Abstract
Abstract This study investigates the mitigation of excessive vibrations in two adjacent elevated storage tanks exposed to sequential nonstationary seismic excitations with time-varying frequency content. The coupling between the adjacent tanks is achieved through a sky-bridge structure that acts as a nonlinear mechanism, which is considered as a system comprising two nonlinear springs, two linear viscous dashpots, and an attached mass element, collectively referred to as a nonlinear energy sink (NES) mechanism. To describe the vibrational response, each tank is formulated using an equivalent multi-degree-of-freedom representation. A parametric analysis is conducted to investigate how the main NES parameters affect the dynamic response of coupled tanks under excitation input. Numerical simulations are performed using a mathematical model of earthquake ground motions consisting of two frequency-varying sequences as representative dynamic inputs. A sensitivity analysis of the mass ratios, nonlinear stiffness, and damping elements is carried out to determine their suitable values to achieve significant attenuation of excessive vibrations. The vibration suppression performance of the NES is investigated and quantitatively compared with that of a tuned mass damper (TMD) absorber. Subsequently, particle swarm optimization (PSO) is applied using a defined objective function to select the optimal NES parameters to improve vibration mitigation. Findings reveal that the connector structural element significantly improves the dynamic performance of the entire system. Accordingly, this configuration provides structural benefits, and reduces seismic responses more effectively than the uncontrolled case.