NEEDS FOR PERFORMANCE-BASED GEOTECHNICAL EARTHQUAKE ENGINEERING Jonathan Bray University of...

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Transcript of NEEDS FOR PERFORMANCE-BASED GEOTECHNICAL EARTHQUAKE ENGINEERING Jonathan Bray University of...

  • NEEDS FOR PERFORMANCE-BASED GEOTECHNICAL EARTHQUAKE ENGINEERING

    Jonathan BrayUniversity of California, Berkeley

    Pacific Earthquake Engineering Research Center

  • SHAKING-INDUCED DAMAGE to Bridges and BuildingsMoehle

  • EERC Slide CollectionSeismic Displacement LIQUEFACTION-INDUCED DAMAGEEERC Slide Collection

  • DV = Decision variable (e.g., down-time, costs)

    DM = Damage Measure (e.g. damage state, cracking)

    EDP = Engineering Demand Parameter (e.g., peak story drift, drift ratio, seismic displacement)

    IM = Intensity measure (e.g., Sa, Arias intensity)

    (IM) = Rate of exceedance of IMFramework for Performance-Based EngineeringPEER{Loss analysis}{Damage analysis}{Dynamic analysis}{Hazard analysis}

  • Decouple the HAZARD analysis from the DYNAMIC RESPONSE

    Minimize the dispersion around the predicted displacements Example Objective: predict seismic Displacements

  • EXAMPLE

  • EFFICIENCYSTIFF SLOPE

  • EFFICIENCY RESULTS

    Period Independent Arias Intensity Spectral Intensity Period Dependent Spectral Acceleration at Ts STIFF SLOPEDUCTILE SLOPETs < 0.5 sTs > 0.5 s

  • Longitudinal drift ratioLongitudinal drift ratio(Mackie and Stojadinovic, 2002)SHORT BUILDING OR BRIDGEIntensity Measures (IM):Sa(T1), PGV, Ia, Sa(T1)[Sa(2T1)/Sa(T1)]0.5

  • SUFFICIENCYln(D) = f(IM) + d M+e ln(R)NO INTENSITY MEASURE IS SUFFICIENT FOR ALL TS and kyStiff Slope

  • VECTORS OF IMs: D = f( SA(Ts), IM2)STRONGERMORE DUCTILE

  • PERIOD-INDEPENDENT INTENSITY MEASURES

    Peak Ground AccelerationPGAPeak Ground DisplacementPGD

    Arias Intensity (Arias, 1970)

    Cumulative Absolute Velocity (Kramer 2002; 5 cm/sec2 threshold)

    Response Spectrum Intensity(Housner, 1959)

    Peak Ground VelocityPGV & Pulse Period Tv

  • PERIOD-DEPENDENT INTENSITY MEASURES

    Spectral Accelerationat Fundamental Period

    Spectral Combination (Cordova et al. 2000)

    Spectral Vector (Conte, 2002)

    Spectral Combination IM1I&2E(Luco and Cornell, 2001)Sa(T1)Sa(T1)

  • Factors Affecting (IM): (m): Rate of earthquakes with magnitude mf(m): relative likelihood of earthquakes with different magnitudesf(IM|m,r): distribution of IM conditioned on m and r

    Stewart et al. PEER Report-2001/09

  • Source Characterization Source locationsSegmentationm-A relations

    f(m) models

    RateLarge events (characteristic)Small eventsSource: WGCEP, 1999

  • SURFACE FAULT RUPTURE

  • Seismic Site EffectsLocal ground conditionsResponse of horizontal sediment layersAccounts for resonance, impedance contrasts, soil non-linearityBasin responseAccounts for 2-D/3-D sediment geometrySurface topographic effectsCombined Influence on Ground Motions

  • Simplified Geotechnical Site (SGS) Categories (Rodrguez-Marek et al. 2001)

    Site

    Description

    Comments

    A

    Hard Rock

    Strong, intact rock

    B

    Rock

    Calif. rock; Dw/s < 6 m

    C

    Weathered/Soft Rock & Shallow Stiff Soil

    6 m < Dw/s < 60 m

    D

    Deep Stiff Holocene Soil

    60 m < Ds

    E

    Soft Clay

    3 m < TC

    F

    Potentially Liquefiable Sand

    Loose sat. sand

  • GROUND MOTION DATABASE1208 records from 75 EarthquakesActive Plate MarginsMagnitudes 4.7 7.6Distances 0.1 250 km Simplified Geotechnical SystemRodriguez-Marek et al. 2001

    Fault TypesRockSoft Rock /Stiff ShallowSoilDeepStiff SoilNormalReverseStrikeSlipReverseOblique15%27%58%

  • Near Fault Ground Motions

    Northridge EQ:

    Rinaldi Receiving Station Newhall - Pico Canyon

    WONT SPEND A LOT OF TIME ON THIS B/C NOT MUCH PEER RESEARCHNeed to identify where sources are:-easy for major strike slip faults such as those shown here-more difficult for reverse slip faults (common in so. Cal), especially blind thrusts-must allow background seismicity for uknown faults

    SEGMENTS: likely future earthquake sources along fault e.g., we might think SH is one likely source, NH is another, or both at once (assign weights to each scenario) - relate fault size to magnitude using empircal relations (m-A scaling relns)

    F(m): we discuss in report several models (exponential, characteristic, maximummagnitude), and what was recommended by a CDMG-USGS working groupfor CA

    RATE: need separate rate for large (characteristic) event on major sources, and small eqks, which is assumed to follow G-R.