Seismic vulnerability of steel tubular structures based on local Buckling driving variables

Resumo

Performance-Based Earthquake Engineering (PBEE) is computationally demanding, due to the multiple high-fidelity non-linear dynamic structural response analyses required to compute fragility curves. In this manuscript we propose an efficient procedure to obtain fragility curves of complex tubular structures prone to fail due to local buckling using a model based on the Lumped Damage Mechanics. A state variable characterizing local buckling is employed as engineering demand parameter in PBEE. This state variable is a scalar, derived from lumped damage mechanics and taking values between 0 and 1, which characterizes the degree of local buckling (LB). A procedure to identify and define global collapse mechanisms using the local buckling state variable at the nodes is proposed, which serves as the EDP for computing the structure's fragility curves. To evaluate the seismic vulnerability, incremental dynamic analyses are conducted. The main results demonstrate efficiency of the mechanical model in a PBEE framework, and that the internal variables indicating local buckling can be considered objective indicators of collapse for Tubular complex steel frames. Results show how to identify the global failure mechanisms that are more likely to appear for each frame.