Seismic Response of the Hwy 46/Cholame Creek Bridge During the 2004 Parkfield Earthquake

On September 28, 2004, a moment magnitude Mw 6.0 earthquake occurred along the San Andreas Fault near Parkfield, California. Peak accelerations of 1.0g and absolute displacements of over 4 inches were measured in the horizontal direction on a pile supported, reinforced concrete slab bridge located around 4 miles southeast of the rupture zone. The duration of the strong motion was approximately 10 seconds at the site. The California Geologic Survey (CGS) serendipitously installed six strong motion accelerometers on the 130-ft long, 44-ft wide, five span bridge prior to the earthquake. The CGS also installed a free-field accelerometer station (Cholame 2W) approximately 200 ft east of the bridge. Subsurface conditions generally consist of medium dense alluvial soils. Evidence of liquefaction was not noted at the ground surface after the earthquake. The earthquake motions resulted in longitudinal soil displacements in front of the abutments and around the rows of bent piles due to the structure swaying back and forth. Structural damage consisted of diagonal cracking of the northern wing wall at the east abutment, minor cracking around the perimeter of the bent piles at the connection to the bridge deck, and transverse cracking through the asphalt concrete at each bridge approach. The California Department of Transportation (Caltrans) inspected the bridge the day of the earthquake and concluded that the damage was not serious and repairs were not necessary. The seismic response of the bridge was studied under a grant from the CGS, Strong Motion Instrumentation Program (CSMIP). The goal of the evaluation was to compare the measured bridge deck displacements with those expected per current Caltrans seismic design criteria. The free-field acceleration time histories from the Cholame 2W Station were rotated into the longitudinal and transverse directions of the bridge to develop site-specific acceleration response spectra. Both elastic dynamic analyses (spectra analyses) and time history analyses were performed using a variety of design assumptions for the bridge foundation. Based on our displacement analyses, we found that using the current Caltrans seismic design approach resulted in a close match with the measured bridge displacements during the 2004 seismic event.

• Corporate Authors:

  Multidisciplinary Center for Earthquake Engineering Research

  State University of New York, 107 Red Jacket Quadrangle, P.O. Box 610025
  Buffalo, NY  United States  14261-0025
• Authors:
  • Boardman, Tom
  • Sanchez, Anthony V
• Conference:
  • Fifth National Seismic Conference on Bridges & Highways
  • Location: San Francisco CA, United States
  • Date: 2006-9-18 to 2006-9-20
• Publication Date: 2006

Language

• English

Media Info

• Media Type: CD-ROM
• Features: Figures; References; Tables;
• Pagination: 12p
• Monograph Title: Fifth National Seismic Conference on Bridges and Highways: Innovation in Earthquake Engineering for Highway Structures

Subject/Index Terms

• TRT Terms: Acceleration (Mechanics); Accelerometers; Asphalt concrete; Bridge decks; Cracking; Dislocation (Geology); Earthquake resistant design; Reinforced concrete bridges; Soils; Spectrum analysis; Support piles
• Identifier Terms: California Department of Transportation; Cholame Creek Bridge; Parkfield earthquake (2004)
• Uncontrolled Terms: Structural damages; Time history
• Geographic Terms: San Andreas Fault
• Subject Areas: Bridges and other structures; Design; Geotechnology; Highways; I24: Design of Bridges and Retaining Walls; I42: Soil Mechanics;

Filing Info

• Accession Number: 01080784
• Record Type: Publication
• Report/Paper Numbers: A23
• Files: TRIS
• Created Date: Nov 15 2007 10:33AM