A Study on Brittle Progressive Fracture of Structures under Dynamic Input

在1995年兵库县南部地震中，许多建筑物发生了渐进性破坏，这被记录为地震开始时的突然破坏。特别是钢筋混凝土结构中的中间层破坏就是这种类型的破坏，本研究从数值模拟的角度对这一问题进行了研究。其目的是确定机制的动力学逐步失败，并提出一种方法来防止这种失败的建筑物。研究结果表明：（1）在具有弹塑性脆性柱的框架结构中，最脆性柱的断裂会引起层内其余柱的渐进性断裂。这一过程在很短的一秒内完成，与地震中观察到的渐进破坏相同。2）这种类型的渐进破坏甚至发生在由柱和梁组成的多层刚性框架中，这与地震中观察到的钢框架的破坏相似。3）提出了防止这种渐进破坏的设计方法，提出了适当提高脆性断裂敏感构件的强度或延性，可以有效地防止构件的渐进破坏，并给出了设计公式。

During the 1995 Hyogoken-Nanbu Earthquake, progressive failure occurred in many buildings, which were recorded as a sudden failure in the beginning of the ground shake. Espesially, the failure of intermediate stories in RC buildings was identified to be this type of failure.This study is focused on this problem from numerical simulation techniques. The aim is to identify the mechanism of dynamics of progressive failure and to propose a method to prevent such failure of buildings. The followings were achieved from this study :1) In a frame having elasto-plastic-brittle columns, fracture of brittlest column causes a progressive fracture the remaining columns in the story. This process is completed in a very short second, which is the same as the progressive failure observed during the earthquake.2) This type of progressive failure occurs even in a multi-story rigid frame composed of columns and beams, which is similar to damage of steel moment frames observed during the earthquake.3) A design method to prevent such a progressive failure is proposed, in which an appropriate increment of strength or ductility of structural members susceptible to brittle fracture can effectively prevent the progressive failure, and design formulae are presented.