More than just a pretty façade
With the steel skeleton of the Albert Sherman Center (ASC) rising swiftly, work will soon turn to the installation of the building’s exterior façade, a complex system known as a curtain wall.
Called a curtain wall because it “drapes” over the exterior of the building, and is not a structural element, the curtain wall system for the ASC will include 1,775 panels composed of glass, aluminum, terra cotta and granite. Before one panel goes up, however, the design and engineering team must complete a rigorous testing process to make sure the curtain wall will work, and look, as planned. (Watch Video)
“We are investing over $20 million in the exterior system of this building, so we want to prove out all the elements of the materials and the design,” said John Baker, associate vice chancellor of facilities management, who is overseeing the project. “We have some history on this campus; we know the pains of a façade that doesn’t work. So it’s very important for us to do this testing and make sure we have a good solid system.”
The curtain wall testing protocol includes construction of two large-scale mock-ups, each some 30 feet high, incorporating all the elements of the ASC façade. One is known as a performance mock-up and is built in a laboratory, then subjected to a battery of physical tests. The other, called a visual mock-up, is now being installed on the corner of the construction site nearest the Medical School quad so the materials can be evaluated in the environment in which the ASC will be built.
“We have a great design team that’s been working on selecting the right materials, but so far that’s all been done with very small samples,” Baker said. “It’s standard practice now to use a visual mock-up to prove things out in full scale. We want to make sure the colors, the textures, the look of the glass panels, the way things fit together, actually match what we have seen on the small samples and will blend well with the other facilities on campus.”
The visual mock-up will be completed in approximately two weeks and left on display for several months. Meanwhile, the performance mock-up has been built inside a large laboratory at Architectural Testing Inc., of Yorktown, Pa., an independent engineering firm that specializes in testing “building-envelope” systems. In March, Baker and other members of the design and construction team traveled to Yorktown to witness a series of tests on the performance mock-up.
The curtain wall was battered by 70-mile-per-hour winds, courtesy of an airplane-sized propeller, while water was sprayed at the mock-up. “We wanted to see if we could drive any water through the seals on the windows, or through the joints where the panels come together,” Baker said.
In other tests, the laboratory was chilled to 10 degrees below zero, and later heated to 150 degrees, with the atmospheric pressure raised and lowered while sensors measured the impact on the curtain wall. The mock-up was also subjected to vibrations, twisting and other forces, to see how all the elements performed under extreme conditions.
“The testing was rigorous, and very cool to watch,” Baker said. “I was happy to see that all the materials appeared to meet or exceed their design specifications. They all came through with flying colors.”
Once the final analysis of the testing data is completed, and the visual mock-up is approved, the curtain wall panels will be manufactured by Enclos, a national curtain wall company headquartered in Michigan. The panes for the ASC will be built at the company’s Pennsylvania plant.