Lap Loi Chung
Bio: Lap Loi Chung is an academic researcher from National Center for Research on Earthquake Engineering. The author has contributed to research in topics: Tuned mass damper & Optimal control. The author has an hindex of 5, co-authored 8 publications receiving 281 citations.
TL;DR: In this paper, an optimal design theory for structures implemented with tuned mass dampers (TMDs) is proposed, and the optimal design parameters of TMDs in terms of damping coefficients and spring constants corresponding to each TMD are determined through minimizing a performance index of structural responses defined in the frequency domain.
TL;DR: In this article, a semi-active feedback control of seismic structures with variable friction dampers is proposed, which forms a semiactive feedback gain by multiplying an active gain with Heaviside functions.
Abstract: Although there are many well-established control methods for vibration mitigation of seismic structures with active devices, their direct application for structures with semi-active control devices are limited. This limitation is primarily contributed by the fact that a semi-active device can only provide a resistant (passive) force to the controlled structure. In this paper, a general method for semi-active feedback control of seismic structures with variable friction dampers (VFD) is proposed. In order to overcome the force limitation of friction dampers, the method forms a semi-active feedback gain by multiplying an active gain with Heaviside functions. Based on this method, two newly developed control laws, i.e., semi-active modal control and semi-active optimal control were numerically investigated. A multiple DOF structural system with various sensor deployments, for either full-state or direct-output feedbacks was considered in the numerical study. The performances of both semi-active control laws for seismic vibration mitigation were compared with those of passive and active controls. The numerical results showed that both semi-active controls resulted in better acceleration reductions than the passive case and were able to closely imitate the performance of their active control counterparts.
TL;DR: In this paper, a modal control scheme where the feedback gain is formulated in an augmented state space is proposed, which increases the number of controllable structural modes without adding extra sensors.
Abstract: In conventional methods of modal control, the number of controllable structural modes is usually restrained by the number of sensors that feedback the structural signals. In this paper a modal control scheme where the feedback gain is formulated in an augmented state space is proposed. The advantage of the proposed method is that it increases the number of the controllable modes without adding extra sensors. The method is verified experimentally by an earthquake simulation test with a full-scale building model. The proposed modal control was also compared with the conventional ones in the test. For the building model tested, the performance of the proposed control with only one feedback signal can be as efficient as that of modal control with full state feedback. Copyright © 2001 John Wiley & Sons, Ltd.
TL;DR: In this article, a control strategy called the least input energy control (LIEC) is proposed for a general variable-stiffness isolation system, which is able to determine the optimal isolation stiffness that minimizes the input seismic energy transmitted onto the isolated object.
TL;DR: In this article, the authors compared the acceleration response spectra with the design response spectras to detect the effects of near-fault ground motions on the collapsed buildings and classified the eventual forms of collapsed buildings into sit-down, knee-down and lie-down types.
Abstract: An earthquake with an epicenter offshore of Hualien City in eastern Taiwan occurred at midnight on February 6, 2018. The Richter magnitude (ML) of the earthquake was 6.26 and the seismic intensity ranged up to level VII, the strongest seismic intensity level regulated in Taiwan. Almost all the major damage resulting from this seismic event was occurred near both sides of the Milun Fault, where records from nearby strong motion stations displayed the characteristics of near-fault ground motions. The main seismic damage was the collapse of four buildings with soft bottom stories, one of which resulted in fourteen of the seventeen total fatalities. Comparing the acceleration response spectra with the design response spectra sheds light on the effects of near-fault ground motions on the collapsed buildings. Based on the eventual forms of collapsed buildings, building collapses that have generally led to major casualties in past seismic events around the world can be classified into sit-down, knee-down and lie-down types. In addition to the four collapsed buildings, seismic reconnaissance on other buildings, bridges, ports, and non-structural components have also been conducted. This study explores the issues and challenges arising from the reconnaissance results and thereby enhances learning from the seismic event.
TL;DR: In this article, a tuned mass-damper-inerter (TMDI) was proposed to suppress the oscillatory motion of stochastically support excited mechanical cascaded (chain-like) systems.
TL;DR: The review clearly demonstrates that the TMDs have a potential for improving the wind and seismic behaviors of prototype civil structures and shows that the MTMDs and d-MTMDs are relatively more effective and robust, as reported.
TL;DR: In this article, the optimum parameters of tuned mass dampers (TMD) are proposed under seismic excitations, and a Matlab program is developed for numerical optimization and time domain simulation.
TL;DR: A novel evolutionary algorithm of particle swarm optimization (PSO) is used for optimization of the required parameters of a TMD system attached to a viscously damped single degree-of-freedom main system.
TL;DR: By applying particle swarm optimization (PSO) algorithm as a novel evolutionary algorithm, the optimum parameters including the optimum mass ratio, damper damping and tuning frequency of the TMD system attached to a viscously damped single-degree-of-freedom main system subject to non-stationary excitation can be obtained when taking either the displacement or the acceleration mean square response, as well as their combination, as the cost function.
Abstract: There are many traditional methods to find the optimum parameters of a tuned mass damper (TMD) subject to stationary base excitations It is very difficult to obtain the optimum parameters of a TMD subject to non-stationary base excitations using these traditional optimization techniques In this paper, by applying particle swarm optimization (PSO) algorithm as a novel evolutionary algorithm, the optimum parameters including the optimum mass ratio, damper damping and tuning frequency of the TMD system attached to a viscously damped single-degree-of-freedom main system subject to non-stationary excitation can be obtained when taking either the displacement or the acceleration mean square response, as well as their combination, as the cost function For simplicity of presentation, the non-stationary excitation is modeled by an evolutionary stationary process in the paper By means of three numerical examples for different types of non-stationary ground acceleration models, the results indicate that PSO can be used to find the optimum mass ratio, damper damping and tuning frequency of the non-stationary TMD system, and it is quite easy to be programmed for practical engineering applications