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To maximize vibration reduction efficiency and reduce the risk of detuning, this study proposes a multiobjective optimization design method for shape parameters affecting the nonlinear characteristics of nonlinear gas-spring damper (NGSD) based on the NSGA-II algorithm. A numerical model of a MDOF structure with attached NGSD is developed and optimized under white noise excitation, and the effectiveness of the optimized NGSD in mitigating structural seismic responses is validated through shaking table tests. By comparing with the optimal TMD, the control effectiveness and parameter sensitivity of the optimized NGSD under various near- and far-field seismic excitations are investigated. Results show that the optimization design is carried out with the performance objective of minimizing the RMS of structural displacement and acceleration response, and a set of relatively optimal piston radius and initial volume parameters are obtained, resulting in the control effectiveness of NGSD on the RMS response of MDOF structure’s displacement and acceleration as high as 77% and 39%, respectively. The maximum reduction effectiveness of optimized NGSD on the peak structural acceleration and displacement response under seismic excitation is 18% and 19% respectively, and the RMS reduction ratios are even as high as 56% and 61%, indicating the efficacy of using NSGA-II for parameter optimization. Moreover, the optimized NGSD demonstrates comparable control effectiveness to the optimal TMD with a shorter stroke and stable performance across different seismic excitations, indicating low sensitivity of optimal parameters to excitation frequency. [ABSTRACT FROM AUTHOR]

Failures of transmission tower-line systems have frequently occurred during large earthquakes. It is essential to control the excessive vibrations of transmission tower-line systems to ensure their safe operation in such events. This paper numerically investigates the effectiveness of using a novel bidirectional pounding tuned mass damper (BPTMD) to control the seismic responses of transmission tower-line system when subjected to earthquake ground motions. A finite element model of a typical transmission tower-line system with BPTMD is developed using the commercial software ABAQUS, with the accuracy of the results verified against a previous study. The seismic responses of the system with and without BPTMD are calculated. For comparison, the control effect of using the conventional bidirectional tuned mass damper is also calculated and discussed. Finally, a parametric study is performed to investigate the effects of the mass ratio, seismic intensity, gap size and frequency ratio on the seismic response of the system, while optimal design parameters are obtained. [ABSTRACT FROM AUTHOR]

• NGSDVA has shorter stroke, similar effect and flexible configuration than optimal DVA. • NGSDVA vibrates in a broadband mode to realize the redistribution of structural energy. • The fundamental tuning mechanism reduces the NGSDVA's amplitude sensitivity. • Note: NGSDVA represents the nonlinear gas-spring dynamic vibration absorber. A gas-spring with adjustable nonlinear capacity is introduced into a conventional linear dynamic vibration absorber (DVA), thus forming a nonlinear gas-spring dynamic vibration absorber for structural seismic response control, which is a nonlinear energy sink with a fundamental tuning function. The mechanical properties of the symmetrical combined gas-spring system are studied first by theoretical analysis and model tests. A series of shaking table tests are designed and conducted to systematically investigate the control effect and nonlinear damping mechanism of the gas-spring DVA for a 5-story structure. A numerical model of the nonlinear gas-spring DVA attached to the structure is established and validated by the experimental results. The experimental results show that the proposed nonlinear gas-spring DVA can effectively mitigate the structural dynamic responses and has a wide damping bandwidth with good stability. The presented system has amplitude-frequency characteristics, and the sensitivity of its control performance to amplitude is significantly reduced by introducing a fundamental tuning mechanism. The nonlinear DVA vibrates in a broadband mode and is capable of resonating with the structure at multiple frequencies so that the nonlinear restoring force of the gas-spring DVA redistributes the structure's vibration energy from its low-order modes to high-order modes. Compared with the optimum tuning DVA, the reasonably designed nonlinear gas-spring DVA has a similar control effect and shorter working stroke, possessing the advantage of flexible parameter configuration capabilities. Moreover, the experimental and numerical simulation results are in good agreement, indicating that the proposed numerical model is accurate in predicting the behaviors of the nonlinear gas-spring DVA. [ABSTRACT FROM AUTHOR]

• An improved ESM-FEM method is proposed to evaluate the performance of the PTMD-MDOF system. • The proposed method can efficiently simulate the nonlinear effect of the PTMD. • It also can accurately obtain the dynamic characteristics of the MDOF structure. • The ESM-FEM method makes it easier to obtain the damping force. • This method can better understand the damping mechanism of the coupled system. This study proposes an improved equivalent simplified method coupled with the finite element method (ESM-FEM) to investigate the control performance of the particle tuned mass damper (PTMD) attached to the multi-degree-of-freedom (MDOF) structure (e.g. transmission tower). To validate the proposed method, the coupled system responses from the ESM-FEM method are compared to the results of the previous study under the free vibration and seismic excitation. The transmission tower is modeled by the FEM in Abaqus, while the PTMD is simulated by the ESM in Python. The damping mechanism of the PTMD-MDOF system is investigated based on the ESM-FEM method, and the PTMD's control effect is evaluated. Besides, the reliability of the system's control performance is also discussed. The results show that the ESM-FEM method is reasonable for evaluating the damping performance of the coupled system, and its accuracy is validated by the experimental data and Matlab program. Meanwhile, the proposed method makes it easier to obtain the damping force to further better understand the damping mechanism of the coupled system. Furthermore, the PTMD system has good robustness, and its control performance is less sensitive to unpredictable seismic excitations. [ABSTRACT FROM AUTHOR]