Probabilistic seismic performance evaluation of steel moment frame using high-strength and high-ductility steel

To shorten a steel building recovery time after an earthquake, a dual and damaged-controlled system is proposed, in which the seismic energy is absorbed by a highly ductile buckling restrained brace (BRB) and the gravity load is resisted by high-strength column. Because the seismic energy is mainly dissipated by the BRB, to accurately simulate the BRB hysteretic behavior is essential. Thus, kinematic hardening and two surface theories are adopted and coded as an ABAQUS user-defined material (UMAT). Particle swarm optimization (PSO) is used to find the optimal design equivalent to a corresponding traditional structure. The performance of the optimal frame is verified by nonlinear time history and fragility analysis. Based on the found optimum, a practical design guideline is recommended. The performance of high-strength steel and a high-ductility structural system such as the inter-story drift, maximum roof acceleration, property of BRB hysteresis, strength ratio between the main frame and BRB and cumulative fatigue damage are investigated. In addition, the economic feasibility of using high-strength steel in the structural system is compared to that using traditional steel materials.