Experimental And Numerical Research On Progressive Collapse Resistance Of Precast Concrete Frame Spatial Substructures

The progressive collapse of building structures is the phenomenon that the destruction of components initially caused by the accidental load leads to partial or whole collapse of buildings which is unproportionate to the initial damage.In recent years,there are large number of tests and numerical analysis on progressive collapse performance of structures carried out by researchers worldwide,which are aimed mostly at steel structures or cast-in place concrete structures but rarely at prefabricated concrete frame structures.Prefabricated concrete frame structure is the building form that conforms to the trend of building industrialization in our country,but there exists weakness in joints and connections of prefabricated structures,which is essential in progressive collapse resistant behavior of building structures.Accordingly,in this paper,the progressive collapse resistance performance of prefabricated concrete frame spatial substructures and the influence of structure parameters on structure collapse resistance are studied by means of experimental and numerical analysis methods.In this paper,a prefabricated concrete frame spatial substructure specimen consisting of three beams and four columns was designed and fabricated by the pseudo-static test way,and the specimen was placed under a monotonic vertical load controlled by force and displacement to simulate the progressive collapse of the substructures in quasi-static way.The collapse of prefabricated concrete frame spatial substructure specimen occurred at a vertical displacement of 588.9mm due to the rupture of top steel bars near the end column.Based on the experimental results of resistance force,displacement,stress,crack development and failure mode,the transition process of force and resistance mechanism of the specimen were analyzed.The finite element model for the prefabricated concrete frame spatial substructure specimen was established based on ABAQUS.The progressive damage and failure model of ductile metals was adopted as the reinforcement constitutive model to achieve its fracture control,and the Coulomb friction model controlled by friction coefficient was used to define the contact properties of the combined interface to simulate the effect of the interface of precast beams.According to the comparison between numerical analysis and experimental results in aspects of load-displacement curve,stress,horizontal displacement of end columns and structural damage condition,the accuracy of the finite element analysis and the rationality of parameters adopted in the numerical model were verified.Based on finite element modeling parameters and methods established from the test results,the structural parameter analysis and study of progressive collapse resistance of the prefabricated concrete frame spatial substructure was performed.By comparing between prefabricated concrete frame structure and cast-in-place structure under same conditions,their discrepancy of resistant force and deformation were discussed.The influence of reinforcement ratio on progressive collapse performance of prefabricated spatial structures was studied by changing top or bottom reinforcement ratios in beams.Through altering friction coefficient of precast beams combined interface,the effect of roughness of combined interface on prefabricated structures was analyzed.The recommendation of structural design of prefabricated concrete frame structure and rough surfaces were proposed according to the results of the parameter analysis.