Over a decade ago, the wheels were set in motion to establish an African American History Museum in Washington, D.C. In 2009, the architectural design was awarded and in 2012 first ground was broken in what became a four-year project to create a place for healing and reconciliation where everyone can explore the story of America through the lens of the African American experience.
The museum comprises approximately 409,000 square feet and occupies the last available space on the National Mall, situated prominently next to the National Museum of American History and the Washington Monument. When it opens to the public this fall, the museum will be a centerpiece venue for ceremonies and performances, as well as a primary exhibition space for African American history and culture.
The primary idea for the design was derived from Yoruban art and architecture, reflecting both African and African-American influences. The museum’s three main design features are its grand porch entrance, the corona shape of the structure, and the building’s façade, which is made up of 3,600 bronze painted alloy panels, reminiscent of the African-American guilds of casting and ironworking in the South after the Civil War.
Sustainability was a cornerstone of the design and development process, aimed at making the project the first LEED-certified museum on the Mall, by incorporating elements such as photovoltaic panels that produce electricity to heat water for the building.
The museum’s compact design and architectural restraints challenged the structural steel detailers and fabricators with extremely large members and a sizable amount of complicated connections. The structure’s first four floors are concrete, while four steel frame core towers of cast-in-place concrete infill walls provide support and keep the above-grade floors free of columns. Because the majority of the above-ground floors are exhibit galleries, it was important to have a column-less space, which required creativity in engineering the structure to transfer loads.
Virginia-based structural steel detailing firm Prodraft Inc., which exclusively uses Tekla Structures, relied on Trimble’s BIM software to create an information-rich constructible model with data for CNC processing, material handling, and robotic welding for SteelFab, Inc. to use in fabricating the steel. In addition to optimizing the fabrication process, the Tekla model was also used in planning erection.
“The most challenging aspects of the job were the sheer number of heavy members, plate girders, box beams, and box columns and extremely complicated connections between those members,” said Ed Jumper, project manager for Prodraft. “The Tekla model played a very important role in helping us identify clashes and interferences and quickly manage changes among the numerous trades involved, throughout the design-build process.”
Tekla Structures helped Prodraft precisely model more than 500 penetrations that were required in the main structural members. Some of the multi-directional connections held over a few hundred field bolts. The fifth floor perimeter plate girders supporting the “corona” were spread over five separate shop drawings, with more than 180 parts for one girder assembly. Connections for the members at the core had to be coordinated with the rebar couplers added to the steel to avoid clashes while maintaining the integrity of both the connection design and core reinforcement.
The 200-foot-long porch that greets visitors as the entrance to the museum, which includes a 16-inch camber at mid-span and was designed with long-span, heavy plate girders and heavy plate box columns, required Prodraft and SteelFab to create subassemblies of very intricate shop drawings. Lifting weights and center of gravity had to be precisely defined for erection feasibility.
SteelFab fabricated 4,050 tons of structural steel for the museum and received a Washington Building Congress Craftsmanship Award.
Collaboration is key
The compact design of the structure required the detailers, design team, and connection designers to work closely together and share 3D models across BIM platforms and other tools. The design-build approach also presented challenges in maintaining quality and staying on schedule, while implementing changes throughout the project. Regular web conferences allowed the designers, fabricators, contractors, and engineers to track progress. During these meetings, Prodraft would share its Tekla model, easily exporting it in IFC and other formats for use by the entire team. This helped Prodraft quickly make changes and deliver its drawings error free and on time.
Owner: Smithsonian Institute Architect: Freelon Group/Adjaye Associates/Davis Brody Bond
Steel Detailer: Prodraft, Inc.
Steel Fabricator: SteelFab, Inc.
Structural Engineer: Robert Silman Associates
General contractor: Clark/Smoot/Russell
“Tekla Structures made collaboration easy,” said Ed Jumper, project manager for Prodraft. “Throughout the project, there were changes that had to be made across disciplines — designers, contractors, and engineers — but we were able to share models between Tekla Structures and other solutions to communicate and manage those changes without extra work or unnecessary errors.”
Information provided by Tekla Structures (www.tekla.com/products/tekla-structures).