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 (slide 2)
- Current AASHTO map (10% PE in 50 years, return period of ~500 years)
- Includes approximately 1,900 state owned bridges
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Proposed Seismic Hazard (slide 3)
- USGS 1996 map (2% PE in 50 years, return period of ~2,500 years)
- Includes approximately 4,000 state owned bridges
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Peak Ground Acceleration (PGA) (slide 4)
______ New (1996) U.S. Geological Survey Map (2%)
- - - - - Current AASHTO Map (1988 USGS) (10%) |
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Implications (slide 5)
- 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
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Questions for Ourselves (slide 6)
- 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?
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Recommendations (slide 7)
- 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
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Thank You! (slide 8)
