Shear Behavior of Lapped Connections Bolted by thread-fixed one-side bolts at elevated temperatures

The Thread-fixed One-side Bolt (TOB) is the bolt that can be installed from outside of a steel tube column, which is anchored by the threads on the bolt hole wall instead of the nuts. A series of tests were carried out to investigate the shear behavior of the lapped connection bolted by TOBs using both the steady state fire tests and the transient state fire tests. The two observed failure modes of TOB connected lapped connections were the bolt hole bearing failure (failure mode 1) and the bolt shank fracture (failure mode 2). The high temperature might cause the change of failure mode from failure mode 1 to failure mode 2. Lapped connections using Standard High Strength Bolt (SHSB) were also tested. The comparison results showed that the ultimate shear resistance of lapped connections using TOBs at different temperatures was about 90% of that using SHSBs with the same configuration at steady state fire test. Applicability of the design equations provided by Eurocode 3 was validated by the steady state fire test results. A Finite Element Model (FEM) was built and validated by the test results and the FEM was used to further study more derailed parameter studies including the influence of bolt strength, the bolt pretension force and the high temperature to the shear behavior of TOB connected lap connections.