Analysis Of Progressive Collapse And Robustness Evaluation Of Rc Frame Considering Slab Action

Since the collapse of the Ronan Point apartment in the UK,the progressive collapse of the building came into the sight of scholars from all over the world.The "911" incident also set off a wave of research on the progressive collapse of the building.In recent years,some scholars have studied the role of slabs in the process of progressive collapse.Most of these studies are qualitative analysis of the mechanism of stress,and there is a lack of quantitative research on the contribution of the slab to the progressive collapse bearing capacity and overall robustness of the structure.In order to accurately and reasonably design the progressive collapse resistance of the structure,it is necessary to quantitatively analyze the contribution of the slab to the progressive collapse bearing resistance and overal l robustness of the structure.In this paper,SAP2000 was used to establish the RC frame structure model.The static nonlinear analysis method was used to analyze the progressive collapse of the 3D frame substructure and the 3D frame overall structure.The influence of the slab on the mechanism of progressive collapse bearing resistance was studied and the robustness of the overall structure was quantitatively evaluated to provide a reference for the design of progressive collapse bearing resistance in actual engineering.The main research contents include:(1)According to the existing experiments,in the SAP2000,the element and material stress–strain relationship are reasonably selected to establish the finite element analysis model of the beam–column structure,T–beam,one–way beam–slab substructures,and two–way beam–slab substructures.The finite element results are in good agreement with the test results,which verifies the rationality of the model and lays the foundation for subsequent research.(2)Taking the 2×2 span RC beam–slab structure as the research object,through the analysis of the load–displacement curve,beam reinforcement stress cloud diagram,slab internal force cloud diagram,etc.,the force mechanism of the RC beam –slab structure in the process of progressive collapse was studied.The results show that slab can significantly increase the progressive collapse bearin g capacity of the reinforced concrete frame structure,and it will advance the conversion point of the load–displacement curve.(3)The effects of concrete strength,slab thickness,slab reinforcement ratio,length–to–width ratio,beam reinforcement ratio and beam height on the bearing capacity of beam–slab substructure are studied,and an empirical design formula for bearing capacity is proposed based on the analysis of various parameters.(4)Pulldown analysis of the overall structure of the 3D frame that meets the Chinese norms.Relative bearing capacity is used as the overall robustness evaluation index of the structure,and the overall robustness level of the pure frame and the frame considering slab action after the column removal is analyzed.The resu lts show that after considering the role of the slab,the overall robustness of the structure is significantly improved.Furthermore,after considering slab action,the overall robustness level of the frames with different positions of column and the frame s with various seismic levels is given,and structural strengthening measures to enhance the overall robustness of the structure are given for practical engineering reference.