A Study on Progressive Collapse of Multi-story Steel Frame

由于爆炸或地震等事件，多层框架在一层垂直倒塌后的行为有两种情况。一个是坍塌到一定程度然后停止的地方，另一个是坍塌持续进行直到所有楼层完全倒塌的地方。后一种情况下的倒塌称为连续倒塌，这是框架自重荷载作用下的一种不稳定现象。试验参数为长细比和宽厚比。阐明了钢柱在大变形范围内的后屈曲行为，并通过试验推导了荷载-轴向变形关系。利用这些关系，对多质量体系模型的竖向动力响应进行了数值分析，研究了钢结构建筑物的连续倒塌，通过比较楼层倒塌释放的重力势能和柱子在压缩荷载作用下完全倒塌前吸收的能量，明确了使楼层抵抗连续倒塌的框架条件。

There are two cases of behavior of multistory frames after the vertical collapse of one story which occurs due to an event such as an explosion or an earthquake. One is where the collapse proceeds to a certain extent and then ceases and the other is where the collapse continuously progresses until all stories have completely collapsed. The collapse in the latter case is called progressive collapse which is an unstable phenomenon resulting from the gravity load of frames.In this study, axial compression tests were carried out on box-section steel columns until complete collapse. The test parameters were the slenderness ratio and width-thickness ratio. The post-buckling behaviour of the steel columns for a large deformation range was clarified, and the load-axial deformation relationships were derived experimentally. Using these relationships, numerical analysis of the vertical dynamic response of multi-mass system models was performed to investigate the progressive collapse of steel buildings.The study clarified the frame conditions which enable stories to resist progressive collapse through comparing the gravity potential energy released by the story collapse with the energy which columns absorb before they completely collapse due to the compressive load.