Tensile behavior of bolted-angle connections at high temperatures under progressive collapse scenarios

Prefabricated steel structures with bolted-angle connections are effective in resisting progressive collapse due to their high load-bearing and rotational capacities. This study investigates the tensile properties of these connections under ambient and high-temperature (500 °C and 800 °C) steady-state tests. A total of 30 tensile tests with various parameters, such as angle thickness, gauge length, and connection type, were conducted to assess their behavior in both ambient and fire conditions. Four failure modes were identified: bolt bending fracture with yielded angles, bolt shear fracture with yielded angles, angle fracture close to heel with yielded bolts, and threads failure with yielded angles. The findings show that at ambient temperature, both angle and bolt failures occur, while high temperatures primarily lead to bolt failure. The study also emphasizes the significant impact of the tensile membrane action on load-bearing during large deformations. A sequential thermal-mechanical coupling analysis using ABAQUS/Explicit accurately modeled the observed mechanical behaviors and failure modes, highlighting the importance of considering thermal properties in the design of these connections. This study examines the high temperature tensile behavior of bolt-angle connections to provide design recommendations and supporting references for their performance under fire conditions.