Experiment And Analysis Of Reinforced Concrete Members Strengthened With High Strength Steel

In order to promote the application of high strength steel used in concrete structural strengthening,this paper presents two types of strengthening methods,which are called reinforced concrete(RC)column strengthened with concrete filled steel jacketing(CFSJ)and inner steel wire hoops and RC beam-column joint strengthened with high strength steel components.To verify the effectiveness of these strengthening methods,the main research works are as follows:1.One unstrengthened RC column,one RC columns strengthened with CFSJ and three RC columns strengthened with CFSJ and inner steel wire hoops were tested under axial compression,and the influences of whether to be strengthened with inner steel wire hoops or not,yield strength of inner steel wire hoops and mass ratio of steel wire hoops to total steel(including steel tube and steel wire hoops)on compressive behavior of these columns have been investigated.It is found that:(1)under the condition that the total steel consumption is almost unchanged,the axial load bearing capacity of the RC column strengthened with CFSJ and inner steel wire hoops is almost equal or slightly lower and ductility index of strengthened column increases up to 50% compared to the RC column strengthened with only CFSJ.Moreover,high strength steel wire hoops can help further enhancing the axial load bearing capacity and ductility index of strengthened column especially improving the latter significantly;(2)the axial performance of RC column strengthened with CFSJ and inner steel wire hoops is influenced slightly with mass ratio of steel wire hoop to total steel changed in the range of 10%?20%,(3)after efficiency factor of yield strength of high strength steel wire hoops has been considered,the suggested formulas can predict the axial load bearing capacity of such columns well.2.Based on ABAQUS,numerical simulation model of RC column strengthened with CFSJ and inner steel wire hoops were modeled.The influences of mass ratio of steel wire hoops to total steel,yield strength of inner steel wire hoops,load ratio,initial width-to-thickness ratio,concrete strength and outside width of steel tube on fire performance of these columns have been analyzed.It is found that:(1)under the condition that the total steel consumption is almost unchanged,the fire performance of the RC column strengthened with CFSJ and inner steel wire hoops is significantly better than that of the RC column strengthened with only CFSJ,and the increasing percentage of fire resistance is larger when initial width-to-thickness ratio is relatively small or load ratio is relatively large;(2)the fire resistance of strengthened column is better but the increasing percentage of fire resistance is lower as mass ratio of steel wire hoop to total steel increased;(3)the fire resistance of strengthened column remains almost the same or slightly increases as yield strength of steel wire increased in the range of 600?1000 MPa.3.One unstrengthened RC beam-column joint and three RC beam-column joints strengthened with steel components were tested under reversed cyclic load,and the influences of yield strength of steel and connection types of steel components and joint on seismic behavior of these joints have been investigated.It is found that:(1)ultimate bearing capacity and equivalent viscous damping coefficient of beam-column joint increase to some extent while ductility coefficient of beam-column joint decrease slightly after strengthened with steel components;(2)ultimate bearing capacity and energy dissipating capacity of joint are improved while ductility coefficient of joint is changed slightly by using high strength polyline steel plate compared with using ordinary strength polyline steel plate;(3)compared with using anchor bolt and cement mortar,using anchor bolt and structural adhesives can improve the ultimate bearing capacity and energy dissipating capacity of joint as well as strength potential of high strength polyline steel plate,and the connection type of steel components and joint makes little influence on ductility coefficient of joint.