A decoupled T-stub component model for the cyclic modelling of steel joints

The reliable estimation of the cyclic behaviour of steel beam-to-column joints is essential for the safe design of steel structures under seismic loading. The T-stub is an essential component in steel beam-to-column joints. This paper presents the framework and implementation of a decoupled component model for the T-stub under cyclic loading. This decoupled model splits the single hysteretic spring representation of the T-stub into two separate hysteretic springs, one representing the quadrant where tensile forces are present and the other the quadrant with compressive forces. The results indicate that because of the degradation of the response of the T-stub with multiple loading cycles, the equivalence between the single spring model, and the decoupled double spring model is not trivial. Exact equivalence rules are proposed for the definition of the properties of the decoupled model. The accuracy of the model is validated by comparison with experimental test results. The decoupled model overcomes the problem of using a single spring to represent the T-stub in a steel joint that is not able to lead to correct results because it is unable to mobilize compressive forces in the T-stub as it occurs.