Abstract: To evaluate the seismic behavior and damage of bridge structures subjected to strong ground motion with reliable accuracy,analysis model is generally recommended.For lifeline structures,highway bridges,it is essential that residual displacement after an earthquake be smaller than the acceptable maximum value so that the bridges can be repaired.Both the maximum displacement and the residual displacement are important in seismic design.Damage indices available in the literature,either based on ductility,energy dissipation or a combination of both are discussed.The concept of residual deformation as a critical complementary indicator to cumulative damage is introduced in the paper.This paper describes analyses of a typical bridge,with different hysteretic characteristics,post-yielding stiffness as affect by P-Delta effects,as well as maximum ductility are found to influent residual deformations greatly.Some important problems are discussed.