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来模拟木框架结构的倒塌过程。首先，通过试验研究了节点部分在动载作用下的力学和断口行为。在0.2 mm/s~2000 mm/s的加载速率下，对柱与梁之间的金属连接节点进行了拉伸和剪切试验。其次，尝试用改进的离散单元法模拟二维框架模型中框架结构的倒塌过程，并编制程序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。在本程序中，每个条形元素由四个不同的元素表示。将这些单元组合起来，就可以分析地下室动力荷载作用下两层框架结构的倒塌过程。以具有非对称支撑布置的结构为例，在实际木结构房屋中可以观察到这种旋转倒塌模式，并利用缩尺模型结构进行了动力加载试验。节点的破坏顺序和建筑物的倒塌过程与模拟结果吻合较好，相信本文的研究可以为木结构结构在大范围地震作用下的行为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.