Performance of practical beam-to-SHS column connections against progressive collapse

• Progressive collapse performance of steel connections are studied.
• Focus is given to practical beam-to-SHS column connections.
• Three full scale tests are performed on double-span systems.
• Comprehensive finite element (FE) models are established and discussed.

This paper comprehensively discussed the performance of practical beam-to-SHS column connections against progressive collapse. Three full scale tests were performed on double-span systems subjected to the typical column loss scenario, where three connection types were covered in the test programme, namely, welded flange-weld web connection with internal diaphragms (specimen I-W), welded flange-bolted web connection with internal diaphragms (specimen I-WB), and welded flange-bolted web connection with short through diaphragms (specimen ST-WB). The test results, including failure modes/sequence, load–deformation responses and stress conditions, were presented in detail, and the load transfer mechanism over the entire loading process was thoroughly discussed. Comprehensive finite element (FE) models were then established to enable further discussion of the test results. Both experimental and FE results showed satisfactory ductility supply and load resistance of the three specimens, although specimen ST-WB exhibited the lowest ductility against initial fracture due to evident non-symmetrical stress distribution over the width of the beam flange. For the post-peak response, specimens I-WB and ST-WB showed reasonable regaining of the resisting load at later catenary stage due to a sufficient redistribution of the stress at the bolted shear tab connections, but limited post-peak load resistance was shown for specimen I-W which underwent quick propagation of the crack over the entire beam section. A simplified energy balance analysis showed that when a sudden column loss scenario is considered, progressive collapse may be triggered upon the initial fracture of the bottom beam flange of all the specimens.