2009 odot geo/hydro/hazmat conference geotechnical aspects of odot seismic bridge design jan six...

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2009 ODOT Geo/Hydro/HazMat Conference Geotechnical Aspects of ODOT Seismic Bridge Design Jan Six P.E. ODOT Bridge Section Slide 2 2009 ODOT Geo/Hydro/HazMat Conference Seismic Design Standards ODOT Geotechnical Manual AASHTO Guide Specifications for LRFD Seismic Bridge Design ODOT Bridge Design & Drafting Manual Slide 3 2009 ODOT Geo/Hydro/HazMat Conference 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? Topics Slide 4 2009 ODOT Geo/Hydro/HazMat Conference Hazard Analysis vs. Ground Response Analysis When is a Site Specific Response Analysis Needed? Site Specific Analysis ????? Slide 5 2009 ODOT Geo/Hydro/HazMat Conference Seismic Hazard Analysis When is a Site Specific Response Analysis Needed? 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. Slide 6 2009 ODOT Geo/Hydro/HazMat Conference Probabilistic Seismic Hazard Analysis (PSHA) When is a Site Specific Response Analysis Needed? 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). Slide 7 2009 ODOT Geo/Hydro/HazMat Conference Seismic Hazard Analysis When is a Site Specific Response Analysis Needed? 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. Slide 8 2009 ODOT Geo/Hydro/HazMat Conference Usually done to either: 1.Develop acceleration response spectra (ARS) or 2.For liquefaction analysis When is a Site Specific Response Analysis Needed? Ground Response Analysis Slide 9 2009 ODOT Geo/Hydro/HazMat Conference AASHTO General Procedure usually adequate Use 2002 USGS Seismic Hazard Maps to obtain bedrock PGA, S 0.2 and S 1 for 500 and 1000 yr return periods Determine soil site class designation (A F) Develop Response Spectra When is a Site Specific Response Analysis Needed? Slide 10 2009 ODOT Geo/Hydro/HazMat Conference General Procedure for determining Response Spectrum When is a Site Specific Response Analysis Needed? Use the program: SeismicDesignUtility_2002.mde Slide 11 2009 ODOT Geo/Hydro/HazMat Conference 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. When is a Site Specific Response Analysis Needed? Slide 12 2009 ODOT Geo/Hydro/HazMat Conference 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. When is a Site Specific Response Analysis Needed? AASHTO 3.4.3.1 For 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. NearFault Effects Slide 13 2009 ODOT Geo/Hydro/HazMat Conference 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 ( 2009 ODOT Geo/Hydro/HazMat Conference 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), When is a Site Specific Response Analysis Needed? Slide 17 2009 ODOT Geo/Hydro/HazMat Conference When is a Site Specific Response Analysis Needed? Evaluation of Liquefiable Soil Conditions (vs. Simplified Methods, when FOS liq 1.0) Very deep soil deposits or thin ( 2009 ODOT Geo/Hydro/HazMat Conference 2475 year Period = 0 sec Period = 0.1 sec Period = 0.2 sec Period = 0.3 sec Period = 0.5 sec Period = 1 sec Period = 2 sec PGA = 0.3923 SA = 0.784 SA = 0.9313 SA = 0.8206 SA = 0.6283 SA = 0.3284 SA = 0.1531 SUMMARY STATISTICS Cont. (%) R (km) M Cont. (%) R (km) M Cont. (%) R (km) M Cont. (%) R (km) M Cont. (%) R (km) M Cont. (%) R (km) M Cont. (%) R (km) M Mean Values --29.76.760.82--24.76.510.87--30.76.780.92--37.27.030.95--55.67.571.05--61.37.731.07--70.57.91.18 Modal Values --7.56.63-0.24--7.76.63-0.05--88.591.42--88.591.29--88.591.03--88.590.95--88.590.94 Gridded Modal 6.40888.59 1 - 2 1 - 25.5437.66.63 0 - 1 6.90988.59 1 - 2 1 - 29.49788.59 16.1388.59 16.988.59 16.9688.59 Principle Sources (contributions >10%) WUS shallow gridded 54.179.55.960.7962.589.85.850.8454.08105.970.946.5110.16.080.9130.5210.16.240.9626.4111.76.35121.514.16.461.14 Wash-Oreg faults 22.559.86.74-0.0719.849.66.720.1221.929.76.720.122.579.76.730.1119.049.56.750.2417.829.96.750.3215.4610.96.750.53 M 9.0 Subduction 13.039891.54--------13.8298.291.5217.9598.991.428.710091.1432.8210191.0634.910291.04 M 8.3 Subduction ------------------------12.3899.38.31.9421.121028.31.7522.341038.31.7527.231088.31.72 Individual fault hazard details (contributions >1%) Grant Butte Fault 1.3417.86.21.941.4917.96.21.91.3417.76.21.881.6917.66.21.871.1617.86.21.961.2118.16.21.91.3816.86.21.9 Helvetia Fault 1.0315.76.380.72--------1.0615.56.380.781.0315.36.390.86------------------------ Portland Hills Fault Char. 6.568.36.96-0.42--------6.088.26.96-0.27-------------------------------- Portland Hills Fault 138.46.72-0.2311.318.26.71-0.0812.298.36.72-0.112.318.36.72-0.0710.658.36.730.139.618.46.730.27.768.36.740.4 877 Portland Hills Fault --------5.518.16.95-0.21--------6.438.26.96-0.295.828.36.96-0.145.578.36.97-0.14.848.36.970.06 Earthquake Source Characterization Design Response Spectra from Ground Response Analysis Slide 30 2009 ODOT Geo/Hydro/HazMat Conference 2475 year Period = 0 sec Period = 0.1 sec Period = 0.2 sec Period = 0.3 sec Period = 0.5 sec Period = 1 sec Period = 2 sec PGA = 0.3923 SA = 0.784 SA = 0.9313 SA = 0.8206 SA = 0.6283 SA = 0.3284 SA = 0.1531 SUMMARY STATISTICS Cont. (%) R (km) M Cont. (%) R (km) M Cont. (%) R (km) M Cont. (%) R (km) M Cont. (%) R (km) M Cont. (%) R (km) M Cont. (%) R (km) M Mean Values --29.76.760.82--24.76.510.87--30.76.780.92--37.27.030.95--55.67.571.05--61.37.731.07--70.57.91.18 Modal Values --7.56.63-0.24--7.76.63-0.05--88.591.42--88.591.29--88.591.03--88.590.95--88.590.94 Gridded Modal 6.40888.59 1 - 2 1 - 25.5437.66.63 0 - 1 6.90988.59 1 - 2 1 - 29.49788.59 16.1388.59 16.988.59 16.9688.59 Principle Sources (contributions >10%) WUS shallow gridded 54.179.55.960.7962.589.85.850.8454.08105.970.946.5110.16.080.9130.5210.16.240.9626.4111.76.35121.514.16.461.14 Wash-Oreg faults 22.559.86.74-0.0719.849.66.720.1221.929.76.720.122.579.76.730.1119.049.56.750.2417.829.96.750.3215.4610.96.750.53 M 9.0 Subduction 13.039891.54--------13.8298.291.5217.9598.991.428.710091.1432.8210191.0634.910291.04 M 8.3 Subduction ------------------------12.3899.38.31.9421.121028.31.7522.341038.31.7527.231088.31.72 Individual fault hazard details (contributions >1%) Grant Butte Fault 1.3417.86.21.941.4917.96.21.91.3417.76.21.881.6917.66.21.871.1617.86.21.961.2118.16.21.91.3816.86.21.9 Helvetia Fault 1.0315.76.380.72--------1.0615.56.380.781.0315.36.390.86------------------------ Portland Hills Fault Char. 6.568.36.96-0.42--------6.088.26.96-0.27-------------------------------- Portland Hills Fault 138.46.72-0.2311.318.26.71-0.0812.298.36.72-0.112.318.36.72-0.0710.658.36.730.139.618.46.730.27.768.36.740.4 877 Portland Hills Fault --------5.518.16.95-0.21--------6.438.26.96-0.295.828.36.96-0.145.578.36.97-0.14.848.36.970.06 Period = 0.1 sec SA = 0.784 Cont. (%) R (km) M --24.76.510.87 --7.76.63-0.05 5.5437.66.63 0 - 1 62.589.85.850.84 19.849.66.720.12 -------- -------- 1.4917.96.21.9 -------- -------- 11.318.26.71-0.08 5.518.16.95-0.21 Period = 2 sec SA = 0.1531 Cont. (%) R (km) Me --70.57.91.18 --88.590.94 16.9688.59 1 - 2 1 - 2 21.514.16.461.14 15.4610.96.750.53 34.910291.04 27.231088.31.72 1.3816.86.21.9 -------- -------- 7.768.36.740.4 4.848.36.970.06 Earthquake Source Characterization Design Response Spectra from Ground Response Analysis Slide 31 2009 ODOT Geo/Hydro/HazMat Conference Most Significant Contributors to Seismic Ground Motion Hazard Design Response Spectra from Ground Response Analysis 0 0.5s period: Shallow Crustal 0.5 2s period: Subduction Zone Mega-Thrust Earthquake Source Characterization In areas where the hazard has a significant contribution from both the Cascadia Sub