A Study on Brittle Progressive Fracture of Structures under Dynamic Input

1995年日本仙谷-南方地震期间，许多建筑物发生了渐进性破坏，记录为地面震动开始时的突然破坏。特别是钢筋混凝土建筑中间层的破坏被认定为此类破坏，本文从数值模拟技术的角度对这一问题进行了研究。其目的是找出渐进破坏的动力学机制，并提出一种防止建筑物发生此类破坏的方法。1)在具有弹塑性脆性柱的框架中，最脆性柱的断裂会导致层中剩余柱的渐进性断裂。这一过程在很短的时间内完成，这与地震中观察到的渐进破坏是相同的。2)即使在由柱和梁组成的多层刚架中也会发生这种渐进破坏，这类似于地震中观察到的钢弯矩框架的破坏。3)提出了一种防止这种渐进破坏的设计方法，其中容易发生脆性断裂的结构构件的强度或延性的适当增加可以有效地防止渐进破坏，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.