New Seismic 1000 Year Return Period – Impact to Bridge Design Methodologies

In July 2007, the American Association of State Highway and Transportation Officials (AASHTO) approved two major changes to the seismic design of highway bridge Specifications. The first change updated the seismic provisions in the “AASHTO LRFD Bridge Design Specifications”, and the second adopted a new “Guide Specification for LRFD Seismic Bridge Design”. The two most significant changes to the updated seismic provisions relate to the seismic hazard level from 500 years to 1000 years and the methodology used in constructing the response spectrum. The new hazard levels maps represent the latest technology in development of ground motion (GM) maps and the new response spectrum methodology will keep the specifications up-to-date and in-line with recent developments in the seismic design of bridges. The new seismic hazard required changing ground motion maps. The new maps not only give peak ground acceleration (PGA) but also two additional values of the spectral acceleration [0.2 seconds and 1.0 second] allowing an improved seismic response spectrum. Consequential changes include new Seismic Category boundaries and soil factors. This paper will illustrate how bridge design is impacted throughout the U.S. by the new seismic hazard level, seismic design category (SDC) boundaries, and Site Coefficients for both the new Guide Specifications and updated AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications. In addition, the affects of seismic demand on the structures will be compared. The comparison will be made with the 500 year response spectrum to the new 3 point, 1000 year response spectrum and ductility factors used to determine deflection capacity for each Specification.

  • Corporate Authors:

    Multidisciplinary Center for Earthquake Engineering Research

    State University of New York, 107 Red Jacket Quadrangle, P.O. Box 610025
    Buffalo, NY  United States  14261-0025
  • Authors:
    • Manceaux, Derrell
  • Conference:
  • Publication Date: 2008


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Maps;
  • Pagination: 9p
  • Monograph Title: Sixth National Seismic Conference on Bridges and Highways: Seismic Technologies for Extreme Loads

Subject/Index Terms

Filing Info

  • Accession Number: 01355103
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Oct 24 2011 12:41PM