Influence Of Infill Walls On The Progressive Collapse Resistance Of Pc Frames

With the progress of urbanization and the introduction of vertical cities,high-rising buildings are becoming popular.Resources continue to aggregate in urban cities,which renders the growth of unpredictable risks.Progressive collapse is one of the risks,and once the progressive collapse occurs,it is often accompanied by a huge loss of life and property.Since the collapse of the Ronan Point apartment and the 9/11 incident,researchers from various countries have placed more efforts on studying the progressive collapse of structure.However,the research of influence of infill walls and their distribution on the progressive collapse resistance of the structure is still lacking now.This paper summarizes the current research of progressive collapse and listed out both national and international progressive collapse design codes and analysis methods,develops small-scale models based on actual buildings,performs bare PC frame and double wall panel tests to attain the displacement-load curve of the middle column.Then carries out FEM analysis.The analysis results are found to agree well with the test data,which proves the validity of the model.A finite element model of a single wall panel is also established.An analytical model for the ultimate bearing capacity of a PC frame containing infill walls was proposed.Finally,macro-models are established to perform nonlinear dynamic analysis of frame structures under several typical wall panel distribution scenarios.It was found that infill walls can significantly improve the ability to resist progressive collapse.The infill walls can be simplified to an equivalent strut when calculating the structure’s resistance of progressive collapse.In view of the asymmetric distribution of infill walls,the introduction of asymmetric distribution coefficient can improve the accuracy of caculaion.Comparing the computation results with the prediction results recommended by the current codes and it appears that the recommend value of displacement for the middle column is suitable for that of a bare PC frame but conservative for the PC frame with infill walls.In the case of the same number of infill walls,the optimal infill wall distribution scheme is related to the position of the failure column.For the loss of supporting column in the long span and the short span,the best distribution of infill walls is the partial floors distribution,followed by the staggered distribution,and single-side distribution.For the loss of corner columns,the optimal distribution is different,because the two adjacent spans are not in the same plane.The best solution is the staggered distribution,followed by partial floors distribution and the single-side distribution.This researche has verified that infill walls have a significant contribution to the structure’s ability to resist progessive collapse.The establishment of analytical models provide the basis for the calculation of the ultimate bearing capacity of precast concrete frames with infill walls.The analysis results of the overall building model provide basis for the conceptual design of the wall panel distribution of the building’s anti-progressive collapse design.