As the lower levels were completed, cranes installed a segregated railroad passenger car and a guard tower from the Louisiana State Penitentiary on November 17, 2013. These items were so large that they could not be dismantled and installed at a later date. Instead, the museum had to be built around them. By late December 2013, construction was just weeks from finishing the five basement levels, and above-ground work was scheduled to begin in late January 2014. At that time, the Smithsonian estimated the museum would be finished in November 2015. Guy Nordenson and Associates were the engineers for the superstructure of the museum building and long-span porch. Robert Silman Associates oversaw the engineering of the below-grade structure and exhibit structural support. The steel was fabricated by SteelFab, Inc. While the below-grade floors were made of reinforced concrete, with columns supporting each floor above, the above-grade floors were primarily exhibit space and needed to be kept column-free. To support the upper floors, four massive walls, consisting of steel frames and cast-in-place concrete infill, were constructed. Design and fabrication of the steel members of the above-ground structure required extreme precision, as the steel elements penetrated one another at more than 500 places and some beams had several hundred bolt-holes in them. All structural steel elements also had to work almost perfectly with the rebar and rebar couplers so that elements would not run into one another and yet maintain structural integrity. A system of girders around the fifth above-ground floor supported the corona. Some of these girders were so complex they required more than 180 parts. The long-span porch that covers the main entrance was built of long plate girders and box columns (also made of plate). A long steel camber beam at the midpoint helps support the porch roof. An elliptical monumental staircase runs continually between the above-ground floors. This staircase has no intermediate supports, and weighs in at more than . SteelFab fabricated more than of structural steel for the museum in conjunction with AIW, Inc. who fabricated the architecturally exposed, and ornamental steel and bronze metal work. SteelFab received an award from the Washington Building Congress for its work. ArchDaily has reported that the museum was named the winner for the architecture category and the overall winner for the Beazley Design of the Year award for 2017. According to the award criteria set by the Design Museum in