Inelastic seismic analysis of RC bridge piers including flexure-shear-axial interaction

The effect of shear coupled with axial force variation on the inelastic seismic behaviour ofreinforced concrete bridge piers is investigated in this paper. For this purpose, a hysteretic axial-shearinteraction model was developed and implemented in a nonlinear finite element analysis program. Thus,flexure-shear-axial interaction is simulated under variable amplitude reversed actions. Comparative studiesfor shear-dominated reinforced concrete columns indicated that a conventional FE model based on flexure-axialinteraction only gave wholly inadequate results and was therefore incapable of predicting thebehaviour of such members. Analysis of a reinforced concrete bridge damaged during the Northridge(California 1994) earthquake demonstrated the importance of shear modelling. The contribution of sheardeformation to total displacement was considerable, leading to increased ductility demand. Moreover, theeffect of shear with axial force variation can significantly affect strength, stiffness and energy dissipationcapacity of reinforced concrete members. It is concluded that flexure-shear-axial interaction should betaken into account in assessing the behaviour of reinforced concrete bridge columns, especially in thepresence of high vertical ground motion.