Safe Enough to Stay - ABAG Earthquake and Hazards Program

Safe Enough to Stayimmediate post-earthquake period but required as normalcy isrecovered. A recent report published by the Structural EngineersAssociation of Northern California has proposed a way to link ASCE31 criteria to recovery time. 43 We recommend applying its principlesin coordination with the SPUR-proposed habitability timeline.For example, SPUR’s proposed shelter-in-place standards call forweather protection provided by exterior windows to be restored withinseven days of the emergency declaration. In ASCE 31 terms, weatherprotection from windows is addressed implicitly with criteria relatedto glazing or, in some window wall systems, cladding. The StructuralEngineers Association of Northern California report puts glazing inthe category of components expected to be repairable within days or,for extensive damage to a large building, weeks. With a seven-daytarget, a typical building would be able to meet the shelter-in-placestandard even if the earthquake did cause glazing damage. Therefore,the evaluation criteria need not consider ASCE 31’s provisions forglazing. In a larger building, or where potential glazing damage wouldnot be repairable in seven days, the glazing details would need to bechecked.Another example: SPUR’s standards call for gas and electricityservice to be restored within each unit within 30 days of service tothe building being restored by PG&E. ASCE 31 addresses a varietyof related items, from equipment attachment to flexible couplingsin hazardous materials piping. Where the Structural EngineersAssociation of Northern California report indicates that repairs wouldtake weeks, the issue would be moot relative to the 30-day target.Where the anticipated repair would take months, the conditionrepresents a potential deficiency and must be checked.Vetting the ASCE 31 criteria in this way is challenging in part becauseresidential structure types range from wood or masonry houses todesignated historic apartment buildings to concrete or steel highrises.In larger buildings, nonstructural functions are often served byspecialized components. In smaller vernacular buildings, structuralelements such as wood-sheathed roofs or stucco walls also affectsecurity, weather tightness, fire safety, etc., so structural damagethat’s acceptable under shelter-in-place guidelines might still affectshelter-in-place capacity.D. Contents deficienciesContents deficiencies are those related to such items as furniture,items stored on shelves, and certain equipment. While contentsdamage can impact functional recovery of certain occupanciesand full recovery of most occupancies, 44 shelter-in-place impactsin typical residential occupancies are expected to be rare. Onlyhazardous materials contents (improperly stored solvents, forexample) might delay reoccupancy in a typical house or smallapartment building. In large residential buildings (with industrialkitchens or central plants, for example) or in mixed-use buildings,other specialty contents might pose shelter-in-place risks.Therefore, we recommend waiving all contents provisions of ASCE 31except for those related to stored hazardous materials. A proceduralprovision should be used to invoke supplemental criteria subject tocode official approval for cases of mixed occupancy.E. Utilities infrastructure deficienciesUtilities infrastructure deficiencies are those related to servicesprovided from outside the building, such as water, gas, electricity,sewage removal and telecommunications. The shelter-in-placecapacity of a given residential building can be impacted by theperformance of utility services. SPUR’s proposed shelter-in-placestandards will generally waive requirements for utilities within a unit(water, gas, electricity, sewer) while service to the building is down.Still, it will be useful for planning purposes to have some estimate ofthe number and location of the residential units most likely to loseservices for extended periods.It is impractical to require the evaluator of a single residential buildingto study and draw conclusions about the recoverability of lifelines.Our proposed solution is for the city and service providers to developrough maps sufficient to allow broad relative statements aboutoutages on a neighborhood basis. Presumably, these would be basedon considerations such as the presence of brittle piping in liquefiablesoil, existing plans and prioritizations, etc. Therefore, we recommendthat assessment of shelter-in-place deficiency relative to utilities bebased on maps or inventories of vulnerable infrastructure producedby service providers, by the city or by the San Francisco LifelinesCouncil.In some cases, alternative services can be provided on a timely andtemporary basis while normal service is being restored. To the extentthat such provisions can be reliably predicted or planned for, shelterin-placeevaluation criteria should allow for these as alternativemeans of compliance.Application to special residential occupanciesSPUR’s proposed shelter-in-place standards do not apply directly tocertain residential occupancies providing assisted living and similarservices. Even for normal residential occupancies, however, someresidents are likely to have disabilities that require accommodationssuch as ramps, elevators, strobe alarms, etc. For these conditions, werecommend the development of supplemental criteria in coordinationwith the Mayor’s Office on Disability.43 Bonowitz, D., “Resilience Criteria for Seismic Evaluation of ExistingBuildings,” (Structural Engineers Association of Northern California August 5,2011) www.seaonc.org/pdfs/SEAONC_SPI_Resilience_110805.pdf44 Ibid.SPUR Report > January 2012 41