The seismic retrofit of two existing, 40-story egress staircases within a massive high-rise required great care in design and sequencing to keep the occupied building safe during construction. Holmes Structures’ retrofit paired with Holmes Fire’s safety strategy kept the egress staircases fully operational throughout construction.
Our solution set a precedent for mitigating existing stair vulnerabilities in a vast portfolio of buildings by achieving the following:
- Accommodated inter-story drifts as expected from the Non-Linear Response History Analysis (NLRHA), without damage or collapse of stairs.
- Minimized disturbance to tenants of the fully occupied building.
- Kept egress undisturbed through coordination with the San Francisco Fire Department.
- Kept stairwells operational 24/7 during construction.
- Resulted in significant cost savings and delivered the project ahead of schedule.