous.”

Moreover, the Architect and the DTU student expected that multi‐story timber structures would be built in the next 10 years in Denmark, whereas the Senior Engineer was aware of three timber buildings that were already in the preparatory phase in Denmark and they would be the first ones to break through the height of 12 metres.

A specific question for the Senior Engineer: It was asked whether he was involved in collaboration within any project, which was working on the development of a timber structure in Denmark, to which he admitted he was part of one such project, analysing timber for high‐rise buildings. As expected, he agreed that improvement was noticeable, but more people were needed to be interested in building

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with wood. The fact agrees with the statistics that timber buildings are primarily built by people who are interested in wood. His respond suggested a similar solution to the Architect´s answer, which was that sustainability should be put into our economy, noting that “the business is harsh towards recyclable constructions.”

Conclusion: From the author’s perspective, even though the Danish regulations function as performance‐based, the competent people who are in position to influence the regulations should re‐ evaluate, re‐phrase and direct them more towards being function‐based to avoid common misconceptions regarding fire safety in the construction field. Moreover, in order to construct buildings with the lowest greenhouse emission footprint using sustainable alternatives, it is required that sustainability be implemented into our economy by regulating the maximum footprint and energy consumption. Just as it was done in the case of energy, when the high demands were set in the regulations, the construction industry started to find the solution to a minimised energy usage.

Considering the findings regarding technical issues in this paper, such as fire safety and shrinkage, and taking into account that nowadays the Danish economy is not yet in position to conduct the experimental tests, this paper shows that we can communicate the aspects with our colleagues, explore the timber high‐rises from abroad and establish the findings into the Danish environment. One of the examples that could be proposed after conducting the research, would be to establish an experimental multi‐story timber building, similarly as in the case of introducing passive houses in Denmark. This would serve to expand the knowledge among specialists in the field as well as an exploration of the primary benefits of timber construction by the society. Personally, I hope that the three new timber buildings will only mark the beginning of a rapid expansion of high‐rise timber structures in Denmark.

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5. CONCLUSION Recent years have been very interesting for high‐rise timber structures, which have been gaining popularity around the globe among specialists as well as residents. Timber is also becoming a sustainable alternative for multi‐story buildings. Even though, in this regard, the Danish construction industry is slightly behind other countries such as Norway or Sweden, the same process can still be undertaken here.

Looking at the extensive findings from a combination of the theoretical descriptive part and the analysis of the case studies and interviews, the main goal of the research has been achieved by proving the statement that, within the respective legal and technical aspects, multi‐story timber structures are feasible in Denmark.

From the research that has been conducted in this paper, it is possible to conclude that the history of the capital city’s damage from conflagration, the evolution of regulations, the building tradition of prefabricated concrete elements and the misconception about fire regulations are the reasons why Denmark is lagging behind in the area of timber construction.

It has been confirmed that wood is a desirable material for the construction industry in terms of sustainability and environmental aspects, in decreasing the high percentage of annual CO2 emissions that the building industry accounts for, and, additionally, brings supplementary advantages to the field.

It can be concluded that even though the legislation towards combustible structures in Denmark is performance‐based, the common misconception within the construction industry that combustible structures are prohibited to be built above four stories still prevails.

The research has clearly determined that nowadays, the major challenge regarding multi‐story timber construction is fire resistance, despite wood burning being predictable already in the design phase as opposed to other materials. The research has also shown that the fire‐safety strategy for high‐rise timber structures is attainable by the combination of the charring and encapsulation methods up to a certain height, while adding automatic sprinkling system leads to dramatically increasing the safety of such constructions.

The paper has looked at another key challenge of timber structures, which is the load bearing system.

The properties of wood in the connections allow for creation of shrinkage on the horizontal elements under cumulative loads, while lightness of the wood causes dynamic actions at a certain height. Even though the load bearing system regarding multi‐story structures poses issues, there is space for innovative structural solutions.

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In addition, it has been indicated that lightness of wood has a positive effect on transportation and mass timber products can thus be imported to “short‐on‐wood” Denmark from long‐distance manufactures, located in Austria or the north of Sweden.

Despite all the technical challenges and limits, it is still possible to design appropriate solutions for multi‐ story timber structure that will have the same or even a higher level of safety and indoor comfort than any other concrete or steel building. Looking at other cases from abroad, it has been found that by following the same methods, similar timber buildings have the potential to be constructed in Denmark as well.

To summarize, it can be said that it is achievable to build flexible timber constructions of up to/around 15 stories despite the shrinkage and lightness of wood. Additionally, results indicate that Denmark is expected to expand multi‐story timber construction in the range of 5 to 10 years.

The findings of the research are quite convincing, and thus the following conclusion can be drawn: building one of the first new multi‐story timber buildings should be done under the circumstances of integrated project delivery (procurement), close collaboration between all parties, including the client, architect, engineer, contractor, manufacturer as well as the sub‐contractor, however, the author considers to undertake the projecting documentations in the study project in the next bachelor phase.

Firstly, the case‐study method in this paper has not been undertaken due to the fact that multi‐story timber construction has not yet been performed in Denmark. Secondly, appropriate documentation and information of any case from abroad would be hard to obtain because of distance. And finally, time constraints also played role. Unfortunately, the prediction of hardly achievable information was confirmed by the fact that none of the six appointed designers or engineers from abroad as well as Denmark have not responded to my questions.

5.1 FUTURE PERSPECTIVES From the outcome of the investigation it is possible to suggest that further study can look into the procedures of pushing sustainability into our economy and regulations as well as examining the proper solutions towards minimizing CO2 emissions, even though the manufactures have slowly been improving in providing the values for the life‐cycle assessments. Moreover, fire departments and authorities could re‐evaluate and update the regulations in terms of avoiding the misconception regarding fire as well as adding life‐cycle assessment into the requirements.

In addition, the research shows that technical examples could be drawn from other cases, since the Danish construction industry does not have enough funds for experimental testing. Even though many high‐rise timber buildings have been constructed around the globe in the recent 5 years, most Page | 48

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improvements have been achieved by building upon the knowledge during each previous project.

Nonetheless, it is possible to further develop and improve the expertise about high‐rise timber constructions by sharing between countries.

Over the 20 years, the research facilities have been conducting wide‐scale testing of mass timber structures in order to obtain better understanding of fire resistance and structural capacity, however, further research in the field to fill the gaps regarding timber behaviour in the height is still required.

Additionally, it has occurred throughout the research that future work could be directed towards exploring the acoustic aspects of timber structures, since there is a general lack of analyses in this area.

5.2 CONTEXTUALIZATION The paper’s research has shown that in terms of legal and technical aspects, multi‐story timber buildings are feasible in Denmark and therefore, the author considers to prepare the project documentation of a multi‐story timber building during the next phase – the bachelor project. After the extensive research of all recent timber construction in the market, the author would like to combine the structural Option 1 from the Case Study – Tall Wood, with the proposed design for the wooden skyscraper in Stockholm74. The structure Option 1 will consist of 12 stories, made of structural core (CLT) and columns‐beams system (glulam) with the Pitzl connecting system. The timber building will have a residential purpose with a coffee shop and a restaurant located on the ground floor, together with a three‐story concrete underground parking lot for the inhabitants. The building shall accommodate mechanical installations, such as the heating recovery system, heating pump system, solar panels as well as the water harvesting system. It will be located at a suitable location in the harbour area of Odense, all after the conducting of proper analyses.

74

(C.F. Moller, 2016, “Wooden skyscraper in Stockholm”)

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Chadwick Dearing Oliver, Nedal T.Nassar, Bruce R. Lippke, James B. McCarter. (2013). "Carbon, Fossil Fuel, and Biodiversity Mitigation With Wood and Forests." [Journal of Sustainable Forestry] 248‐ 275(33.3), p. 261‐270. Available at: http://www.tandfonline.com/doi/pdf/10.1080/10549811.2013.839386 [Accessed Mon. 29 Aug. 2016].

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Danzig Ilana. (2013). “Tall wood in Canada: Feasibility study, Technical Guide, and Wood Innovation and Design centre.” [case study] (11). Available at: http://www.forum‐ holzbau.com/pdf/IHF_13_Danzig.pdf [Accessed Web. 31 Aug. 2016].

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https://www.ted.com/talks/michael_green_why_we_should_build_wooden_skyscrapers#t‐235693 [Accessed Fri. 12 Aug. 2016].

Green Michael. (2016). "Fast.Co Design: Can Timber Skyscrapers Really Help Save The Planet? ‐ MICHAEL GREEN ARCHITECTURE." [online] Available at: http://mg‐architecture.ca/news/can‐timber‐ skyscrapers‐really‐help‐save‐the‐planet/ [Accessed Tue. 20 Sep. 2016].

Green Michael. (2013). “Finding the Forest Through the Trees: Building Tall with Timber ‐ Council on Tall Buildings and Urban Habitat.” [Journal] (issue 3). p. 46‐49 Grondahl Mika. (2010). “Building with Engineered Timber.” [online] Available at: http://www.nytimes.com/interactive/2012/06/05/science/0605‐timber.html?src=recg&_r=0 [Accessed Wed. 14 Sep. 2016].

Kremer, P. D., and Symmons, M. A. (2015). "Mass Timber Construction as an Alternative to Concrete and Steel in the Australia Building Industry: A PESTEL Evaluation of the Potential." [International Wood Products Journal] 138‐147(6.3), p. 143. Available at: http://www.forestbusinessnetwork.com/wp‐ content/uploads/Kremer‐Symmons‐2015‐Mass‐Timber‐Construction‐PESTEL‐Review.pdf [Accessed Tue. 13 Sep. 2016].

Leonardo da Vinci, Pivotal Project. (2008). “Handbook 1 Timber Structures, Educational Materials for Designing and Testing of Timber Structures – TEMTIS.” First Edition, p. 1‐5, 15‐28. Available also in pdf. form: http://fast10.vsb.cz/temtis/documents/handbook1_final.pdf [Accessed Web. 07 Sep. 2016].

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Minik Lange Pedersen. (2016). “Clarification of the possibilities of using timber as bearing structure in multi‐storey building in Greenlad.” [master dissertation], p. 14‐33.

MGB Architecture + Design, Green Michael. (2012). “The Case For Tall Wood Buildings – How Mass Timber Offers a Safe, Economical, and Environmental Friendly Alternative for Tall Building Structures.” [case study] (240), p. 32‐38, 42‐49, 111‐113, 134‐135.

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Skidmore, Owings, Merrill, LPP. (2013). “Timber Tower Research Project.” [case study] p. 4‐18.

Stora Enso Wood Products. (2016). “CLT – Cross Laminated Timber – Fire Protection.” [research report], p. 14‐15. Available at: http://www.clt.info/wp‐content/uploads/2015/10/CLT‐ Documentation‐on‐fire‐protection‐EN.pdf [Accessed Thr. 25 Aug. 2016].

Survey of International Tall Wood buildings ‐ Forte. (2012). “Bulletin of Lessons Learned – Forté, Melbourne, Australia.” [survey] Available at: http://www.rethinkwood.com/sites/default/files/Forte_Bulletin.pdf [Accessed Web. 31 Aug. 2016].

Survey of International Tall Wood buildings ‐ Lifecycle Tower One. (2012). “Bulletin of Lessons Learned – Lifecycle Tower One, Dornbirn, Austria.” [survey] Available at: http://www.rethinkwood.com/sites/default/files/LCT‐1_Bulletin.pdf [Accessed Web. 31 Aug. 2016].

White Gavin, Dowdall Alan, Neve Oliver. (2015). “Building With Timber.” [online] Available at: http://www.ramboll.co.uk/about‐us/key‐ themes/~/media/5256B3D2E9E14B9FB46A141F1F002DB0.ashx [Accessed Thr. 08 Sep. 2016].

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Wood Solutions, design and build – Lifecycle Tower One. (2012). “Lifecycle Tower One.” [case study] Available at: https://www.woodsolutions.com.au/Inspiration‐Case‐Study/LifeCycle‐Tower‐One [Accessed Web. 31 Aug. 2016].

SECONDARY LITERATURE GO2WOOD (2016). “National goal to promote sustainable building in Denmark.” Available at: http://choraconnection.dk/en/national‐maalsaetning‐skal‐faa‐danmark‐til‐at‐bygge‐mere‐i‐trae/ Karacybeyli Erol (2013). “CLT Handbook – Cross‐laminated timber.” Available also in pdf. form: http://www.rethinkwood.com/sites/default/files/clt/CLT_USA‐Chapter‐6_0.pdf Leonardo da Vinci, Pivotal Project. (2008). “Handbook 2 Design of Timber Structures according to Eurocode 5, Educational Materials for Designing and Testing of Timber Structures – TEMTIS.” First Edition. Available also in pdf. form: http://fast10.vsb.cz/temtis/documents/Handbook_2_Final_version.pdf The most natural resource. (2016). “Why to use wood.” Available at: http://www.themostnaturalresource.com/why‐build‐with‐wood/

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APPENDICES APPENDIX 1: Preparation of the Interview questions INTERVIEW DATE: INTERVIEW PLACE:

RESEARCHER INFORMATION NAME: PROFESSION:

INTERVIEWEE INFORMATION NAME: PROFESSION:

The research paper is written as part of the 7th semester mandatory dissertation for the Bachelor in Architectural Technology and Construction Management at EAL. The problem statement of the research paper is describing and analyzing of multi‐story timber buildings have not constructed in Denmark yet with comparison to other countries where multi‐ story timber buildings are raising one by one, higher and higher at the present time.

The aim of this interview is to gain the qualitative date from chosen relevant interviewees about multi‐story timber buildings in order to conducted appropriate analysis for dissertation.

MAIN INTERVIEW QUESTIONS

ESSENTIAL BENEFITS 1. Do you think that multi‐story timber buildings should be a primary focus of Danish construction industry? If yes, why?

LEGAL CONSIDERATIONS AND TECHNICAL ISSUES 2. Danish regulations are open up for any alternative solutions as long as the building proposal can be documented, similarly as in Norway and Sweden. Have you experienced that tradition may be the reason why multi‐story timber buildings have not been constructed in Denmark compare to other Scandinavian countries yet?

3. Where do you see the biggest problems of concern in multi‐story timber buildings up to 12 floors and above the 12 floors except regulations? Is it structure, fire safety, shrinkage, moisture or acoustic?

4. In your opinion, could charring method be more economical approach towards passive fire protection compare to encapsulation method in order to keep the wood visible and bring natural footprint to the interior? Would you consider to using the untreated wood in front of treated wood?

5. Do you think that lack of knowledge about engineering timber elements and lack of manufactures on the market may be the reasons for not executing any multi‐story timber

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buildings in Denmark yet? If yes, what would your recommendations be to Danish construction industry?

6. Have you considered that weather conditions in terms of moisture might be the major obstacle for timber buildings in Denmark, because Danish weather conditions does not have enough hot period as well as frosty period in order to get rid of moisture? If yes, do you have an example?

7. What do you think, how might the ration of water be predicted and/or controlled in load‐ bearing timber elements for long‐time period in order to avoid shrinkage or expansion of timber?

8. Do not you think that multi‐story timber structures will require more maintenance services in long‐time compare to steel and concrete structures?

POSSIBLE IMPROVEMENTS 9. From your perspective, what do you see as main obstacles in the industry regarding multi‐ story timber buildings in Denmark? How would you propose to solve the challenges?

10. Generally, based on your experiences and expectations, what changes may Danish construction industry be expecting from upcoming updates of regulations about timber building in coming years?

11. When would you expect that the first timber building above 12 floors will be executed in Denmark?

SPECIFIC INTERVIEW QUESTIONS 1. As involved collaborate within Go2wood project and other initiative organizations, what are your further goals in order to bring more developments of timber buildings in Denmark?

2. What main challenges have you experienced during designing the Vanløse Station project?

3. What challenges have you experienced during designing timber structure of 8 story building in Greenland?

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Appendix 2 INTERVIEW TRANSCRIPT WITH JONAS SANGBERG, ARCHITECT INTERVIEW DATE: 02.09.2016 INTERVIEW PLACE: Bygmestervej 55, CPH

RESEARCHER INFORMATION NAME: David Patoprsty PROFESSION: Undergraduate student of Architectural Technology and Construction Management at Lillebælt Academy of Professional Higher Education (EAL)

INTERVIEWEE INFORMATION NAME: Jonas Sangberg PROFESSION: Creative Director and Architect MAA, MDL at Sangberg Architects

MAIN INTERVIEW QUESTIONS

The research paper is written as part of the 7th semester mandatory dissertation for the Bachelor in Architectural Technology and Construction Management at EAL. The problem statement of the research paper is describing and analyzing of multi‐story timber buildings have not constructed in Denmark yet with comparison to other countries where multi‐ story timber buildings are raising one by one, higher and higher at the present time.

The aim of this interview is to gain the qualitative date from chosen relevant interviewees about multi‐story timber buildings in order to conducted appropriate analysis for dissertation.

ESSENTIAL BENEFITS 1. Do you think that multi‐story timber buildings should be a primary focus of Danish construction industry? If yes, why?

Answer: Definitely, it should. In timber buildings is a big potential. The reason is because of this co2 issues which concrete produces and 90% of Danish buildings is built with concrete. If you start to look into the sustainable discussion then everything about energy efficiency is solved in building regulations in DK, but the fire is issue regarding timber which has to be updated in regulations. Yes, the wood is sustainable material in terms of reducing CO2 emotions. It also has back side that if everybody will be built by wood then there would not be enough forest. The forest has to be managed carefully.

LEGAL CONSIDERATIONS AND TECHNICAL ISSUES 2. Danish regulations are open up for any alternative solutions as long as the building proposal can be documented, similarly as in Norway and Sweden. Have you experienced that tradition may be the reason why multi‐story timber buildings have not been constructed in Denmark compare to other Scandinavian countries yet?

A: It was not allowed to build wooden houses for many years, because there wasn’t a forest.

Therefor we have brick tradition. That’s why it hasn’t been so much constructive, because we

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have not raw materials, but in Sweden and Norway is the forest everywhere. And it is also in Austria and Germany for example. Yes, definitely it is!

3. Where do you see the biggest problems of concern in multi‐story timber buildings up to 12 floors and above the 12 floors except regulations? Is it structure, fire safety, shrinkage, moisture or acoustic?

A: I am not sort of expert in construction, but it seems that the biggest issue right now is fire safety in Denmark, but these mass timber elements do not burn very well. Of course, the structure is also the issue. There is one project in Norway when the building has the power floor every fifth floor. So again, you have to think different as you did before. Similarly, we have worked with wooden models while they had to be supported by steel every fifth floor.

Another issue is moisture and they are explaining because of new building regulations the building has to be constructed so air tight because the blow door test has to be conducted.

For instance, the window frames are constructed into the wall construction with minimum heat losses and indoor engineers said that in this kind of connection should be used minimum amount of different materials because of chance of moisture occurrence. Due to building density, the building is commonly wrapped to be air tight by plastic membrane which is kindly living in plastic bag.

4. In your opinion, could charring method be more economical approach towards passive fire protection, compare to encapsulation method in order to keep the wood visible and bring natural footprint to the interior? Would you consider to using the untreated wood in front of treated wood?

A: I think, it would be weird to put bricks outside of the wooden building. It would not be standard to keep wood open to outside in Denmark, but there are some possibilities; you can do it by protection layer or use burned wood cladding, it is quite beatific.

It always uses untreated wood in order to be in sustainable way. In some of the areas, actually you are not able to used treated wood.

5. Do you think that lack of knowledge about engineering timber elements and lack of manufacturers on the market may be the reasons for not executing any multi‐story timber buildings in Denmark yet? If yes, what would your recommendations be to Danish construction industry?

A: I think definitely it is. Sort of when we are talking about housing production, we meet people in the field who says, they have to come home and calculate it, because everything is so standardise. When you are doing standard concrete building, then you are doing the same

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thing what you did yesterday. By these new things, you have to invent new approach and spend more time. Of course it is always easier to do what you use to do because you have to do tests. Nowadays you can also get findings from government. In edition we are also looking for some findings here in the office, because the government is interesting in the innovation.

We have already applied for some, but have not got any yet.

6. Have you considered that weather conditions in terms of moisture might be the major obstacle for timber buildings in Denmark, because Danish weather conditions does not have enough hot period as well as frosty period in order to get rid of moisture? If yes, do you have an example?

A: This issue is what I was always listing in Denmark, why not doing wooden houses. But again, when you start to look the brick houses, they also made the cracks, so of course it is about how you construct the building. If you see some of the houses in Switzerland, they are standing on fewer points and you get the air around the house. That is one of the way, but of course it has to be dry.

7. What do you think, how might the ratio of water be predicted and/or controlled in load‐ bearing timber elements for long‐time period in order to avoid shrinkage or expansion of timber?

A: Sort of, here we are getting out of my knowledge, I would say. I am more like a creative designer, I am not engineer. So no comments.

8. Do not you think that multi‐story timber structures will require more maintenance services in long‐time compare to steel and concrete structures?

A: I think, this is quite important issue. Definitely, when you want to have free standing wood, you have to maintain it more. It is becoming interesting when you have to look for the products which does not require a lot of maintenance. It is mandatory to look at the maintenance perspective as one of the first design parameters.

POSSIBLE IMPROVEMENTS 9. From your perspective, what do you see as main obstacles in the industry regarding multi‐ story timber buildings in Denmark? How would you propose to solve the challenges?

A: It is sort of tradition in Denmark and it has a dinosaur business of concrete elements in the industry. If you see, Denmark is leading country of prefabricated concrete compare to other European countries when they still do on‐site casting. The reasons why Denmark has a lot of concrete prefabrication, is weather conditions, mainly the price and erection speed.

Generally, it is like a monopoly which is hard to break, but everybody knows that. I think, it is

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really clear that the regulation will be the best way of solving it. I think, when you start to regulate the CO2 footprint of the building and life span of the materials. You could say for example, that the building must gain certain amount of energy after 2020 and the building must not have certain amount of CO2 footprint. Then you will not say that you have to use the wood, but you would use the alternative material. You also have sustainable certification as DGNB, but they are volunteer and this way the timber buildings may get popular where people will like to live. You could see it in energy manner, when after the set regulations, people have started to solve and find solution to minimised energy uses, so I think, and this is a one way of implementing it. On the other way, there are people who are interested to building with wood, but there is not enough them.

10. Generally, based on your experiences and expectations, what changes may Danish construction industry be expecting from upcoming updates of regulations about timber building in coming years?

A: Also 20 years ago, there was this kind of experimental wood buildings. I think there will be some of those coming very soon. And people will see this big movement going on and big potential and they going to realise that it is not dangerous because some people are septic about it and how it going to be.

11. When would you expect that the first timber building above 12 floors will be executed in Denmark?

A: In 10 years, you never know.

SPECIFIC INTERVIEW QUESTIONS 1. What main challenges have you experienced during designing the Vanløse Station project?

A: It was fire definitely! You have a shopping mall made of concrete, up to 2‐3 storey.

Therefore, the shopping mall was under construction while the client wanted to built apartment buildings of 4 storey on top of it, so residential building on top have to be design by wood. So they treated the roof of shopping mall as 0, in same time it is ground level for residential row houses.

In addition, the shopping mall has big skylights, functioning as smoke ventilation, therefore, the skylights have to have certain distance from row houses. Due to much regulations for smoke ventilation, the ventilation ducts have to be brought above the 4 storey row houses.

There were many other challenges involved, because of also many parties included in the project.

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INTERVIEW TRANSCRIPT WITH FINN LARSEN, SENIOR ENGINEER INTERVIEW DATE: 02.09.2016 INTERVIEW PLACE: Hannemans Alle 51, CPH

RESEARCHER INFORMATION NAME: David Patoprsty PROFESSION: Undergraduate student of Architectural Technology and Construction Management at Lillebælt Academy of Professional Higher Education (EAL)

INTERVIEWEE INFORMATION NAME: Finn Larsen PROFESSION: Senior Engineer of Fire Safety engineering (MiB) / Structural engineering (M.Sc.) / (PhD) at Rambøll Denmark

MAIN INTERVIEW QUESTIONS

The research paper is written as part of the 7th semester mandatory dissertation for the Bachelor in Architectural Technology and Construction Management at EAL. The problem statement of the research paper is describing and analyzing of multi‐story timber buildings have not constructed in Denmark yet with comparison to other countries where multi‐ story timber buildings are raising one by one, higher and higher at the present time.

The aim of this interview is to gain the qualitative date from chosen relevant interviewees about multi‐story timber buildings in order to conducted appropriate analysis for dissertation.

ESSENTIAL BENEFITS 1. Do you think that multi‐story timber buildings should be a primary focus of Danish construction industry? If yes, why?

Answer: Yes, definitely they should. They have a many advantages in terms of sustainability, however, there are issues which have to be solved in near future. The wood is the most sustainable material than any other materials, in fact. In the paper industry, there will be produced less and less paper in the future than before and all this wood which is used for paper industry, they are very keen to move the wood to be used for something else. So it would be very sustainable to use these wood in construction industry. Otherwise, the wood mass will grow, especially in countries like Sweden, Norway, Finland, large part of Russia, Poland, Germany, Austria, etc. So it will be sustainable to use that amount of wood.

It is not that costly to fabricated, it just cut it down, shaped. Only most energy consumption of timber prefabrication is coming from drying the wood to appropriate moisture content.

When you look at that sometimes, you use the wood cut‐outs for heating up the drying process (Biomass). These are main reasons for introducing the wood into the buildings.

LEGAL CONSIDERATIONS AND TECHNICAL ISSUES 2. Danish regulations are open up for any alternative solutions as long as the building proposal can be documented, similarly as in Norway and Sweden. Have you experienced that tradition

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may be the reason why multi‐story timber buildings have not been constructed in Denmark compare to other Scandinavian countries yet?

A: The reason why timber buildings are not building in Denmark yet, is because of tradition.

About 200 years ago, the part of the city burned out, it was damaged and ruined. In that time, 2‐3 storey timber buildings were normal to build while the brick was too expensive. Later it came tradition where the facade has to be built by bricks, whereas floors could be built by wooden construction, but it has to be fire resistance. The fire resistance was proofed by clay, for instance. Then concrete came into the market and especially reinforced concrete was very used building material in Denmark. In addition, it becomes governing material until now.

Concrete is till governing material, Denmark has large tradition working with concrete, specially prefabricated concrete elements. The prefabrication in Denmark is much larger than everywhere else. Our tradition to building multi‐story buildings is by using concrete. Concrete has the advantages of being stronger and stiffer material, compare to other materials as wood. And this tradition working with non‐combustible materials has sort of made preferences to prescribed regulations, which are in our Danish system. If you see Danish fire regulations, it says that the combustible material for structure is allow to used up to 12 m of uppermost storey. If you go above the 12 m, the building structure has to be made of non‐ combustible materials. It says that if the building solution will be documented the same safety with combustible materials, then you will be allow to build it. We have to find out how this tradition can be changed that we will also be able to build by combustible materials.

3. Where do you see the biggest problems of concern in multi‐story timber buildings up to 12 floors and above the 12 floors except regulations? Is it structure, fire safety, shrinkage, moisture or acoustic?

A: We have to be aware that we cannot build high‐rises of 20 storey or something similar.

Personally, I think that there will be competitive limit of 12 – 15 storey, especially because of stiffness and shrinkage problems.

There is funny storey from Stockholm where they want to raise 100 meters building of 30 storey. However, it will get major problems in long term, because of shrinkage. They have calculated that the wooden part of building would fall by half a meter down while concrete core would stay on same position. Well, it would be pretty awkward to look the solution where you would get up to topmost floor by elevator and step down half a meter to apartment. Resulting that there will be limits around 15 storey. It will be hard to break a tradition of building high‐rise buildings which are made of steel in some way in London or New York nowadays. When you compare steel and wood in term of fire, that we know how

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much wood will last while in term of steel we are not able to know bearing capacity under fire exposure. The benefit is that wood does not expand when it is heated whereas steel and concrete do. Every material has advantages and disadvantages, but when you talk about high‐ rise, you get limits for wood. How many high‐rise building do we need and how many do we want in city above 10 storey? Not many! Usually, the buildings in Denmark will be around 5‐7 storey and then we get some few extraordinary tall‐iconic buildings. It is also appropriate high of building for residential, because when you get higher, you get additional problems regarding installation.

Our department in Norway tried to solve this problem, to provide building solution as safe as concrete structure. They made the 9 storey building in Trondheim. The department in UK, they are going to raise the 10 storey building by CLT elements. If you see 10 storey timber building, actually you do not see that much wood, when it is finished. All walls will be hidden by using plasterboard to fire‐protected. The main issue for using wood in multi‐storey building is fire and then it will be the stiffness around it. You know when you build with wood, it is orthographical material. Meaning that the wood has very different strengths and stiffness in each direction. If you look at piece of concrete, it has the same stiffness in y, x and z direction. However, the wood has three different stiffness and you have 6 different strengths depend of which direction you compress it or maintain the stretches. It is very complex material to work with and that is one of the challenges to using the wood in high‐rise building.

However, it is manageable, we can do it, and we can work with this system, so there is no problem.

Some of the solution today is, where you have a piece of CLT element in vertical direction, the floor element in horizontal direction comes on top of the wall element and then you get the wall on top of floor element. In fact, you get 10 times more stiffness in vertical direction of wooden element than in horizontal direction. This issue, they are trying to solve by putting the hard pieces into the horizontal floor element (concrete).

The CLT will be the most used product for high‐rise timber buildings. If you have seen the multi‐storey timber building in Bergen, they built in the way of trusses structural system with CLT modules of 5‐6 storey inside and repeat again. This could be one approach to get into the height. The good thing about transporting of wood element is, that it uses the less space compare to steel or concrete. Another advantage is that the timber elements are manufactured precision and with large span. Wooden elements are more precise than the concrete elements.

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In connections, CLT elements get compressions/shrinkage. Bearing capacity of wood is 24 normally in vertical direction, whereas in horizontal direction is just 2.5. This fact, you have to take it into the account when you design the connections by CLT. In London project, they solved by inserting the pieces of timber (hard wood) in the vertical direction as well as pieces of concrete, inserted inside to the horizontal floor elements.

This is the experiment where you load it the top of the wall on horizontal floor element and horizontal floor element got damaged after more and more loads. These can be some of the ways, how to handle the CLT connections.

Somebody is working with idea of hybrid structures, to create concrete core in the middle to make a stable, but problem with this solution will be, if you look the stiffness in the height of the building, then the concrete will be much stiffer than the wood structure around.

Personally, I am bit sceptic about hybrid systems in long terms, because you use concrete as top layer and concrete has different life time properties whereas wood has long term deflection. It would be interesting if these two materials can work together, and it also is pretty challenging way of design it. I can see some advantages, but firstly I have seen this system, it was introduced 15 years ago in USA. Because they have a lot of wood, they have tried to reinforce the bridges by concrete as top layer and it brought the issues about shear stress. It has different stiffness and elasticity, but I do not know how much the construction market has worked with hybrid system.

4. In your opinion, could charring method be more economical approach towards passive fire protection compare to encapsulation method in order to keep the wood visible and bring natural footprint to the interior? Would you consider to using the untreated wood in front of treated wood?

A: The CLT element has shown that horizontal element (floor slabs) has much larger charring time as they have expected early. Vertical burning capacity of wood is 0.6 mm per minute plus 0.7 mm, while the horizontal burning capacity is 1.1 mm per minute. Some pieces of wood falls down during wood burning and it will raise the fire. If you consider the wall with charring method, it will require oversizing by 50 – 60 mm. But it could be manageable in manner of floor elements by oversizing.

If we should compare the prices of both method, it will be more less the same cost. Probably, it might be cheaper to just oversize the floor elements, because then it will not require any additional work on site. However, in term of wall, it will be cheaper to use the encapsulation method. Additionally, the walls become dirty and scratched by the time and exposed wood will not look clean any more. In this matter, I recommend to plaster boarded.

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5. Do you think that lack of knowledge about engineering timber elements and lack of manufacture on the market may be the reasons for not executing any multi‐story timber buildings in Denmark yet? If yes, what would your recommendations be to Danish construction industry?

A: Well, we have a CLT producers in Austria, Switzerland, and south of Germany, which is pretty far from here. We also know that in north of Sweden will be one of the CLT producers, but it will be the same transport distance as from Austria or south of Germany, for instance.

As I can see, the transport is not big problem because it has much more volume than the weight. You can have almost 8 CLT panels in one truck.

CLT is relatively new product on the market and we have some mass timber producers in DK as glulam, but there will not be any CLT producers unless we will have some volume of wood (m3). If you want to do export of products, you have to have your own market in order to shows how to use the product. The main reason why timber building have not come to Denmark yet, is regulation. Denmark has very good prefabricated industry of light wood elements and they are economically comparable to CLT elements. Danish construction industry introduces new products to the market when it is just for benefit. CLT panels obtain shear stresses where you could imagine that wooden frame always get some cladding and it functions as plate, and it is one of the positives. In wood industry, we have talked that we do not need to use CLT elements for everything. These panels also get some limits, the spans can get up to 6 meters for flooring while concrete is much better for lengths, for instance. For open spaces as offices building will be more adequate to use concrete or steel than wood, but we can work with combination of glulam systems or concrete.

6. Have you considered that weather conditions in terms of moisture might be the major obstacle for timber buildings in Denmark, because Danish weather conditions does not have enough hot period as well as frosty period in order to get rid of moisture? If yes, do you have an example?

A: That’s one of the main issues, when we talk about the using timber in DK. Usually when you use the wood as a structural elements, you will use the damp proof membrane. When I see this mass timber elements, they will dry out very fast, but you have to make sure that the elements will not be exposed to outside. They have to be protected by DPM as well as they have to be protected during construction period too.

In other countries, they thought that they can dry out the wood elements afterwards, it can be fare into some extend, I think. Here in Denmark we have skiben mould which must not occurred. The mould occurs when you have wet piece of wood for very long time, but if you

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are able to dry out fast that it is not big a problem. The advantages of wood building should be that it will be dry building. You can work day after you raised the timber elements.

Harvesting of concrete is gamble of construction process, because you do not know when exactly it will be dry out. That’s one of the disadvantages using concrete. We use to store the concrete elements outside which is our tradition.

7. What do you think, how might the ration of water be predicted and/or controlled in load‐ bearing timber elements for long‐time period in order to avoid shrinkage or expansion of timber?

A: It is important to keep the moisture content stable as possible. That is large issue! Well, before you glue and manufacture the element, the raw wood is dried down to 10 – 12 % ratio of moisture content. It is same like in the compartment. The compartment in building will be amount between 8 – 12% ratios of moisture in the wood. That is related to building elements which are come to the site. In this sense, you have to be just aware that elements cannot get wet before you build it in.

The CLT connection in horizontal direction will shrink in dry condition by 5%, while 10 % would shrink in wet condition. In the same time, it will just shrink 1% in vertical direction.

Therefore, the connection of CLT elements have to be improved with some hard wood breaking system or some steel plate, it will be advantage. I do not like idea with using concrete! Why using concrete while you could extend the wall elements and connect them every 1 meter, for instance. But this make the wall element more difficult to produce when they want to have clean cuts and hence the elements will be more expensive. One of the solution for this connection issue would be steel nail connection (hidden) which has 30 MPa in order to gain stiffness for connection. Another introduced solution is bracket system. In this system, you will get more eccentricity to the wall element, which is the reason why they do not like the idea, but it may be solved by oversizing the element thickness.

8. Do not you think that multi‐story timber structures will require more maintenance services in long‐time compare to steel and concrete structures?

I do not think so, if you will constructed building correctly. If you use the wood on dry side of the façade, then it should not be a problem.

Regarding long term matter, I have to add that we have wrong debates about long term duration. When we design the building, we expect to last for 50 years and bridges for 100 years that are normal scope we are working with. If you look at the development in building industry from 10 years ago until now, you will see that insulation in facades has increase from 100 to 250 and in floors has raised from 100 to 400 mm, in addition it demands more

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technical solutions for indoor climate, more tight building and so forth. Nowadays, you expect to get light from everywhere. This is one thing which will change over the time, and we get a many building which are outdated rather fast. Then we can ask, why to have the building for more than 50 years? So I think, we should look on the building as a product, similar as car.

Look more on the life cycle of the building, because we have to tear down the building in some time. We should take care more about recycling of materials during design. You cannot recycle the concrete, you can use it just for roads. Into the end, we change demands for buildings every time. For instance, we require to have more space than 60 years ago.

Therefore, buildings get outdated very fast and of course, we keep some building in order to show tradition, however, most of the building are demolished. We should look on the building as product – car. I know, when you try to install more insulation to old building, you just create more problems into the building.

POSSIBLE IMPROVEMENTS 9. From your perspective, what do you see as main obstacles in the industry regarding multi‐ story timber buildings in Denmark? How would you propose to solve the challenges?

A: The major obstacle is regulation and it will be nice if we get the economy to provide more tests, but we can look on cases from other countries and say that while they can do it, then we also can do it. Additionally, we have to transfer that into the Danish environment.

In Danish construction industry had case when they introduced new MDO board for wind breaks on light facades. It was very good board of class 1, it could withstand large amount of fire and it was opened for diffusion. Only disadvantage was when moisture occurred over 85%, it realised the asset drops which have high effect on human health. Until now there is 1 million area of this board. This was new material 5 years ago and it showed that we have to be careful when we introduce new materials to the market. We have to be sure that we are bringing right material among all aspects.

10. Generally, based on your experiences and expectations, what changes may Danish construction industry be expecting from upcoming updates of regulations about timber building in coming years?

A: We will expect more sensible attitude towards material choice. I think the solution would be that we can build by any material we would like, but with fire safety in the first place. If we will build by non‐combustible material, it will be used less active protection as if we will build by combustible material. We can get very far with sprinkling system in term of fire safety. The

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college in Bergen, they showed that the sprinkling system is very good solution for even though none protected timber elements.

We expect to get away the demand of not using combustible material, but instead to get more flexibility into the designed solutions.

11. When would you expect that the first timber building above 12 floors will be executed in Denmark?

A: I do not know, but I know that in Denmark will be 3 timber building which are getting started. One of them will be in Østerbro, Copenhagen. The elderly utility will be demolished and will be built by timber. The architectural completion have been won by C.F. Moller, who will be the first to break the wall of timber structures above 12 meters in Denmark.

SPECIFIC INTERVIEW QUESTIONS 1. As involved collaborate within Go2wood project and other initiative organizations, what are your further goals in order to bring more developments of timber buildings in Denmark?

A: Personally, I am not that large part of this project, but I am part of one of the project which is analysing the wood for high‐rise building. It is improving by time and we need people who would like to build by wood. Statistic also show that wooden buildings are primary built by people, whom are interesting about wood. The problem is that we always talk about economy when we want to introduce new product. However, we have to put sustainability into our economy that construction materials should be documented how they will be recycled in the end of life time. The budget of building should be calculated with long term perspectives because the client or developers just look on how much is capital cost of rising the building and how much I can gain from the tenants. They do not care about sustainability and business case is bit harsh towards sustainability. We are working with matter of concrete delivery time, which can be advantage for wood. It has started in England, where the concrete producers have been booked out for 1 and half year in front because of Olympic Games in that time. So one architect said to client, if you want to have the building, it has to be built by other material, for example wood. And they did it. Entire building is built by CLT elements and it is nice story.

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INTERVIEW TRANSCRIPT WITH MINIK LANGE PEDER, DTU STUDENT INTERVIEW DATE: 02.09.2016 INTERVIEW PLACE: Baresso Coffee ‐ Lyngby Hovedgade

RESEARCHER INFORMATION NAME: David Patoprsty PROFESSION: Undergraduate student of Architectural Technology and Construction Management at Lillebælt Academy of Professional Higher Education (EAL)

INTERVIEWEE INFORMATION NAME: Minik Lange Peder PROFESSION: DTU absolved of MSc in Civil Engineering, Junior Civil Engineer at NIRAS

MAIN INTERVIEW QUESTIONS

The research paper is written as part of the 7th semester mandatory dissertation for the Bachelor in Architectural Technology and Construction Management at EAL. The problem statement of the research paper is describing and analyzing of multi‐story timber buildings have not constructed in Denmark yet with comparison to other countries where multi‐ story timber buildings are raising one by one, higher and higher at the present time.

The aim of this interview is to gain the qualitative date from chosen relevant interviewees about multi‐story timber buildings in order to conducted appropriate analysis for dissertation.

ESSENTIAL BENEFITS 1. Do you think that multi‐story timber buildings should be a primary focus of Danish construction industry? If yes, why?

Answer: I do not know if I can answer it, yes or no. I think, it should be more explored and researched because it is something renewable. Additionally, regarding the CO2 positional, they should definitely do it.

LEGAL CONSIDERATIONS AND TECHNICAL ISSUES 2. Danish regulations are open up for any alternative solutions as long as the building proposal can be documented, similarly as in Norway and Sweden. Have you experienced that tradition may be the reason why multi‐story timber buildings have not been constructed in Denmark compare to other Scandinavian countries yet?

A: Yes, it is! I read some article that some Danish expert discussed the evolution of regulations and timber and they said that it is because of big fire in the past. And this directed to change prescribed regulation to be strict towards combustible materials.

3. Where do you see the biggest problems of concern in multi‐story timber buildings up to 12 floors and above the 12 floors except regulations? Is it structure, fire safety, shrinkage, moisture or acoustic?

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A: Actually, my case study was in Greenland and they have more wind forces than in Denmark and it also may be main obstacle in DK. This issue is linking with the structure, so from my perspective it is structure and additionally fire safety. I do not know that much about any other mentioned obstacles, but I know that wooden buildings can have big problems with moisture and occurred mould. Of course, it can be solved.

Regarding shrinkage, CLT panels are crossed‐rise and it has different strengths and stiffness in each of horizontal and vertical direction.

I did the calculations of fire resistance for 180mm CLT wall and in scenario, if fire will go off on both sides of wall, it would totally burn out during 2 hours.

4. In your opinion, could charring method be more economical approach towards passive fire protection compare to encapsulation method in order to keep the wood visible and bring natural footprint to the interior? Would you consider to using the untreated wood in front of treated wood?

A: I am not sure which one is more economical in my project, I used to protect the building by encapsulation method (pasteboards). I have also considered to use the charring method (painting), it is more expensive than plasterboards.

5. Do you think that lack of knowledge about engineering timber elements and lack of manufactures on the market may be the reasons for not executing any multi‐story timber buildings in Denmark yet? If yes, what would your recommendations be to Danish construction industry?

A: Yes, I agree. There is lack of knowledge about the timber products on the market, because in Denmark have not executed any timber buildings yet. The industry is in the progress right now and maybe there will raise one in 4‐5 years. I recommend to construction industry to improve knowledge by asking neighbours that have already constructed the timber buildings as Norway or Germany.

CLT elements are still pretty expensive on the market due to lack of manufactures. But personally, I see the potential to reducing the prices.

6. Have you considered that weather conditions in terms of moisture might be the major obstacle for timber buildings in Denmark, because Danish weather conditions does not have enough hot period as well as frosty period in order to get rid of moisture? If yes, do you have an example?

A: I think, it will be one of the main obstacle in Denmark. I experienced the example during my interviews one of the Danish specialist said that never build timber buildings, you cannot protect timber against moisture. So it is really depend of personal opinions.

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MULTI‐STORY TIMBER STRUCTURES IN DENMARK

OCTOBER, 7 2016

7. What do you think, how might the ration of water be predicted and/or controlled in load‐ bearing timber elements for long‐time period in order to avoid shrinkage or expansion of timber?

A: I think, it can be monitor by the same way as they did it to timber building in Australia.

They used the sensors to monitor water ration in CLT elements. I do not know exactly the way how they did it, but I know that there is the approach how it can be monitored during life time.

8. Do not you think that multi‐story timber structures will require more maintenance services in long‐time compare to steel and concrete structures?

A: I am not sure, but if the timber building system will use the screws, it requires the maintenance and screws will have to be checked by the time, same as the steel system. In addition, there is not enough data about maintenance, because this system is very new and fresh on market.

POSSIBLE IMPROVEMENTS 9. From your perspective, what do you see as main obstacles in the industry regarding multi‐ story timber buildings in Denmark? How would you propose to solve the challenges?

A: Actually, when I did my Master dissertation about multi‐story timber buildings and the way I understand it in order to raise the high‐rise timber buildings are the regulations (fire).

Because they do not permit the timber building more than 4 storey. I would propose to update the fire regulations and direct to be used performance based regulations. However, I do not see any additional obstacles, which can be seen in Norway or Austria, for example.

And the technical issues can be solved.

10. Generally, based on your experiences and expectations, what changes may Danish construction industry be expecting from upcoming updates of regulations about timber building in coming years?

A: Danish construction industry should expect more flexibility between material choices. Also I expect that the timber buildings will be more explored by time and timber building will be raise one by one.

11. When would you expect that the first timber building above 12 floors will be executed in Denmark?

A: In the beginning of next decade, between 2020 and 2025.

SPECIFIC INTERVIEW QUESTIONS

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MULTI‐STORY TIMBER STRUCTURES IN DENMARK

OCTOBER, 7 2016

1. What challenges have you experienced during designing timber structure of 8 story building in Greenland?

A: It was the wind and wind costs the issues of dynamic actions. It was the main challenge. My goal was to use as few shear walls as possible, so I started with some shear walls and regarding dynamic problem of building, the number of shear walls had to be increased.

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