轴向荷载作用下箱形柱内填混凝土的局部屈曲和混凝土约束

在单调轴向荷载作用下使用9个焊接方形截面内填混凝土箱形柱模型进行测试。用有限元分析软件ABAQUS模拟荷载试验,并证实了有限元模型的可行性。根据试验和有限元模型的模拟结果可得出如下结论:明确箱形柱内填混凝土的混凝土约束机能的发展过程;混凝土破碎发生后,由水平拱提供的混凝土约束变得显著;柱壁发生屈曲后,由垂直拱提供给混凝土更多的额外约束;水平拱和垂直拱的共同作用提供了重要的混凝土约束,以获得并修复混凝土的强度;柱壁较大的宽厚比会导致垂直拱的初期发展;从混凝土约束机能来看,荷载-轴向应变曲线中,混凝土构件将会有强度降低和强度修复的过程;Mander混凝土约束模型和Sakino混凝土分析模型并不能合理地预测箱形柱内填混凝土的混凝土应力-应变性能。

Local Buckling and Concrete Confinement of Concrete-filled Box Columns Under Axial Load

Nine square concrete-filled box column (CFBC) specimens were fabricated and tested under monotonic axial loading. The loading tests were simulated with the commercial finite element program ABAQUS. The feasibility of the finite element models was verified. Based on tests and FEM simulation results, the following conclusions can be made. The development procedure of the concrete confinement mechanism of CFBCs was identified. After concrete crushing occurs, concrete confinement provided by the horizontal arch action starts to become noticeable. After buckling of the column wall, vertical arch action, which provides additional concrete confinement, is developed. Horizontal arch action acting together with vertical arch action provides significant confinement for the concrete to gain and recover its strength. A larger width-to-thickness ratio of the column wall results in the earlier development of vertical arch action. From the concrete confinement mechanism, there will be a strength drop and a strength recovery in the concrete component of the load versus axial strain curve. As a result of these findings, Mander's concrete confinement model and Sakino's concrete analytical model were not able to reasonably predict the stress–strain behavior of the concrete inside CFBCs.