This iconic NYC corporate fitout would not be complete without the addition of a feature monumental stair that shapes the arrangement of open space with three distinct runs. As part of the new tenant’s massive office space redevelopment, McLaren worked with United Structural Works, serving as Engineer of Record (EOR) for the monumental stair design. The team was responsible for the full performance of the delegated design for strength and serviceability limits associated with both deflection and human induced vibrations. Finite element analysis was completed using a combination of RISA-3D and SAP2000 modeling software.
The lower stair framing presented unique challenges to accommodate the intermediate level “U” shape switchback landing desired by the Architectural team. An appearance of the “floating” landing was a main design requirement which was complicated by limited support points available from the existing structure below. To accomplish the desired look a series of cantilevering members were provided within the landing with only two structural support posts provided to the existing structure below.
The two upper-level stair runs were not as complex from an Architectural standpoint as they were straight runs. However, the distance between support points exceeded 40’ which created serviceability complications with deflection and vibration due to the slender stringer sizes. To control these limit states, both the top and bottom of the stairs were moment connected at the existing structure.
Additionally, our construction engineers provided rigging and erection assistance to ensure the monumental stairs were constructable within the limitations of the existing corporate landmark building.