Makeover of theWitte Museum included addition of a new building (Mays Family Center) to host special events and changing exhibits, reconfigured galleries and interior spaces, and addition of a large entry and exhibit hall (Susan Naylor Center). Image: Lake|Flato
The final roof solution included a 1-1/2-inch steel roof deck supported on 8-inch-wide-flange purlins, spanning 15 feet between trusses. The trusses consist of 10-inch by10-inch wood timber verticals, paired with 8-inch steel channel chords and steel rods for both the truss diagonals and the truss bridging. The truss configuration allowed the design team to open up the space and make room for the suspended wood ceiling panels, lighting, and ductwork. Consistently throughout the project, the roofing system transitions from steel metal of roof deck over interior spaces to exposed wood tongue-and-groove roof decking outside. Thermal breaks are provided in all the steel members crossing through the building envelope to ad- dress thermal bridging. In the case of the Mays building, this included the wide flange roof purlins and the top chord extensions of the truss. The ground floor for the changing exhibits proved to be an equal chal- lenge. Near the San Antonio River, most of the building’s footprint lies in the 100-year floodplain. The team decided to elevate the Mays Center’s ground floor above the floodplain, which will help reduce the potential for flooding of future campus structures. Datum worked to coordinate the floodplain cross section with the project’s civil engineer, Pape Dawson. In this process, pier sizes and shapes as well as those portions of the building that would have to remain below the floodplain were minimized. The program also required lateral circulation between the Mays Center and an adjacent existing building, setting an invariable finished floor el- evation. Subtracting the floodplain limitation and required under-floor insulation and finish left only 10 inches for the ground floor structural system. Datum proposed a 10-inch, two-way concrete slab supported on 24-inch and 30-inch drilled concrete shafts. Linbeck cleverly inte-
grated the under-floor insulation into the flat-slab formwork to reduce post-construction labor. The ground floor slab was designed for 150 psf to accommodate the most intense uses required by the changing exhibits. Designs also in- corporated locations for electrical floor boxes arrayed throughout the changing exhibits room, as well as recesses and drains for bathroom, kitchen, and lobby flooring. The floor for the exterior open porch was subject to the same overall depth limitation. As the porch was elevated significantly above adja- cent grades, the team transitioned to a hardwood (Massaranduba) floor deck supported on wide flange steel beams and paired-channel girders for a visually appealing exposed structure. Structural archeology As the Mays Center progressed, work began on the renovations and additions to the existing facilities. The 37,000 square feet of renovations required seamless integration of the architectural spaces and mechanical services across multiple gener- ations of building additions, including demolition of the northernmost wing of the original 1926 building and removal or strengthening of existing structural components. The initial hurdle for the renovation work was gaining a reasonable understanding of the existing conditions. Early in the schematic design phase, arrangements were made for after-hours investigations into the Witte structures. Datum staff crept through the length of the building’s accessible crawl space, explored the attic, and chipped into the plaster soffits of floors through ports cut in the plaster ceilings.
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april 2018
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