Structural Terra Cotta Mullion

FTI VITRUVIAN AWARDS 2021

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The Structural Terra Cotta Mullion is a collaborative project for the Boston Valley ACAW program 2021. The Mockup is built at BV’s Buffalo NY Facility.

STRUCTURAL TERRA COTTA MULLION

ACAW 2021 HOK, TriPyramid, Josef Gartner-Permasteelisa NA, Boston Valley

FTI Vitruvian Award HOK

Boston Valley Terra Cotta

John Neary Sr. Façade Specialist

Victoria Ereskina Façade Designer

Blake Kurasek Façade Specialist

Francesca Meola Sr. Structural Engineer

Marie Achalabun Architect

John Krouse President & CEO

Andrew Pries Preconstruction Manager

TriPyramid Structures Inc.

Patrick & Marzena Bernard, Project Photography & Video Virtual Team Meeting- Zoom Michael Mulhern President

Jeff Anderson Design Manager

Matt Bull, Project Manager

Nate White Head of Engineering

Dylan Schwallie, Intern

Josef Gartner USA – Permasteelisa NA

Roberto Bicchiarelli Design Manager

Bernhard Rudolf Director of Engineering

Leonardo Flores, Project Manager; Khalil Rahmani, Project Manager; Andrew McBride, Designer / Draftsman

TERRA COTTA MULLION Team

Façade Tectonics Institute Vitruvian Awards 2021 HOK, TriPyramid, Josef Gartner-Permasteelisa NA, Boston Valley

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FTI Vitruvian Award Challenge: Explore new ways of using Terra Cotta to design more sustainable buildings.

Terra Cotta is most familiar in contemporary facades as rainscreen cladding-- plank and baguette, some cast shapes.

Recent projects evidence growing interest in alternatives to flat glass facades.

Our concept is to use terra cotta prestressed by stainless steel tension elements to resist bending force.

We conceived this as re-thinking the mullion, and went back to the original example at Reims Cathedral, c. 1230 AD.

It is a structural element resisting bending under wind by its mass and depth.

We wanted to capture its sculptural quality in a terra cotta mullion that spans between inside and outside.

Traditional/ Pre-Modernist Terra Cotta facades were representations of stone architecture in less expensive material. The Woolworth Building’s explicitly Gothic style included carved terra cotta sculpture that mimicked stone ornament.

This cladding was wired and clamped and pinned to structural backup steel. It created the illusion of structural surface.

With its plastic ability to achieve intricate molding and carving, as in Sullivan’s ornament, Terra Cotta has been used to create surfaces of a richness never matched except in carved stone or cast bronze.

TERRA COTTA MULLION Concept

Façade Tectonics Institute Vitruvian Awards 2021 HOK, TriPyramid, Josef Gartner-Permasteelisa NA, Boston Valley

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FTI Vitruvian Award

TriPyramid tested the Terra Cotta under 10 to 20 kips of compression for behavior under impact.

The material seemed to self-heal when cracking occurred, though pieces did spall off the surface.

Nate white declared it “Tough as Nails.” Structural redundancy is achieved by the two sets of tension rods and separate TC extrusions tied at the nominally 5’ segment joints by stainless plates. Many versions were studied.

TERRA COTTA MULLION TriPyramid

Façade Tectonics Institute Vitruvian Awards 2021 HOK, TriPyramid, Josef Gartner-Permasteelisa NA, Boston Valley

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FTI Vitruvian Award

Permasteelisa modeled the mockup assembly including all terra cotta clips, support angles, fasteners, flashings and the viewing enclosure.

Initially we imagined the Terra Cotta Mullion as natural clay color but decided that glaze is integral to architectural terra cotta traditionally. BV tested a number of colors and textures on samples.

TERRA COTTA MULLION Details & Surface

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Façade Tectonics Institute Vitruvian Awards 2021 HOK, TriPyramid, Josef Gartner-Permasteelisa NA, Boston Valley

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FTI Vitruvian Award

TriPyramid developed assembly drawings for the Mullion based on a process for pre-stressing the continuous highstrength stainless steel rods that hold the sections of Terra Cotta together. Springs at the top of the rods maintain the compression force against thermal expansion or deflection, which is severely limited to L/5000. The rods pass through the plates which spread the force evenly through the clay sections, and are connected with couplings at each joint to allow for replacement of damaged sections of terra cotta, in theory.

TERRA COTTA MULLION TriPyramid

Façade Tectonics Institute Vitruvian Awards 2021 HOK, TriPyramid, Josef Gartner-Permasteelisa NA, Boston Valley

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FTI Vitruvian Award 4.5 4

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Ton ECe

1.96

2

1 .56 .43

.28

.21

.092

0

Aluminum –

Steel Painted –

Laminated Glass –

Laminated Timber –

13.2 ton ECe/ton

3 ton ECe/ ton

1.56 ton ECe/ ton

.512 ton ECe/ ton

Aluminum Tee x 2:

Steel Tee x 2: 65 plf (489 pcf, 1" x 11“/2 plus 1" x 4", 32.6 plf x 2) x 20 = 1,304 pounds

Glass Fin x 2:

Timber x 2:

34 plf (170 pcf, 2" x 2" plus 1" x 10", 14 si = 17plf x 2) x 20 = 680 pounds

Total = 4.5 tons ECe

Total = 1.96 tons ECe

Source: ICE Data Base 3.0- U. of Bath u.n.o.

36 plf (156 pcf, 1.5" x 12" = 18 plf x 2) x 20 = 720 pounds

18 plf (36 pcf, 3" x 12" = 9 plf x 2) x 20 = 360 pounds

Total = .56 tons ECe

Total = .092 tons ECe

.25 ECe / ton (10' spacing)

Terra Cotta – .24 ECe/ ton St Stl – 3.3 ton ECe/ton

Terra Cotta – .24 ECe/ ton St Stl – 3.3 ton ECe/ton

Precast Concrete:

Terra Cotta:

Terra Cotta Spar:

112.5 plf (150 pcf, 6" x 18“ = 112.5 plf x 2) x 20 = 2250 pounds

TC 40 plf, St Stl 10 plf (not incl anchors) = 800 pounds TC, 200 pounds St Stl = .10 tons Ece TC plus .33 tons ECe St Stl

TC 20 plf, St Stl 5 plf (not incl anchors) = 400 pounds TC, 100 pounds St Stl = .05 tons ECe TC plus .16 tons ECe St Stl

Total = .28 tons ECe

Total = .43 tons ECe

Total = .21 tons ECe

Precast –

We compared the Embodied Carbon-equivalent of the TCM to conventional mullions. The cross section as tested is designed to span 30’ and the stiffness would allow 10’ spacing, twice the norm for the aluminum, steel, glass and timber. We envision a spar version as well.

TERRA COTTA MULLION Embodied Carbon Eq.

Façade Tectonics Institute Vitruvian Awards 2021 HOK, TriPyramid, Josef Gartner-Permasteelisa NA, Boston Valley

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FTI Vitruvian Award

The concept might extend to a unitized curtain wall system that would have the aesthetic qualities and embodied carbon benefits of the mullion. Terra Cotta has the advantages of imperviousness to UV exposure and non-combustibility as well, compared to wood and plastic alternatives to aluminum.

TERRA COTTA MULLION Façade Studies

Façade Tectonics Institute Vitruvian Awards 2021 HOK, TriPyramid, Josef Gartner-Permasteelisa NA, Boston Valley

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FTI Vitruvian Award

TERRA COTTA MULLION Fabrication

www.Patrickbernardphoto.com

Façade Tectonics Institute Vitruvian Awards 2021 HOK, TriPyramid, Josef Gartner-Permasteelisa NA, Boston Valley

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FTI Vitruvian Award www.Patrickbernardphoto.com

Gartner brought Iron Workers from NYC Local 580 to Buffalo to erect the Mock Up. The assembly went together as designed. We hope to do more.

TERRA COTTA MULLION Permasteelisa VMU

Façade Tectonics Institute Vitruvian Awards 2021 HOK, TriPyramid, Josef Gartner-Permasteelisa NA, Boston Valley

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Structural Terra Cotta Mullion FTI Vitruvian Award Submision

Façade Tectonics Institute Vitruvian Awards Submission 2021 Outstanding Innovation & Collaborative Achievement Categories The Structural Terra Cotta Mullion, a collaborative prototype design by HOK Facades, TriPyramid Structures, Josef Gartner USA/ Permasteelisa NA and Boston Valley Terra Cotta.

Please view the video on the creation of the visual mockup at Boston Valley’s facility on Youtube or posted on Permasteelisa’s LinkedIn and HOK’s website. https://www.youtube.com/watch?v=YPUNAKgxDTo (Video and photography by Marzena and Patrick Bernhard).

1. Project Information • Project Name: The Structural Terra Cotta Mullion • Project Address: Prototype Mockup, Boston Valley Terra Cotta, Orchard Park, NY 14127 • Completion Date: August, 2021 2. Project Data • Structural Material: Terra Cotta and Stainless Steel • Monumental Stick-Type Curtain Wall • Mockup Dimensions, appr. 17’ high x 12’ wide.

• Insulated-laminated glass.

• Project Processes: Collaborative workshops for Boston Valley ACAW program between October 2020 and August 2021.

• Performance Principle: Rainscreen, Thermally Broken, Pre-Tensioned Terra Cotta Mullion spanning exterior and interior of glass.

• Performance Design Criteria: U Value: .30; Condensation Risk: 0dF Exterior, 70dF Interior, 30%RH; Wind Pressure 30 psf, Deflection H/5000.

• Performance Achieved: Calculated, per Design Criteria.

3. Project Team (see Key Team Member Bios) • Owner/ Developer: TriPyramid Structures, Josef Gartner USA/Permasteelisa NA, Boston Valley Terra Cotta • Architect: HOK Façades- John Neary AIA, LEED AP, Sr. Façade Specialist; Victoria Ereskina, Façade Designer; Blake Kurasek, Façade Specialist: HOK Architecture- Marie Achalabun, Architect: HOK Structures- Francesca Meola, Sr. Structural Engineer.

• Engineers: TriPyramid Structures- Michael Mulhern, President; Jeff Anderson, Design Manager; Nate White, Head of Engineering; Matt Bull, Design Manager; Dylan Schwallie, Mechanical Engineering Intern; Permasteelisa, NA- M. Shaik, PE. • Façade Contractor: Josef Gartner USA/ Permasteelisa NA- Roberto Bicchiarelli, Business Development Manager and Lead Concept Designer; Bernhard Rudolph, Head of Engineering, Gartner Germany; Leo Flores, Project Manager; Khalil Rahmani, Project Manager; Andrew McBride, Designer; M. Shaik, PE. • Project Managers: HOK, John Neary; TriPyramid Structures, Nate White, Michael Mulhern, Matt Bull; Josef Gartner USA, Roberto Bicchiarelli; Boston Valley, Andrew Pries.

• Material Suppliers: TriPyramid Structures, Permasteelisa NA, Boston Valley Terra Cotta.

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Structural Terra Cotta Mullion FTI Vitruvian Award Submision

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Structural Terra Cotta Mullion FTI Vitruvian Award Submision

4. Description: • The Structural Terra Cotta Mullion HOK was invited to participate in the 2021 Boston Valley Terra Cotta Architectural Ceramics Assemblies Workshop, a program where architects explore new ideas for architectural assemblies, typically enclosure-related, incorporating terra cotta, with the express objective of finding ways of improving the sustainability of buildings.

Permasteelisa project managers and engineers designed the mockup, with glass provided by them, including wind engineering and fabrication drawings.

Many people at each of the collaborating firms were critical to the success of the conceptual design process and in turn the realization of a constructed mockup in this fairly short period.

John Neary of HOK directed the design process and generated the initial sketches.

Victoria Ereskina of HOK modeled many versions of the concept and technical components in Rhino and did Thermal performance calculation simulation on the final design.

Michael Mulhern, Jeff Anderson and Matt Bull of TriPyramid made the initial determination that a pre-stressed composite structural mullion was a feasible concept.

Nate White of TriPyramid did the structural analysis that validated the concept and defined the structural components and assembly process including pre-tensioning to approximately 10 kips. Dylan Schwallie, Mechanical Engineering Intern at TriPyramid was responsible for assembling the mullions with Nate White.

Roberto Bicchiarelli of Gartner made the initial determination that the mullion was a viable basis for a working façade assembly, and he engaged Bernhard Rudolph, Director of Engineering of Gartner Germany, to evaluate concepts for glazing, sealing and insulating the system.

John Krouse, Mitch Bring and Andrew Pries of Boston Valley had originally agreed to the proposed concept by HOK facades, and contributed technical advice on the shape, dimensions and assembly of the terra cotta mullion sections. Andy Brayman as Glaze consultant advised on the selection of the ochre glaze for the mullion.

William Carty, Professor emeritus at SUNY Alfred, provided empirical data on the tensile and compressive strength of the Boston Valley material which TriPyramid used in engineering the mullion.

The fabrication experts at Permasteelisa NA, including Project Managers Leo Flores and Khalil Rahmani and Structural Engineer Mehaboob Shaik enabled the creation of the large visual mock up.

Our concept was to investigate whether rather than just being a rainscreen cladding, as it is commonly used, Terra Cotta could be exploited for its compressive strength as a fired clay product similar to tile and brick to create a thermally non-conductive, noncombustible, durable and aesthetically potent structural alternative to the aluminum, steel and laminated glass mullions we typically see on monumental facades. The low embodied carbon index for terra cotta suggests it could provide a substantial benefit by replacing other more carbonintensive materials in facades.

In addition, the simple mechanical nature of the assembly would afford efficient dismantling and recycling of the material if desired if its useful life should run out.

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Roles of Team Members: HOK initiate the project with contact of Boston Valley and proposing to explore the concept of a pre-stressed structural terra cotta mullion. HOK asked TriPyramid if they would participate to provide the tensile component of the composite assembly, and then invited Gartner/Permasteelisa to advise on how to create a holistic façade assembly with the prestressed mullion as its major element.

The mullion spanning the plane of the glass to animate the exterior surface and to exist as a substantial architectural element simultaneously on the exterior and interior of the façade, similar to the archetypal stone mullion of the Gothic Cathedral, was a design objective from the outset. Articulating the mullion to allow structural redundancy and replacement in case of a piece of ceramic being broken was a primary design consideration as well.

HOK defined the objectives of the concept and coordinated the engineering and assembly studies by TriPyramid, Boston Valley and Gartner. Animated design meetings on Zoom each week over approximately 8 months resulted in the scheme which is built. This process was one of the most cooperative and positive design collaborations I have been involved with in almost 40 years of practice. The ideas were openly discussed and debated, but the concepts were judged essentially workable at the outset. The various challenges addressed were creatively solved without any competition for credit. This kind of complementary participation by experts in the different aspects of designing and building a façade system should be a model for engaging the manufacturers and fabricators and installers in the initial stages of design to realize innovative new and better ways of building. As a model for conducting Research and Development its success in producing a built, almost full-size mockup in a matter of months should be an example for future collaborations.

Unsung Hero: Unsung in terms of visibility in the presentations at the ACAW virtual event on August 19, 2021, or in the notices after that which have included many positive comments, but well-known and highly valued to everyone on the team, is Victoria Ereskina, Façade Designer at HOK who volunteered tirelessly of her time and talent to visualize and communicate the concepts that were initiated in rough sketches and verbal discussions over the 10-month period of development. The process would not have achieved anything like the level of success it did without her efforts.

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Description of wall type: Materials: Glazed Terra Cotta with stainless steel tension rods and plates at joints, stainless steel gravity anchor assembly at the base, lateral anchor assembly at the head of the mullion; painted steel horizontal HSS supports, inboard of continuous air-vapor barrier flashing, for rainscreen terra cotta cladding on transoms at sill and head supported on aluminum clips; stainless steel and silicone sheet flashings; pocket glazing in thermally-

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Structural Terra Cotta Mullion FTI Vitruvian Award Submision broken channels supported on stainless plates at mullions with field-applied silicone seals.

As a monumental/ lobby wall type system it is approximately 70% vision glass by area, dependent upon design of the sill and head spandrel areas.

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Description of façade related innovations: To our knowledge, terra cotta in this kind of extruded and cast form typically used in rainscreen and traditional mortar-set cladding has never been used structurally in combination with tensile reinforcing in a façade or otherwise. Terra cotta tile has been employed as a structural compressive material in the famous vaults of the Guastavinos, and in combination with pre-stressed thin concrete and tile composite shells by Eliado Dieste, and in the late 19-century floor systems of shallow block vaults, which suggested to us it has the capacity to be significantly re-stressed to create a mullion which can span a high distance under significant wind load with highly limited deflection. But these precedents are assemblies which are similar to modular masonry, not adaptable to monolithic monumental mullions.

The plastic and fiberglass-based alternatives to aluminum and steel mullions which have been explored over the past couple of decades for their relative thermal inertness and resistance to corrosion have significant issues related to durability in UV exposure, and to combustibility and restrictions in the building codes, and untested long-term structural performance. Timber has the same set of problems with UV and combustibility, which may be overcome but so far have proved inhibiting to use of wood mullions. Precast concrete does not have the plastic capacity for detail and cannot be glazed like terra cotta, and it lacks terra cotta’s durability as an almost impervious ceramic material, which is enhanced by glazing.

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Description of Importance of Innovations and Potential Disruptive Influence on the Industry as a Whole: Aluminum and steel and laminated glass are the most common materials used as mullions-effectively beams taking wind loads and weight of glass—in monumental facades. We have estimated that the wall incorporating the Structural Terra Cotta Mullions could have a significantly lower quantity of embodied carbon by comparison with conventional assemblies. The terra cotta requires a significant cross section for stability, and the prestress force to limit deflection to avoid concentrated stresses on the edges of the sections is significant, making the ,mullion capable of taking higher levels of wind force than most conventional fin-type back up mullions are designed for. This offsets the likely high cost of the composite assembly—which would become more economical with repeated use as well.

Additionally, we have discussed the feasibility of applying the concept of pre-stressed, tension-reinforced terra cotta ceramic mullions to a panelized curtain wall system and believe it has potential. This could open up the possibility of enormous impact on the façade industry by providing a durable, corrosion-resistant, thermally inert, non-combustible, lowembodied carbon alternative to aluminum framing.

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Structural Terra Cotta Mullion FTI Vitruvian Award Submision •

Describe the Holistic Integration of the Facade System with the Building and other Building Systems.

The terra cotta mullion concept is adaptable to façade schemes which could incorporate shading, ventilation and automatic controls to integrate with the other environmental control systems in the building.

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Description and Quantitative Analysis of the sustainability and resilience attributes of the submission.

Aesthetically-- which relates to wellness by enhancing the experience of building visitors and occupants-- the potential for terra cotta to create facades rich in inherent detail and character and also in historical associations, is clear.

Thermally, the two-part mullion connected by stainless steel plates with low thermal conductance—and which could readily include a true thermal separator connection between exterior and interior halves—is high-performing. The relatively low proportion of framing to vision glass allows for better thermal performance than conventional systems.

We calculated the U value of the mullion typical cross-section at 0.3867. This compares to an aluminum fin for a similar scale assembly at 0.95 with structural glazing and thermal breaks.

The over-all U value of a panel of the assembly in the mockup with the glass used, which has a COG U of 0.25, is 0.265. This compares to a standard steel mullion wall with an overall U of .33.

We estimated the embodied carbon of the mullion assembly in comparison to conventional examples of Aluminum, Steel, Laminated Glass, Timber and Precast Concrete at .43 tons of ECe/ ton of assembly for Terra Cotta and Stainless Steel, compared to 4.5 tons ECe for Aluminum, 1.96 tons ECe for Steel, .56 tons ECe for laminated glass, .092 tons ECe for Timber and .28 tons ECe for Precast (see figure in presentation).

We have discussed a more refined and efficient version which could reduce the weight of the Terra Cotta mullion by about half, and would have approximately .21 tons ECe/ton, less than all the others except for timber.

Regarding resilience, terra cotta has a well-known history of durability on building facades including the 19th-century buildings in North American cities and older buildings in Europe and Asia. Ceramics are inherently impervious to UV, resistant to freeze-thaw damage, resistant to corrosion and staining, and are repairable, restorable and replaceable. The Structural Terra Cotta Mullion was explicitly designed to allow replacement of damage parts, and its assembly would lend itself to efficient dismantling and either re-use or recycling.

End.