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