Inelastic Earthquake Response of Steel Columns with Variable Cross-Section Subjected to Bi-Axial Bending

本课题研究地震动作用下钢柱的非弹性地震反应。注意柱的变截面。(1)采用MARC-K62有限元程序对钢柱进行地震反应分析，其中假定南向和东向地震波分量为输入水平地震动。2)纵、西向地震波共同作用下柱的双轴弯曲损伤比纵、西向地震波共同作用下柱的损伤更严重。(3)截面较小的柱由于抗弯矩小于柱基底截面，其上部塑性变形造成的损伤较大。4)对门式刚架在梁中部剪切破坏时的破坏机理进行了数值研究。5)柱底部分对耗散滞回能起重要作用。(2)锥形柱基础部分的弹塑性性能1)对悬臂柱基础部分在恒定垂直和交变水平荷载作用下的弹塑性性能进行了数值和实验研究。2)实验证实，塑性变形沿锥形基底沿距离传播较广。这就是为什么柱基础部分的抗力矩变化均匀的原因。3)这一事实暗示了使地震破坏减小的可能性，而不是具有等截面的柱基础部分。4)锥形基础部分的抗震性能受局部屈曲最终位置的影响较大。5)有必要制定一种合适的方法对锥形底座进行加劲。

This research project studies the inelastic earthquake response of steel columns subjected to earthquake ground motion. Attention is paid to the variable cross-section of column.(1)Inelastic Earthquake Response Analysis of Steel Bridge Piers1)The earthquake response analysis of steel columns was performed by using Finite Element Code MARC-K62, in which the NS and EW earthquake wave components were assumed as the input horizontal ground motions.2)In the case of columns subjected to bi-axial bending which is caused by the combination of NS and EW earthquake ground motions, the damage of columns become severe compared with the damage of columns subjected to which of NS or EW motion.3)The plastic deformation in the upper potion of columns with smaller cross-section results in the heavy damage because the resistant moment is smaller than the column base cross-section.4)The damage machanism of steel portal frames with the shear collapse in the middle of beam were also investigated numerically.5)The column base parts are very important to dissipate the hysteretic energy.(2)Elasto-Plastic Behavior of Tapered Column Base Parts1)The elasto-plastic behavior of cantilever columns with tapered base part is investigated numerically and experimentally under the constant vertical and alternating horizontal loads.2)It was confirmed by experiment that the plastic deformation propagates widely with distance along the tapered base part. This is reason why the resistant moment varies uniformly in the column base part3)This fact implies the possibility of making the earthquake damage decrease rather than the column base part with equivalent cross-section.4)The earthquake performance of tapered base part is much influenced by the final location of local buckling.5)It is necessary to develop an appropriate method for stiffening the tapered base part.