Behavior of beam-to-column welded connections in steel structures after fire

Beam-to-column welded connections are widely used in steel structures, and the post-fire behavior of connections is of great importance to the resistance of steel structures after fire. Five beam-to-column welded connections made up of Q345B steel were first heated to specified temperature levels, and then cooled to ambient temperature and tested to failure under lateral force. Five temperature levels from 500℃ to 900℃ were considered, and natural cooling was employed in the test. Test at ambient temperature was also conducted for bench mark comparison. The results show that failure mode of connection specimens changes from beam flange buckling to the butt weld cracking after the connections exposed to 500℃ to 900℃ high temperatures. The effects of exposed temperature on bending bearing capacity and rotation ability of beam-column welded connections are discussed. These results are compared to existed results from research on mechanical properties of post-elevated temperature of butt welds and fillet welds after fire. These results can provide reference for detection and safety assessment of post-fire steel structures.