The glass-enclosed spiral staircase, a 16,100-sf glass wall and an 9,500-sf skylight presents a modern addition that coexists with the traditional architecture of the museum and its historical neighborhood. The design’s intent is to invite people into the building. With every step new perspectives open up in both the light-flooded entrance hall and the architecture at the heart of the city outside.
LERA designed new multi-level stairs which were incorporated into the post-tensioned concrete building by creating cut outs into the ﬂoor levels. 909 Third Avenue is one of New York’s few post tension ofﬁ ce buildings. The design of the space required the installation of two sets of stairs. The ﬁ rst stair connects two ﬂ oors and the second stair connects three ﬂ oors. Each cut of a steel tendon is clamped at each end to hold the ﬂ oor in place when creating a cut a stair opening.
The project includes five different bridges. A pair of stacked vehicular bridges and a single pedestrian bridge provides the sole means of access to the museum's offshore location in the bay. The bridges are cast-in-situ tapered sections of architectural concrete. Inside the facility, two pedestrian bridges span structured in metal and glass span the central atrium. The bridges span 203-ft (62-m).
The form for the exposed structure was devised to complement the architect’s vision and reflect the structure-as-exhibit desire of the Hall of Science. Additionally, the existing Great Hall, which was constructed for the original World’s Fair, has had an exterior façade restoration and an interior renovation is under way.
Design considerations included four below-grade levels which are built with reinforced concrete. A sixteen-inch thick foundation retains soil at the building’s perimeter.
The building is formed of two distinct structures: a terracotta volume containing galleries, conference, and administrative space; and a glass volume, containing additional exhibition space, which cantilevers onto Independence Mall. Stair.....