Experimental and numerical study on tensile behavior of blind-bolted T-stub connections at ambient and elevated temperatures

The performance at elevated-temperature of the T-stub component in the tension zone of blind-bolted beam-to-column end-plate connections remains insufficiently understood. To address this issue, this study investigates the tensile performance of blind-bolted T-stub connections under ambient, steady-state, and transient-state fire conditions through experiments and finite element (FE) analysis. 29 specimens were tested to investigate failure modes and load-transfer mechanisms under different thermo-mechanical paths and to quantify the effects of key design parameters. The test results showed that, at ambient temperature, the failure modes of blind-bolted T-stub connections include flange yielding, bolt fracture, and distinctive sleeve fracture. While at elevated temperatures, sleeve fracture was not observed. Increasing flange thickness enhanced the ambient yield load by at least 81% but reduced deformation capacity. Under transient heating, the non-monotonic dependence of critical and ultimate temperature on flange thickness indicates the existence of an optimal thickness for fire performance. Increasing bolt spacing significantly enhanced connection deformation capacity under ambient and transient conditions, with peak displacement and ultimate displacement increasing by up to 75% and 87%, respectively. Higher bolt shank strength reduced the deformation capacity at ambient temperature but enhanced it under transient heating. Compared with standard bolted connections, blind-bolted connections exhibited superior deformation capacity and fire resistance. The fire resistance decreased monotonically as the load ratio increased. The steady-state tests provided more conservative predictions than the transient-state tests. The FE results showed that bolt slip made a noticeable contribution to the overall deformation under ambient and steady-state conditions, but its influence became much less significant under transient-state conditions.