displacement-based approach for seismic design of highway bridges according to new aashto guide specifications

Following the san fernando earthquake (1971), significant effort was expended to develop comprehensive design guidelines for the seismic design of bridges in the united states. that effort led to updates of both the aashto and caltrans design provisions and ultimately resulted in the development of atc-6, seismic design guidelines for highwaybridges, which was published in 1981. that document was subsequently adopted by aashto as a guide specificationin 1983; the guidelines were formally adopted into the standard specifications for highway bridges in 1991, then revisedand reformatted as division i-a. later, division i-a became the basis for the seismic provisions included in the aashtolrfd bridge design specifications. iranian road and railway bridges seismic resistant design code (publication no.463) has been published according to aashto division i-a and most of modern bridges in iran, has been designed ccording to that provisions with 475-yr return period earthquake ground motion and 50-year design life.