Seismic Control Of Structures Research Articles

Design and performance evaluation of toroidal TLCDs in bidirectional seismic control of structures using a modified dynamic model

In this study, a modified dynamic model which distinguishes between liquid oscillation and sloshing in vertical columns is derived for toroidal tuned liquid column dampers (TLCDs). In the modified model of toroidal TLCDs, the primary sloshing mode within vertical columns is modeled as mass–spring-dashpot systems, whereas the oscillatory behavior of the liquid is analyzed employing the conventional theory of TLCDs. The accuracy of the modified dynamic model in capturing bidirectional liquid responses is verified by computational fluid dynamics (CFD)-based simulations. A large number of CFD-based simulations are performed to establish a ready-to-use suggested formula for a newly introduced parameter (which is related to the geometric configuration of liquid containers and the initial liquid depth) in the modified model. Subsequently, considering the maximum allowable liquid displacement in vertical columns, an optimized design approach for toroidal TLCDs installed in symmetric and asymmetric structures is illustrated. On the basis of the proposed optimization design method, the bidirectional vibration control effects of toroidal TLCDs are comprehensively analyzed under El Centro, Loma Prieta, Northridge, and Chi–Chi seismic excitations in both the time and frequency domains. The results demonstrate the effectiveness of toroidal TLCDs for bidirectional seismic control of structures.

Experimental and analytical studies on a novel double-stage coupling damper

A series of experimental and numerical studies on the novel double-stage coupling damper (DSCD) are presented in this paper. The effects of the damper configuration, friction-yield ratio (Rfy), and loading protocol on the hysteresis performance of the DSCD are investigated via quasi-static tests on seven specimens, and the variation in the failure mode, compression-strength adjustment factor, energy dissipation capacity, and equivalent viscous damping ratio of the DSCD is discussed. The test results demonstrate that the arrangement of ribs in the DSCD increased the average energy dissipation per loading cycle, compared to the device without these elements. The damper exhibits double-stage energy dissipation characteristics for several friction-yield ratios, however, relatively low values of this parameter (Rfy = 0.5) leads to reduced energy dissipation capacity, due to significant variations in the friction force associated with creep, ploughing, and preload effect. Furthermore, a detailed finite element model of the DSCD is conducted based on the experimental data, focusing on exploring the effectiveness of the device. Numerical analysis revealed that the cumulative energy dissipation and peak force of the DSCD reduced with increasing the length of the friction mechanism (Lf). A large clearance between the yield segment and the restraining system (Cb) reduces the stability of the equivalent viscous damping ratio of the damper under compression, but Cb has no effect in the cumulation energy dissipation of the damper, which has important implications in the design of these devices for the seismic control of structures. Based on these results design recommendations for the DSCD are provided.

Mass ratio factor in control performance of optimum tuned liquid dampers

SummaryTuned liquid dampers provide structure control with the help of the liquid mass in tanks that are attached to the structure. The mass ratio affects the optimum tuned liquid damper (TLD) parameters. This study examines the effect of mass ratio on the control performance of TLD devices in providing seismic control of structures with different damping ratios. For this purpose, TLD devices with different mass ratios were placed on two different single‐story steel and reinforced concrete structure models, and their performance under earthquake excitation was investigated. TLD parameters for obtaining the optimum displacement level in the 0.5‐ and 1.0‐s structure natural period for both structure types were optimized with the Jaya algorithm (JA), which is a metaheuristic algorithm. By using the optimum TLD parameters, the structural displacement and total acceleration values were obtained by the critical earthquake analysis. When the results are examined, it is understood that TLD mass increase from a 20% mass ratio for both structure types and selected structure periods does not have a significant effect on TLD control performance.

A new seismic control framework of optimal PIλDµ controller series with fuzzy PD controller including soil-structure interaction

A new framework of optimal fractional order proportional-derivative-integral (FOPID) controller series with fuzzy proportional-derivative (PD) controller, namely OFPD-FOPID controller, is proposed in this study for seismic control of structures equipped with active tuned mass damper (ATMD). Three controllers including optimal PID, optimal FOPID, and fuzzy PID (FPID) controllers are also implemented for comparison purposes. Simulation results carried out on a 15-story building show the FOPID controller than the PID and FPID controllers can remarkably reduce the maximum floor displacement, but they represent a poor performance in mitigation of the maximum floor acceleration in different soil conditions, while the proposed OFPD-FOPID controller tracking the amount of the maximum floor acceleration to estimate the optimal control force of the actuator can provide superior performance. An average reduction of 41%, 45%, and 33% in the maximum floor displacement; 36%, 33%, and 20% in the maximum inter-story drift are given by FOPID in the dense, medium, and soft soils, while it results in an increase of 45%, 52% and 24% in the maximum floor acceleration. Similarly, the proposed OFPD-FOPID controller represents an average reduction of 52%, 55%, and 45% in the maximum floor displacement; 42%, 44%, and 28% in the maximum inter-story drift in the dense, medium, and soft soils, while it also slightly reduces the maximum floor acceleration of the studied structure located on different soil conditions.

Parameter design and performance evaluation of tuned mass damper (TMD) for seismic control of structure considering soil-structure interaction (SSI)

Tuned mass damper (TMD) is a practical tool for reducing structural vibration. The current TMD design often use the dynamic characteristics of structures with fixed base. However, in terms of resisting earthquakes especially when the soil-structure interaction (SSI) effect is prominent, the TMD designed for the fixed base situation behaves unfavorably and even amplifies the structural response. In this paper, a parameter design and performance evaluation of TMD for seismic control of structure considering SSI is studied. The contents include the SSI modeling, structural dynamic characteristic identification, and TMD parameter designing. A seismic SSI model that the soil is simulated by an accurate lumped parameter models (LPMs) is built firstly. A simple and practical method is then used to identify the structural dynamic characteristic of SSI model. The identified structural frequency is used to compute the parameters of TMD. Finally, two types of structures, three kinds of soils, and 100 ground motions are applied to comprehensively evaluate the TMD performance through the comparison with the fixed-ground-based design and optimization-algorithm-based design. The research shows the TMD designed by the proposed method can show a good performance and robustness.

Sliding sector–based adaptive controller for seismic control of structures equipped with active tuned mass damper

Active tuned mass damper (ATMD) as a reliable active device of structural control can protect structures subjected to earthquake excitations from the severe seismic damages. The present study focus on the design of an adaptive sliding sector controller (ASSC) employed in the ATMD system to mitigate the seismic responses of an 11–story shear building under earthquake excitations. The ASSC technique is designed based on the hyper-surface of the sliding mode which is surrounded by a sector and can consider the uncertainty of system parameters. In this study, the design of the ASSC strategy is first implemented for the structure subjected to an artificial earthquake excitation. Then, the performance of the ASSC strategy is evaluated in mitigating the seismic responses of the structure under four near– and far–fault earthquake excitations. Furthermore, the efficiency of the ASSC strategy is also compared against that of a few control techniques including proportional-integral-derivative [PID], linear-quadratic regulator [LQR], fuzzy logic control [FLC], optimal sliding mode control [OMSC]. Comparative results of the numerical simulation confirm the robustness and ability of the ASSC strategy for the reduction of the structural responses under real earthquake excitations.

Seismic structural control using magneto-rheological dampers: A decentralized interval type-2 fractional-order fuzzy PID controller optimized based on energy concepts

In this paper, a combination of the interval type-2 fuzzy logic controller (IT2FLC) with the fractional-order proportional–integral–derivative (FOPID) controller, namely optimal interval type-2 fractional-order fuzzy proportional–integral–derivative controller (OIT2FOFPIDC), is developed for enhancing the seismic performance and robustness in seismic structural control applications. Based on the energy concepts, a decentralized framework of the OIT2FOFPIDC is proposed for easy and simple implementation in structures during earthquakes. For this purpose, a coot optimization algorithm (COA), as a powerful optimization algorithm, is also applied to adjust the membership functions (MFs), scaling factors, and the main controller parameters. Three controllers, namely optimal type-1 fuzzy proportional–integral–derivative controller (OT1FPIDC), optimal interval type-2 fuzzy proportional–integral–derivative controller (OIT2FPIDC), and optimal proportional–integral–derivative controller (OPIDC), are also proposed for comparison purposes. The seismic performances of the suggested controllers are examined with the evaluation of nine seismic performance indices and different ground accelerations in a 6-story smart structure equipped with two dampers. The robustness of the four controllers in the presence of the stiffness uncertainties is also compared in this study. On average, a reduction of 25.0%, 18.8%, and 18.5% in peak displacement, inter-story drift, and acceleration of stories is obtained for the OIT2FOFPIDC over the OT1FPIDC, respectively. Similarly, these reductions in comparison with the OIT2FPIDC are 16.3%, 13.3%, and 12.0%. Also, these reductions, in comparison with the OPIDC, are 33.3%, 27.8%, and 25.8%. Furthermore, simulation results show that the OIT2FOFPIDC is more robust than the other proposed controllers against uncertainties due to structural stiffness.

Friction Tuned Mass Dampers in Seismic-Excited High-Rise Buildings with SSI Effects: A Reliability Assessment

The probabilistic performance of the seismic-excited structures supplemented with passive control devices has recently received attention. Friction tuned mass damper (FTMD) devise as a novel passive control device is inspired by the idea of the combination of the friction mechanism with the traditional tuned mass damper (TMD) device. Although the application of the FTMD device has recently been considered for seismic control of structures, to the best of the authors’ knowledge, a probabilistic reliability evaluation of the high-rise building equipped with FTMD under near-field earthquakes considering soil-structure interaction (SSI) effects has not yet been addressed in the literature. In the presence of uncertainties considered for the structural model, FTMD model, foundation and soil model, and stochastic near-fault ground motion model, the reliability analyses are carried out on a benchmark 40-story building equipped with FTMD considering SSI effects to estimate the failure probabilities of both structures with and without FTMD. Three soil types, three earthquake magnitudes, three fault distances, and three seismic performance levels which include 162 reliability analyses are considered for the extension of the study. Considering different near-fault earthquake model parameters, a total average reduction of 51.13%, 49.42%, and 17.50% is given for the maximum inter-story drift ratio response of the structure equipped with FTMD than the uncontrolled ones. It is found that ignoring the uncertainties may result in an inaccurate estimation of the seismic responses of the tall buildings especially those built on soft soil near faults. The results show that the FTMD passive device is not able to satisfy the requirements of the seismic codes at the performance level of immediate occupancy, especially in high earthquake magnitudes and structures built near the fault. However, for the seismic performance levels of life safety and collapse prevention, the FTMD reduces failure probabilities of the structures for most conditions of the earthquake magnitudes and fault distances. The efficiency of the FTMD in the reduction of failure probability is often declined by increasing the softness of soils, especially for severe earthquakes closer to the fault.

Introduction of a new metallic-yielding pistonic damper for seismic control of structures

A new damper with pistonic performance is presented in this research for seismic control of structures. A set of rectangular metallic yielding plates has been considered as the energy dissipating part for this device. The damper is configured in such a way that can provide the loading conditions as pure-bending for this part during cyclic motions. This configuration makes the damper to have an optimized flexural yielding mechanism and consequently a high-level of force capacity and damping ratio. The dissipator part is placed into a steel surrounding rigid box which has only one sliding translational degree of freedom along its longitudinal axis. Accordingly, the device can perform as a tension/compression piston with sufficient stability in other directions. The proposed metallic-yielding pistonic (MYP) damper can be used in various types of structural systems such as moment-resisting or braced frames and even coupled shear wall systems with the capability of dual or multiple-installation in each frame bay. In this research the hysteresis behavior of this damper has been numerically investigated. Then as a parametric study, the effects of various MYP design parameters on the damper hysteretic behavior were studied. Finally, the control performance of this device was seismically investigated in a one-story moment-resisting frame considering possible beam flange out-of-square imperfections. According to observed results, the proposed damping system is high-performance in seismic structural protection at low-value story drifts. Besides, it was able to significantly reduce the structural responses and residual deformations as well as the out-of-plane frame motions.

Sensitivity and Reliability Analyses in to Actively Controlled Structures Under Earthquake

This study aims for a probabilistic assessment of active seismic control of structures in the presence of uncertainties of the structural model and the stochastic model of the ground acceleration. First, sensitivity analyses based on the Borgonovo sensitivity index are conducted to measure the effect of uncertainty sources on the maximum and root mean square (RMS) of the main structural responses in different seismic hazard regions. Then, the reliability analyses are conducted using Monte Carlo simulation (MCS) and importance sampling (IS) methods to the estimation of failure probabilities and reliability indices of the structures in different seismic hazard regions, force capacity of actuators, and seismic performance levels. Numerical studies carried out on a 10-story structure show that the uncertainties in peak ground acceleration (PGA) and story stiffness have the most effects on the seismic responses of the structure. The effect of the considered uncertainties is negligible on the maximum demand control force. The results also show that equipping the structure with an active control system results in a significant reduction in the failure probabilities of the structure. The target reliability index for the uncontrolled structure in life safety seismic performance level may not be satisfied in high and very high seismic hazard regions, it can however be easily dealt with, using the proposed technique, in the corresponding controlled structures. By increasing the control force capacity, an increment is observed in the reliability index. A high and suitable reliability index is given for both controlled and uncontrolled in the collapse prevention seismic performance level.

Seismic control of structure with phase control active tuned mass damper

Seismic control of structure with phase control active tuned mass damper

Emotional Learning based adaptive control algorithm for Semi-Active seismic control of structures

A tuned mass damper (TMD) is a passive mass-spring system, widely accepted as an effective response control strategy for a structure under external excitation. The inherent passive nature, optimum tuning requirements of TMDs are known to lead to sensitivity problems and/or detuning of the TMDs for changing vibration conditions, limiting their performance to narrow band of input excitation. Due to these limitations, semi-active control concepts are used to introduce adaptability in passive TMDs. Semi-active response control using TMD is much researched in recent years for protection of civil engineering structures against earthquake. In this study, the efficacy of a semi-active mass driver (MD) system coupled with magnetorheological (MR) damper is investigated for seismic response control of a primary structure. The input current to the MR damper in the semi-active MR-MD is controlled using an adaptive Brain Emotional Learning Based Intelligent Controller (BELBIC) control algorithm in a closed loop architecture. The efficiency of the damping addition from the MR damper to the mass driver which is reducing the response of the primary structure is investigated using analytical and simulation studies, considering off-tuning, emulated using three different tuning cases of the MR-MD. From the studies, it is found that semi-active MR-MD is performing satisfactorily in reducing the seismic response of the primary structure and BELBIC algorithm performs efficiently even during off-tuning conditions and presence of physical constraints.

Characterization and quarter car analysis with magnetorheological fluid damper using modified algebraic model (mAlg)

Magnetorheological (MR) dampers have received the ever-increasing attention of many researchers considering their wide range of applications ranging from large seismic control of structures to prosthetics in the medical field. One such application is in semi-active vehicle suspension with MR damper. Modeling the dynamic behavior of MR damper is an intriguing challenge and many mathematical models are put forth to address this task. In this work, the MR damper is initially developed and characterized using in-house prepared MR fluid. This study aims at using a modified algebraic model (mAlg) for modeling the hysteretic behavior of the MR damper using experimental force data. Also, the study uses a Genetic algorithm toolbox to find optimal parameters for the mAlg model, and the accuracy of mAlg is visualized with various plots. The work also aims at analyzing the response of the quarter car model with MR damper to three kinds of road excitations using Simulink.

Design of series tuned mass dampers for seismic control of structures using simulated annealing algorithm

Design of series tuned mass dampers for seismic control of structures using simulated annealing algorithm

Torsional control of asymmetric buildings using online 3‐D damage detection and adaptive stiffness devices

Developing a smart civil structure, in which the structure instantaneously identifies damages during vibration and makes decisions to compensate or reduce them, is one of the new issues in the seismic control of structures. One of the most important challenges in asymmetric buildings is the torsion due to the damage occurrence in the structure during severe excitation. The aim of this study is to try to reduce the torsional effects and dynamic responses of the structure by combining two strategies, including real time structural health monitoring (SHM) and semi-active control. Hence, a new damage detection method based on identified Markov parameters of the system is proposed to identify the damage in 3-D shear model structures. Also, in order to create a smart structure, a new controller is designed to regulate mechanical characteristics of the installed adaptive stiffness devices based on the detected damages and eccentricity variations in the structure. The performance of the proposed controller and damage detection method is investigated through numerical examples under the influence of various earthquake records. The obtained results reveal that the proposed method estimates the location, amount, and type of damages with acceptable accuracy even with noise contamination of the measured data. Moreover, the presented controller can effectively reduce the increase in the torsional response of the structure owing to the damage occurrence during strong ground motions.

Reliability assessment and seismic control of irregular structures by magnetorheological fluid dampers

The catastrophic damages of past earthquakes show that irregular structures are more vulnerable to seismic excitation. On the other hand, dynamic responses depend on the severity of irregularity which is hard to be determined precisely. In this study, performance and reliability of magnetorheological (MR) fluid dampers in controlling torsional-lateral responses of irregular structures are evaluated. In this regard, plan-asymmetry is studied by considering mass eccentricity; whereas vertical-irregularity is investigated by creating mass difference in adjacent stories of the structure. The performance of MR dampers in seismic control of the structure is then evaluated for passive and semi-active control scenarios. The reliability of the structure-MR damper system is then studied by considering uncertainties in severity of irregularities using the Monte Carlo simulation method. Six types of limit state function are defined and the reliability of the system for controlling the desired responses are derived. The results show satisfactory performance of MR dampers in controlling coupled torsional-lateral responses of the structure in which semi-active control system outperforms the passive control system. The results also confirm that the performance of the control system highly depends on the structure irregularity which should be taken into account for design of a safe and reliable structure.

Reliability assessment of MR fluid dampers in passive and semi-active seismic control of structures

In this paper, the reliability assessment of magnetorheological (MR) dampers in reducing structures’ seismic responses is studied. Two passive and semi-active control scenarios are considered and discussed. For semi-active control scenario, the Lyapunov control algorithm is used. In order to minimize the structure’s responses under a given earthquake excitation, an unconstrained optimization problem is first defined and solved via genetic algorithm to find an optimal diagonal matrix in Lyapunov’s control algorithm. The procedure is explained for a three-storey benchmark shear structure equipped with MR damper in all storeys. The structure’s responses reliability for various uncertainties are derived and interpreted based on standard Monte Carlo simulation approach. In the reliability problem, for the limit state function two cases based on human comfort and structural safety criteria are defined and investigated. Furthermore, the most influential uncertain variables and control scenarios on structures’ reliability are identified. Finally, a sensitivity analysis on the coefficient of variations of random variables on the structure’s responses reliability is accomplished. The results show that in the joint event, the MR damper is more reliable for acceleration control rather than drift control in passive control scenario. The aforementioned trend is reversed for semi-active control scenario. Additionally, passive control scenario is more reliable than the semi-active control scenario in reducing maximum acceleration of structure. However, in reducing maximum drift of structure, the values of the reliability in semi-active control scenario are almost similar to passive control scenario.

Evaluation of a pendulum pounding tuned mass damper for seismic control of structures

The pendulum pounding tuned mass damper (PPTMD) is an effective passive control device for structures under harmonic excitations. The primary objective of this study is to evaluate the performance of PPTMD for vibration control of SDOF and MDOF structures subjected to ground motions. The dynamic equations of motion for a primary structure controlled by a PPTMD are formulated and the parameter of the PPTMD was obtained through minimizing the root mean square (RMS) of the free vibration response of the controlled structure. The control performance of PPTMD with the optimized parameters was verified by shake table tests of a SDOF structure under three different earthquakes. The effect of the mass ratio and frequency detuning of the PPTMD on its control performance under 17 different earthquake records with different frequency components was further investigated, and the comparison with the classic tuned mass damper (TMD) was also conducted. Additionally, the influence of the inherent damping ratio of primary structure and earthquake intensity to the control performance was discussed. It is shown that the proposed optimum parametric formulas can be used for the optimal PPTMD design, and both numerical and experimental results demonstrated that the PPTMD effectively suppressed the structural responses, even under detuning situations. The inherent damping of primary structure decreases the control efficiency of PPTMD. Moreover, the control performance of the PPTMD on 10-storey shear structure was studied. As a single-mode controller, the PPTMD is more effective when the structural vibration of target mode is mainly excited under seismic excitations.

Relative Performance of Linear Quadratic Regulator and Pole Placement Technique for Active Seismic Control of Structures

This paper presents the study conducted on the comparison of the performance of the two popular active control algorithms viz. Linear Quadratic Regulator (LQR) and Pole Placement technique in terms of their capability to alleviate the response of a structure to an earthquake. To compare the performance of the two control algorithms, a ten story regular shear building frame with three active tendons located in 1st, 4th and 5th Storys and subjected to an El Centro earthquake has been considered. A comparison of the numerical results shows that the reductions of maximum top floor displacement, maximum story drift and base shear obtained using LQR control algorithm are 71.48%, 59.70% and 62.7% while the reductions obtained using Pole Placement technique are 73.77%, 73.14% and 77% respectively. The percentage reduction of the three performance parameters per unit control force obtained using the two methods have also been estimated and compared. Pole placement technique gives higher reduction while the LQR algorithm gives more reduction per unit control force.

Numerical Investigation of a New Method for Seismic Control of Structures

Vertical mass isolation (VMI) method is used for the seismic control of structures. In this method, the entire structure is considered to be a combination of two mass and stiffness subsystems with an isolator layer located in-between. A magnetorheological (MR) damper is used as the isolator layer to control the structure. The semi-active control technique is applied to control the MR damper based on the applied controlling voltage. Several single degree of freedom structures with the same masses and main periods of 0.5, 1.0, 2.0 and 3.0 seconds are studied. Finally, a comparison between the results of this method with three passive control methods was performed. Results indicated that the semi-active control method based on maximum voltage of 9V will reduce, on average, the maximum roof displacement by 25% and 51% more than the Copt and passive-off methods and is equal to the passive-on method at 9V. However, the efficiency of the semi-active method in controlling the maximum absolute acceleration of the roof and the base shear of the structure was on average 28% and 45% lower than the Copt and passive-off methods, respectively and 2% higher than the passive-on method.