ANALYSIS OF EARTHQUAKE-RESISTANT BEHAVIORS OF RC COLUMNS UNDER VARIABLE AXIAL LOADS

Precise prediction for the hysteretic behaviors of reinforced concrete (RC) column under seismic load is important to assess the aseismic performance of RC structures.Due to the overturning moment in the earthquakes, besides being subjected to seismic lateral forces, RC columns also experience variable axial loads.Therefore the influence of variable axial forces must be taken into account when to study the hysteretic behaviors of RC columns under cyclic loads.A numerical analysis model based on a fiber model program has been validated firstly through the rational hysteretic simulations of two RC columns under various patterns of axial loads, Then a frame column has been simulated under various patterns of variable axial loads by numerical method.The analytical results indicate that the variety of axial loads has considerable effect on the hysteretic behaviors of RC columns.Because of the randomness of axial loads and to facilitate carrying on experimental researches and analyzing earthquake- resistant behaviors of RC structures, a equivalent fixed axial load method is put forward to determine the seismic behaviors of RC columns in structures under earthquake.