Category:756 Seismic Design

All new bridges on the state system shall include some level of seismic design and/or detailing to resist earthquakes per the Bridge Seismic Design Process Flowchart and an expected seismic event for a given return period. For example, for a multi span bridge in Seismic Performance Categories B, C or D, both design and detailing work is needed or detailing work only needed shall be determined as per “Bridge Seismic Design Process Flow chart”.

Seismic Performance Categories The entire state of Missouri outside of Categories B, C and D is Category A.

St. Louis Area

When existing bridges are identified as needing repairs or maintenance, a decision on whether to include seismic retrofitting in the scope of the project shall be determined per the “Bridge Seismic Design Process Flowchart”, the extent of the rehabilitation work and the expected life of the bridge after the work. For example, if the bridge needs painting or deck patching, no retrofitting is recommended. However, redecking or widening the bridge indicates that MoDOT is planning to keep the bridge in the state system with an expected life of at least 30 more years. In these instances, the project core team should consider cost effective methods of retrofitting the existing bridge.