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 Bray
University of California, Berkeley
Pacific Earthquake Engineering Research Center
SHAKING-INDUCED DAMAGE to Bridges and Buildings
Moehle
EERC Slide Collection
Seismic Displacement
LIQUEFACTION-INDUCED DAMAGE
EERC 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 IM
dIMdEDPdDMIMIMEDPpEDPDMpDMDVpDV ][]/[]/[]/[
Framework for Performance-Based EngineeringPPEEEERR
{Loss analysis}{Damage analysis}{Dynamic analysis}{Hazard analysis}
D
M, R, Site, Fault
Decouple the HAZARD analysis from the DYNAMIC RESPONSE
Minimize the dispersion around the predicted displacements
Example Objective: predict seismic Displacements
IM
IM: characterizes the strong ground motion
3. INTENSITY MEASURES amplitude: PGA, PGV, PGD, SA, SV frequency content: Tp, Tm
duration: D5_95, Dbracketed
other: Arias Intensity Housner Spectral Intensity
EXAMPLE1. SLOPE MODEL equiv-linear, SDOF, coupled stiffness (Ts) - strength (ky)
Ts
kyD
2. EARTHQUAKE DATABASE 45 EQ - 1447 records
EFFICIENCYSTIFF SLOPE
EFFICIENCY RESULTS
Period Independent Arias Intensity Spectral Intensity Period Dependent Spectral Acceleration at Ts
STIFF SLOPE DUCTILE SLOPE
Ts < 0.5 s Ts > 0.5 s
Longitudinal drift ratio
Longitudinal drift ratio(Mackie and Stojadinovic,
2002)
SHORT BUILDING OR BRIDGEIntensity Measures (IM):
Sa(T1), PGV, Ia, Sa(T1)[Sa(2T1)/Sa(T1)]0.5
)ln( aI
RN
DC
FfFf
SMssSMss
hRcMcMcc
21
22211211
224321
))6(())6((
)ln()6/ln()6(
SUFFICIENCY ln(D) = f(IM) + d M+e ln(R)
NO INTENSITY MEASURE IS SUFFICIENT FOR ALL TS and ky
Stiff Slope
VECTORS OF IM’s: D = f( SA(Ts), IM2)
STRONGER
MORE DUCTILE
PERIOD-INDEPENDENT INTENSITY MEASURES
Peak Ground Acceleration PGAPeak Ground Displacement PGD
Arias Intensity (Arias, 1970)
Cumulative Absolute Velocity (Kramer 2002; 5 cm/sec2 threshold)
Response Spectrum Intensity(Housner, 1959)
Peak Ground Velocity PGV & Pulse Period Tv
dt)t(axCAV
0
5
52
10
050.
.
dt)T,.(PSVSI
dt)t(ag
Ia 0
2
2
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)
0 *
hE
Y
*h
E
Y*h
EC
CF
Sa(T1)
Sa(T1)
)T(Sa)T(Sa
)T(SaSaC1
11
2
Factors Affecting (IM): (m): Rate of earthquakes with magnitude
m
• f(m): relative likelihood of earthquakes with different magnitudes
• f(IM|m,r): distribution of IM conditioned on m and r
Stewart et al. PEER Report-2001/09
Source Characterization
• Source locations Segmentation m-A relations
• f(m) models
• Rate Large events (characteristic) Small events
Source: WGCEP, 1999
SURFACE FAULT RUPTURE
Seismic Site Effects
• Local ground conditions– Response of horizontal sediment layers– Accounts for resonance, impedance
contrasts, soil non-linearity
• Basin response– Accounts for 2-D/3-D sediment
geometry
• Surface topographic effects
Combined Influence on Ground Motions
Simplified Geotechnical Site (SGS) Categories (Rodríguez-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
Northridge EQ Loma Prieta
T = 0.3 s T = 1.0 s T = 0.3 s
Site SGS UBC SGS UBC SGS UBC
B .40(.08)
.46(.07)
.45(.11)
.52(.09)
.51(.10)
.52(.10)
C .54(.05)
.54(.06)
.60(.05)
.54(.06)
.38(.05)
.36(.05)
D .41(.04)
.42(.03)
.36(.03)
.41(.03)
.39(.07)
.39(.06)
GROUND MOTION DATABASE
1208 records from 75 EarthquakesActive Plate MarginsMagnitudes 4.7 – 7.6Distances 0.1 – 250 km
Simplified Geotechnical SystemRodriguez-Marek et al. 2001
Fault Types
Rock
Soft Rock /Stiff
ShallowSoil
DeepStiff Soil
Normal
ReverseStrikeSlip
ReverseOblique
15%
27%58%
17
3117
10
0 . 1 1 1 0 1 0 0 1 0 0 0Distance (km)
4
5
6
7
8
Mag
nit
ud
e
Near Fault Ground Motions
Northridge EQ:
Rinaldi Receiving Station Newhall - Pico Canyon