Baker JW

Chandramohan R

Deierlein GG

UC Research Repository

Influence of ground motion durationon structural collapse riskPEER Transportation Systems Research ProgramPrincipal Investigators: Gregory G. Deierlein & Jack W. BakerStudent Investigator: Reagan ChandramohanJohn A. Blume Earthquake Engineering Center, Stanford UniversityBackground and MotivationI Current standards and guidelines for ground motionselection focus only on response spectra; they do notexplicitly consider durationI Previous studies using spectrally equivalent long and shortduration ground motions have demonstrated that groundmotion duration does influence structural collapse capacityI The eect of duration is aributed to the in-cycle and cyclicdeterioration of structural strength and stiness, and theratcheting of dris due to destabilizing P − ∆ eectsObjectivesI Characterize seismic hazard in terms of the durations andresponse spectra of the anticipated ground motionsI antify the influence of ground motion duration onstructural collapse risk at dierent sitesI Incorporate the eect of duration into structuralperformance assessment and design guidelines(ongoing research)Chosen sites and seismic sources0 200 400kmEugeneSeattleSan FranciscoSeattle fault zone(crustal)CascadiasubductionzoneCalifornia faults(crustal)I The Cascadia subduction zone produces two types ofearthquakesI Large magnitude interface earthquakes, e.g. 2011 Tohoku (MW = 9.0)I Deep in-slab earthquakes, e.g. 2001 Nisqually (MW = 6.8)Seismic hazard deaggregationSealeMagnitude98Interface (35%)765In-slab (24%)200150Crustal (41%)Distance (km)100500400302010Percentage contributionEugeneMagnitude9Interface (93%)8765In-slab (7%)200150Distance (km)100500010203040Percentage contributionSan FranciscoMagnitude9876Crustal (100%)5200150Distance (km)100501003040020Percentage contributionI Deaggregation results are conditional on the 2 % in 50 yearexceedance probability of Sa(1 s)Typical interface and crustal ground motions0 100 200 300a(t) Ds5−75 = 80 sInterface record from 2011 Tohoku (MW = 9.0)0 100 200 300t (s)a(t) Ds5−75 = 5 sCrustal record from 1989 Loma Prieta (MW = 6.9)Median source-specific targets at Seale0.1 1 4T (s)0.020.112S a(T)(g)Interface (Ds5−75 = 32 s)In-slab (Ds5−75 = 7 s)Crustal (Ds5−75 = 5 s)Uniform hazard spectrumI Target distributions of 5-75% significant duration (Ds5−75)are computed similar to a conditional spectrum usingI deaggregation resultsI prediction equation for Ds5−75I model for the correlation between the ε-values of Ds5−75 and Sa(T ∗)Ground motions selected for SealeI CS and duration groupI Selected to match duration and response spectrum targetsI Interface records were selected from large magnitude earthquakeslike 2011 Tohoku (Japan) and 2010 Maule (Chile)I In-slab and crustal records were selected from the PEER NGAdatabaseI CS only control groupI Selected to match response spectrum targets onlyI All records were selected from the PEER NGA databaseI Each group contains 8 sets of records chosen at dierentintensity levels; each set contains 100 records1 10 1002000.00.51.0CumulativeprobabilityCS and duration groupInterface(47/100 records)Targetµ = 36 s1 10 100200In-slab(22/100 records)Targetµ = 9 s1 10 100200Crustal(31/100 records)Targetµ = 5 s1 10 100200Ds5−75 (s)0.00.51.0CumulativeprobabilityCS only control group1 10 100200Ds5−75 (s)1 10 100200Ds5−75 (s)Durations0.1 1 40.010.1110S a(T)(g)CS and duration group0.1 1 4 0.1 1 40.1 1 4T (s)0.010.1110S a(T)(g)CS only control group0.1 1 4T (s)0.1 1 4T (s)TargetResponse SpectraStructural modelI Eight-story reinforced concrete moment frame building,designed for a site in SealeI Concentrated plastic hinge model incorporates the in-cycleand cyclic deterioration of strength and stiness, anddestabilizing P − ∆ eectsRotationMomentCyclicdeteriorationIn-cycledeteriorationCollapse risk estimatesSeale0.15 0.2 0.3 0.4 0.5 0.6 0.7 0.8Sa(1.76 s) (g)0.00.10.20.30.40.5Probabilityofcollapse0246810Meanannualfrequencyofexceedance(×10−4)λcollapse ↓ 29 %Hazard curveCS and durationgroupCS onlycontrol groupEugene0.15 0.2 0.3 0.4 0.5 0.6 0.7 0.8Sa(1.76 s) (g)0.00.10.20.30.40.5Probabilityofcollapse0246810Meanannualfrequencyofexceedance(×10−4)λcollapse ↓ 59 %Hazard curveCS and durationgroupCS onlycontrol groupSan Francisco0.15 0.2 0.3 0.4 0.5 0.6 0.7 0.8Sa(1.76 s) (g)0.00.10.20.30.40.5Probabilityofcollapse0246810Meanannualfrequencyofexceedance(×10−4)λcollapse ↓ 7 %Hazard curveCS and durationgroupCS onlycontrol groupConclusionsI Selecting ground motions from the PEER NGA databasewithout considering their durations can lead to theunconservative underestimation of structural collapse riskat sites where the seismic hazard is dominated by largemagnitude (MW ∼ 9.0) interface earthquakesI This warrants the explicit consideration of ground motionduration, in a manner similar to response spectra, instructural performance assessment and designContact InformationReagan ChandramohanEmail : reaganc@stanford.eduWebsite : sites.google.com/site/reaganch

Influence of ground motion duration on structural collapse risk

https://ir.canterbury.ac.nz/bitstream/handle/10092/15275/Chandramohan_Baker_Deierlein_%282016%29_duration_collapse_risk_%5b2016PAM%5d.pdf?sequence=2&isAllowed=y

Influence of ground motion duration on structural collapse risk

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