Seismic performance assessment of steel buildings equipped with a new semi-active displacement-dependent viscous damper

This paper investigates numerically the seismic behavior of multi-degree-of-freedom (MDOF) systems with novel 2–4 direction and displacement-dependent (2–4DDD) and 2–4 Displacement-Velocity- (2–4DVD) Semi-Active (SA) controls. This study builds upon the novel SA 2–4DDD control system, in which the damper forces are controlled by inter-story drifts. For the first time, this paper investigates numerically the behavior of an MDOF system with 2–4DDD controls. A 3-story steel frame is modeled in OpenSees and then subjected to real earthquake records. The frame is modeled considering three control systems: (i) conventional passive nonlinear viscous dampers (NVDs), (ii) SA 2–4DDD dampers, and (iii) a new 2–4DVD SA damper. Parametric studies are conducted to determine the optimal parameters of 2–4DVD control in the designed frames. New design methodologies for MDOF systems with 2–4DVD and 2–4DDD controls are also proposed. The results are discussed in terms of inter-story drift, base shear force, acceleration, dissipated energy and required damper force. Results from Nonlinear Time History Analyses show that, compared to a frame with traditional NVDs, the inter-story drifts and base shear of the frame with 2–4DVD control are up to 72% and 32% lower, respectively. 2–4DVD control also reduces damping forces and acceleration by up to 60% and 87%, respectively, compared to 2–4DDD control. It is also shown that the 2–4DDD control was not stable in high-frequency earthquake records. Conversely, the new 2–4DVD control leads to smoother damping force changes between quadrants for the case study investigated in this paper. This study contributes toward the development of new seismic retrofitting dampers for nonlinear MDOF systems.