San Francisco's new guidance document on performance-based design of buildings 240 ft or taller could become a model for other cities grappling with review of seismic designs that do not follow the code's prescriptive requirements. The city's Building Inspection Commission on June 20 unanimously approved the guideline using "alternate rational analysis" to justify a single lateral-load-resisting system instead of a dual system required under the prescriptive provisions of the code. The vote lifts a city moratorium on plan reviews of performance-based designs for high-rises.