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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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