Development of Experimental Systems for Simulation of Complete Failures of Steel Structures Subjected to Earthquake Loading

这项研究的重点是发展的实验技术，模拟完全失败的结构受到地震荷载。研制了一套由超大行程加载千斤顶、高分辨率数字位移传感器和在线数字计算机控制组成的实验系统。利用所开发的系统，进行了试验模拟完全破坏的钢梁和柱。这里，完全失效被定义为构件断裂并完全分离和/或构件失去承受重力载荷的能力。测试所得的主要结果如下。(1)强烈的几何非线性改变了梁的阻力模式从弯曲到轴向伸长/收缩。(2)这种模式的变化产生了额外的阻力，即使在梁遭受重大损害。(3)钢柱的完全破坏是由裂纹的扩展和截面的后续断裂决定的。(4)一定的轴向荷载能延缓裂缝的萌生和扩展，有助于提高柱的承载力，使其完全破坏。使用有限元方法进行数值分析，以模拟实验结果，它被发现，分析是有效的，即使在政权的强几何非线性，但未能模拟实验行为，一旦成员的拓扑结构被显着改变。

This study focuses on development of experimental techniques for the simulation of complete failures of structures subjected to earthquake loading. An experimental system that consists of very large stroke loading jacks, high resolution digital displacement transducers, and on-line digital computer control was developed. Using the system developed, tests were conducted for the simulation of complete failures of steel beams and columns. Here, complete failure was defined such that the member was fractured and separated completely and/or the member loses the capacity of sustaining gravity load. The major findings obtained from the tests are as follows.(1) Strong geometrical nonlinearity changed the mode of beam resistance from flexure to axial elongation/contraction.(2) This change of mode generated additional resistance even after the beam sustained significant damage.(3) Complete failure of steel columns was governed by the growth of cracks and succeeding fractures of the section.(4) A certain amount of axial load retarded the initiation and growth of cracks, which assist the increase of column capacity to complete failure. Numerical analysis using the finite element method was performed to simulate the experimental results, and it was found that the analysis is effective even in the regime of strong geometrical nonlinearity but fails to simulate the experimental behavior once the member topology is altered significantly.