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Open access Jul 2026

A ridge-isolated tuned mass damper for seismic rehabilitation of a 3D structure under bidirectional earthquakes.

Efficient and practical seismic control of structures-particularly through isolation systems-remains a significant challenge due to high implementation costs and construction complexity. Moreover, their application in retrofitting existing structures often requires extensive modifications.To address these challenges, this study proposes a novel and cost-effective seismic control system, termed the Ridge-Isolated Tuned Mass Damper (RITMD), which integrates the advantages of tuned mass damping and seismic isolation. A reduced-order two-degree-of-freedom (2DOF) model is developed to capture the coupled dynamic behavior of the primary structure and the RITMD system. An optimization framework based on the Particle Swarm Optimization (PSO) algorithm is employed to determine the optimal tuning parameters. Subsequently, closed-form design expressions are obtained using nonlinear regression analysis to facilitate practical engineering applications .The proposed approach is further extended to three-dimensional structural systems, and its performance is evaluated through nonlinear time-history analyses under bidirectional earthquake excitations. The results demonstrate that the RITMD system significantly reduces structural responses, including displacements, accelerations, inter-story drifts, torsional demands, and their corresponding root-mean-square (RMS) values.Overall, the proposed system provides an efficient, practical, and versatile solution for enhancing the seismic performance of both new and existing structures.

S. Etedali · 0 citations
Open access Jul 2026

High Mass Ratio Tuned Mass Dampers Obtained Through Building Superelevations for Seismic Retrofit

Tuned Mass Dampers (TMDs) are widely adopted passive vibration control devices used to mitigate structural oscillations induced by wind and seismic actions. Conventional TMD systems typically involve relatively small auxiliary masses installed near the top of tall buildings. This paper investigates an alternative strategy for seismic retrofitting of existing structures based on large mass ratio TMDs obtained through building superelevations. In this approach, one or more additional storeys supported by seismic isolation devices behave as large tuned masses capable of reducing structural response during earthquake excitation. A comprehensive parametric numerical investigation is carried out in order to evaluate the influence of the mass ratio, structural period and damping characteristics on the effectiveness of the system. The results are summarized in a set of design charts that allow engineers to determine optimal tuning parameters. In particular, by using the obtained design abaci they can find a solution which minimizes both displacement and acceleration.

R. Montuori, E. Nastri, P. R. Marrazzo · 0 citations
Open access Aug 2026

Reinforcement learning-based adaptive gyroscopic control for torsional response mitigation: a proof-of-concept study

Torsional vibrations induced by seismic excitation can significantly increase structural demand, particularly in systems with geometric or stiffness irregularities. This proof-of-concept study proposes a hybrid adaptive control framework that combines passive gyroscopic damping with reinforcement learning (RL)-based adaptive torque control for torsional response mitigation. A simplified three-degree-of-freedom (3DOF) structural model is evaluated under bidirectional earthquake loading, while the control policy is trained using the Proximal Policy Optimization (PPO) algorithm to generate adaptive torque directly from measured system states without explicit system identification. Numerical simulations using recorded earthquake ground motions show that the proposed approach reduces root-mean-square torsional displacement to 0.012 ± 0.001 rad, representing a 65.7% reduction relative to the uncontrolled case and improved performance over passive gyroscopic control alone. Sensitivity analyses involving variations in mass, stiffness, and damping indicate stable controller performance across the structural parameter ranges considered. The trained controller achieved sub-millisecond inference time with minimal computational overhead, supporting its computational feasibility for future real-time implementation. The results demonstrate the potential of integrating physically grounded gyroscopic damping with data-driven adaptive control for intelligent torsional vibration mitigation.

S. Stephen, Ali Hadi, O. Akinradewo et al. · 0 citations
Jul 2026

Robust Optimization of Multiple Tuned Mass Dampers for the Offshore Monopile-Supported Wind Turbine

Offshore wind turbine (OWT) towers are continuously subjected to highly variable wind-wave excitations, where structural parameter uncertainties arising from manufacturing tolerances and material heterogeneity may significantly degrade vibration control performance. Conventional tuned mass dampers (TMDs), particularly single-TMD configurations, are highly sensitive to detuning effects and thus lack robustness under uncertain operating conditions. This study proposes a robust optimization framework for vibration mitigation of offshore wind turbine towers using multiple tuned mass dampers (MTMDs). Structural parameter uncertainties in total mass and stiffness are explicitly considered through Latin hypercube sampling (LHS), enabling a sample-based evaluation of control performance. Inverse Element Exchange Method with Multi-level Programming (MulIEEM) is applied to determine the optimal distribution of damping coefficient, mass, and for the TMDs. Three objective functions are investigated, including minimization of the sample mean, sample standard deviation, and single-sample response, allowing a systematic assessment of vibration reduction effectiveness and robustness. Stochastic wind and wave loads are synthesized using the Kaimal wind spectrum and JONSWAP wave spectrum, while structural uncertainties are represented through Latin Hypercube Sampling (LHS). The statistical characteristics of the displacement responses across all samples are used to evaluate robustness and provide an indirect measure of sensitivity to uncertainty-induced detuning effects. Three objective functions are investigated, including minimization of the sample mean, sample standard deviation, and single-sample response, allowing a systematic assessment of vibration reduction effectiveness and robustness, defined herein as reduced sensitivity to structural uncertainties. Numerical results demonstrate that the proposed MulIEEM-based MTMD designs significantly reduce both the mean and variability of tower displacement responses across a wide range of wind speeds. Furthermore, single-sample-based optimization is shown to achieve a favorable balance between control effectiveness and computational efficiency. The proposed framework provides a practical and robust design strategy for vibration control of offshore wind turbine towers under structural uncertainty.

Peng-Tai Chan, Ching Yen · 0 citations
Open access Jul 2026

Implementation and Numerical Validation of a Semi-Active Tuned Mass Damper for Vibration Mitigation in Lightweight Pedestrian Structures

The application of semi-active control systems in lightweight civil engineering structures is still limited even though several studies have shown an improvement in mitigating vibrations under uncertainty scenarios. In comparison with passive systems, a smart device is employed in a Semi-active Tuned Mass Damper (STMD) system to modify its response in real time, usually the damping force. Based on a control law, a degree of adaptability can be achieved in the smart device, leading to the desired tuning between the structure and the STMD to mitigate the vibration induced by the external force, especially when a detuned response between the structure and the control system is caused by external uncertainties. The magneto-rheological (MR) damper is the most common device used for this purpose. Thus, the practical implementation of an STMD in lightweight structures subjected to human-induced vibrations is presented in this paper. An STMD equipped with two sponge MR dampers is developed, modeled, and installed in a fiber-reinforced polymer footbridge, which fulfills the state requirements but exhibits excessive vibrations when its first vertical vibration mode is excited. Numerical simulations are also carried out considering human-structure-STMD interaction. For the analyses, a Mass-Spring-Damper system is used to depict a pedestrian, and the functioning of the MR dampers is represented through a hyperbolic tangent model. Additionally, three different phase control laws are considered for the numerical and experimental implementation of the STMD, namely: (i) an On-Off controller, (ii) a fixed gain controller, and (iii) a variable gain controller. The comparison of the numerical and test results shows that the model used for the MR damper and the STMD are adequate.

Christian A. Barrera-Vargas, C. Gallegos-Calderón, Iván M. Díaz · 0 citations
2026

Integrated Active Vibration Control and Structural Health Monitoring of Flexible Spacecraft Panels

Abstract. This paper presents an integrated active vibration control (AVC) and structural health monitoring (SHM) framework for flexible spacecraft panels using offset piezoelectric stack actuators (OPSA). A three-dimensional ANSYS finite-element model of a hub–panel assembly with eccentric OPSA mounting is reduced to a low-order state-space model retaining the first two bending modes. Based on this model, a mixed-sensitivity H_∞ controller is designed for robust vibration suppression and compared with an LQR baseline. For SHM, root delamination is represented as an equivalent stiffness loss at the clamp over a 0–40% damage range, and damage-sensitive features are extracted from the closed-loop impulse response, including modal frequency drops, RMS control voltage, residual tip vibration, and settling time. A physics-informed Gaussian process regressor trained on 200 virtual experiments accurately estimates the damage parameter, achieving R^2≈1.000and an RMSE of about 0.25% damage. Over the investigated range, RMS control voltage increases from 48.2 V to 144.6 V, while residual tip amplitude rises from 0.315 mm to 0.633 mm, confirming strong monotonic sensitivity to structural degradation. The results demonstrate that the OPSA–H_∞ loop can provide both robust vibration suppression and a dual-use sensing channel for quantitative damage estimation without additional dedicated SHM hardware.

Muhammad Nadeem · 0 citations