Failure mechanism and deformation limit of square tubular T-joints under impact loading

Previous research has indicated that the width ratio of the brace to the chord (/1) of square tubular T-joints governs their failure modes and ultimate strength under static loads. In this study, a series of impact tests on square tubular T-joints with different /1 are conducted to investigate the failure mechanism and determine the deformation limit of T-joints under impact loading. Although the T-joints under an impact load fail in a failure mode similar to that under static loading, the impact responses are significantly influenced by the inertial effect, which leads to dynamic buckling of the chord flange and web, as well as a complicated deformation pattern between the overall chord bending and local indentation. The impact deformation limit and ultimate strength of T-joints are proposed based on the test results. Furthermore, the impact failure and dynamic force transfer mechanisms are clarified in detail based on the strain development with the numerical simulations. Finally, the ultimate strength at the proposed deformation limit is compared with the typical existing design formulae. The effect of /1 on the dynamic ultimate strength of T-joints is discussed.