The Board of Supervisors enacted an ordinance amending the Existing Building Code to define “Rigid-Wall-Flexible-Diaphragm” and “Concrete Buildings,” require the Department of Building Inspection to inventory seismically vulnerable buildings citywide, and establish voluntary seismic retrofit standards. Chapter 5G creates a mandatory screening and notification process for eligible buildings, with an 18-month form submittal deadline and owner exemptions for low-risk structures. Appendix A, Chapter A6 introduces two performance-based retrofit options under ASCE 41 for concrete buildings, addressing deficiencies such as weak stories, shear-governed columns, and punching shear vulnerabilities. The ordinance affirms CEQA compliance, adopts local findings under California Health and Safety Code, and directs transmittal to the California Building Standards Commission.