Designed by Heller Manus Architects, 181 Fremont, a 56-story mixed-use tower, will be San Francisco’s third tallest structure when completed and will also become the most earthquake-resilient building in the city, or any city on the West Coast, after officially achieving a Resilience-based Earthquake Design Initiative (REDi) Gold Rating.
Arup designed the REDi Rating System with contributions from a diverse group of external collaborators. The system outlines holistic design and planning criteria within a resilience-based framework for architects and engineers to enable owners to resume business operations and provide livable conditions for tenants quickly after an earthquake. A structure designed to REDi guidelines will be able to withstand the impact of a 475-year seismic event.
The REDi Gold Rating that 181 Fremont - which Arup was the structural engineer, geotechnical engineer, and resilience consultant for - achieved includes enhanced structural and non-structural design to limit damage, improved egress systems, contingency plans to reduce post-earthquake recovery times, and development of a tenant’s resilience manual of recommendations to keep their space earthquake-ready. A building with a REDi Gold Rating can expect its repair costs to be cut by approximately 10 times compared to code-designed buildings and can also reduce the expected functionality downtime from 18 months to less than a few weeks.
One of the main design elements used and designed by Arup in 181 Fremont to achieve the rating were viscous dampers, which were integrated into the steel megabraces and uplifting megacolumns to significantly reduce the potential for earthquake damage. These viscous dampers also resulted in material savings of approximately 3,000 tons of steel. Additionally, the entire penthouse floor was freed up for occupancy as the dampers allowed for the removal of a tuned mass roof damper.
As a sign of industry acceptance, the USGBC has developed new Resilient Design Pilot Credits for the LEED Rating System that reference REDi by name and Arup is in the process of creating a version of REDi for flooding and has been approached to investigate an application for hurricanes and tornadoes, as well.