Study On Mechanical Behavior Of Prefabricated CFST Composite Column And PEC Beam Assembly Joints

Concrete-filled steel tube composite column is a kind of composite column formed by binding steel bars around the steel tube and pouring concrete inside and outside the tube.Partially encapsulated concrete composite beam is a kind of composite beam,which is composed of H-section steel flange and web bounded with steel bars and filled with concrete.Because of the high bearing capacity,good ductility,excellent fire and corrosion resistance,excellent economy and other advantages,components have been applied in super high-rise buildings,bridges,underground projects,large-span space structures and other engineering fields.At present,scholars worldwide have carried out numerous researches on the basic performance of concrete filled steel tube composite columns and partially encapsulated concrete composite beams.At the same time,a small number of rigid joints of concrete filled steel tube composite columns and semi-rigid joints of partially encapsulated concrete composite beams have been tested and theoretically analyzed.However,the mechanical behavior and failure mechanism of prefabricated concrete filled steel tubular composite columns and prefabricated partially encapsulated concrete composite beams are not studied.Therefore,the research in this field has important theoretical and engineering significance.The main research work is as follows:(1)Based on ABAQUS finite element software,the finite element analysis models of three types of prefabricated concrete filled steel tubular composite columns and prefabricated partially encapsulated concrete composite beams under static loads are established respectively.Meantime,the corresponding steel beam connection joints are compared.Considering material nonlinearity and complex contact pairs,the constitutive relationship model of concrete and steel under static loads is determined.The rationality of mesh generation and convergence is solved.The accuracy of the finite element model is verified by relevant experiments.(2)Three types of prefabricated concrete filled steel tubular composite columns and prefabricated partially encapsulated concrete composite beams are analyzed under static loads.The stress distribution law of key parts and important components of composite joints is obtained.The mechanical properties and failure mechanism are revealed.And the stress state of different componentsunder ultimate failure is analyzed in depth.(3)By means of ABAQUS finite element software,the static performance of three types of prefabricated concrete filled steel tubular composite columns and prefabricated partially encapsulated concrete composite beams are systematically analyzed from three aspects: material parameters,geometric parameters and load parameters.The main parameters and influencing rules affecting the mechanical properties of the joints are clarified.(4)On the basis of finite element analysis,according to the failure modes of various types of joints,the proposed formulas of bearing capacity and initial stiffness of three types of assembled joints are proposed respectively,and the reasonable construction measures are suggested,such as the outer steel plate in the core area and the stiffening rib in the end plate.On this basis,the proposed moment-rotation relationship model and engineering design suggestions are given for the actual project.This paper provides a reliable reference for the engineer practice.