Seismic Design Aids for Nonlinear Pushover Analysis of Reinforced Concrete and Steel Bridges
mon procedure in current structural engineering practice (ATC-40, 1996; FEMA-
273, 1997; FEMA-356, 2000). The American Association of State Highway and
Transportation Officials (AASHTO) Guide Specifications for load and resistance fac-
tors design (LRFD) Seismic Bridge Design explicitly require pushover analysis for
seismic design category D (SDC D) bridges. The 2006 FHWA Seismic Retrofitting
Manual for Highway Structures: Part I—Bridges (FHWA, 2006) adopted pushover
analysis in evaluation method D2 for bridges of seismic retrofit categories C and D
(SRC C and SRC D) to assess bridge seismic performance.
The highway bridge design code in the United States has evolved several times over
the past 70 years. The first highway bridge design code was published in 1931 by the
American Association of State Highway Officials (AASHO), later by the AASHTO.
From 1931 through 1940, AASHO codes did not address seismic design. The 1941
edition of the AASHO code required that bridges be designed for earthquake
load; however, it did not specify how to estimate that load. In 1943, the California
Department of Transportation (Caltrans) developed various levels of equivalent
static lateral forces for the seismic design of bridges with different foundation types,
with individual members designed using the working stress design (WSD) method
the past 70 years. The first highway bridge design code was published in 1931 by the
American Association of State Highway Officials (AASHO), later by the AASHTO.
From 1931 through 1940, AASHO codes did not address seismic design. The 1941
edition of the AASHO code required that bridges be designed for earthquake
load; however, it did not specify how to estimate that load. In 1943, the California
Department of Transportation (Caltrans) developed various levels of equivalent
static lateral forces for the seismic design of bridges with different foundation types,
with individual members designed using the working stress design (WSD) method
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