Resistance of flush endplate connections under tension and shear in fire

• Fire tests were performed on endplate connections under shear and tension.
• Numerical simulations were validated and connection failure modes were obtained.
• Tension and shear force distributions among bolt rows were studied.
• Qualitative relation of bolt shear force and tensile capacity was observed.
• Interactive relationship of tension–shear at different temperatures was established.

This paper presents an experimental and numerical study to the resistance of flush endplate connections in fire. Six transient fire tests were performed on two types of connections with flexible and stiff endplate. For each connection, three load combinations were tested and the test results were reported. The test shows that most connections failed within the range of 500 °C to 650 °C. Extreme bending deformation of the endplate and flexural deformation of the bolt were observed when the plate thickness was 8 mm. When the endplate thickness became 16 mm, deformations occurred to the column flange and the bolts as the endplate became thicker than the column flange. Connection fire resistances were found to decrease with increase of either tension or shear, but the connection deformations were similar regardless of the load combination within the range tested. The three-dimensional finite element simulations of the tests with flush endplate connections were conducted with general-purpose finite element program ABAQUS. The results obtained from analysis showed a good agreement with the experimental responses. Parametric study was performed to the connection failure mechanisms under an extensive range of load combinations of tension and shear in fire using the finite element model. Conclusions were drawn regarding the tension and shear interactive relationships for the two typical connections at different temperatures.