• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2005.04a
• /
• pp.209-216
• /
• 2005

The controller that can control the smart base isolation system consisting of M damper and friction pendulum systems(FPS) is developed in this study. A fuzzy logic controller (FLC) is used to modulate the M damper force because the FLC has an inherent robustness and ability to handle non-linearities and uncertainties. A genetic algorithm (GA) is used for optimization of the FLC. When earthquake excitations are applied to the structures equipped with smart base isolation system, the relative displacement at the isolation level as well as the acceleration of the structure should be regulated under appropriate level. Thus, NSGA-II(Non-dominated Sorting Genetic Algorithm) is employed in this study as a multi-objective genetic algorithm to meet more than two control objectives, simultaneously. NSGA-II is used to determine appropriate fuzzy control rules as well to adjust parameters of the membership functions. Effectiveness of the proposed method for optimal design of the FLC is judged based on computed responses to several historical earthquakes. It has been shown that the proposed method can efficiently find Pareto optimal sets that can reduce both structural acceleration and base drift from numerical studies.

• Geomechanics and Engineering
• /
• v.14 no.2
• /
• pp.161-174
• /
• 2018

The present study investigates the soil-structure interaction (SSI) effects on the seismic performance of smart base-isolated structures. The adopted control algorithm for tuning the control force plays a key role in successful implementation of such structures; however, in most studied carried out in the literature, these algorithms are designed without considering the SSI effect. Considering the SSI effects, a linear quadratic regulator (LQR) controller is employed to seismic control of a smart base-isolated structure. A particle swarm optimization (PSO) algorithm is used to tune the gain matrix of the controller in both cases without and with SSI effects. In order to conduct a parametric study, three types of soil, three well-known earthquakes and a vast range of period of the superstructure are considered for assessment the SSI effects on seismic control process of the smart-base isolated structure. The adopted controller is able to make a significant reduction in base displacement. However, any attempt to decrease the maximum base displacement results in slight increasing in superstructure accelerations. The maximum and RMS base displacements of the smart base-isolated structures in the case of considering SSI effects are more than the corresponding responses in the case of ignoring SSI effects. Overall, it is also observed that the maximum and RMS base displacements of the structure are increased by increasing the natural period of the superstructure. Furthermore, it can be concluded that the maximum and RMS superstructure accelerations are significant influenced by the frequency content of earthquake excitations and the natural frequency of the superstructure. The results show that the design of the controller is very influenced by the SSI effects. In addition, the simulation results demonstrate that the ignoring the SSI effect provides an unfavorable control system, which may lead to decline in the seismic performance of the smart-base isolated structure including the SSI effects.

• Smart Structures and Systems
• /
• v.6 no.1
• /
• pp.57-72
• /
• 2010

This paper presents the most significant results obtained within a broad-ranging experimental program aiming to evaluate both the effectiveness and the robustness of a Base Isolation (BIS) and a Tuned Mass Damper (TMD) combined control strategy (BI & TMD). Following a brief description of the experimental model set-up and the adopted kinematic scaling technique, this paper describes the identification procedures carried out to characterize the system''s model. The dynamic response of a small-scale model to recorded earthquake excitations, which has been scaled by using the Buckingham pi-theorem, are later presented and discussed. Finally, the effectiveness and robustness of the combined control strategy is evaluated by comparing the model's dynamic response. In particular, reduction in relative displacements and absolute accelerations due to the application of different mass damping systems is investigated.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.17 no.5
• /
• pp.13-20
• /
• 2013

In order to reduce seismic responses of a structure, additional dampers and vibration control devices are generally considered. Usually, control performance of additional devices are investigated for optimal design without variation of characteristics of a structure. In this study, multi-objective integrated optimization of structure-smart control device is conducted and possibility of reduction of structural resources of a building structure with smart top-story isolation system has been investigated. To this end, 20-story example building structure was selected and an MR damper and low damping elastomeric bearings were used to compose a smart base isolation system. Artificial earthquakes generated based on design spectrum of low-to-moderate seismicity regions are used for structural analyses. Based on numerical simulation results, it has been shown that a smart top-story isolation system can effectively reduce both structural responses and isolation story drifts of the building structure in low-to-moderate seismicity regions. The integrated optimal design method proposed in this study can provide various optimal designs that presents good control performance by appropriately reducing the amount of structural material and damping device.

• Computational Structural Engineering
• /
• v.27 no.1
• /
• pp.16-25
• /
• 2014

• Smart Structures and Systems
• /
• v.2 no.4
• /
• pp.329-337
• /
• 2006

This paper illustrates an analytical investigation of the vibration parameters of buildings on sliding seismic isolation bearings with elastic limiters of the relative displacement. The installation scheme of sliding bearings and elastic limiters for the separate unit of a 4 storey hospital building with brick walls is designed. The analysis of the vibrations of the hospital building is conducted for harmonic base excitation.

• Smart Structures and Systems
• /
• v.29 no.4
• /
• pp.549-560
• /
• 2022

The optimum damping and tuning frequency ratio of the tuned mass damper-inerter (TMDI) for the base-isolated structure is obtained using the numerical searching technique under stationary white-noise and filtered white-noise earthquake excitation. The minimization of the isolated structure's mean-square relative displacement and absolute acceleration, as well as the maximization of the energy dissipation index, were chosen as the criteria for optimality. Using a curve-fitting technique, explicit formulae for TMDI damping and tuning frequency for white-noise excitation are then derived. The proposed empirical expressions for TMDI parameters are found to have a negligible error, making them useful for the effective design of base-isolated structures. The effectiveness of TMDI and its optimum parameters are influenced by the soil condition and isolation frequency, according to the comparison made of the optimized parameters and response with different soil profiles. The effectiveness of an optimally designed TMDI in controlling the displacement and acceleration response of the flexible isolated structure under real and pulse-type earthquakes is also observed and found to be increased as the inertance mass ratio increases.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.9 no.2 s.42
• /
• pp.37-46
• /
• 2005

To date, many viable smart base isolation systems have been proposed and investigated. In this study, a novel friction pendulum system (FPS) and an MR damper are employed as the isolator and supplemental damping device, respectively, of the smart base isolation system. A fuzzy logic controller (FLC) is used to modulate the MR damper because the FLC has an inherent robustness and ability to handle non linearities and uncertainties. A genetic algorithm (GA) is used for optimization of the FLC. The main purpose of employing a GA is to determine appropriate fuzzy control rules as well to adjust parameters of the membership functions. To this end, a GA with a local improvement mechanism is applied. This method is efficient in improving local portions of chromosomes. Neuro fuzzy models are used to represent dynamic behavior of the MR damper and FPS. Effectiveness of the proposed method for optimal design of the FLC is judged based on computed responses to several historical earthquakes. It has been shown that the proposed method can find optimal fuzzy rules and the GA optimized FLC outperforms not only a passive control strategy but also a human designed FLC and a conventional semi active control algorithm.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.24 no.4
• /
• pp.169-178
• /
• 2020

In a previous paper, ambient vibration tests were conducted on a cable stayed bridge with resilient-friction base isolation systems (R-FBI) to extract the dynamic characteristics of the bridge and compare the results with a seismic analysis model. In this paper, a nonlinear seismic analysis model was established for analysis of the bridge to compare the difference in seismic responses between nonlinear time history analysis and multi-mode spectral analysis methods in the seismic design phase of cable supported bridges. Through these studies, it was confirmed that the seismic design procedures of the "Korean Highway Bridge Design Code (Limit State Design) for Cable Supported Bridges" is not suitable for cable supported bridges installed with R-FBI. Therefore, to reflect the actual dynamic characteristics of the R-FBI installed on cable-supported bridges, an improved seismic design procedure is proposed that applies the seismic analysis method differently depending on the seismic isolation effect of the R-FBI for each seismic performance level.

• Smart Structures and Systems
• /
• v.20 no.3
• /
• pp.303-309
• /
• 2017

Structural control through seismic isolation using elastomeric rubber bearing, which is also known as High Damping Rubber Bearing (HDRB), has seen an increase in use to provide protective from earthquake, especially for new buildings in earthquake zones. Besides, HDRB has also been used in structural rehabilitation of older yet significant buildings, such as museums and palaces. However, the present design approach applied in normal practice has often resulted in dissimilar HDRB dimension requirement between structural designers and bearing manufacturers mainly due to ineffective communication. Therefore, in order to ease the design process, most HDRB manufacturers have come up with catalogs that list all necessary and relevant product lines specifically for structural engineers to choose from. In fact, these catalogs contain physical dimension, compression property, shear characteristic, and most importantly, the total rubber thickness. Nonetheless, other complicated issues, such as the relationship between target isolation period and displacement demand (which determines the total rubber thickness), are omitted due to cul-de-sac fixing of these values in the catalogs. As such, this paper presents a formula, which is derived and extended from the present design approach, in order to offer a simple guideline for engineers to estimate the required HDRB size. This improved design formula successfully minimizes the discrepancies stumbled upon among structural designers, builders, and rubber bearing manufacturers in terms of variation order issue at the designing stage because manufacturer of isolator is always the last to be appointed in most projects.