No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Active Vibration Control for Base-Isolated Structures Using a PID Controller against Earthquakes
Abstract
In this paper, a closed loop control approach for controlling the vibration of buildings under earthquake excitations is introduced. An active hybrid control combining base isolation and active tuned mass damper (AMD) installed on the lowest floor of a base-isolated frame building is investigated. The Active control force is controlled by the mean of a proportional–integral–derivative (PID) controller, incorporated with a negative feedback error closed loop. The difference between the base displacement and equilibrium position of the structure is used to evaluate the error and feed the PID controller. A simulation is carried out on a six degrees of freedom base-isolated frame structure using MATLAB. The performances of the proposed active hybrid control system are tested under El Centro, Northridge, and Loma Pietra earthquakes.Compared results with base-isolated structure and base-isolated structure equipped with a passive and active tuned mass damper (TMD)/ (ATMD) showed that the active hybrid control system is more efficient. A reduction of 70% in base displacement, velocity and 15% in base acceleration is obtained.
... Others proposed a seismic hybrid control systems for a flexible and rigid structures using a modified linear quadratic controller developed by [8] . To overcome limitations of the passive TMD, especially the detuning phenomena and the large space needed, many efforts have been made to enhance the system performance by incorporating an active [9] or semi-active control to the purely passive TMD device [10,11] . Tested the performance of using an active tuned mass damper on the top of the building where the force is controlled using fuzzy logic and genetic algorithm. ...
The aim of the present research is to verify the effectiveness of a hybrid control strategy. The hybrid control consists of a seismic isolation device and non-traditional tuned mass damper (TMD). In the evaluation, the study was conducted for structures with a ten-story reinforced concrete buildings exposed to various far-field and near-field earthquake records. The structure is modeled as a system with two degrees of freedom. One degree of freedom reflects the main structure and the other degree of freedom represents the auxiliary system, and the Bouc-Wen model is used to describe the hysteresis behavior of the base insulator. The results of the study clearly confirmed that the response of high-rise buildings during earthquakes could be significantly reduced using base isolation devices and TMDs. Buildings analyzed in the study, the application of TMD alone resulted in a reduction not larger than 20%, as compared to the response without any system. On the other hand, the response of buildings equipped with only base isolation devices was reduced by more than 35% under different ground motions. However, the largest reductions (larger than 50%) were obtained for the cases when both control systems (base isolation and TMDs) were used simultaneously.
... While the TMDs systems have been demonstrated to be effective when the device's natural frequency is close to the excitation frequency, some inherent limitations of this device can be mentioned. A TMD's effectiveness is highly dependent on its mass ratio (i.e., the ratio between physical masses of secondary and primary structure) [6,9]. A large TMD mass is usually required to achieve the desired control performance, which is challenging for engineers regarding space requirement, vertical loadings, and construction cost. ...
Tuned mass damper inerter (TMDI) is commonly reported to be a lightweight tunable device that can significantly reduce buildings' seismic response. However, the backward action produced by the inerter and returned to the building in conventional TMDIs may either reduce the device performance or limit the inerter potential. This study proposes and investigates a novel control scheme using large physical mass ratios generated by lightweight inerters. Hence, a double mass tuned damper inerter (DMTDI) is formulated. The proposed control scheme consists of two TMDs placed at the roof of the building and connected via an inerter. Thus, the inerter backward action is transmitted to the secondary mass instead of the building. Both TMDI and DMTDI parameters are optimized using a genetic algorithm (GA). The top floor displacement transfer function's H2- norm is considered as the objective function for minimization. The optimally tuned devices are then tested under one hundred (100) near and far-field ground motions. The results obtained show a significant response improvement in peak displacement, acceleration, and base shear. The structure energy is also investigated; the lowest energy response in the studied structure is observed while using the proposed DMTDI scheme.
... In recent years, seismic vibration control constituted a field of interest for a large number of researchers. The motivation behind such interest is the protection of lives and structures against earthquakes; this can be achieved by introducing passive, active, or semi-active control devices [1,2]. ...
The recent earthquakes history shows that the conception of resistant, safe, and economical structures is daily challenges for structural engineers. Among the newest vibration control devices figures the inerter which is a device capable of developing a large fictive mass using rotational inertia. In this research work, a conventional passive tuned mass damper (TMD) is compared with an inerter based mass damper (TMDI) which consists of tuned mass damper attached to an inerter. The two devices are used to control the vibration of a base-isolator structure (BI) submitted to earthquake excitations. For this purpose, an eight (8) storey structure is equipped with a (TMDI) at the base floor compared with case TMDI in zeros inertance case TMD, the inerter is fixed to the (TMD) on one side and grounded on the second side. A set of dynamic parameters are optimized by exploring predefined bounds, the optimal parameters (frequency tuning, damping tuning, inertance ratio, mass ratio) are then used to confirm and perform a time history analysis is under different earthquake records. The obtained results demonstrated good performance and effectiveness of the structure equipped with a (TMDI) in terms of bearing displacement as well as top floor acceleration.
... It is constituted of a moving mass attached to the structure through a spring and a dashpot, the frequency of the TMD as a single degree of freedom system is tuned to the frequency of the main structure, with the participation of it mass inertia the TMD acts as a restoring force to prevent large displacement of the main structure during dynamical loading (wind, earthquake) [4,5]. Hence, it is obvious that TMD requires relatively a large mass to achieve a response reduction, which may constitute a structural problem in terms of space, vertical load and even cost [6]. ...
The introduction of improved structural control systems is an efficacious solution for reducing the seismic damage induced to structures. Due to the high development in control systems and the growing interest for this research area, multiple control devices were developed , tested and used with a remarkable efficiency. During the last few years, a novel passive damper, called inerter has been introduced, mainly known for its ability to develop a large fictive mass and largely used in combination with tuned mass damper TMD resulting in a TMD-Inerter device. This research work presents a double tuned mass damper inerter DTMDI, which consists of two masses connected with an inerter, this configuration will result in large fictive mass ratio without any retroaction force on the structure. The effectiveness of the double tuned mass damper inerter DTMDI has been demonstrated using a multi-degree of freedom structure submitted to seismic excitations. The results obtained show a significant response reduction compared to simple tuned mass damper inerter TMDI and classical tuned mass damper TMD. The dynamical parameters investigated in this study are the top floor displacement , top floor acceleration, inter-story drift and base shear. The study also underlines optimal parameters for the double tuned mass damper inerter DTMDI.
... Contrary to the above mentioned RK4M method, SMD is adopted to solve equations (2.1) to (2.3) by logically connecting Simulink built-in blocks. Referring to researchers in [12,[32][33][34][35][36][37], equations (2.1) to (2.3) can be combined into a single equation (2.21) to represent the structure as a whole, and then transformed into a state-space form of first order equations i.e., a continuous-time state-space model of the system as shown in equations (2.22) and (2.23). ...
Numerical studies for a structural dynamic system are performed in Matlab and Simulink environments. Six different earthquakes filtered and corrected using Seismosignal software, are used as seismic loads during implementation. In the first part of this study, the fourth order Runge-Kutta based Matlab code (RK4M) and Simulink Model-Based Design (SMD) are appropriately developed. Both RK4M and SMD are used to solve the governing equations for single storey structure isolated by Lead Core Rubber Bearing (LCRB). The second part compares the developed modelling methods in terms of outputs’ accuracy and Time of Implementation (TI). It is shown that both methods agree well in terms of resulting floor accelerations and displacements with slight but justifiable average differences of only 1.3 and 0.98 % respectively; thus, indicating that any of these techniques can be adopted. However, concerning TI, it is observed that SMD is in general quicker to display results as compared to the developed RK4M, which is approximately 58s longer. This leads to suggesting that SMD can be more effective, particularly for earthquakes with long-duration, and most importantly for cases where time is a governing factor during implementation. Besides, long-period and long-duration earthquakes are observed to have particular influence on structural behaviour. This reveals a need for special consideration requirements that are currently not taken into account.
... Where, M, K, C, are masse, stiffness and damping matrices of the system respectively, r is influence vector. In control theory; the governing Eq. (1) can be written in state-space form as [1,10]: ...
Base isolation (BI) is a worldwide used protection strategy known by its effectiveness in decreasing the earthquake responses of buildings. The principal of BI functioning is decoupling the structure from the foundations using highly deformable material. Hence, the earthquake motion cannot be transmitted to the superstructure. However, this system may show some limitation in high-rise buildings or during strong near fault earthquakes, mainly large displacement. Some researchers suggested the installation of a tuned mass damper (TMD) to reduce the large displacement that may occur in a base isolated structure. A Tuned mass damper (TMD) consists of a mass, spring and a dashpot that are attached to the structure in order to reduce it vibrations. In this study, a hybrid control system combining a base isolation system and TMD is studied. The numerical simulation is performed on a 10 story isolated building submitted to different earthquakes (El Centro, Chi Chi , Erzikan , Kocaeli , Loma prieta), a comparative study is conducted between the base isolated building and the building equipped with a hybrid system consisting of a base isolation and a TMD. The obtained results show a good performance of the hybrid system compared to the isolation system and, in terms of base and top displacements as well as the inter-storey drift, and finally the base shear force.
... They used a benchmark bridge (bridge deck) for numerical validation of their control algorithm as shown in Fig. 12. A closed loop control approach for controlling the vibration of buildings under earthquake excitations was presented in [20]. Active vibration control for seismic excited building structures in presenting of actuator saturation, stochastic measurement noise and quantization was proposed in [21] (see Fig. 13). ...
This paper is written to present the state of the art of the new active and semi active approaches during the last decade. This is achieved by reviewing the active control approaches and semi-active control policies that have been proposed and validated analytically or numerically in the last ten years. All the papers reviewed in this study are within the scope of earthquake engineering. Brief information about these active control approaches and some of the resulting control policies are presented. To be able to show the effectiveness of the proposed approaches, the numerical examples of these papers are presented in this study. Because of the latest technological and computational advances, some of the most effective and complex algorithms have been studied and numerically validated during the last decade in earthquake engineering. This is the reason that this review considers the period of 2008-2018. The authors also include some of the new semi-active control policies that have been proposed numerically during the last decade. It has been concluded that, although there is an impressive research on numerically and/or analytically validating new active control approaches and new semi-active control policies of the years 2008-2018, there is not any real-building / real structure implementation of these active control approaches. Additionally there is a need of experimental validation of these active control methods that have been presented during the last decade.
... Tuned mass dampers (TMDs) are considered as one of the most used passive control devices; it consists of a mass connected to the primary structure by a spring and a viscous damper. TMDs have been employed in a large number of structures around the word [1]. The formulation for a classic TMD design is described by Den Hartog [2]. ...
Seismic control of adjacent buildings has received considerable attention in recent years because of two reasons: i) for the control of the response of the two buildings simultaneously by a single control device and ii) for the reduction of the possibility of interaction between the two buildings. Various types of coupling devices have been introduced and their effectiveness in controlling the responses of the adjacent building is studied. Out of the different types of the coupling devices, MR damper is one which is widely investigated. In this paper, the responses of the two buildings are controlled by using two strategies: i) a shared tuned mass damper (TMD) and ii) a hybrid system using both a TMD and a MR damper. The shared TMD is mounted such that it can effectively control the responses of both buildings and it is tuned to the fundamental frequencies of (i) the coupled structure and (ii) the two adjacent buildings vibrating separately. The shared TMD has the obvious advantage that the two separate TMDs are not required to control the two buildings separately. The response control includes the control of the top story displacement, base shear and maximum drift. Results of the study show that i) a shared TMD can provide adequate response reduction compared to that obtained by using two TMDs separately, ii) the frequency ratio between the two adjacent building is the most important parameter which dictates the response reduction, iii) the hybrid control provides a significant improvement in response reduction over that obtained by a shared TMD alone.
... To overcome limitations of the passive TMD, especially the detuning phenomena and the large space needed, many efforts have been made to enhance the system performance by incorporating an active [15] or semi-active control to the purely passive TMD device. [28,29] Tested the performance of using an active tuned mass damper on the top of the building where the force is controlled using fuzzy logic and genetic algorithm. ...
This paper deals with the efficiency of a hybrid vibration control for rigid buildings
structures under earthquakes. The hybrid control consists of a base isolator and tuned mass
damper (TMD) or active tuned mass damper (ATMD). The active control force is calculated
within a feedback loop by the mean of the linear quadratic controller (LQR) designed to
penalize the displacement and the velocity of the floor on which the ATMD is installed. A
total of four cases are studied based on the placement and the type of the control system
either passive TMD or active TMD. The lower and top floor alternatively carries the TMD
control system. The case of a rigid six-degree of freedom base isolated frame structure
illustrates the effectiveness of the hybrid control through simulations. Simulation results,
obtained from real time-history data of three earthquakes (El Centro, Northridge and Loma
Prieta) show that the proposed control is effective. The hybrid control system is able to
reduce the vibration amplitudes especially the base isolator displacement and acceleration
without affecting the super-structure response regardless of the placement of the TMD
control system. Such a hybrid control system can protect high importance buildings
containing sensitive equipment.
In this study, the combination of magnetorheological dampers and tuned mass dampers (MR + TMD) as a hybrid control system is investigated on a 15-story shear building where MR damper is attached to the TMD to generate active control force of TMD. The seismic responses of the structure are reduced by employing MR + TMD on rooftop of the structure. The MR damper's control voltage is generated by combining IT2FLC and FOPID. The FOPID + IT2FLC, TMD, and control voltage parameters are optimized using the observer-teacher-learner-based optimization (OTLBO) algorithm to minimize the maximum displacement of the building rooftop under far-field and near-field earthquake excitations. To conduct additional research, the same method was used to mitigate structural responses for PID, FOPID, IT2FLC, and a combination of fuzzy logic type-1 (FLC) and FOPID (FOPID + FLC). All of these controllers' performances in mitigating seismic responses are compared to those of the uncontrolled system and to each other. The results indicate that FOPID + IT2FLC outperforms PID, FOPID, and FOPID + FLC controllers. Additionally, the building's rooftop displacement was reduced by an average of 35.06% using the FOPID + IT2FLC system for sixteen far-field and near-field earthquake records. Moreover, the hybrid MR + TMD system performs better than other conventional controllers.
This paper presents a sensitivity analysis on the performance of optimal proportional-integral-derivative (PID) controller for use in nonlinear smart base-isolated structures with uncertainties. A set of nine performance indices is defined to evaluate the performance of the controller in the presence of uncertainties in the superstructure, lead rubber bearing (LRB) seismic isolation system, and applied loads. The time delay effect on the stability and performance of the PID controller is also examined. The results show that the PID controller is robust against the uncertainties up to ±15% in the damping and stiffness coefficients of the superstructure, the yield force of the LRB and the artificial earthquake. In the case with ±15% of uncertainty, the input energy entering into the structure is increased with respect to the nominal model. However, the changes of the performance indices related to the damage energies are negligible. An uncertainty of -20% in the stiffness coefficient and stiffness ratio of the LRB gives an increase of 15% in the maximum and root mean square (RMS) of the structural responses. In the case with -20% of uncertainty, the damage and damping energies do not change in comparison with the case of the nominal model, but a significant decay in the performance index related to the input energy response is obtained in this case. Not all performance indices are sensitive to time delay. For large time delays, the performance index for the seismic input energy increases significantly, while the maximum damage and damping energies increase up to 5% and 10%, respectively.
The use of advanced structural control devices is an effective engineering solution to reduce earthquake induced damages to structures. Owing to rapid advancement in technology and persistent research efforts, a variety of control devices have been developed and successfully implemented. Quite recently, a new passive damper, called inerter has been introduced, which is capable of developing a fictive mass. This study presents a novel inerto-elastic damper, which combines the inerter devices with classical elastic dampers, and demonstrates the effectiveness of these devices in achieving seismic response reduction. The inerto-elastic device employs the inerter and elastic damper in parallel to control the seismic structural response. The effectiveness of the inerto-elastic dampers has been demonstrated through the response of a multi-degree of freedom system subjected to seismic excitations. The results of the analysis show a significant reduction in the response of the structure with novel inerto-elastic damper, as compared to those of structures with normal elastic damper as well as no dampers. The response quantities of interest, considered for this study are top floor displacement, inter-storey drift and base shear. The study also underlines optimal parameters for the inerter fictive mass and the elastic damper stiffness on the basis of the results obtained.
In this paper, a closed loop control approach for controlling vibration under harmonic excitation is introduced. A Semi-Active Tuned Mass Damper (SATMD) with time variable damping installed on the lowest floor of a base-isolated structure is investigated. The damping is controlled by a fuzzy logic controller, in which displacement and velocity of the base isolator are used as inputs. The numerical simulation is carried out on two types of 6-degrees of freedom base-isolated structures: the first structure is equipped with a base isolator having low damping, while the second structure is equipped with a base isolator having high damping. Simulation by MATLAB is carried out to test the proposed SATMD under harmonic excitation and the results are compared to those of a classical passive TMD. Results showed that a SATMD with variable damping is more efficient than a classic TMD with constant damping under harmonic excitation, leading to a reduction of 50% in base displacement and acceleration, as well as a reduction of nearly 15% in inter-story drift.
Based on the theory of continuous sliding-mode control, control methods are presented for seismic-excited buildings isolated by a frictional-type sliding-isolation system. The dynamic behavior of the building equipped with a base-sliding-isolation system is highly nonlinear, and the sliding-mode-control method is ideal for such nonlinear systems. In addition to full-state-feedback controllers, a simple static-output-feedback controller using only the measured information from a few sensors installed at strategic locations without an observer is presented. The continuous sliding-mode controllers presented do not have undesirable chattering effect. Simulation results for an eight-story building indicate that (1) the control methods are robust; and (2) the control performance is outstanding. A shaking-table experimental program was conducted to verify the proposed static output control method. For the shaking-table tests, a three-story quarter-scale building model was mounted on a base mate that was supported by four frictional bearings. Experimental test results indicate that the control performance is quite remarkable, although a slight degradation was observed due to noise pollution and system time delays.
Semi-active control devices have received significant attention in recent years because they offer the adaptability of active control devices without requiring the associated large power sourc- es. Magnetorheological (MR) dampers are semi-active control devices that use MR fluids to pro- duce controllable dampers. They potentially offer highly reliable operation and can be viewed as fail-safe in that they become passive dampers should the control hardware malfunction. To devel- op control algorithms that take maximum advantage of the unique features of the MR damper, models must be developed that can adequately characterize the damper's intrinsic nonlinear be- havior. Following a review of several idealized mechanical models for controllable fluid dampers, a new model is proposed that can effectively portray the behavior of a typical magnetorheological damper. Comparison with experimental results for a prototype damper indicates that the model is accurate over a wide range of operating conditions and is adequate for control design and analy- sis.
Vibration mitigation using smart, reliable and cost-effective mechanisms that requires small activation power is the primary objective of this paper. A semi-active controller-based neural network for base-isolation structure equipped with a magnetorheological (MR) damper is presented and evaluated. An inverse neural network model (INV-MR) is constructed to replicate the inverse dynamics of the MR damper. Next, linear quadratic Gaussian (LQG) controller is designed to produce the optimal control force. Thereafter, the LQG controller and the INV-MR models are linked to control the structure. The coupled LQG and INV-MR system was used to train a semi-active neuro-controller, designated as SA-NC, which produces the necessary control voltage that actuates the MR damper. To evaluate the proposed method, the SA-NC is compared to passive lead–rubber bearing isolation systems (LRBs). Results revealed that the SA-NC was quite effective in seismic response reduction for wide range of motions from moderate to severe seismic events compared to the passive systems. In addition, the semi-active MR damper enjoys many desirable features, such as its inherent stability, practicality and small power requirements. The effectiveness of the SA-NC is illustrated and verified using simulated response of a six-degree-of-freedom model of a base-isolated building excited by several historical earthquake records. Copyright © 2006 John Wiley & Sons, Ltd.
This paper investigates the effectiveness of the MR damper-based control systems for seismic protection of base-isolated building structures employing some semi-active control algorithms, such as the modified clipped-optimal control, the maximum energy dissipation, the modulated homogeneous friction, and fuzzy logic-based control algorithms, by examining the Phase I smart base-isolated benchmark building problem. The results of the numerical simulations showed that most of the control systems considered herein could be beneficial in reducing seismic responses, especially the base displacement or the isolator deformation, of the base-isolated building. If the base displacement is to be primarily reduced without regard to variation of the floor acceleration, the original clipped-optimal control algorithm could be recommended. On the other hand, if it may be required to reduce the base displacement without increasing the floor acceleration, the modified clipped-optimal control algorithm proposed in this study could be considered as one promising candidate for the linear benchmark base-isolated system. Copyright © 2005 John Wiley & Sons, Ltd.
Active tuned mass damper (ATMD) control systems for civil engineering structures have attracted considerable attention in recent years. This paper emphasizes on the combined application of genetic algorithms and fuzzy logic (GFLC) to design and optimize the different parameters of the ATMD control scheme for getting the best results in the reduction of the building response under earthquake excitations. Therefore, the proposed method has the advantages of both the fuzzy logic controller (FLC) and genetic algorithms (GAs) to handle the uncertain, as well non-linear phenomena. The building is modeled as a shear frame and the problem is solved in state space. The proposed method is applied to an 11-story realistic building, located in the city of Rasht, Islamic Republic of Iran. The results obtained from the proposed control scheme (GFLC) are compared with those obtained from the TMD, and linear quadratic regulator (LQR) control methods. It is found that integration of the GAs and FLC is highly effective in reduction of the seismically excited example building.
The influence of isolator characteristics on the seismic response of multi-story base-isolated structure is investigated. The isolated building is modeled as a shear type structure with lateral degree-of-freedom at each floor. The isolators are modeled by using two different mathematical models depicted by bi-linear hysteretic and equivalent linear elastic–viscous behaviors. The coupled differential equations of motion for the isolated system are derived and solved in the incremental form using Newmark’s step-by-step method of integration. The variation of top floor absolute acceleration and bearing displacement for various bi-linear systems under different earthquakes is computed to study the effects of the shape of the isolator hysteresis loop. The influence of the shape of isolator force-deformation loop on the response of isolated structure is studied under the variation of important system parameters such as isolator yield displacement, superstructure flexibility, isolation time period and number of story of the base-isolated structure. It is observed that the code specified equivalent linear elastic–viscous damping model of a bi-linear hysteretic system overestimates the design bearing displacement and underestimates the superstructure acceleration. The response of base-isolated structure is significantly influenced by the shape of hysteresis loop of isolator. The low value of yield displacement of isolator (i.e. sliding type isolation systems) tends to increase the superstructure accelerations associated with high frequencies. Further, the superstructure acceleration also increases with the increase of the superstructure flexibility.
In the current code requirements for the design of base isolation systems for buildings located at near-fault sites, the design engineer is faced with very large design displacements for the isolators. To reduce these displacements, supplementary dampers are often prescribed. These dampers reduce displacements, but at the expense of significant increases in interstorey drifts and floor accelerations in the superstructure. An elementary analysis based on a simple model of an isolated structure is used to demonstrate this dilemma. The model is linear and is based on modal analysis, but includes the modal coupling terms caused by high levels of damping in the isolation system. The equations are solved by a method that avoids complex modal analysis. Estimates of the important response quantities are obtained by the response spectrum method. It is shown that as the damping in the isolation system increases, the contribution of the modal coupling terms due to isolator damping in response to the superstructure becomes the dominant term. The isolator displacement and structural base shear may be reduced, but the floor accelerations and interstorey drift are increased. The results show that the use of supplemental dampers in seismic isolation is a misplaced effort and alternative strategies to solve the problem are suggested. Copyright (C) 1999 John Whey & Sons, Ltd.
Long-period pulses in near-field earthquakes lead to large displacements in the base of isolated structures. To dissipate energy in isolated structures using semi-active control, piezoelectric friction dampers (PFD) can be employed. The performance of a PFD is highly dependent on the strategy applied to adjust its contact force. In this paper, the seismic control of a benchmark isolated building equipped with PFD using PD/PID controllers is developed. Using genetic algorithms, these controllers are optimized to create a balance between the performance and robustness of the closed-loop structural system. One advantage of this technique is that the controller forces can easily be estimated. In addition, the structure is equipped with only a single sensor at the base floor to measure the base displacement. Considering seven pairs of earthquakes and nine performance indices, the performance of the closed-loop system is evaluated. Then, the results are compared with those given by two well-known methods: the maximum possive operation of piezoelectric friction dampers and LQG controllers. The simulation results show that the proposed controllers perform better than the others in terms of simultaneous reduction of floor acceleration and maximum displacement of the isolator. Moreover, they are able to reduce the displacement of the isolator systems for different earthquakes without losing the advantages of isolation.
The paper addresses the problem of designing stabilizing output feedback controllers for a class of nonlinear seismically excited base isolated structures with unknown parametrical uncertainties. Two types (non-adaptive and adaptive) of sliding mode controllers are presented. In both schemes, only the information on the displacements and velocities of the base and the first floor is used in the controller design. A numerical example is given to illustrate the effectiveness of the proposed strategy to a 10-storey frictional base isolated structure being subject to the El Centro earthquake.
The low stiffness of laminated rubber bearings utilized in base isolation could potentially cause large lateral displacements which must be reduced by some energy-dissipation mechanism. The effect of applying tuned-mass dampers towards reducing the lateral deformation of the isolators was studied in this paper. The choice of the proper parameters of the tuned-mass damper and the influence of excitation frequency on the response were investigated. Through the numerical simulation of a five-storey base-isolated building subjected to different earthquake records, it was found that although the tuned-mass damper had little effect on structural response during the first few seconds of earthquake excitation, the damper may add damping to the structure to reduce the subsequent response. The idea of the accelerated tuned-mass damper was proposed and demonstrated the capability of decreasing the maximum deformation of the isolators which occurred at the beginning of earthquake excitation.
The sensitivity of base-isolated structures to wind loadings is studied. The wind velocity is decomposed into mean and random fluctuating parts. A stationary random model for the fluctuating part of wind velocity is considered and the method of equivalent linearization is used for response analysis. Displacementresponse statistics, including autocorrelation, power spectrum, and variance of a rigid structure, are evaluated for the laminated rubber bearing (LRB), the high damping rubber bearing, and the resilient-friction base isolator (R-FBI) baseisolation systems. The results show that base-isolated structures are not sensitive to wind loading during common storms. However, for severe hurricanes, displacements on the order of a few centimeters may be expected. The presence of a frictional element in the base-isolation system significantly reduces its sensitivity to strong wind loadings. High damping in the base-isolation system decreases the displacement due to the fluctuating part of wind excitation.
A hybrid seismic control system for building structures is considered, which combines a class of passive nonlinear base isolator with an active control system. The active control forces are applied to the structural base with the objective of reducing its absolute displacements. An adaptive control law is formulated to compute the control forces to assure a form of stable behavior of the system under seismic excitation and in the presence of uncertainties in the characteristics of the building and the base isolator. Numerical simulations are performed to assess the effectiveness of the hybrid control system. The global behavior of the structure-base-isolator system is such that the absolute base displacement is significantly reduced, the price paid being a slight increase of the response of the structure.
1 Seismic Isolation for Earthquake-Resistant Design.- 1.1 Introduction.- 2 Vibration Isolation.- 2.1 Introduction.- 2.2 Theory of Vibration Isolation.- 2.3 Frictional Vibration Isolators.- 3 Seismic Isolation.- 3.1 Review of Fixed-Base Structural Analysis.- 3.2 Linear Theory of Base Isolation.- 3.3 Isolation of Very Flexible Structures.- 4 Extension of Theory to Buildings.- 4.1 M-Degree-of-Freedom Equations of Motion.- 4.2 Modal Analysis of M-DOF System.- 4.3 Estimates of Displacements and Forces for M-DOF System.- 5 Earthquake Regulations for Seismically Isolated Structures.- 5.1 Introduction.- 5.2 1994 Uniform Building Code.- 5.3 Design Methods.- 5.4 Static Analysis.- 5.5 Dynamic Analysis.- 5.6 Computer Programs for Analysis of Seismically Isolated Structures.- 5.7 Other Requirements for Nonstructural Components.- 5.8 Review.- 5.9 Design Requirements for Isolators.- 5.10 Base-Isolated Structures under Extreme Earthquake Loading.- 6 Coupled Lateral-Torsional Response of Seismically Isolated Buildings.- 6.1 Introduction.- 6.2 Case I: Three Close Frequencies.- 6.3 Case II: Equal Lateral Frequencies, Distinct Torsional Frequency.- 7 Behavior of M?ltilayered Bearings Under Compression and Bending.- 7.1 Introduction.- 7.2 Shear Stresses Produced by Compression.- 7.3 Bending Stiffness of a Single Pad.- 7.4 Pure Compression of Single Pads with Large Shape Factors.- 7.5 Compression Stiffness for Circular Pads with Large Shape Factors.- 7.6 Compression Stiffness for Square Pads with Large Shape Factors.- 7.7 Bending Stiffness of Single Pads with Large Shape Factors.- 8 Buckling Behavior of Elastomeric Bearings.- 8.1 Stability Analysis of Bearings.- 8.2 Stability of Annular Bearings.- 8.3 Influence of Vertical Load on Horizontal Stiffness.- 8.4 Downward Displacement of the Top of a Bearing.- 8.5 A Simple Mechanical Model for Bearing Buckling.- 8.6 Postbuckling Behavior.- 8.7 Influence of Compressive Load on Bearing Damping Properties.- 8.8 Rollout Stability.- 9 Design Process for Multilayered Elastomeric Bearings.- 9.1 Preliminary Bearing Design Process.- 9.2 Experimental Studies of Elastomeric Isolator Performance.- 9.3 Compact Design Bearings.- Afterword.- References.- Appendix A.- A.I Base-Isolated Buildings and Projects in the United States.- A.2 Retrofit Base-Isolated Buildings and Projects in the United States.- Appendix B.- B.I N-PAD.- B.2 3D-BASIS.- B.3 SADSAP.- B.4 General Nonlinear Three-Dimensional Analysis Programs.
Three analytical studies of base-isolated structures are carried out. First, six pairs of near-fault motions oriented in directions parallel and normal to the fault were considered, and the average of the response spectra of these earthquake records was obtained. This study shows that in addition to pulse-type displacements, these motions contain significant energy at high frequencies and that the real and pseudo-velocity spectra are quite different.
The second analysis modelled the response of a model of an isolated structure with a flexible superstructure to study the effect of isolation damping on the performance of different isolation systems under near-fault motion. The results show that there exists a value of isolation system damping for which the superstructure acceleration for a given structural system attains a minimum value under near-fault motion. Therefore, although increasing the bearing damping beyond a certain value may decrease the bearing displacement, it may transmit higher accelerations into the superstructure.
Finally, the behaviour of four isolation systems subjected to the normal component of each of the near-fault motions were studied, showing that EDF type isolation systems may be the optimum choice for the design of isolated structures in near-fault locations. Copyright
This study investigates the application of a semi-active control method utilizing a magnetorheological (MR) damper to reduce the response of an isolated structure subjected to earthquake excitations. A series of performance tests were carried out on a 2 kN MR damper and the Bouc–Wen model was utilized to establish the numerical model of the MR device. A fuzzy logic control algorithm was then applied to establish the controller. Results of numerical simulation indicated that the established control algorithm is useful to reduce displacement and acceleration responses of base-isolated structures. Copyright © 2003 John Wiley & Sons, Ltd.
Sample controllers for a three-dimensional smart base-isolated building benchmark problem with linear and frictional isolation system are presented in this paper. A Kalman filter is used to estimate the states based on absolute acceleration measurements. Input filters are used to better inform the controller of the spectral content of the earthquake excitations. A reduced order control-oriented model of the benchmark structure with a linear isolation system is developed. A H2/linear quadratic Gaussian controller is presented for the active case; additionally, a clipped optimal controller is presented for the semiactive case. A preliminary ‘skyhook’ semiactive controller is also presented for the benchmark problem. Magnetorheological fluid dampers are used for control in the semiactive case and ideal actuators are used for control in the active case. The focus of this phase I study is on the linear isolation system only. Computed results for the passive, semiactive, and active cases are presented. Detailed comparisons of benchmark performance indices for base-isolated structures with a nominal linear isolation system, with and without control, for a set of strong near-field earthquakes are presented. The modeling and sample control designs demonstrated in this paper can be used to form the basis for studying a wide variety of active and semiactive control strategies—to be developed by the participants in the benchmark study—for linear base-isolated buildings. Copyright © 2005 John Wiley & Sons, Ltd.
Base isolation is a quite sensible structural control strategic design in reducing the response of a structural system induced by strong ground motions. It is clear that the effects of near-fault (NF) ground motions with large velocity pulses can bring the seismic isolation devices to critical working conditions. In the present paper, nonlinear time history analyses were performed using a commercial structural analysis software package to study the influence of isolation damping on base and superstructure drift. Various lead-rubber bearing (LRB) isolation systems are systematically compared and discussed for aseismic performances of two actual reinforced concrete (RC) buildings. Parametric analysis of the buildings fitted with isolation devices is carried out to choose the appropriate design parameters. The efficiency of providing supplemental viscous damping for reducing the isolator displacements while keeping the substructure forces in reasonable ranges is also investigated.
Full-scale experiments are carried out on a single-degree-of-freedom mass that is equipped with a hybrid base isolation system. The isolator consists of a set of four friction pendulum system (FPS) bearings and a magnetorheological (MR) damper. The 13,620 kg mass and its hybrid isolation system are subjected to various intensities of near- and far-fault earthquakes on a large shake table. The proposed fuzzy controller uses feedback from displacement or acceleration transducers attached to the structure to modulate resistance of the semi-active damper to motion. Results from several types of passive and semi-active control strategies are summarized and compared. The study shows that a combination of FPS bearings and an adjustable MR damper can provide robust control of vibration for a large full-scale structure undergoing a wide variety of seismic loads. Low power consumption, real-time feedback control, and fail-safe operation are validated in this study. A combination of the FPS bearings and the MR damper appears to offer significant possibilities for reduction of displacement and acceleration due to seismic load. A neuro-fuzzy model is used to represent behavior of the damper for various displacement, velocity, and voltage combinations that are obtained from a series of laboratory evaluation tests. Modeling of the FPS bearings is carried out with a nonlinear analytical equation and neuro-fuzzy training. Numerical simulation using neuro-fuzzy models of the MR damper and FPS bearings predict the response of the hybrid base isolation system very well. Results show that dynamic behavior of the FPS bearings and MR damper can be successfully estimated using these neuro-fuzzy models.
In this paper, the efficiency of providing supplemental elastic stiffness to seismic-isolated bridges (SIBs) for reducing the isolator displacements while keeping the substructure forces in reasonable ranges is investigated. Conventional supplemental elastic devices (SEDs) such as elastomeric bearings placed in parallel with seismic isolators between the superstructure and substructures are used for this purpose. A parametric study, involving more than 400 nonlinear time history (NLTH) analyses of realistic and simplified structural models of typical SIBs are conducted using simulated and actual NF ground motions to investigate the applicability of the proposed solution. It is found that providing SEDs is beneficial in reducing the isolator forces to manageable ranges for SIBs subjected to NF ground motions with moderate to large magnitudes regardless of the distance from the fault. It is also found that the stiffness of the SED may be chosen in relation to the velocity pulse period (or magnitude) of the NF ground motion to minimize the isolator displacements by avoiding resonant response. Further analyses conducted using a realistic structural model of an existing bridge and five NF earthquakes with moderate to large magnitudes confirmed that SEDs may be used to reduce the displacement of the isolators while keeping the substructure base shear forces in reasonable ranges for SIBs located in NF zones.
In this study, a friction pendulum system (FPS) and a magnetorheological (MR) damper are employed as the isolator and supplemental damping device, respectively, of a smart base-isolation system. Neuro-fuzzy models are used to represent dynamic behavior of the MR damper and FPS. A fuzzy logic controller (FLC) is used to modulate the MR damper so as to minimize structural acceleration while maintaining acceptable base displacement levels. To this end, a multi-objective optimization scheme that uses a nondominated multi-objective genetic algorithm (NSGA-II) is used to optimize parameters of membership functions and find appropriate fuzzy rules. To demonstrate the effectiveness of the proposed multi-objective genetic algorithm for FLC, a numerical study of a smart base-isolation system is conducted using several historical earthquakes. It is shown that the proposed method can find optimal fuzzy rules and that the NSGA-II-optimized FLC outperforms not only a passive control strategy but also a human-designed FLC and a conventional semiactive control algorithm.
International conference of building officials
- U B Code
Code, U.B., International conference of building officials. Whittier, CA, 1997.
International building code2000: International Code Council
- I C Council
Council, I.C., et al., International building code2000: International Code Council.
Combined control strategy: base isolation and tuned mass damping
- B Palazzo
- L Petti
Palazzo, B. and L. Petti, Combined control strategy: base isolation and tuned mass damping.
ISET Journal of Earthquake Technology, 1999. 36(2-4): p. 121-137.