自定心抗弯钢框架后张柱脚的抗震性能

对一个后张柱脚连接部件的循环响应进行了试验和分析研究。这种柱脚可消除地震荷载作用下自定心抗弯钢框架的结构损伤。连接部件的软化性能取决于后张型钢的开口度和伸长率提供而不受柱子屈服影响;承压板提供额外的抗剪强度,防屈曲钢板则产生额外的能量耗散。为了研究后张柱脚连接部件的循环响应,对一系列的后张柱脚连接部件施加轴向载荷和循环横向位移。试验参数包括初期的后张力、柱子初期的轴向力(恒量或变量)、柱子的尺寸和加载历程。对后张柱脚连接部件的极限状态进行调查研究,其中包括防屈曲钢板中后张型钢的屈曲和破裂。试验结果证明,设计恰当的后张柱脚连接部件可承受的侧向位移高达层间位移4%,而柱子和基础梁仍保持弹性。同样,防屈曲钢板通过了其在拉伸和压缩状态下屈曲但不破裂的表现显示了其良好的能量耗散能力。在柱基处发生的结构损伤被限制在可替换耗能装置的防屈曲钢板。此外,分析模型能够预测后张柱脚连接部件的弯矩-转角关系,并显示了与试验数据良好的相关性。

Seismic Behavior of Post-Tensioned Column Base for Steel Self-Centering Moment Resisting Frame

This paper presents experimental and analytical investigation of cyclic response of a post-tensioned column (PT) base connection. The PT column base connection is designed to eliminate structural damage at column bases in self-centering moment resisting frames (SC-MRFs) under seismic loading; the softening behavior at the connection is provided by gap opening and elongation of PT bars rather than yielding in the column. Additional shear resistance is provided by bolted keeper plates; additional energy dissipation is provided by buckling restrained steel (BRS) plates. To investigate the cyclic behavior of the PT column base connection, a series of PT column base connection subassemblies were subjected to axial load and cyclic lateral displacements. Test parameters included initial post-tension force, initial axial force in column (constant or varying), column size and loading history. Limit states investigated for the PT column base connections included PT bar yielding and fracture of BRS plates. The test results demonstrated that properly designed PT column base connections were able to undergo lateral displacement up to 4% interstory drift while the columns and grade beams remained elastic. Also, the BRS plates showed good energy dissipation capacity by yielding in tension and compression without fracture. Structural damage at column bases was limited to the replaceable fuse BRS plates. In addition, analytical models were developed to predict the moment–rotation relationship of the PT column base connection and showed good correlation with the experimental data.