一、引言在作框架的地震反应分析时,通常是将建筑物按平面框架切出,研究它在一个方向地震力作用下的反应性质。但当水平的两个方向地震力同时作用时,柱将发生绕两个轴的双向弯曲。当柱进入塑性阶段时,两向受力的变形将比单向受力时大得多。这种变形 I. INTRODUCTION In the framework of the seismic response analysis, the building is usually cut out as a plane frame and its response to seismic forces in one direction is studied. However, when horizontal two-direction seismic forces act simultaneously, the column will undergo bi-directional bending around two axes. When the column enters the plastic stage, the deformation in both directions will be much greater than when one-way forces are applied. This deformation