scope:

BACKGROUND

The state of practice of the seismic design of bridges is continually evolving, and the AASHTO Guide Specifications for LRFD Seismic Bridge Design was developed to incorporate improvements in the practice that have emerged since publication of ATC 6, Seismic Design Guidelines for Highway Bridges, the basis of the current AASHTO seismic design provisions. While small improvements have been incorporated into the AASHTO seismic design procedures in the intervening years since ATC 6 was published in 1981, these Guide Specifications and related changes to the current AASHTO LRFD Bridge Design Specifications represent the first major overhaul of the AASHTO procedures. The development of these Guide Specifications was performed in accordance with the recommendations of the NCHRP 20-07/Task 193 Task 6 Report. The Task 6 effort combined and supplemented existing completed efforts (i.e., AASHTO Standard Specifications Division I-A, NCHRP 12-49 guidelines, SCDOT specifications, Caltrans Seismic Design Criteria, NYCDOT Seismic Intensity Maps (1998), and ATC-32) into a single document that could be used at a national level to design bridges for seismic effects. Based on the Task 6 effort and that of a number of reviewers, including representatives from State Departments of Transportation, the Federal Highway Administration, consulting engineers, and academic researchers, these Guide Specifications were developed.