DBI outlines performance-based review, peer review for tall buildings and Transbay context

DBI engineers told the joint hearing that San Francisco evaluates tall buildings through the California Building Code with local amendments, supplemented by a performance-based approach and peer review for landmark projects such as the proposed Transbay tower.

Ray Louie, a structural engineer with DBI, said tall-building design follows national and state standards but that the department has implemented a three-step performance approach that evaluates service-level, design-basis and maximum-considered earthquake performance. He noted the department has adopted a local performance-based design document (referred to in the hearing as a performance standard used for tall buildings) and has used structural peer review panels for recent high-rise projects.

Commissioners asked whether tall buildings should include additional redundancy such as a third means of egress or a firefighter-rated elevator. Louie said some provisions are now part of the fire-marshals' code requirements for a dedicated firefighter elevator and that progressive-collapse and extreme-load design elements can be added for landmark buildings at the owner's direction and cost.

Commissioners and public speakers raised questions about site-specific issues such as liquefaction, curtain-wall glazing hazards, and the role of geotechnical investigations. DBI staff said geotechnical reports and site-specific ground-motion analyses are routine parts of tall-building design and that peer-review panels will be assembled when the Transbay tower design is formally submitted.