Analysis of the fracture process of wooden frame structure under seismic loading by modified distinct-element method.

本研究旨在开发一种新的方法，能够模拟木框架结构的倒塌过程。首先，通过试验研究了动载荷作用下连接件的力学和断口行为。在0.2 mm/sec ~ 2000 mm/sec的不同加载速率下，对柱与基/梁之间的金属连接节点进行了拉伸和剪切试验。结果表明，在低速加载和高速加载条件下，连接件的断裂形貌有所不同。其次，尝试用改进的离散元法在二维框架模型中模拟框架结构的坍塌过程，并编制了一个程序，可以显示框架从矩形到平行四边形的变化过程。在下一步，我们开发了一个三维程序。在这个程序中，每个条形元素由四个不同元素的low表示。将这些元素组合起来，就可以对两层框架建筑在动力荷载作用下的倒塌过程进行分析。例如，具有非对称支撑布置的结构呈现出旋转塌陷模式，这可以在实际的木屋中观察到。我们还使用一个缩小比例的模型结构进行了动态加载实验。模拟结果与实验结果吻合较好，接缝破坏的顺序和建筑物倒塌的过程吻合较好。我们相信我们的研究可以为木结构在大地震作用下的性能分析提供有力的手段。

This study was aimed to develop a new method, that enables to simulate the collapsing processes of wooden frame structure.Firstly, the mechanical and fractographical behaviors of the joint parts under the dynamic loading were examined by experimental studies. Tensile and shearing tests of metal-fastened joints, which are made between the column and sill / beam, were made under various loading rate from 0.2 mm/sec to 2000 mm/sec. It was found that the fracturing aspects of the joint parts were different between the slow loading case and the high speed one.Secondly, we tried to simulated the collapsing process of the frame structure in two dimensional frame models by a modified distinct element method, and we could make a program that can show the changing process of the frame from a rectangle to a parallelogram. In the next step, we developed a three dimensional program. In this program, each bar element was represented by four lows of distinct element. Composing these elements, we could arrive to analyze the collapsing process of two- story frame buildings under dynamic loading to the basement. For examples, a structure that have non-symmetric brace arrangement showed a rotating collapsing pattern, which can be observed in actual wooden house.We also made a dynamic loading experiment using a reduced scale model structure. The order that joints destroy and the process of the buildings fall down agreed well between the simulation and the experiment.We believe that our research can provide a powerful mean for the analysis of the wooden frame structure's behavior under a large scale earthquake.