Response Control Of Structures Research Articles

Mechanics performance test of MR damper and its application in structural seismic response control

Mechanics performance test of MR damper and its application in structural seismic response control

STUDIES ON ACTIVE CONTROL OF STRUCTURES USING HYPER VISION TECHNOLOGY

Vibration control technologies, both passive and active, have recently seen significant improvements due to technological advancements in computers, sensors, and actuators. Though passive control methods provide greater advantages in terms of maintenance and reliability, active methods are expected to be adopted for important civil engineering structures since they promise more effective structural response control. In this paper we investigate an active control method using hyper vision technology, and derive recurrence relations for time integration which include controlling forces. The feasibility of the active control method is confirmed by numerical simulations and by shaking table tests.

A new type of damper with friction-variable characteristics

Professor T. T. Soong is one of the early pioneers in field of earthquake response control of structures. A new type of smart damper, which is based on an Energy Dissipating Restraint (EDR), is presented in this paper. The EDR by Nims and Kelly, which has a triangle hysteretic loop, behaves like an active variable stiffness system (AVS) and possesses the basic characteristics of a linear viscous damper but has difficulty in capturing the output and large stroke simultaneously needed for practical applicataions in engineering structures. In order to overcome this limitation, the friction surface in the original Sumitomo EDR is divided into two parts with low and high friction coefficients in this paper. The results of finite element analysis studies show that the new type of smart friction damper enables large friction force in proportion to relative displacement between two ends of the damper and has a large allowable displacement to fit the demands of engineering applications. However, unlike the EDR by Nims and Kelly, this type of friction variable damper cannot self re-center. However, the lateral stiffness can be used to restore the structure. The nonlinear time history analysis of earthquake response for a structure equipped with the proposed friction variable dampers was carried out using the IDARC computer program. The results indicate that the proposed damper can successfully reduce the earthquake response of a structure.

Future Aspects of Structural Response Control and Base Isolation

Future Aspects of Structural Response Control and Base Isolation

Seismic Response Control of a Soft First-Story Building

A structure with a building plane 7.75 × 8.35 m, 47.8 m high, and having a height/width aspect ratio exceeding 6 has a building response that is difficult to control in both seismic and wind loading. We therefore changed the vibration mode from rocking to swaying by softening first-story translation stiffness and concentrating building deformation to make the first story energy-absorbing. The soft first-story structure we introduce involves (1) stiffening the structure above the second story, (2) making first-story columns laterally flexible and axially rigid, and (3) developing a response-hardening oil damper. The sections below detail these structural elements and dynamic response control performance against wind and seismic loading through time-history response analysis.

Benchmark structural control problem for a seismically excited highway bridge: Phase I and II

Benchmark problems in structural response control have served the international structural controls community as virtual test beds to compare different control algorithms since the first benchmark problem was proposed in 1996 through the sponsorship of the ASCE Structural Control Committee and Task Group on Benchmark Problems, the U.S. Panel on structural control, and International Association of Structural Control and Monitoring (IASCM). These problems offer well-developed models of structural system focusing on the response control of seismic and wind-excited buildings, seismically excited long-span cable-stayed bridges and seismically excited base-isolated buildings using prescribed earthquakes and standard set of evaluation criteria. They have been used by the entire community of researchers, educators, students and practitioners to investigate numerous control devices and algorithms. In 2004, the authors, in collaboration with Professor Ping Tan of Guangzhou University in China and Professor Jian Zhang of the University of California, Los Angeles, developed the benchmark structural control problem for a seismically excited highway bridge through the sponsorship of the ASCE committee on Structural Control and Task Group on Benchmark Problems, the U.S. Panel on structural control and International Association of Structural Control and Monitoring (IASCM). This special issue focuses on contributions to this benchmark structural control problem for a seismically excited highway bridge. Copyright © 2009 John Wiley & Sons, Ltd.

Application of lattice probabilistic neural network for active response control of offshore structures

The reduction of the dynamic response of an offshore structure subjected to wind-generated random ocean waves is of extreme significance in the aspects of serviceability, fatigue life and safety of the structure. In this study, a new neuro-control scheme is applied to the vibration control of a fixed offshore platform under random wave loads to examine the applicability of the proposed method. It is called the Lattice Probabilistic Neural Network (LPNN), as it utilizes lattice pattern of state vectors as the training data of PNN. When control results of the LPNN are compared with those of the NN and PNN, LPNN showed better performance in effectively suppressing the structural responses in a shorter computational time.

Active control of large structures using a bilinear pole-shifting transform with [formula omitted] control method

A bilinear pole-shifting technique with H ∞ control method is proposed for the dynamic response control of large structures. The proposed control method is a direct pole-placing design approach which can make the structural systems have a certain target damping ratio. The performance requirement is considered as a target damping ratio. And a bilinear transform is adopted to locate the closed-loop poles in a specific region within the H ∞ controller design framework. The relationship between the closed-loop poles and the transform parameters is derived as a quadratic form, which leads to a new non-iterative design procedure. Moreover, robust control features can be incorporated within the H ∞ robust control framework. Thus, the proposed technique effectively combines the desirable features of pole placement and H ∞ control method. To prove the validity of the proposed control method, example designs and numerical simulations of earthquake-excited ten-story buildings are performed and comparative results are presented.

Control Structure Interaction of Electromagnetic Mass Damper System for Structural Vibration Control

To investigate the effect of control-structure-interaction (CSI) between the innovative electromagnetic mass damper (EMD) control system and the test structure, three computational models are first developed in this paper. Then, typical driving voltages are applied to the servo-amplifier of the EMD system to excite the structure and to examine the dynamic behavior of the EMD system when it is implemented into the structure. Furthermore, the test results are compared with the predictions based on the proposed parametric models, namely on-line examination. Finally, shaking table tests of structural seismic response control employing the EMD control system are conducted to validate and compare the effectiveness of those parametric models. All the test results have shown that only when the CSI effect (especially the higher-order CSI effect) is fully considered, can the on-line dynamical property of the EMD system be accurately predicted and its control performance fully exerted. This is essential to achieve the highest performance when employing such EMD systems in suppressing structural vibrations.

Seismic Response Control of Building Structures with Superelastic Shape Memory Alloy Wire Dampers

This paper presents a simulation-based benchmark control study in which shape memory alloy (SMA) wire dampers are utilized to control the seismic response of a three-story nonlinear steel frame building. The SMA wire damper uses superelastic Nitinol wires for energy dissipation because of its high fatigue life and large recoverable strain. An analytical model which considers the training effect of SMA wires is used to describe the stress-strain relationship of superelastic SMA wires. The performance of SMA wire dampers is investigated in the framework of the third-generation benchmark problem on structural control. A comparative study of the seismic response control performance of SMA wire dampers with either unprestrained or prestrained SMA wires was also conducted. The results of this simulation-based benchmark control study show that SMA wire dampers, as a passive structure control measure, can effectively reduce the seismic responses of the three-story nonlinear benchmark building structure and has the potential to withstand several design earthquakes without the need for repair.

A STUDY ON CONTROL METHOD BY MAGNETO RHEOLOGICAL FLUID DAMPER IN BASE ISOLATED STRUCTURES

Recently, study on structural control with semi-active damping devices is focused. The semi-active damping devices can vary their damping characteristics without large power source and improve seismic response of building. MR damper (Magneto rheological fluid damper) is one of the suitable devices for semi-active seismic response control of structures. The purpose of this study is to develop a simple and effective semi-active control method to reduce seismic response of base isolated structures by MR damper. Proposed method is based on the response displacement of base story. By applying this control method, the displacement and acceleration response can be reduced with relatively smaller damper force.

추계학적 선형화 방법 및 다목적 유전자 알고리즘을 이용한 지진하중을 받는 인접 구조물에 대한 비선형 감쇠시스템의 최적 설계

Optimal design method of nonlinear damping system for seismic response control of adjacent structures is studied in this paper. The objective functions of the optimal design are defined by structural response and total amount of the dampers. In order to obtain a solution minimizing two mutually conflicting objective functions simultaneously, multi-objective optimization technique based on genetic algorithm is adopted. In addition, stochastic linearization method is embedded into the multi-objective framework to efficiently estimate the seismic responses of the adjacent structures interconnected by nonlinear hysteretic dampers without performing nonlinear time-history analyses. As a numerical example to demonstrate the effectiveness of the proposed technique, 20-story and 10-story buildings are considered and MR dampers of which hysteretic behaviors vary with the magnitude of the input voltage are considered as nonlinear hysteretic damper interconnecting two adjacent buildings. The proposed approach can provide the optimal number and capacities of the MR dampers, which turned out to be more economical than the uniform distribution system while maintaining similar control performance. The proposed damper system is verified to show more stable performance in terms of the pounding probability between two adjacent buildings. The applicability of the proposed method to the design problem for optimally placing semi-active control system is examined as well.

Towards error‐free hybrid simulation using mixed variables

AbstractTwo procedures are developed and implemented in a hybrid simulation system (HSS) with the aim of enhancing the accuracy and reliability of the online, i.e. pseudo‐dynamic, test results. The first procedure aims at correcting the experimental systematic error in executing the displacement command signal. The error is calculated as the difference between command and feedback signals and correlated to the actuator velocity using the least‐squares method. A feed‐forward error compensation scheme is devised leading to a more accurate execution of the test. The second procedure employs mixed variables with mode switching between displacement and force controls. The newly derived force control algorithm is evaluated using a parametric study to assess its stability and accuracy. The implementation of the mixed variables procedure is designed to adopt force control for high stiffness states of the structural response and displacement control otherwise, where the resolution of the involved instruments may favour this type of mixed control. A simple pseudo‐dynamic experiment of steel cantilever members is used to validate the HSS. Moreover, two experiments as application examples for the two developed procedures are presented. The two experiments focus on the seismic response of (a) timber shear walls and (b) reinforced concrete frames with and without unreinforced masonry infill wall. Copyright © 2007 John Wiley & Sons, Ltd.

준능동 동조질량감쇠기의 탄성 및 비탄성 지진응답 제어성능 평가

본 연구에서는 지진하중을 받는 탄성 및 비탄성 구조물에 대하여 수동 및 준능동 TMD의 지진응답제어성능을 평가하였다. 먼저 기존의 연구에서 제안된 식을 사용하여 최적 설계된 수동형 TMD와 본 연구에서 제시된 준능동 TMB가 설치된 탄성 구조물의 변위스펙트럼을 구하였으며, 준능동 TMD가 TMD보다 작은 스트로크를 가지고도 최대변위응답제어에 있어 우수함을 확인하였다. 또한 구조물의 주기와 TMD의 주기가 일치하지 않은 경우의 성능저하에 대한 TMD의 강인성을 평가하였다. 최종적으로 Bouc-Wen 모델을 사용하여 모사된 비탄성이력 특성을 가지는 구조물에 대한 수치해석을 수행하였으며, 이를 통해 탄성구조물에 대하여 최적화된 수동형 TMD의 성능은 구조물 응답의 비탄성이력 부분이 증가함에 따라 크게 저하되는 반면 준능동 TMD는 수동형 TMD보다 약 15-40% 정도의 더 많은 응답감소효과를 가짐을 확인하였다. In this study, tile performance of a passive tuned mass damper (TMD) and a semi-active tuned mass damper (STMD) was evaluated in terms of seismic response control of elastic and inelastic structures under seismic loads. First, elastic displacement spectra were obtained for the damped structures with a passive TMD, which was optimally designed using the frequency and damping ratio presented by previous study, and with a STMD proposed in this study. The displacement spectra confirm that STMD provides much better control performance than passive md with less stroke. Also, the robustness or the TMD was evaluated by off-tuning the frequency of the TMD to that of the structure. Finally, numerical analyses were conducted for an inelastic structure of which hysteresis was described by Bouc-Wen model and the results indicated that the performance of the passive TMD of which design parameters were optimized for a elastic structure considerably deteriorated when the hysteretic portion or the structural responses increased, while the STMD showed about 15-40% more response reduction than the TMD.

Structures with Semiactive Variable Stiffness Single/Multiple Tuned Mass Dampers

This paper proposes application of single and multiple semiactive variable stiffness tuned mass dampers (STMD/SMTMD) for response control of multistory structures under several types of excitation. A new semiactive control algorithm is developed based on real-time frequency tracking of excitation signal by short time Fourier transform. A parametric study is performed in the frequency domain to investigate the dynamic characteristics and effectiveness of STMDs. Time history responses of single-degree-of-freedom and five-degree-of-freedom structures equipped with STMDs at the roof level, subjected to harmonic, stationary, and nonstationary excitations are presented. STMD/SMTMD are most effective when they have low damping ratios and the excitation frequency can be tracked. They are superior than their passive counterparts in reducing the response of the main structure both under force and base excitations. In case the fundamental frequency changes due to damage or deterioration of the main structure then th...

Seismic response control of a building complex utilizing passive friction damper: Analytical study

Control of structural response due to seismic excitation in a manner of coupling adjacent buildings has been actively developed, and most attention focused on those buildings of similar height. However, with the rapid development of some modern cities, multi-story buildings constructed with an auxiliary low-rise podium structure to provide extra functions to the complex become a growing construction scheme. Being inspired by the positively examined coupling control approach for buildings with similar height, this paper aims to provide a comprehensive analytical study on control effectiveness of using friction dampers to link the two buildings with significant height difference to supplement the recent experimental investigation carried out by the writers. The analytical model of a coupled building system is first developed with passive friction dampers being modeled as Coulomb friction. To highlight potential advantage of coupling the main building and podium structure with control devices that provide a lower degree of coupling, the inherent demerit of rigid-coupled configuration is then evaluated. Extensive parametric studies are finally performed. The concerned parameters influencing the design of optimal friction force and control efficiency include variety of earthquake excitation and differences in floor mass, story number as well as number of dampers installed between the two buildings. In general, the feasibility of interaction control approach applied to the complex structure for vibration reduction due to seismic excitation is supported by positive results.

Improvement and Assessment of Neural Networks for Structural Response Prediction and Control

In an extension of a previous paper, prediction accuracy is improved for neural networks to be used as part of an adaptive structural control system. This improvement will enable reliable predictions of performance variables such as displacements and control forces further into the future. This allows more lead time for controller adjustment should a performance variable be predicted to violate a prescribed constraint. The improved prediction accuracy is due to the use of the Levenberg–Marquardt algorithm in training the neural network and the use of a single neural network for more than one performance variable simultaneously. With these improvements, far fewer iterations (and more importantly less computer processor time) are used in the neural network training, and most importantly the prediction accuracy is greatly improved. These improved neural network predictions are then compared to other prediction methods: a polynomial fit of past data and the use of the state transition matrix.

Approximate analysis method for interstorey shear forces in structures with active variable stiffness systems

It has been demonstrated that active variable stiffness (AVS) systems may be effective for response control of building structures subjected to earthquake excitations. Because the performance of structures with AVS systems exhibits strong nonlinearity, the classical dynamic analysis method for linear structures, such as the mode-superposition method, is not applicable to structures with AVS systems. In this paper, an approximate analysis method is proposed for the maximum interstorey shear forces in structures with AVS systems. Firstly, a new equivalent relationship between single-degree-of-freedom (sdof) structures with AVS systems and so-called fictitious linear structures is established. Then, the new equivalent relationship is used to revise the approximate-mode-superposition (AMS) approach for multi-degree-of-freedom (mdof) structures with AVS systems, which was previously suggested by the authors. Subsequently, extensive numerical studies are conducted using the revised AMS approach for building structures equipped with AVS systems and subjected to different types of artificial earthquake excitations. Based on the simulation results, an approximate analysis method is proposed for the maximum interstorey shear forces in structures with AVS systems. The maximum interstorey shear forces in example structures subjected to actual earthquake excitations are obtained using the proposed method, and the results are compared with those obtained using the time-history analysis method. It is shown that the results estimated using the proposed method generally agree well with those obtained using the time-history analysis method.

周囲拘束型鉛ダンパーの減衰性能に関する実験的研究

This paper presents the damping performance characteristics of Peripheral Restraining Lead Damper, which is a hysteretic type damper used for the seismic structural response control and consists of the lead plug and the projective bond plates pressed into the hole of hexahedron laminated rubbers. As a result of dynamic tests, the damping performance characteristics depend on the amount of cumulative hysteretic energy absorption, the environmental temperature, the excitation frequency, and the shear deformation specified. Considering these dependencies, the new analytical hysteresis model was presented, and it was confirmed that the model had enough accuracy from the engineering viewpoint to reproduce the experimental results.

Bounded nonlinear stochastic control based on the probability distribution for the sdof oscillator

In the response control of building structures subjected to strong excitations, the controller saturation problem needs be considered in the design stage. The nonlinearity of saturated controllers, however, makes the exact probabilistic evaluation of control effectiveness difficult. In this study, a stochastic nonlinear control algorithm with bounded control force is proposed and the closed-loop system's joint probability density function (PDF) governed by the reduced Fokker–Planck equation is derived. Based on the derived joint PDF, the bound of the control force that restricts the first-passage failure probability of the displacement response to a prescribed value is determined. Numerical analyses results show that the proposed controller reduces the maximum required control force considerably compared to the linear controller for the same displacement reduction, and the proposed approximation of the failure probability is considerably accurate.