EE151
Case Study: Arena Stage
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Learning Objectives 1. Describe how the architects and engineers designed the tallest
free-standing timber-backed façade in the world.
2. Explain how the use of wood allowed for time and labor savings for the Arena Stage project.
3. Observe how the Arena Stage design team satisfied code officials’ concerns to realize this groundbreaking project.
4. Examine how extensive modeling and prefabrication played an essential role in the construction of Arena Stage.
Case Study:
Arena Stage Washington, D.C.
Cheryl Ciecko, AIA, CSI , ALA, LEAD AP, GGP Senior Technical Director, WoodWorks
Arena Stage
Location: Washington, D.C.
Completed: 2010
Size: 200,000 s.f.
Budget: $100 million
Architect: Bing Thom Architects Engineer: Fast + Epp General contractor: Clark Construction Timber façade design-builder: StructureCraft Builders
Background
• Founded in 1950
• By late ’90s, facility was no longer meeting
needs spatially or technically
• Needed twice as much space
• Dated aesthetics
• Performances interrupted by outside noise
After its founding in 1950, Arena Stage built a reputation for cutting-edge performances in the Washington, DC area. A new artistic director who came in 1997 found herself with a complex that no longer met the theater company’s needs, spatially or technically: they needed twice as much space, the aesthetics were dated, and performances were interrupted by noise.
Design Vision
• Artistic director wanted to celebrate all that
was “deep, dark and dangerous” in the
American spirit
• Historic structure in a city that highly values
history
• Lobby large enough for 1,400 patrons from all
three theaters at the same time
In her direction to the architects, the artistic director said she wanted to celebrate all that was “deep, dark and dangerous” in the American spirit At the same time, it is a historic structure in a city that highly values history, so Bing Thom had to determine how to meet the director’s needs without compromising the character of the existing theaters.
Bing Thom and his team decided to cover and wrap the two existing theaters, and the new theater, with a heavy timber-supported roof and glazing system. The design enclosed the new and old spaces while creating a new, larger lobby and offices.
Developing a glass wall was important to create transparency and ensure the old theaters were visible. The insulated glass wall also provided much-needed acoustic separation from the nearby airport They added a new third theater, and covered it all with a 500-foot-long cantilevered roof, creating 200,000 square feet of enclosed space.
Overall Concept
200,000 s.f. of new space
created:
• Insulated glass wall
covers and wraps the
two existing theaters
• New third theater
• 500-foot-long
cantilever roof
enclosing everything
The premier feature of the new Arena Stage, the Insulated glass wall encloses the theaters and lobby, and is the tallest free-standing timber-backed façade in the world. It is 650 feet long and features large wood column cross-sections shaped according to the internal stresses, increasing transparency
The glass wall was created with 18 PSL columns around the perimeter of the façade. Each column measures 45 to 63 feet tall and supports the steel roof trusses, which cantilever beyond the envelope to create the overhang that runs around the structure. • The wood columns are spaced 36 feet apart and are elliptically shaped for structural efficiency, as well as to minimize their visual impact and to create a feeling of transparency into and throughout the space. • They’re designed to brace the tall glass façade against wind loads and to carry the roof loads (up to 400,000 pounds) from the steel roof trusses, some as long as 170 feet. • The PSL columns are unreinforced solid engineered wood using no internal steel support.
Glass Wall
18 parallel strand lumber
(PSL) columns around the
perimeter
• 45 to 63 feet tall, 36 feet
apart
• Elliptical shape
• No internal steel
support
The glass panels are supported by 324 muntins and 216 support arms, all made from custom-shaped PSL. Fifty-four spring-loaded stainless steel cables stretch between the roof and floor to carry the glazing. Conventionally, the designers would have a building structure holding up the roof, and then have a separate structure to hold the curtain wall. Here, wood did double duty: The columns hold up the windows and the roof. When comparing the cost of an integrated wood system against a conventional steel column and separate aluminum curtain wall system, the wood system came out as being less expensive.
Glass Wall
• Panels supported by
324 muntins and 216
support arms
• 54 spring-loaded
stainless steel cables
stretch between the
roof and floor to carry
the glazing
PSL consists of long veneer strands laid in parallel formation, bonded together with adhesive to form the finished structural section. PSL is commonly used for long-span beams, heavily loaded columns, and applications where high bending strength is needed.
PSL was chosen both for its structural capacity and its aesthetic—consistency, nice texture/pattern StructureCraft cut slabs from PSL, laminated them into larger billets, and bolted them together to create a rough rectangular cross-section. Bolting, rather than gluing, helped control checking The columns were then shaped into elliptical cross-sections with tapered ends. Finally, they were sanded and coated with two layers of clear coat. StructureCraft then de-slivered to the bottom 10 feet, and added a third layer of clear coat. The third coat was added to that section because they knew the beauty of the PSL would draw people to touch it. The beams were installed with the narrow direction in the same plane as the glazing to minimize them visually Muntins and support arms brace the columns against buckling Additional details: • Columns are tapered near the floor to
make them seem lighter and less obtrusive • Columns are sized identically for visual
consistency • Columns are installed at a four-degree tilt
to minimize glare from the glass
PSL Beams
• PSL slabs cut and shaped
into elliptical cross-sections
with tapered ends
• Installed with the narrow
direction in the same plane
as the glazing to minimize
them visually
• Muntins and support arms
brace the columns against
buckling
Connections were key to this design. With timber construction, the connections are usually the most expensive component, so when you develop a connection that can be repeated over and over again, you save money. Since they repeated the same connection 18 times, they could spend time making it quite beautiful. The custom-designed ductile-iron castings for the column bases bring enormous forces down to a single pin. The castings were mounted on all of the columns before they were shipped: It was a complex connection. With 400,000 pounds coming through the columns, they needed a positive bearing connection, which required accurate shaping between the bottom of the PSL column and the top of the casting.
Connections
• Custom-designed ductile-
iron castings for column
bases
• Delicate-looking but
structurally efficient
• Castings mounted on
columns before shipping
Here’s an additional interior view of the glass wall
The director wanted the third theater to be smaller than the other two and designed in a way that allowed the actors to take more risks. The resulting, unique space is womb-shaped, with a spiraling entrance form, lending itself to the name “The Cradle” The Cradle also played an important role because it serves as a structural anchor to support the roof.
The Cradle
• Third theater
• Smaller, womb-
shaped
• Structural anchor of
roof
This rendering provides a better idea of the theater’s unique shape. But while it’s unique aesthetically, unfortunately, the shape created strange sound reflections
To solve the acoustic challenge, Bing Thom developed a wall system that would appear visually substantive, but could absorb and disperse sound. The result was a wood slat system, made from poplar, designed in a basketweave. The material and shape provided character as well as the necessary acoustic dispersion. Despite its intricate appearance, the slat system was simple enough to be installed by the drywall contractor.
The Cradle
Poplar slat
system in
basketweave
pattern
Here’s a wider view of the poplar slat system
Performance Assurance
• Column cross-section governed by deflection under
wind-loading
• Scale model underwent wind-tunnel test
• Full-height mock-up five panels wide, lab-tested to
hurricane conditions
Column cross-section was governed by deflection under wind loading. While some supported smaller tributary areas, all columns were sized identically for visual consistency. To verify the design, the team built a scale model and conducted a wind tunnel test in London, Ontario. StructureCraft also built a full-height mock-up five panels wide, and the general contractor tested the assembly in a Pennsylvania lab under hurricane conditions. Although cost of the mock-up and testing was considerable, the process helped the team fine-tune connection details and erection procedures. The investment more than paid for itself in terms of avoiding problems during installation.
3-D Modeling
• Customized production process linked to a
parametric 3-D solids computer model; tied together
shop prefabrication, quality control, and on-site
erection
The pre-fabricated elements were made off-site while the base structure was being constructed, which simplified and shortened installation time. And StructureCraft used its own crews for installation.
Overcoming Fire Concerns
• In-depth fire report
• Smoke study
• Computer modeling
• Char analysis
Local code authorities were skeptical about allowing wood; they had concerns about fire safety. So the design team presented an in-depth fire report, along with a smoke study done by a code consultant working for the team. Through computer modeling, they showed that effects of a fire on the structure would be minimal, and there would be plenty of time for safe building evacuation. They also did a char analysis, and showed District of Columbia code officials how char actually protects the interior of the wood. While charring would leave a column of reduced size, calculations showed that because the column was sized mainly for deflection, it already had additional strength capacity. It was a long but productive process educating D.C. code officials. As a result, the process will be much easier for the next project.
Wood at this scale isn’t common in Washington, D.C., which is dominated by historic masonry and stone, or modern concrete and glass. As mentioned, code officials required convincing from a fire perspective. But wood was the right material for several reasons. First was budget. The warm aesthetic achieved via the PSL columns came without the need for expensive finishes, and is a natural complement to the views outside the wall. It also served triple duty—holding up the roof, holding up the glass, and serving as a finish material. Arena Stage demonstrated what’s possible with wood, how timber can be used for structures in ways that may not have been considered before. The beauty is that wood works well with other materials—for Arena Stage, they integrated wood with the steel roof trusses and cables, with the aluminum connection plates, with the ductile iron castings and the glass curtain wall, and with other connections.
Benefits of Wood to Arena Stage
Budget
• Beautiful without
pricey finishes
• Triple duty—holds
up the roof, holds
up the glass, final
finish material
Wood lowers a building’s carbon footprint in two ways. • It continues to store carbon absorbed during the tree’s growing cycle, keeping it out of the atmosphere for the lifetime of the building—longer if the wood is reclaimed and used elsewhere. • When used in place of fossil fuel-intensive materials such as steel and concrete, it also results in ‘avoided’ greenhouse gas emissions. As a result, the total potential carbon benefit for Arena stage is 675 metric tons of CO2. This is in addition to wood’s other sustainable benefits: renewability, responsible sourcing, and biophilia, to name a few.
Benefits of Wood to Arena Stage
Carbon Reduction
• Stores carbon
• Replaces fossil-fuel-
intensive materials
Wood was definitely the right material to use for this project. Arena Stage is an indicator of not only what’s possible, but what we plan for the future—which is to keep innovating with wood.
Contact Information
Cheryl Cieko AIA, CSI , ALA, LEAD AP, GGP
Midwest Regional Director, WoodWorks
708. 354.3480 | [email protected]