Safe Enough to Stay - ABAG Earthquake and Hazards Program

Safe Enough to StaySection II:What engineering criteriashould be used to determinewhether a home has adequateshelter-in-place capacity?Seismic evaluation is not like a smog check. There is no law requiringan existing building to be evaluated every few years. Even when thebuilding code for new construction changes, new regulations arenot retroactive. Consequently, most San Francisco buildings, whilelegally occupied and quite safe in day-to-day conditions, do not meetthe current seismic codes for new buildings — and are not requiredor expected to do so. Only when a building undergoes a triggeringevent such as an addition, alteration, repair or change of occupancyis it likely that it will be evaluated for earthquake performance and,if highly deficient, subject to retrofit. There are some exceptions. SanFrancisco’s unreinforced masonry buildings have been subject tomandatory evaluation and retrofit since 1992. And many owners andtenants voluntarily evaluate their buildings, but this voluntary work istypically not required to meet any upgrade standard.Whether mandated by ordinance or triggered by the building code,seismic evaluations in San Francisco use criteria based on structuralsafety alone. With few exceptions, the criteria consider only whetherthe building would threaten lives by collapsing or would suffersevere damage during an earthquake. The criteria do not requirean explicit consideration of whether a damaged building would besafe to reoccupy or how long it might have to remain vacant whileundergoing repairs.SPUR recognizes that San Francisco’s resilience requires more thanbasic safety during the earthquake. It requires that buildings remainhabitable and repairable so that occupants can shelter safely in themeven before repairs begin.To support the move to resilience-based earthquake planning, the cityshould revisit its existing structural-evaluation criteria. Specifically,the city needs to determine what shelter-in-place means from anengineering perspective and to develop criteria for analyzing now,before the earthquake, whether a building is likely to serve as shelterin-placehousing afterward. The purpose of this section is to discusswhat shelter-in-place capacity means in engineering terms and tooutline the engineering criteria that building owners and policymakersmight adopt for pre-earthquake shelter-in-place evaluations.32 Comerio, Mary C., “Performance Engineering and Disaster Recovery,” inBracing Berkeley: A Guide to Seismic Safety on the UC Berkeley Campus(Pacific Earthquake Engineering Research Center, January 2006).The need for shelter-in-placecriteriaWhen and why would a shelter-in-place evaluation be done? Theshort answer is: in the same cases and for the same reasons thatsafety-based evaluations are done now. An overarching themeof SPUR’s Resilient City initiative is that planning and regulatorypriorities should shift from personal safety to community resilience.Thus, wherever current programs, regulations or ordinances callfor seismic evaluation or upgrade, that work should (or could) bebased on shelter-in-place capacity instead of on safety alone. If newprograms are put in place to improve citywide resilience, they woulduse shelter-in-place engineering criteria as well.Seismic work (i.e., evaluations and upgrades) can be classified asvoluntary, mandatory or triggered. Each type of project or programcould use shelter-in-place engineering criteria, as opposed toprovisions that look solely at safety.The good news is that much voluntary work already prioritizesreoccupancy and recovery. UC Berkeley, for example, recognizedthat even if its buildings have been deemed safe, not being able touse them during repairs could jeopardize the university’s mission, soit adopted an earthquake recovery goal to limit closure to no morethan 30 days. 32 In the housing sector, however, voluntary work forshelter-in-place or recovery purposes is rare. Where it does occur,it is done without a commonly adopted standard and without thebenefit of plans that have been checked and approved by the buildingdepartment, because voluntary work falls outside the scope of mostbuilding regulations. Further, even if the city’s plan-checkers andinspectors were to certify voluntary work, they currently have nocriteria by which to judge a shelter-in-place evaluation or retrofit.While a shelter-in-place evaluation is in some ways a prediction of abuilding’s performance during and after an earthquake, it is importantto recognize that actual post-earthquake reoccupancy will depend onthe nature of ownership and on individual owners’ or tenants’ choicesabout whether to stay or leave. In owner-occupied housing, theowner is more likely to tolerate (or waive liability for) certain damage,so reoccupancy is likely to happen sooner. But an owner of rentalhousing might not allow tenants to reoccupy the building if remainingdamage would increase the owner’s liability or if reoccupancy woulddelay building repairs or increase their cost. Rent control will also playa significant role in the choices made by both renters and owners.The evaluation criteria recommended here do not account for thesevariables. The best strategy for promoting reoccupancy might nothave much to do with engineering standards; we encourage the cityto work with owners to incentivize quick reoccupancy through GoodSamaritan laws or otherwise waive liability or relocation penalties.22 SPUR Report > January 2012