Experimental Study On Shear Capacity Of Beam-Column Joints Of Truss Steel Reinforced Concrete

Truss steel reinforced concrete structure is a new type of open web steel reinforced concrete structure,which is composed of angle steel.gusset plate and batten plate by welding,and by outsourcing concrete.The joints of beam column frame in this structure form are the stress skeleton of beam column joints with angle steel instead of ordinary steel bars.For the steel reinforced concrete joint in the form of angle steel,the steel skeleton in the beam can be directly penetrated from the inner side of the column chord angle steel to avoid the trouble of welding the solid web steel reinforced concrete jointThis paper designs and fabricates five frame inner joints of shear failure in the core area,mainly considering the two test parameters of axial compression ratio and steel content and carrying out low-cycle reciprocating load test on it.The main research work and results are as follows(1)The experiment mainly investigated the failure process of the joint under different axial compression ratios and steel contents,studied the seismic performance of the joint's ultimate bearing capacity,stiffness,ductility and energy dissipation capacity.The strain variation law of beam end column end and core chord is discussed.The test results show that when the horizontal load on the top of the column reaches the peak,the concrete in the core area of the joint is crushed diagonally,and typical joint shear failure occurs;the load-displacement hysteresis curves of all specimen joints show a certain pinch phenomenon,Indicating that there is a certain amount of bond slip between the steel truss and concrete;increasing the axial compression of the column top is beneficial to the improvement of the ultimate bearing capacity of the core area of the joint,but the ductility and energy dissipation capacity become worse;increasing the core area The amount of steel can significantly improve the shear capacity of the joint,and the ductility will also be improved(2)Based on the ABAQUS platform,a refined numerical finite element model of frame inner joints was established,and the horizontal load-displacement monotonic loading curve of the column top was simulated.Based on the comparison of the monotonic loading curve and the hysteretic skeleton curve of the test,the whole process of the failure of the joint is studied.the stress state of the concrete and truss steel frame of the frame joint is investigated,and the failure mechanism of the joint is explored.(3)Based on the results of parameter analysis,the influences of axial compression ratio,concrete strength,steel ratio of diagonal web member in the core area and yield strength on the horizontal load displacement curve of the joint column top are studied,and the shear capacity expression suitable for the joint is obtained by fitting analysis.The research results show that when the horizontal load of the joint reaches the peak point,the cross diagonal web members in the core area yield and the concrete in the core area is crushed.Based on this,the calculation formula of the shear bearing capacity in the core area of this kind of hollow joint is proposed for reference in engineering design.