The behavior of reinforced concrete piers under strong seismic actions

A fibre column finite element based on Timoshenko beam theory has been developed to model the cyclical response of the end critical zones of bridge piers having low-to-intermediate shear slenderness. Shear resistance is obtained by modelling the principal resisting mechanisms; these are linked to the flexural behaviour by means of suitable kinematics assumptions. In flexure the element differs from standard fibre beam element since, to account for the contribution to shear resistance due to arch action and for the inclined trust-line which develops in squat elements subjected to shear, the principal direction of the compressive stress, which is normal to the cross- section in standard fibre elements, is here rotated. Non linear behaviour of material is taken into account by means of appropriate constitutive relations. The proposed element, implemented in a well established non linear computer code, has been tested by comparison with some experimental results.