Experimental Research And Theoretical Analysis On Progressive Collapseresistanceof Rc Special-shaped Columns Frame Structures

Accidents lead to structures' partial failure,such as gas explosion,bomb attack and vehicle strike,causing chain reaction,making the failure spread to other parts,finally leading to a large scale's collapse which is disproportionate to the structure's initial destruction.This kind of accident happens frequently in recent years and the harm it brings to life and property is self-evident.The scholar at home and abroad made an intensive study of the method of avoiding structure's progressive collapse led by partial failure and they got some research achievement.Special-shaped column frame structure is widely applied in multi-story and high-rise buildings in recent years in that the structure system obviously enlarges the effective usable area and increases the flexibility of the housing arrangement.But its anti-seismic property and anti-progressive collapse property are becoming more complex because of the smaller and irregular column cross-section than the rectangular column.And the scholar at home and abroad make little research on these aspects and the majority of the research are software model analysis.This paper designed and made a 1/3 scale,two layer and 3x2 large-span special-shaped column frame solid model and carried on two stage test as following:first stage,a sudden unloading experiment on its corner column has been carried out to simulate the sudden failure dynamic process of special-shaped columns;second stage,after the corner column lose its carrying capacity,carrying vertical load on the top of the column in second story.Through the two stage test,we make study on the anti-progressive collapse property of the special-shaped column frame structure.This test aimed at studying the whole collapse process of the structure after the failure of the corner column,the structure's force transmission way of resisting the progressive collapse,the mechanical characteristics,failure mechanism and ultimate failure pattern of the special-shaped column frame's collapse process.Conclusions drew through the research are as follows:When the corner column failed,the overhang stress mechanism composed by the beam-slab resists the load beared by the failed column before it failed and transmits the load to the surrounding columns,the components more closer to the failed column are more important.The whole structure is still in the elastic deformation range.The frame's collapse process can be divided into four stages: elastic stage,elastic-plastic stage,plastic stage and damage stage.During the frame's whole collapse process,the damage always occur in the beams' edges,not in the beam-column-joints and the shorter beam which is connected with the failed column,its far-end section is the most dangerous section.This section is easy to be destroyed and should be focused in the progressive collapse design process.The beam-slab space mechanism composed by beam-end's plastic hinge and slab's hogging moment plastic hinge line is the main system to resist the frame's collapse damage.