Investigation On Mechanical Performance And Design Theory On Partially Prefabricated Steel Reinforced Concrete Columns

Partially Prefabricated Steel Reinforce Concrete(PPSRC)column is a new type of column member,whose precast outer-part is prefabricated in factory,and then casting the inner concrete after transporting the outer-part to the construction site.This kind of column can effectively reduce the site construction procedure,solve the key problems of poor integrity and insufficient seismic performance of fully prefabricated steel reinforced concrete columns,and promote the process of industrial prefabrication of steel reinforced concrete columns.At present,there is little research on the mechanical performance of PPSRC columns,which greatly restricts the application and popularization of the composite columns.In this paper,the basic mechanical behavior and design theory of PPSRC column is studied by means of experimental research,numerical simulation and theoretical analysis.To investigate the axial behavior of the PPSRC column,eighteen column specimens subjected to the axial loading were carried out in the test.By means of the experimental research and ABAQUS finite element analysis software,the key effects of several parameters including the compression strength of the inner concrete,spacing of the stirrups,studs arrangement and the cross section type on the axial capacity were emphatically explored.Combined with the experimental results and numerical analysis results,the stress distribution of the normal section of PPSRC columns was deeply analyzed,a concrete constrained constitutive model of in "rigid core zone" was proposed,and a formula for calculating the axial bearing capacity considering the confinement effect of steel and stirrups on concrete was also established.The calculated results were agreed well with the experimental results and the finite element simulation values,and the accuracy of the proposed formula was verified.To explore the compression performance of the PPSRC column,fourteen PPSRC columns were conducted under eccentric loading,and the key influences of the compression strength of the inner concrete,load eccentricity,cross section type on the eccentric behavior of PPSRC column were investigated comprehensively.Besides,the effects of both the steel ratio and the prefabrication ratio on the eccentric bearing capacity were further analyzed.Based on superposition method,the calculation methods for predicting the normal section eccentric bearing capacity and bending stiffness of PPSRC columns were analyzed and deduced,and the calculated results were in good agreement with the experimental values.Based on the balanced failure theory of PPSRC columns under eccentric loading,the formula for calculating the limit value of axial compression ratio of PPSRC columns was derived,with taking into account the confinement provided from the stirrups,and the recommended value of the limit value of axial compression ratio is given.Eighteen PPSRC columns subjected to the axial load and shear force were conducted to investigate the shear performance of PPSRC column.The effects of the compression strength of the inner concrete,shear span ratio,axial compression ratio and the section type were focused.On the basis of the truss-arch model of the reinforced concrete column,a model for evaluating the shear strength of the PPSRC column was put forward.This model takes into account the deformation coordination of truss part,arch part and steel section part,as well as the influence of axial pressure on the oblique compression angle of columns.The calculated results were in good agreement with the experimental values,which demonstrated that this formula could be used to calculate the shear capacity of oblique section of PPSRC columns.