Download - 2009 ODOT Geo/Hydro/HazMat Conference Geotechnical Aspects of ODOT Seismic Bridge Design Jan Six P.E. ODOT Bridge Section

2009 ODOT Geo/Hydro/HazMat Conference

Geotechnical Aspects of Geotechnical Aspects of ODOT Seismic Bridge ODOT Seismic Bridge

DesignDesign

Jan Six P.E.Jan Six P.E.

ODOT Bridge SectionODOT Bridge Section


Seismic Design StandardsSeismic Design Standards

ODOT Geotechnical Manual

AASHTO Guide Specifications for LRFD Seismic Bridge Design

ODOT Bridge Design & Drafting Manual


When is a Site Specific Response Analysis Needed?

What does a Ground Response Analysis consist of?

How is liquefaction and lateral spread quantified?

How are these results used in design?

When is liquefaction mitigation needed?

TopicsTopics


Hazard Analysisvs.

Ground Response Analysis

When is a Site Specific Response Analysis Needed?When is a Site Specific Response Analysis Needed?

Site Specific Analysis ?????


Seismic Hazard Analysis


• Probabilistic seismic hazard analysis (PSHA) or

• Deterministic seismic hazard analysis

A deterministic hazard analysis (DSHA) involves evaluating the seismic hazard at a site for an earthquake of a specific magnitude occurring at a specific location, considering the attenuation of the ground motions with distance. The DSHA is usually conducted without regard for the likelihood of occurrence.


Probabilistic Seismic Hazard Analysis (PSHA)


• Focuses on the spatial and temporal occurrence of earthquakes, and evaluates all of the possible earthquake sources contributing to the seismic hazard at a site with the purpose of developing ground motion data consistent with a specified uniform hazard level.

• Quantifies the uncertainties associated with the seismic hazard, including the location of the source, extent and geometry, maximum earthquake magnitudes, rate of seismicity, and estimated ground-motion parameters.

• Produces a uniform hazard acceleration response spectrum based on a specified uniform hazard level or probability of exceedance within a specified time period (i.e., 7% probability of exceedance in 75 years).


Seismic Hazard Analysis


• Site specific hazard analysis are typically not performed on routine ODOT projects. Only if new information on new or existing sources was uncovered and documented.

• The 2002 USGS Probabilistic Seismic Hazard Maps are typically used.


Usually done to either:

1. Develop acceleration response spectra (ARS) or

2. For liquefaction analysis




AASHTO “General Procedure” usually adequate

• Use 2002 USGS Seismic Hazard Maps to obtain bedrock PGA, S0.2 and S1 for 500 and 1000 yr return periods

• Determine soil site class designation (A – F)

• Develop Response Spectra



General Procedure for determining Response Spectrum


Use the program:SeismicDesignUtility_2002.mde


A site-specific ground motion response analyses should be performed if any of the following apply (AASHTO):

• The site consists of Site Class F soils, as defined in Article 3.4.2.1.

• The bridge is considered critical or essential according to Article 4.2.2, for which a higher degree of confidence of meeting the seismic performance objectives of Article 3.2 is desired.



AASHTO 3.4:

If the site is located within 6 mi of a known active fault capable of producing a magnitude 5 earthquake and near fault effects are not modeled in the development of national ground motion maps, directivity and directionality effects should be considered as described in Article 3.4.3.1 and its commentary.


AASHTO 3.4.3.1For sites located within 6 mi of an active surface or shallow fault, as depicted in the USGS Active Fault Map, near-fault effects on ground motions should be considered to determine if these could significantly influence the bridge response.

Near–Fault Effects


AASHTO 3.4 definition:

• An active fault is defined as a near surface or shallow fault whose location is known or can reasonably be inferred and which has exhibited evidence of displacement in Holocene (or recent) time (in the past 11,000 yr, approximately).

• Use USGS Quaternary Fault database to determine if fault is considered “active” (<15ka) and for description of fault characteristics.




• Directivity effects that increase ground motions for periods greater than 0.5 sec if the fault rupture propagates toward the site, and

• Directionality effects that increase ground motions for periods greater than 0.5 sec in the direction normal

(perpendicular) to the strike of the fault.

AASHTO 3.4.3.1:These effects are significant only for periods longer than 0.5 sec and normally would be evaluated only for essential or critical bridges having natural periods of vibration longer than 0.5 sec.




• Currently no ODOT classification of “essential” or “critical” bridges.

• All bridges considered subject to near fault effects if criteria is met.

• Ground Response Analysis typically not required. Currently researching procedures to use for modifying general response spectrum.




Site Class F soils, as defined in Article 3.4.2.1:

•Peat or highly organic clays, greater than 10 ft in thickness,

•Very high plasticity clays (H > 25 ft with PI > 75)

•Very thick soft/medium stiff clays (H >120 ft),




• Evaluation of Liquefiable Soil Conditions

(vs. Simplified Methods, when FOSliq ≈ 1.0)

• Very deep soil deposits or thin (<40 – 50 feet) soil layers over bedrock.

• Obtain better information for evaluating lateral deformations, near surface soil shear strain levels or deep foundation performance.

• Obtain ground surface PGA values for abutment wall or other design.

A site-specific ground motion response analyses should be considered if any of the following apply:



Primary uses:

• Developing Site Specific Design Acceleration Response Spectra (ARS)

• Developing ground motion data for use in liquefaction evaluation



Evaluates the response of a layered soil deposit subjected to earthquake motions.

One-dimensional, equivalent-linear models are commonly utilized in practice.

What does a Ground Response study consist of?What does a Ground Response study consist of?



This model uses an iterative total stress approach to estimate the nonlinear elastic behavior of soils.

Modified versions of the numerical model SHAKE (e.g., SHAKE2000, ProSHAKE, SHAKE91) are routinely used to simulate the propagation of seismic waves through the soil column


Output consists of:

•acceleration response spectra at ground surface or at depths of interest,

•time histories at selected depths in the soil profile, •plots of ground motion parameters with depth (e.g., PGA,

maximum shear stress and shear strain), •induced cyclic shear stresses in individual soil layers, which may be used in liquefaction analysis.



Earthquake Source Characterization (deaggregation of Earthquake Source Characterization (deaggregation of uniform seismic hazard)uniform seismic hazard)

Develop input ground motions (time-histories)Develop input ground motions (time-histories) Develop soil profile and dynamic properties for soil modelDevelop soil profile and dynamic properties for soil model Run program and develop response spectrum from Run program and develop response spectrum from

outputoutput

Acceleration Response SpectraAcceleration Response Spectra

Development StepsDevelopment Steps



Develop Uniform Hazard Spectrum from 2002 USGS Develop Uniform Hazard Spectrum from 2002 USGS Seismic Hazard maps (“target bedrock spectrum”)Seismic Hazard maps (“target bedrock spectrum”)

Use the deaggregation information from the 2002 USGS Use the deaggregation information from the 2002 USGS Seismic Hazard database to obtain information on the Seismic Hazard database to obtain information on the primary sources that affect the site. primary sources that affect the site.

Review USGS deaggregation data to:Review USGS deaggregation data to: Determine and characterize primary seismic sourcesDetermine and characterize primary seismic sources Determine magnitude (M) and distance (R) of each Determine magnitude (M) and distance (R) of each

sourcesource

Earthquake Source Earthquake Source CharacterizationCharacterization

Design Response Spectra Design Response Spectra from Ground Response Analysisfrom Ground Response Analysis




All seismic sources (M-R pairs) that contribute more All seismic sources (M-R pairs) that contribute more than about 5% to the hazard in the period range of than about 5% to the hazard in the period range of interest should be considered.interest should be considered.

Scale (or spectrally match) earthquake time histories to Scale (or spectrally match) earthquake time histories to the “target” spectrumthe “target” spectrum




2002 USGS PSHA maps2002 USGS PSHA maps




USGS Web Site:USGS Web Site:http://earthquake.usgs.gov/research/hazmaps/http://earthquake.usgs.gov/research/hazmaps/Custom Mapping Analysis ToolsCustom Mapping Analysis Tools


*** Deaggregation of Seismic Hazard for PGA & 2 Periods of Spectral Accel. *** *** Data from U.S.G.S. National Seismic Hazards Mapping Project, 2002 version *** PSHA Deaggregation. %contributions. site: Portland,_Oregon long: 122.680 W., lat: 45.580 N. USGS 2002-03 update files and programs. dM=0.2. Site descr:ROCK Return period: 975 yrs. Exceedance PGA =0.2688 g. #Pr[at least one eq with median motion>=PGA in 50 yrs]=0.01407 DIST(KM) MAG(MW) ALL_EPS EPSILON>2 1<EPS<2 0<EPS<1 -1<EPS<0 -2<EPS<-1 EPS<-2 6.3 5.05 1.803 0.212 0.948 0.643 0.000 0.000 0.000 12.7 5.05 1.370 0.593 0.777 0.000 0.000 0.000 0.000 22.0 5.05 0.135 0.135 0.000 0.000 0.000 0.000 0.000 22.6 5.40 0.422 0.409 0.014 0.000 0.000 0.000 0.000 33.6 6.01 0.086 0.086 0.000 0.000 0.000 0.000 0.000 6.5 6.20 2.737 0.100 0.634 1.322 0.666 0.014 0.000 14.3 6.20 7.493 0.894 4.409 2.119 0.071 0.000 0.000 23.3 6.20 0.766 0.321 0.444 0.001 0.000 0.000 0.000 33.9 6.40 0.153 0.134 0.019 0.000 0.000 0.000 0.000 6.2 6.59 5.440 0.150 0.956 2.364 1.747 0.222 0.000 5.7 6.78 6.255 0.149 0.949 2.373 2.192 0.583 0.009 13.7 6.79 1.049 0.054 0.328 0.529 0.137 0.000 0.000 168.7 7.00 0.051 0.051 0.000 0.000 0.000 0.000 0.000 5.8 7.29 0.157 0.004 0.023 0.057 0.056 0.016 0.001 89.4 8.30 7.067 1.643 5.424 0.000 0.000 0.000 0.000 93.9 8.30 1.433 0.381 1.052 0.000 0.000 0.000 0.000 112.7 8.30 3.533 1.643 1.890 0.000 0.000 0.000 0.000 190.8 8.30 0.068 0.068 0.000 0.000 0.000 0.000 0.000 89.4 9.00 9.236 1.042 6.617 1.577 0.000 0.000 0.000 108.9 9.00 2.647 0.417 2.230 0.000 0.000 0.000 0.000 135.3 9.00 1.667 0.417 1.250 0.000 0.000 0.000 0.000 162.4 9.00 0.500 0.208 0.291 0.000 0.000 0.000 0.000 Summary statistics for above PSHA PGA deaggregation, R=distance, e=epsilon: Mean src-site R= 37.3 km; M= 6.80; eps0= 0.50. Mean calculated for all sources. Modal src-site R= 89.4 km; M= 9.00; eps0= 0.87 from peak (R,M) bin Gridded source distance metrics: Rseis Rrup and Rjb MODE R*= 89.4km; M*= 9.00; EPS.INTERVAL: 1 to 2 sigma % CONTRIB.= 6.617 Modal source dmetric: distance to rupture surface (Youngs et al.,SRL,1997) Principal sources (faults, subduction, random seismicity having >10% contribution) Source Category: % contr. R(km) M epsilon0 (mean values) WUS shallow gridded 52.17 11.7 5.89 0.51 Wash-Oreg faults 18.92 9.0 6.61 -0.71 M 9.0 Subduction 14.05 101.1 9.00 1.00 M 8.3 Subduction 13.92 103.9 8.30 1.52 Individual fault hazard details if contrib.>1%: Grant Butte f 4.22 14.1 6.20 0.93 Helvetia f 1.04 14.6 6.37 0.04 Portland Hills F-Char 3.90 5.8 6.95 -1.65 Portland Hills F-GR mag 8.61 5.9 6.71 -1.40

Deaggregation of Seismic Hazard for PGA & 2 Periods of Spectral Accel. *** *** Data from U.S.G.S. National Seismic Hazards Mapping Project, 2002 version *** PSHA Deaggregation. %contributions. site: Portland,_Oregon long: 122.680 W., lat: 45.580 N. USGS 2002-03 update files and programs. dM=0.2. Site descr:ROCK Return period: 975 yrs. Exceedance PGA =0.2688 g. #Pr[at least one eq with median motion>=PGA in 50 yrs]=0.01407


Earthquake Source Characterization Earthquake Source Characterization (Deaggregation)(Deaggregation)


*** Deaggregation of Seismic Hazard for PGA & 2 Periods of Spectral Accel. *** *** Data from U.S.G.S. National Seismic Hazards Mapping Project, 2002 version *** PSHA Deaggregation. %contributions. site: Portland,_Oregon long: 122.680 W., lat: 45.580 N. USGS 2002-03 update files and programs. dM=0.2. Site descr:ROCK Return period: 975 yrs. Exceedance PGA =0.2688 g. #Pr[at least one eq with median motion>=PGA in 50 yrs]=0.01407 DIST(KM) MAG(MW) ALL_EPS EPSILON>2 1<EPS<2 0<EPS<1 -1<EPS<0 -2<EPS<-1 EPS<-2 6.3 5.05 1.803 0.212 0.948 0.643 0.000 0.000 0.000 12.7 5.05 1.370 0.593 0.777 0.000 0.000 0.000 0.000 22.0 5.05 0.135 0.135 0.000 0.000 0.000 0.000 0.000 22.6 5.40 0.422 0.409 0.014 0.000 0.000 0.000 0.000 33.6 6.01 0.086 0.086 0.000 0.000 0.000 0.000 0.000 6.5 6.20 2.737 0.100 0.634 1.322 0.666 0.014 0.000 14.3 6.20 7.493 0.894 4.409 2.119 0.071 0.000 0.000 23.3 6.20 0.766 0.321 0.444 0.001 0.000 0.000 0.000 33.9 6.40 0.153 0.134 0.019 0.000 0.000 0.000 0.000 6.2 6.59 5.440 0.150 0.956 2.364 1.747 0.222 0.000 5.7 6.78 6.255 0.149 0.949 2.373 2.192 0.583 0.009 13.7 6.79 1.049 0.054 0.328 0.529 0.137 0.000 0.000 168.7 7.00 0.051 0.051 0.000 0.000 0.000 0.000 0.000 5.8 7.29 0.157 0.004 0.023 0.057 0.056 0.016 0.001 89.4 8.30 7.067 1.643 5.424 0.000 0.000 0.000 0.000 93.9 8.30 1.433 0.381 1.052 0.000 0.000 0.000 0.000 112.7 8.30 3.533 1.643 1.890 0.000 0.000 0.000 0.000 190.8 8.30 0.068 0.068 0.000 0.000 0.000 0.000 0.000 89.4 9.00 9.236 1.042 6.617 1.577 0.000 0.000 0.000 108.9 9.00 2.647 0.417 2.230 0.000 0.000 0.000 0.000 135.3 9.00 1.667 0.417 1.250 0.000 0.000 0.000 0.000 162.4 9.00 0.500 0.208 0.291 0.000 0.000 0.000 0.000 Summary statistics for above PSHA PGA deaggregation, R=distance, e=epsilon: Mean src-site R= 37.3 km; M= 6.80; eps0= 0.50. Mean calculated for all sources. Modal src-site R= 89.4 km; M= 9.00; eps0= 0.87 from peak (R,M) bin Gridded source distance metrics: Rseis Rrup and Rjb MODE R*= 89.4km; M*= 9.00; EPS.INTERVAL: 1 to 2 sigma % CONTRIB.= 6.617 Modal source dmetric: distance to rupture surface (Youngs et al.,SRL,1997) Principal sources (faults, subduction, random seismicity having >10% contribution) Source Category: % contr. R(km) M epsilon0 (mean values) WUS shallow gridded 52.17 11.7 5.89 0.51 Wash-Oreg faults 18.92 9.0 6.61 -0.71 M 9.0 Subduction 14.05 101.1 9.00 1.00 M 8.3 Subduction 13.92 103.9 8.30 1.52 Individual fault hazard details if contrib.>1%: Grant Butte f 4.22 14.1 6.20 0.93 Helvetia f 1.04 14.6 6.37 0.04 Portland Hills F-Char 3.90 5.8 6.95 -1.65 Portland Hills F-GR mag 8.61 5.9 6.71 -1.40

Principal sources (faults, subduction, random seismicity having >10% contribution) Source Category: % contr. R(km) M epsilon0 (mean values) WUS shallow gridded 52.17 11.7 5.89 0.51 Wash-Oreg faults 18.92 9.0 6.61 -0.71 M 9.0 Subduction 14.05 101.1 9.00 1.00 M 8.3 Subduction 13.92 103.9 8.30 1.52


DIST(KM) MAG(MW) ALL_EPS EPSILON>2 1<EPS<2 0<EPS<1 -1<EPS<0 -2<EPS<-1 EPS<-2 6.3 5.05 1.803 0.212 0.948 0.643 0.000 0.000 0.000 12.7 5.05 1.370 0.593 0.777 0.000 0.000 0.000 0.000 22.0 5.05 0.135 0.135 0.000 0.000 0.000 0.000 0.000 6.3 5.20 3.277 0.323 1.539 1.415 0.000 0.000 0.000


2475 year2475 year

Period = 0 secPeriod = 0 sec Period = 0.1 secPeriod = 0.1 sec Period = 0.2 secPeriod = 0.2 sec Period = 0.3 secPeriod = 0.3 sec Period = 0.5 secPeriod = 0.5 sec Period = 1 secPeriod = 1 sec Period = 2 secPeriod = 2 sec

PGA = 0.3923PGA = 0.3923 SA = 0.784SA = 0.784 SA = 0.9313SA = 0.9313 SA = 0.8206SA = 0.8206 SA = 0.6283SA = 0.6283 SA = 0.3284SA = 0.3284 SA = 0.1531SA = 0.1531

SUMMARY STATISTICSSUMMARY STATISTICS Cont. Cont. (%)(%)

R R (km)(km) MM Cont. Cont.

(%)(%)R R

(km)(km) MM Cont. Cont. (%)(%)


(%)(%)R R



(%)(%)R R


R R (km)(km) MM

Mean ValuesMean Values ---- 29.729.7 6.766.76 0.820.82 ---- 24.724.7 6.516.51 0.870.87 ---- 30.730.7 6.786.78 0.920.92 ---- 37.237.2 7.037.03 0.950.95 ---- 55.655.6 7.577.57 1.051.05 ---- 61.361.3 7.737.73 1.071.07 ---- 70.570.5 7.97.9 1.181.18

Modal ValuesModal Values ---- 7.57.5 6.636.63 -0.24-0.24 ---- 7.77.7 6.636.63 -0.05-0.05 ---- 88.588.5 99 1.421.42 ---- 88.588.5 99 1.291.29 ---- 88.588.5 99 1.031.03 ---- 88.588.5 99 0.950.95 ---- 88.588.5 99 0.940.94

Gridded ModalGridded Modal 6.4086.408 88.588.5 99 1 - 21 - 2 5.5435.543 7.67.6 6.636.63 0 - 10 - 1 6.9096.909 88.588.5 99 1 - 21 - 2 9.4979.497 88.588.5 99 1 - 21 - 2 16.1316.13 88.588.5 99 1 - 21 - 2 16.916.9 88.588.5 99 1 - 21 - 2 16.9616.96 88.588.5 99 1 - 21 - 2

Principle Sources (contributions >10%)Principle Sources (contributions >10%)

WUS shallow griddedWUS shallow gridded 54.1754.17 9.59.5 5.965.96 0.790.79 62.5862.58 9.89.8 5.855.85 0.840.84 54.0854.08 1010 5.975.97 0.90.9 46.5146.51 10.110.1 6.086.08 0.910.91 30.5230.52 10.110.1 6.246.24 0.960.96 26.4126.41 11.711.7 6.356.35 11 21.521.5 14.114.1 6.466.46 1.141.14

Wash-Oreg faults Wash-Oreg faults 22.5522.55 9.89.8 6.746.74 -0.07-0.07 19.8419.84 9.69.6 6.726.72 0.120.12 21.9221.92 9.79.7 6.726.72 0.10.1 22.5722.57 9.79.7 6.736.73 0.110.11 19.0419.04 9.59.5 6.756.75 0.240.24 17.8217.82 9.99.9 6.756.75 0.320.32 15.4615.46 10.910.9 6.756.75 0.530.53

M 9.0 SubductionM 9.0 Subduction 13.0313.03 9898 99 1.541.54 ---- ---- ---- ---- 13.8213.82 98.298.2 99 1.521.52 17.9517.95 98.998.9 99 1.41.4 28.728.7 100100 99 1.141.14 32.8232.82 101101 99 1.061.06 34.934.9 102102 99 1.041.04

M 8.3 Subduction M 8.3 Subduction ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- 12.3812.38 99.399.3 8.38.3 1.941.94 21.1221.12 102102 8.38.3 1.751.75 22.3422.34 103103 8.38.3 1.751.75 27.2327.23 108108 8.38.3 1.721.72

Individual fault hazard details (contributions >1%)Individual fault hazard details (contributions >1%)

Grant Butte FaultGrant Butte Fault 1.341.34 17.817.8 6.26.2 1.941.94 1.491.49 17.917.9 6.26.2 1.91.9 1.341.34 17.717.7 6.26.2 1.881.88 1.691.69 17.617.6 6.26.2 1.871.87 1.161.16 17.817.8 6.26.2 1.961.96 1.211.21 18.118.1 6.26.2 1.91.9 1.381.38 16.816.8 6.26.2 1.91.9

Helvetia FaultHelvetia Fault 1.031.03 15.715.7 6.386.38 0.720.72 ---- ---- ---- ---- 1.061.06 15.515.5 6.386.38 0.780.78 1.031.03 15.315.3 6.396.39 0.860.86 ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----

Portland Hills Fault Portland Hills Fault Char.Char. 6.566.56 8.38.3 6.966.96 -0.42-0.42 ---- ---- ---- ---- 6.086.08 8.28.2 6.966.96 -0.27-0.27 ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----

Portland Hills FaultPortland Hills Fault 1313 8.48.4 6.726.72 -0.23-0.23 11.3111.31 8.28.2 6.716.71 -0.08-0.08 12.2912.29 8.38.3 6.726.72 -0.1-0.1 12.3112.31 8.38.3 6.726.72 -0.07-0.07 10.6510.65 8.38.3 6.736.73 0.130.13 9.619.61 8.48.4 6.736.73 0.20.2 7.767.76 8.38.3 6.746.74 0.40.4

877 Portland Hills Fault877 Portland Hills Fault ---- ---- ---- ---- 5.515.51 8.18.1 6.956.95 -0.21-0.21 ---- ---- ---- ---- 6.436.43 8.28.2 6.966.96 -0.29-0.29 5.825.82 8.38.3 6.966.96 -0.14-0.14 5.575.57 8.38.3 6.976.97 -0.1-0.1 4.844.84 8.38.3 6.976.97 0.060.06




2475 year2475 year

Period = 0 secPeriod = 0 sec Period = 0.1 secPeriod = 0.1 sec Period = 0.2 secPeriod = 0.2 sec Period = 0.3 secPeriod = 0.3 sec Period = 0.5 secPeriod = 0.5 sec Period = 1 secPeriod = 1 sec Period = 2 secPeriod = 2 secPGA = 0.3923PGA = 0.3923 SA = 0.784SA = 0.784 SA = 0.9313SA = 0.9313 SA = 0.8206SA = 0.8206 SA = 0.6283SA = 0.6283 SA = 0.3284SA = 0.3284 SA = 0.1531SA = 0.1531



(%)(%)R R



(%)(%)R R



(%)(%)R R


R R (km)(km) MM











Helvetia FaultHelvetia Fault 1.031.03 15.715.7 6.386.38 0.720.72 ---- ---- ---- ---- 1.061.06 15.515.5 6.386.38 0.780.78 1.031.03 15.315.3 6.396.39 0.860.86 ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----Portland Hills Fault Portland Hills Fault Char.Char. 6.566.56 8.38.3 6.966.96 -0.42-0.42 ---- ---- ---- ---- 6.086.08 8.28.2 6.966.96 -0.27-0.27 ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----



Period = 0.1 secPeriod = 0.1 sec

SA = 0.784SA = 0.784

Cont. Cont. (%)(%) R (km)R (km) MM

---- 24.724.7 6.516.51 0.870.87---- 7.77.7 6.636.63 -0.05-0.05

5.5435.543 7.67.6 6.636.63 0 - 10 - 1

62.5862.58 9.89.8 5.855.85 0.840.8419.8419.84 9.69.6 6.726.72 0.120.12

---- ---- ---- -------- ---- ---- ----

1.491.49 17.917.9 6.26.2 1.91.9

---- ---- ---- -------- ---- ---- ----

11.3111.31 8.28.2 6.716.71 -0.08-0.085.515.51 8.18.1 6.956.95 -0.21-0.21

Period = 2 secPeriod = 2 sec

SA = 0.1531SA = 0.1531

Cont. Cont. (%)(%) R (km)R (km) MM ee

---- 70.570.5 7.97.9 1.181.18---- 88.588.5 99 0.940.94

16.9616.96 88.588.5 99 1 - 21 - 2

21.521.5 14.114.1 6.466.46 1.141.1415.4615.46 10.910.9 6.756.75 0.530.5334.934.9 102102 99 1.041.04

27.2327.23 108108 8.38.3 1.721.72

1.381.38 16.816.8 6.26.2 1.91.9---- ---- ---- -------- ---- ---- ----

7.767.76 8.38.3 6.746.74 0.40.44.844.84 8.38.3 6.976.97 0.060.06




Most Significant Contributors to Seismic Ground Motion Hazard


0 – 0.5s period: Shallow Crustal 0.5 – 2s period: Subduction Zone Mega-Thrust


In areas where the hazard has a significant contribution from both the Cascadia Subduction Zone (CSZ) and from crustal sources, both earthquake sources need to be included in the analysis and development of a site specific response spectra.

Bridge Creek Bridge Acceleration Response Spectra

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.10 1.00 10.00

Period, sec.

Sp

ectr

al A

ccel

erat

ion

, (g

)

AASHTO General Procedure


Selection of Time HistoriesSelection of Time Histories


considering tectonic environment and style of faulting (subduction zone, Benioff zone, or shallow crustal faults),

seismic source-to-site-distance, earthquake magnitude, duration of strong shaking, peak acceleration, site subsurface characteristics, predominant period, spectral shape

Principal sources (faults, subduction, random seismicity having >10% contribution) Source Category: % contr. R(km) M epsilon0 (mean values) WUS shallow gridded 52.17 11.7 5.89 0.51 Wash-Oreg faults 18.92 9.0 6.61 -0.71 M 9.0 Subduction 14.05 101.1 9.00 1.00 M 8.3 Subduction 13.92 103.9 8.30 1.52 Individual fault hazard details if contrib.>1%: Grant Butte f 4.22 14.1 6.20 0.93 Helvetia f 1.04 14.6 6.37 0.04 Portland Hills F-Char 3.90 5.8 6.95 -1.65 Portland Hills F-GR mag 8.61 5.9 6.71 -1.40


Selection and Scaling of Time Selection and Scaling of Time HistoriesHistories


AASHTO (2009) allows two options for the selection of time histories to use in ground response analysis. The two options are:

a) Use a suite of 3 response-spectrum-compatible time histories with the design response spectrum developed enveloping the maximum response, or

b) Use of at least 7 time histories and develop the design spectrum as the mean of the computed response spectra.



Use at least three (3) spectrum-compatible time histories, representing the seismic source characteristics.

Used for single primary source sites

Match the selected time-histories to the “target” spectrum using response spectrum matching techniques.

Develop the design response spectrum by enveloping the caps of the resulting response spectra.

Selection and Scaling of Time Selection and Scaling of Time HistoriesHistories


Selection and Scaling of Time Selection and Scaling of Time Histories:Histories:


Sites with multiple primary sources Difficult to match time histories from every source to the entire

target spectrum (gives unrealistic results) Use a collection of time histories that include at least three (3)

ground motion records representative each primary source (typically subduction zone events and shallow crustal earthquakes)

Scale the records associated with each primary source so that the average of the records closely matches the target spectrum in the period range of significance.

Develop the mean spectrum for each primary source Design response spectrum is developed as an envelope with

minor reductions in the spectral peaks (mean + one standard deviation).


Four earthquake records based on PSHA deaggregation, deterministic specta

Two Shallow Crustal (SC-1, SC-2) Two Subduction Zone (CSZ-1, CSZ-2)

EarthquakeEarthquake StationStation DirectionDirection MagnitudeMagnitude DistanceDistance

SC-1SC-1 Northridge, CANorthridge, CA Santa Monica Santa Monica City HallCity Hall

360 deg.360 deg. 6.76.7 18 km18 km

SC-2SC-2 Northridge, CANorthridge, CA Santa Monica Santa Monica City HallCity Hall

90 deg.90 deg. 6.76.7 18 km18 km

CSZ-1CSZ-1 Michoacán, MEXMichoacán, MEX La UnionLa Union 90 deg.90 deg. 8.18.1 83.9 km83.9 km

CSZ-2CSZ-2 Michoacán, MEXMichoacán, MEX ZihuatenejoZihuatenejo 90 deg.90 deg. 8.18.1 132.6 km132.6 km

Scaling of Time HistoriesScaling of Time Histories



Scaling to get the geometric mean matched to period range of Scaling to get the geometric mean matched to period range of predominate hazard contributionpredominate hazard contribution




Once the time histories have been scaled or spectrally matched, they can be used directly as input into the ground response analysis programs to develop response spectra and other seismic design parameters.

Five percent (5%) damping is typically used in all site response analysis.




Select bent locationSelect bent locationDevelop input parameters Develop input parameters dependent on type of analysis, total dependent on type of analysis, total

or effective stress (nonlinear)or effective stress (nonlinear) Shear wave velocity profileShear wave velocity profile static and dynamic soil propertiesstatic and dynamic soil properties

Site CharacterizationSite Characterization



Total Stress AnalysisTotal Stress Analysis SHAKE91 Computer Program (Shake2000, Proshake)SHAKE91 Computer Program (Shake2000, Proshake) One Dimensional Wave Propagation TheoryOne Dimensional Wave Propagation Theory Vertical Propagation of Shear WavesVertical Propagation of Shear Waves Equivalent Linear AnalysisEquivalent Linear Analysis


Effective Stress, Nonlinear AnalysisEffective Stress, Nonlinear Analysis D-MOD, DESRA Computer ProgramD-MOD, DESRA Computer Program One Dimensional Wave Propagation TheoryOne Dimensional Wave Propagation Theory Vertical Propagation of Shear WavesVertical Propagation of Shear Waves Models pore water pressure generationModels pore water pressure generation Models nonlinear soil degradationModels nonlinear soil degradation




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MICHON90W.EQ MICHON00W.EQ PERU_6_01_EW.EQPERU_6_01_NS.EQ D-SKH360_AT2.EQ D-SKH270_AT2.EQTUJ262_AT2.EQ AASHTO General Procedure 2/3 AASHTO General Procedure


2/3 AASHTO General Procedure




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Liquefaction Assessment from Liquefaction Assessment from Ground Response Analysis Ground Response Analysis

Preliminary ScreeningPreliminary ScreeningLiquefaction Assessment not required if:

The bedrock PGA (or Acceleration Coefficient, As) is less than 0.10g, The ground water table is more than 75 feet below the ground surface, The soils in the upper 75 feet of the profile have a minimum SPT resistance, corrected for overburden depth and hammer energy (N’60), of 25 blows/ft, or a cone tip resistance qc of 150 tsf.

Liquefaction Assessment Procedures Liquefaction Assessment Procedures

(AASHTO 6.8 and GDM Section 6.5.2.2)(AASHTO 6.8 and GDM Section 6.5.2.2)


Preliminary Screening (cont.)Preliminary Screening (cont.)Liquefaction Assessment not required if:

All soils in the upper 75 feet are classified as “cohesive”, and Have a PI ≥ 18.

Note that cohesive soils with PI ≥ 18 may still be very soft or exhibit sensitive behavior and could therefore undergo significant strength loss under earthquake shaking. This criterion should be used with care and good engineering judgment.

Liquefaction Assessment Procedures Liquefaction Assessment Procedures

(AASHTO 6.8 and GDM Section 6.5.2.2)(AASHTO 6.8 and GDM Section 6.5.2.2)



Simplified (empirical-based) Procedures (Seed & Idriss and others)Simplified (empirical-based) Procedures (Seed & Idriss and others) Limited to depths of about 50 feetLimited to depths of about 50 feet

Total stress ground response analysis methods, used to obtain Total stress ground response analysis methods, used to obtain parameters for use in simplified procedures parameters for use in simplified procedures Limited to low to moderate cyclic strain and moderate peak Limited to low to moderate cyclic strain and moderate peak

accelerations accelerations Effective stress, nonlinear ground response analysis methods are used Effective stress, nonlinear ground response analysis methods are used

to obtain pore pressure ratio to assess liquefaction potentialto obtain pore pressure ratio to assess liquefaction potential More sophisticated analysis, requires peer reviewMore sophisticated analysis, requires peer review

Liquefaction Assessment Procedures (AASHTO Liquefaction Assessment Procedures (AASHTO 6.8)6.8)



Simplified Procedures (Seed & Idriss and others)Simplified Procedures (Seed & Idriss and others) Limited to depths of about 50 feetLimited to depths of about 50 feet Stress reduction factor (rStress reduction factor (rdd), becomes ), becomes

highly variable and uncertain with depthhighly variable and uncertain with depth

Liquefaction Assessment ProceduresLiquefaction Assessment Procedures



Simplified Procedures Simplified Procedures (Seed & Idriss and others)(Seed & Idriss and others)

Liquefaction Assessment ProceduresLiquefaction Assessment Procedures

Cyclic Resistance Ratio (CRR)



Earthquake Source CharacterizationEarthquake Source Characterization Identify primary sources contributing to the hazardIdentify primary sources contributing to the hazard

Attenuate PGA from primary source(s) to site (given M-R pairs)Attenuate PGA from primary source(s) to site (given M-R pairs) Develop soil profile and dynamic properties for soil modelDevelop soil profile and dynamic properties for soil model

Apply soil amplification factors to obtain surface PGA for use with Apply soil amplification factors to obtain surface PGA for use with simplified proceduressimplified procedures

OROR Perform ground response analysisPerform ground response analysis

total stress ortotal stress or effective stress, nonlinear analysiseffective stress, nonlinear analysis

Ground Response Analysis for Liquefaction Ground Response Analysis for Liquefaction AssessmentAssessment



2475 year2475 year

Period = 0 secPeriod = 0 sec Period = 0.1 secPeriod = 0.1 sec Period = 0.2 secPeriod = 0.2 sec Period = 0.3 secPeriod = 0.3 sec Period = 0.5 secPeriod = 0.5 sec Period = 1 secPeriod = 1 sec Period = 2 secPeriod = 2 secPGA = 0.3923PGA = 0.3923 SA = 0.784SA = 0.784 SA = 0.9313SA = 0.9313 SA = 0.8206SA = 0.8206 SA = 0.6283SA = 0.6283 SA = 0.3284SA = 0.3284 SA = 0.1531SA = 0.1531



(%)(%)R R



(%)(%)R R



(%)(%)R R


R R (km)(km) MM











Helvetia FaultHelvetia Fault 1.031.03 15.715.7 6.386.38 0.720.72 ---- ---- ---- ---- 1.061.06 15.515.5 6.386.38 0.780.78 1.031.03 15.315.3 6.396.39 0.860.86 ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----Portland Hills Fault Portland Hills Fault Char.Char. 6.566.56 8.38.3 6.966.96 -0.42-0.42 ---- ---- ---- ---- 6.086.08 8.28.2 6.966.96 -0.27-0.27 ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----



Period = 0 secPeriod = 0 sec

PGA = 0.3923PGA = 0.3923

Cont. Cont. (%)(%) R (km)R (km) MM

---- 29.729.7 6.766.76 0.820.82---- 7.57.5 6.636.63 -0.24-0.24

6.4086.408 88.588.5 99 1 - 21 - 2

54.1754.17 9.59.5 5.965.96 0.790.7922.5522.55 9.89.8 6.746.74 -0.07-0.0713.0313.03 9898 99 1.541.54

---- ---- ---- ----

1.341.34 17.817.8 6.26.2 1.941.941.031.03 15.715.7 6.386.38 0.720.726.566.56 8.38.3 6.966.96 -0.42-0.421313 8.48.4 6.726.72 -0.23-0.23---- ---- ---- ----





Three Primary Sources for considerationThree Primary Sources for consideration Shallow Crustal Shallow Crustal Gridded (random) Gridded (random) Subduction ZoneSubduction Zone

For the crustal and “gridded” sources, review the For the crustal and “gridded” sources, review the individual fault details to select fault characteristics individual fault details to select fault characteristics (M, R, fault mechanism, etc.) most relevant to the (M, R, fault mechanism, etc.) most relevant to the hazard. hazard.



Summary of Magnitude, Distance and PGA (1000-yr return period)

Magnitude and Distance pairs represent weighted averages of the individual sources

Attenuate PGA from Source to SiteAttenuate PGA from Source to Site

Source Magnitude Distance, (km)

Depth, (km)

Crustal 6.72 8.4 10.5

Subduction 9.0 98 20



Shallow Crustal:Shallow Crustal: Boore et al. (1997)Boore et al. (1997) Abrahamson and Silva (1997)Abrahamson and Silva (1997) Sadigh et al. (1997) Sadigh et al. (1997) Spudich et al., 1999, Spudich et al., 1999, Campbell and Bozorgnia (2003).Campbell and Bozorgnia (2003).

Cascadia Subduction Zone:Cascadia Subduction Zone: Youngs et. al. (1997)Youngs et. al. (1997) Sadigh et al. (1997)Sadigh et al. (1997)

Ground motion attenuation relationships Ground motion attenuation relationships used in 2002 USGS PHSAused in 2002 USGS PHSA



Summary of Magnitude, Distance and PGA (1000-yr return period)

Source Magnitude Distance, (km)

Depth, (km) PGA rock

Crustal 6.72 8.4 10.5 0.38

Subduction 9.0 98 20 0.09

Magnitude and Distance pairs represent weighted averages of the individual sources




Select bent locationSelect bent locationDevelop input parameters Develop input parameters dependent on type of analysis, total dependent on type of analysis, total

or effective stress (nonlinear)or effective stress (nonlinear) shear wave velocity profileshear wave velocity profile static and dynamic soil propertiesstatic and dynamic soil properties

Site CharacterizationSite Characterization



Total Stress AnalysisTotal Stress Analysis SHAKE91 Computer Program (Shake2000, Proshake)SHAKE91 Computer Program (Shake2000, Proshake) Calculate cyclic shear stress ratio (CSR) with depthCalculate cyclic shear stress ratio (CSR) with depth Calculate cyclic resistance ratio (CRR) with depthCalculate cyclic resistance ratio (CRR) with depth FOS against liquefaction equals (CRR/CSR)FOS against liquefaction equals (CRR/CSR)

Effective Stress, Nonlinear AnalysisEffective Stress, Nonlinear Analysis Used in areas of high accelerations and high cyclic shear Used in areas of high accelerations and high cyclic shear strainsstrains D-MOD, DESRA or other computer ProgramD-MOD, DESRA or other computer Program Calculates pore pressure ratio, Ru, with depth in soil Calculates pore pressure ratio, Ru, with depth in soil profileprofile Determine where Ru Determine where Ru ≥≥ 0.80 – 0.90 for liquefaction 0.80 – 0.90 for liquefaction



Selection of Time Histories use at least:Selection of Time Histories use at least:

3 motions representative of subduction zone 3 motions representative of subduction zone events and events and

3 motions appropriate for shallow crustal 3 motions appropriate for shallow crustal earthquakesearthquakes

Scaled to the bedrock PGA determined from Scaled to the bedrock PGA determined from attenuation relationshipsattenuation relationships



Shake Analysis; Peak AccelerationShake Analysis; Peak Acceleration



CSR(Shake) vs. CSR Simplified ProcedureCSR(Shake) vs. CSR Simplified Procedure



Shake Analysis; FOS Against LiquefactionShake Analysis; FOS Against Liquefaction

Subduction Zone



Subduction Zone





Subduction Zone CSR vs. CRR (SHAKE2000); Subduction Zone EQs

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Crustal EQs

Shake Analysis; FOS Against LiquefactionShake Analysis; FOS Against LiquefactionCSR vs. CRR (SHAKE2000);

Crustal EQs

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FOS Against LiquefactionFOS Against Liquefaction


• FOS < 1.1 » Liquefaction (also indicates the potential for liquefaction-induced ground movement (lateral spread and settlement).

• FOS between 1.1 and 1.4 » reduced soil shear strengths due to excess pore pressure generation.

• FOS > 1.4 » excess pore pressure generation is considered negligible and the soil does not experience appreciable reduction in shear strength.


Crustal and

Subduction Zone EQs

DMOD Analysis; Liquefaction AssessmentDMOD Analysis; Liquefaction Assessment



Use deepest liquefaction depth with Use deepest liquefaction depth with UHS Design Response Spectra (from UHS Design Response Spectra (from either AASHTO General Procedure or either AASHTO General Procedure or Ground Response Analysis)Ground Response Analysis)

Design Response Spectrum cannot be Design Response Spectrum cannot be lower than 2/3lower than 2/3rdrd of spectrum from the of spectrum from the AASHTO General ProcedureAASHTO General Procedure

RecommendationsRecommendations


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CSR vs. CRR (SHAKE2000); Subduction Zone EQs

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Lateral Spread AssessmentLateral Spread Assessment

• Residual shear strengths are used in liquefiable layers,

• Typically don’t use Kh or Kv (de-coupled analysis),

• If FOS < 1.0; Flow failure

• If FOS ≥ 1.0; Deformation Analysis

Use conventional limit equilibrium analysis to assess slope failure potential



• Empirically-based displacement estimates for lateral spreading (Youd et al. (2002),

• Newmark-type analyses using acceleration time histories generated from site-specific soil response modeling.

• Simplified charts based on Newmark-type analyses (Makdisi and Seed, 1978)

Methods to estimate the magnitude of seismically induced lateral slope deformation include:



• Simplified procedures based on refined Newmark-type analyses (Bray and Travasarou 2007, Saygili and Rathje 2008)

• Simplified charts based on nonlinear, effective stress modeling (Dickenson et al, 2002)

• Two-dimensional numerical modeling of dynamic slope deformation.

Methods to estimate the magnitude of seismically induced lateral slope deformation include:



Several of these methods should be used as appropriate, and engineering judgment applied to the results, to determine the most reasonable range of predicted displacements


How are these results used in design?How are these results used in design?

Liquefaction effects include:

• reduced axial and lateral capacities and stiffness in deep foundations,

• ground settlement and possible downdrag effects

• lateral spread, global instabilities and displacements of slopes and embankments,

• loads transferred to foundation piles and shafts from lateral displacements



Bridge Approach Fills:

• Assess performance requirements (no-collapse & serviceability)

• Global stability• Settlement• Allowable deformation and foundation damage


Designer has two options:• Use passive resistance • Don’t use passive resistance

If using presumptive values in AASHTO the longitudinal passive soil pressure shall be less than 0.70 of the value obtained using the procedure given in Article 5.2.3

Abutment Resistance for Seismic LoadsAbutment Resistance for Seismic Loads



Presumptive Pp

(AASHTO 5.2.3)



Presumptive Pp



• Passive soil pressure less than 0.70 of the value obtained using presumptive method = no Agency Approval Required

• Passive soil pressure greater than 0.70 of the value obtained using presumptive method = Agency Approval Required



Bridge Foundations (Extreme Limit State I):

• Loss of strength due to liquefaction generally assumed to be concurrent with the peak loads in the structure • Unless nonlinear effective stress analysis is performed.



Bridge Foundations (Extreme Limit State I):

For bridge sites where liquefaction occurs bridges should be analyzed and designed in two configurations as follows:

• Nonliquefied Configuration: no liquefaction occurs, using the ground response spectrum appropriate for the site soil conditions in a nonliquefied state.

• Liquefied Configuration: The structure as designed in the nonliquefied configuration should be reanalyzed assuming that the layer has liquefied and the liquefied soil provides the appropriate residual resistance for lateral and axial deep foundation response analyses consistent with liquefied soil conditions The design spectrum should be the same as that used in a nonliquefied configuration.



Bridge Foundations

Spread Footings:• Not recommended over liquefiable soils unless ground improvement provided

Piles & Drilled Shafts:• Tips located below deepest liquefiable layer• Friction resistance in liquefiable layer not included in Extreme Event I state loading case• Provide modified soil parameters for modeling p-y curves in liquefied soil layers (don’t use built-in DFSAP program option for estimating liquefied lateral stiffness parameters)• Provide estimates of downdrag loads due to liquefaction settlement



Bridge Foundations

Piles & Drilled Shafts (cont.):• Assess effects of lateral spread deformations on deep foundations and the ability of the pile/shaft foundation to resist these loads

• ATC/MCEER reports: Recommended LRFD Guidelines for the seismic design of bridges (Design Examples & Liquefaction Study Report); MCEER/ATC 49-1/49-2.

• Determine if mitigation is necessary


Earthquake Resisting Elements not permittedEarthquake Resisting Elements not permitted

Full plastic hinging of pile foundations under seismic loads is not permitted (BDDM)


• Mitigation is required when the bridge performance requirements cannot otherwise be met.

• Design deviations can be considered by the Bridge Section

• All mitigation designs are to be reviewed by the Bridge Section

When is liquefaction mitigation needed?When is liquefaction mitigation needed?


Performance Requirements (New Bridges)

1000-year “No-Collapse” Criteria• Under this level of shaking, the bridge and approach structures, bridge foundation and approach fills must be able to withstand the forces and displacements without collapse of any portion of the structure.

• If large embankment displacements (lateral spread) or overall slope failure of the end fills are predicted, the impacts on the bridge end bent, abutment walls and interior piers should be evaluated to see if the impacts could potentially result in collapse of any part of the structure.

• Slopes adjacent to a bridge or tunnel should be evaluated if their failure could result in collapse of a portion or all of the structure.




500-year “Serviceability” Criteria

• Under this level of shaking, the bridge and approach fills, are designed to remain in service shortly after the event (after the bridge has been properly inspected) to provide access for emergency vehicles.

• In order to do so, the bridge is designed to respond semi-elastically under seismic loads with minimal damage. Some structural damage is anticipated but the damage should be repairable and the bridge should be able to carry emergency vehicles immediately following the earthquake. This holds true for the approach fills leading up to the bridge.




500-year “Serviceability” Criteria (cont.) • Approach fill settlement and lateral displacements should be minimal to provide for immediate emergency vehicle access for at least one travel lane.

• For mitigation purposes approach fills are defined as shown on Figure 6-12.

• As a general rule of thumb, an estimated lateral embankment displacement of up to 1 foot is considered acceptable in many cases as long as the “serviceable” performance criteria described above can be met. Vertical settlements on the order of 6” to 12” may be acceptable depending on the roadway geometry and anticipated performance of the bridge end panels.




500-year “Serviceability” Criteria (cont.) These displacement criteria are to serve as general guidelines only and engineering judgment is required to determine the final amounts of acceptable displacement that will meet the desired criteria. It should be noted that these estimated displacements are not at all precise values and may easily vary by factors of 2 to 3 depending on the analysis method(s) used. The amounts of allowable vertical and horizontal displacements should be decided on a case-by-case basis, based on discussions and consensus between the bridge designer and the geotechnical designer and perhaps other project personnel.




BDDM Section 1.1.10.6 & GDM Appendix 6C


Mitigation Zone at Bridge Approaches



Thank You For Your Attention

Download - 2009 ODOT Geo/Hydro/HazMat Conference Geotechnical Aspects of ODOT Seismic Bridge Design Jan Six P.E. ODOT Bridge Section

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