BEHAVIOR EVALUATION OF RECTANGULAR HOLLOW CROSS-SECTION OF RC PIERS SUBJECTED TO AXIAL COMPRESSION AND BIAXIAL BENDING

In order to evaluate the behavior of reinforced concrete (RC) rectangular hollow cross-section of bridge piers under axial compression and biaxial bending, the paper derives the calculation formula for loading capacity and moment-curvature relationship according to the distribution type of neutral axial. The loading capacity and rotation ductility of the bottom control section of three RC specimen bridge piers with rectangular hollow cross-section under different axial compression ratio, reinforcement ratio and stirrup ratio are analyzed based on these calculation formulas. The M_x-M_y curves and moment-curvature curves are obtained under a given constant axial force. The theoretical analytical results are proved to be accurate through a comparison with experimental results of cyclic testing of three RC bridge pier specimens under axial compression and biaxial bending. The load capacity and deformation of continuous rigid frame bridge with RC rectangular hollow cross-section columns are analyzed. The results show that the coupling effect between M_x and M_y reduces the load capacity of bridge piers and the design for hollow cross-section is unsafe considering uniaxial load and bending only. With the increasing of the angle between neutral axial and one principle direction, the ultimate moment and curvature along that direction increase, while along the perpendicular direction they decrease. The research results can be utilized for seismic design and behavior evaluation of RC bridge columns with rectangular hollow cross-section.