Analysis On Mechanical Properties Of Square Concrete Filled Steel Tubular Column To Beam Connections

For square concrete filled steel tubular structures, column-beam joints significantlyaffect mechanical performance of structures. However, previous researches oncolumn-beam connections focus on simplified frame joints, and rarely involve other typesof joints. In order to ensure the safety and reliability of the whole structures, detailedanalysis on mechanical behaviors of edge column connections, corner column connections,ordinary frame connections and simplified frame connections is carried out. It will providean important reference for the design and engineering applications of joints.By using FEM software ABAQUS, mechanical performances of above four types ofjoints are studied. The effect of displacement load’s different directions on the behavior ofjoints is analyzed; the effect of the same displacement load on different types of joints isstudied; the effect of the same axial pressure ratio on the performance of joints is analyzed.Mechanical behaviors of connections such as hysteresis curves, skeleton curves, stiffnessdegradation, strength degradation, joint’s ductility are analyzed.The Finite element analysis shows that:(1) For ordinary frame connections, the loadpeak value is slightly higher, energy dissipation capacity and seismic performance is moreexcellent when displacement load is along the direction of the main beam. For edgecolumn connections, hysteretic behavior and energy d issipation capacity is better, thedegradation of strength is slightly slower, and the degradation of stiffness is more obviouswhen displacement load is along the direction of45degrees. Load peak value is largerwhen displacement load is along the direction of the main beam. The effect ofdisplacement load’s different on the corner column joint is not so obvious.(2) For the samedisplacement load, bearing capacity of ordinary framework joint is relatively higher, andthe corner column joint’s is relatively lower; the tendency of joint’s stiffness degradation isbasically same. The extent of ordinary frame joint’s stiffness degradation is higher, and itsultimate stiffness is higher than that of other joints. Simplified frame joint’s ultimatelystiffness is lower than that of other joints, and its strength degradation is more obvious; hysteretic behavior and energy dissipation capacity of edge column joint are the mostexcellent, simplified frame joint’s is close to ordinary frame joint’s;(3) For ordinary framejoint and simplified frame joint, the load peak values decline, hysteresis behavior andenergy dissipation capacity decrease along with the increase of axial compression ratios.Strength degradation is gradually obvious, the extent of stiffness degradation decreases,ultimate stiffness decreases. Therefore, it is necessary to consider the influence of axialcompression ratio in the design of square concrete filled steel tubular connections.