Progressive Collapse Analysis Of Multi-storey Frame Structures

Progressive collapse is defined as situation where the spread of an initial local failure from element to element eventually results in the collapse of an entire structure or a disproportionately large part of it. In recent years, the prevention of progressive collapse under abnormal loading events was widely concerned all over the world.Based on the Alternate Path Method, nonlinear static and nonlinear dynamic analysis are conducted to study the progressive collapse resistance of planar and spatial reinforced concrete frames subjected to vertical loadings in case of one bottom column-removal by means of SAP2000 program. The primary research work in this dissertation includes:(1) Planar frame model subjected to destroy of middle or perimeter column at bottom is developed. Progressive collapse feature of structure is studied from the resistance of its, deformation of structure, development of plasticity and the approach of load conduction. The fact that progressive collapse of structure is sensitive to the failure of the edge column is proofed. This is reflected from the feature that the progressive collapse resistance of the residual structure is smaller after the damage of the edge column, worse ductility and large vertical displacement of the column-removed point in the same vertical loading case.(2) Simple spatial frame models are established considering six threat-independent, column-removed conditions. The development of plastic hinges, ductility property, the progressive collapse resistance and the redistribution of the inner force are investigated for the residual structure corresponding to each failure case. Results show that a higher ductility is obtained for the failure of the middle column than those of corner or perimeter columns. The two cases corresponding to the failure of middle column at long side have the lowest ultimate resistance which indicates a weak location for progressive collapse resistance of structure.(3) Dynamic amplification factor (DAF) based on the load definition is introduced. Numerical comparison with dynamic magnification factors corresponding to each failure case is conducted. Result shows that the dynamic amplification factor decreases with the displacement of failure point. The force-based dynamic magnification factor has a value of 1.2 at the plastic state of structure. This reveals that a constant DAF equal to 2.0 will lead to conservative estimation of the progressive collapse resistance if the column-removed building has ductile nonlinear response.