Composite joints with fin plate connections under a middle column removal scenario

Five simple beam-column joints with composite slabs were tested under a middle column removal scenario. Fin plate connection was used in all the joints. The influences of joint type, slab thickness, number of shear studs and bolt holes were investigated. Load-resisting mechanism of the composite joints against the applied ‘push-down’ load was investigated and the respective contribution of flexural action, compressive arch action and catenary action was quantified. Structural behaviour of the joints in terms of axial force, bending moment, failure mode and energy absorption was presented. To evaluate design values provided by current design guidelines and building codes, test results of the joints were compared with design values. It was found that the composite slab was beneficial to flexural resistance of the joints. Although tying capacity was reduced due to bending moment, tie force requirement could be met for conventional composite joints with 75 mm thick slab. A proposed novel fin plate connection with slotted bolt holes had better performance than conventional connection in terms of energy absorption and tying resistance. The test results provided a better quantitive understanding of FP connections under progressive collapse scenario and were able to serve as benchmark for further simplified numerical models.