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 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 (for example, 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 is needed to provide guidance to help bridge owners and designers define enhanced seismic performance objectives and design bridges to meet those objectives.
The objectives of this research are to develop: (1) proposed AASHTO guidelines for performance-based seismic bridge design and (2) 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.
Accomplishment of the project objectives will require at least the following tasks.
(1). Conduct a literature review of relevant domestic and international performance-based seismic research and guidelines. The domestic review should include research conducted through the NCHRP; Strategic Highway Research Program 2 (SHRP2); FHWA; and other national, state, and pooled-fund sponsored research. The review should cover research findings, existing design guidelines, and owner and industry experience. (2). Synthesize the literature review to identify the knowledge gaps for performance-based seismic bridge design. These gaps should be addressed in the final product and in the recommended future research. (3). Propose a methodology, to be developed and executed in Phase II, to achieve the project objectives. At a minimum, the methodology should consider: (a) different bridge types, bridge configuration and geometry, and materials; (b) deformation limits; (c) damage states; (d) performance objectives and levels; (e) seismic hazard levels and the nature of the design ground motion (e.g., geometric mean vs. maximum component, deterministic vs. probabilistic, uniform hazards vs. risk targeted, etc.); and (f) analytical methods. (4). Prepare a detailed outline of the proposed AASHTO guidelines and identify any required revisions to the AASHTO Guide Specifications for LRFD Seismic Bridge Design to link it with the proposed AASHTO guidelines. Propose design examples to demonstrate the proposed methodology and guidelines. (5). Prepare Interim Report No. 1 that documents Tasks 1 through 4 and provides an updated work plan for the remainder of the research no later than 4 months after contract award. The updated plan must describe the process and rationale for the work proposed for Phases II though IV.
PHASE II—Methodology Development
(6). Fully develop and execute the methodology according to the approved Interim Report No.1. (7). Complete sample section of the guidelines to be selected by NCHRP. This section should be publication ready (i.e., AASHTO-style format) with appropriate level of details. (8). Prepare Interim Report No. 2 that documents Tasks 6 and 7 and provides an updated work plan for Phases III and IV no later than 8 months after approval of Phase I.
PHASE III—Guidelines Development
(9). Develop the remaining sections of guidelines and prepare illustrations (e.g., flowcharts, graphs) and identify interdependencies with existing AASHTO seismic bridge design standards. Prepare proposed revisions to AASHTO Guide Specifications for LRFD Seismic Bridge Design. The recommended guidelines shall be provided in AASHTO-style format. Submit the design examples. (10). Prepare Interim Report No. 3 that documents Task 9 and provides an updated work plan for the remainder of the project no later than 9 months after Phase II approval. The updated plan must describe the process and rationale for the work proposed for Phase IV.
PHASE IV—Final Products
(11). Revise the guidelines after consideration of the panel’s review comments. (12). Prepare final deliverables including: (1) a final report that documents the entire research effort; (2) the proposed AASHTO guidelines, revisions to the AASHTO Guide Specifications for LRFD Seismic Bridge Design, and examples; and (3) a stand-alone technical memorandum titled “Implementation of Research Findings and Products.”
STATUS: Research in progress.