Progressive Collapse Analysis And Robustness Of Monolithic Precast Concrete Frame Structures

The precast concrete structures have the advantages of industrialization,low labor intensity,short construction period,and environmentally friendly,and are widely used in building projects,bridge projects,and underground projects.Most studies on precast concrete structures focus on their seismic performance,the ability to resist progressive collapse has yet to be further studied.In this paper,the nonlinear finite element method is used to analyze the resistance of progressive collapse,the mechanical behavior in this process,and the robustness of precast concrete frame structures.The main research works are as follows:(1)Using appropriate element types and material constitutions,analytical models of precast concrete frame structure were established in the finite element software SAP2000.The numerical models are validated through comparisons with 7 pushdown test data.Based on the analysis results,the mechanism of the compressive arch action and the catenary action were analyzed.(2)By contrast with the loading capacity according to the conventional plastic analysis approach,coefficients of increase of the loading capacity due to compressive arch action and of the loading capacity due to catenary action are defined.Based on previous model validation,the influence of parameters such as flexural reinforcement ratio,ratio of beam span to depth,relative column bending stiffness,number of stories,number of spans,position of removed column,and thickness of superimposed concrete on the loading capacity due to compressive arch action and on the loading capacity due to catenary action was analyzed.(3)PKPM software is used to design 3 monolithic precast concrete frame structures and 1 cast-in-place concrete frame structure that meet Chinese codes.The structures are designed with different seismic fortification intensity.Apply RRI(relative robustness index)as a tool to quantify structural robustness based on the nonlinear static Pushdown method,influencing factors are analyzed including different position of removed column,different seismic fortification intensity,and two different ways of strengthening.Suggestions are made for the design of monolithic precast concrete frame structures to resist progressive collapse for practical engineering reference.