Arup, San Francisco
The 181 Fremont Tower is designed to achieve immediate re-occupancy following a 475-year seismic event and functionality once utilities are restored, far exceeding code standards. It has a faceted, tapering façade that folds along the diagonal expression of the external structural megaframe. A perimeter lateral force-resisting system was utilized to resist wind and seismic demands, because a traditional concrete or steel core system would be too slender, given the tower’s small footprint.
The scheme was arrived at through a resilience-based design approach, which accounts not only for life safety, but the reparability and functionality of the building after an earthquake. It was determined that using an integrated damping system would reduce wind and seismic forces, as well as control wind vibrations in the tower. A perimeter megabrace system resists wind and seismic loads and provides an excellent opportunity to incorporate damping. Across the lower two-thirds of the tower, megabraces span up to 75 meters across the façade.