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MoDOT’s Concerns with Proposed Seismic Specifications

MoDOT’s Concerns with Proposed Seismic Specifications . Bryan A. Hartnagel for Shyam Gupta State Bridge Engineer Missouri Department of Transportation (MoDOT) Presented to the Midwest Seismic Workshop Collinsville, Illinois, February 10-11, 2003. Current Seismic Hazard.

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MoDOT’s Concerns with Proposed Seismic Specifications

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  1. MoDOT’s Concerns with Proposed Seismic Specifications Bryan A. Hartnagel for Shyam Gupta State Bridge Engineer Missouri Department of Transportation (MoDOT) Presented to the Midwest Seismic Workshop Collinsville, Illinois, February 10-11, 2003

  2. Current Seismic Hazard • Current AASHTO map (10% PE in 50 years, return period of ~500 years) • Includes approximately 1,900 state owned bridges

  3. Proposed Seismic Hazard • USGS 1996 map (2% PE in 50 years, return period of ~2,500 years) • Includes approximately 4,000 state owned bridges

  4. Peak Ground Acceleration (PGA) ______ New (1996) U.S. Geological Survey Map (2%) - - - - - Current AASHTO Map (1988 USGS) (10%)

  5. Implications • Number of bridges in seismic zone increases by 110% (2100 state owned bridges) • Cost increase due to proposed seismic specifications changes around $ 300 million (state owned bridges only) • County bridges outnumber state bridges by 13 to 10

  6. Questions for Ourselves • As guardians of national infrastructure, what level of seismic protection is justifiable and affordable? • As design provisions and seismic hazard definitions change, what retrofits are necessary for existing bridges?

  7. Recommendations • Provide additional funding for site specific ground motion studies in the NMSZ • Provide information on return interval to use based on a justifiable criteria (ADT, cost, route type, importance, etc.) • Leave the current research findings as a stand alone document

  8. Thank You!

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