NCHRP Research Report 949: Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design presents a methodology to analyze and determine the seismic capacity requirements of bridge elements expressed in terms of service and damage levels of bridges under a seismic hazard. The methodology is presented as proposed AASHTO guidelines for performance-based seismic bridge design with ground motion maps and detailed design examples illustrating the application of the proposed guidelines and maps. This report will be of immediate interest to bridge engineers.
The current AASHTO Guide Specifications for LRFD Seismic Bridge Design “guide specifications” do not address performance-based seismic bridge design or provide design criteria for bridges that are critical or essential. Furthermore, the AASHTO guide specifications do not provide direction to assist owners and designers who wish to consider seismic risk mitigation beyond the life safety objective. A bridge may have different operational requirements depending on the post-earthquake functions (e.g., serving the community by providing emergency vehicle access), which would suggest a higher performance objective than the basic levels included in the design codes. Research was needed to provide guidance to help bridge owners and designers define enhanced seismic performance objectives and design bridges to meet those objectives.
Modjeski and Masters, Inc., performed research under NCHRP Project 12-106, “Proposed Guidelines for Performance-Based Seismic Bridge Design,” to develop the following:
Proposed AASHTO guidelines for performance-based seismic bridge design,
Proposed revisions to the AASHTO Guide Specifications for LRFD Seismic Bridge Design to link with the proposed AASHTO guidelines for performance-based seismic bridge design, and
Proposed ground motion maps for inclusion in the AASHTO LRFD Bridge Design Specifications, as well as the AASHTO Guide Specifications for LRFD Seismic Bridge Design.
Two deliverables were provided as appendices and are not included within the published report but are available on TRB’s website at www.trb.org by searching on NCHRP Research Report 949. The appendices are as follows:
Appendix A: SDOF Column Investigation Sample Calculations and Results
Appendix B: Hazard Comparison