Mechanical Properties of Steel Square Tube Columns with Standard Flange Connections

Experiments under monotonic and cyclic loading conditions， along with simulations， were conducted to investigate the mechanical properties of steel square tube columns with standard flange connections. The constraint stiffness， failure mode， bearing capacity， hysteretic performance， and stiffness degradation of the steel square tube columns under different design strengths were studied. The results showed that the design strength of the flange connection significantly affected the mechanical properties of the steel square tube column. The constraint effect of the flange connection on the column could be adjusted by changing the design strength multiplier of the flange connection. When the connection strength multiplier was small （0.25-0.85）， the flange’s constraint effect on the column behaved as a semi-rigid connection. Under such connection conditions， the column rapidly lost its bearing capacity. The bearing capacity of the specimen was linearly and positively correlated with the with design strength multiplier of the connection in this range. When the connection strength multiplier was large （1-1.6）， the flange’s constraint effect on the column was that of a rigid connection， which allowed full utilization of the bending performance of the square tube column. In this case， the bearing capacity of the specimen remained almost unchanged with an increase in the connection strength parameter. As the flange connection strength increased， the cyclic stiffness degradation of the specimen showed a decreasing trend.