Seismic Response Control Research Articles

Wind and Seismic Response Control of Dynamically Similar Adjacent Buildings Connected Using Magneto-Rheological Dampers

Wind and/or earthquake-imposed loadings on two dynamically similar adjacent buildings cause vigorous shaking that can be mitigated using energy dissipating devices. Here, the vibration response control in such adjacent structures interconnected with semi-active magneto-rheological (MR) dampers is studied, which could also be used as a retrofitting measure in existing structures apart from employing them in new constructions. The semi-active nature of the MR damper is modeled using the popular Lyapunov control algorithm owing to its least computational efforts among the other considered control algorithms. The semi-active performance of the MR damper is compared with its two passive states, e.g., passive-off and passive-on, in which voltage applied to the damper is kept constant throughout the occurrence of a hazard, to establish its effectiveness even during the probable electric power failure during the wind or seismic hazards. The performance of the MR damper, in terms of structural response reduction, is compared with other popular energy dissipating devices, such as viscous and friction dampers. Four damper arrangements have been considered to arrive at the most effective configuration for interconnecting the two adjoining structures. Structural responses are recorded in terms of storey displacement, storey acceleration, and storey shear forces. Coupling the two adjacent dynamically similar buildings results in over a 50% reduction in the structural vibration against both wind and earthquake hazards, and this is achieved by not necessarily connecting all the floors of the structures with dampers. The comparative analysis indicates that the semi-active MR damper is more effective for response control than the other passive dampers.

Seismic response control effects for reinforced-concrete buildings incorporating a passive variable friction device

The seismic response behavior and control effects of reinforced concrete (RC) structures incorporating a variable friction damper were numerically investigated in this study. The damper considered was a passive displacement-dependent variable friction device (VFD), whose sliding force decreases as the device displacement increases. A nonlinear response simulation was carried out using a single-degree-of-freedom system model under various input motions. The results showed that the VFD was effective for controlling the response of the RC structure, not only for reducing the displacement but also for mitigating the increase in the story shear force and acceleration. Also, the nonlinear earthquake response of a three-dimensional frame model representing a historic RC temple building retrofitted with VFDs was assessed. The results showed that the VFDs clearly mitigated the peak story shear of the device-installed story, compared with a passive conventional friction device (CFD). The VFD significantly reduced the peak story drift of the device-installed story compared with the uncontrolled case. Moreover, the peak story drift at the base story for the VFD was decreased compared to the CFD. The VFD contributes to enhancing the aseismic performance of RC superstructures while suppressing the stress increase in the foundation. • Assessment of the response control effects of RC structures with a variable friction device (VFD). • Sliding force of the VFD decreases as the device displacement increases. • Numerical nonlinear responses of SDOF and 3D frame models representing RC structures. • The VFD can mitigate the peak story shear force compared to a conventional friction device. • The VFD can reduce the peak story drift compared with the uncontrolled case.

Vibration isolation performance and optimization design of a tuned inerter negative stiffness damper

A tuned inerter negative stiffness damper (TINSD) is a vibration isolation and energy dissipation device providing a negative stiffness effect, which has the dual damping enhancement effect of negative stiffness and inertance. To date, there have been several studies on TINSDs; however, these studies are incomplete in terms of optimization, isolation system parameter analysis and application in seismic engineering. Therefore, a systematic study of a TINSD in an isolation system is needed. This paper presents a theoretical and numerical study of a SDOF-TINSD system and a realistic structure-TINSD subjected to ground motion. The absolute transmissibility and stability condition of the SDOF-TINSD are derived, and the absolute stiffness value of the negative stiffness element should be less than the primary structural stiffness. The TINSD parameters are optimized based on the H∞ and H2 norms, and analytical solutions for the optimal parameters are obtained. The parameter and sensitivity analyses of the TINSD are carried out. For a known inertance-mass ratio, the vibration isolation performance can be improved by the negative stiffness. The TINSD is very sensitive to deviations of the positive stiffness ratio, and its optimal parameters require special attention. Finally, the vibration control effect of the optimal TINSD is evaluated for harmonic excitation, stationary random excitation and seismic excitation, and an optimization method based on nonstationary random seismic waves (NRSW) for isolators in realistic structures is proposed. The control effect of the TINSD is better than that of the TID and TVMD with the same inertance-mass ratio. Moreover, the TINSD optimized by NRSW has a better seismic response control effect than the H∞ and H2 optimization methods.

Development of a long-period vertical base isolation device with variable stiffness for steel frame structures

The current isolation technology is mainly developed for seismic response control of structures in horizontal direction. Seismic records and shaking table test results show that there is a strong need to mitigate the vertical responses of structures. This paper proposes a three-dimensional (3D) isolation device that consists of a traditional horizontal bearing and a newly developed long-period vertical isolation device with variable stiffness (LVIVS). The LVIVS includes three layers of springs and two of them are prestressed. With the aid of displacement constraint components, the non-prestressed springs work independently or in series with the prestressed springs at different loading stages to realize variable stiffness characteristic. As designed, the LVIVS has large vertical stiffness in the normal stage to restrain the displacement under live loads and ground motions with small amplitudes, small vertical stiffness in the isolation stage to prolong the vertical period of the base isolation system, and large vertical stiffness in the limit stage to restrain large vertical displacement at extreme events. The prestress of the springs leads to a self-centering feature of the device. Also, the variable stiffness characteristic shortens the deformation demand of the device under self-weight which enhances the stability of the device significantly and thus it is easier to achieve a long isolation period in the isolation stage. The hysteretic model for the LVIVS is derived, and sinusoidal excitation tests are conducted to verify the proposed hysteretic model of the LVIVS and its variable stiffness mechanism. The experimental results show that the variable stiffness characteristics of the LVIVS can be achieved, and the isolation period reaches 0.95 s. Finite element simulations are also conducted for a steel frame structure to verify the isolation effect of the proposed 3D isolation device.

Active structural control framework using policy-gradient reinforcement learning

This paper presents a novel data-driven approach for active structural control through the use of deep reinforcement learning, wherein, the control system learns to react in an optimal manner through a training process that utilizes deep neural networks within a reinforcement learning framework. The key advantage of this paradigm is the data-driven approach to active control which helps circumvent the need for high-fidelity modeling that typically requires extensive prior knowledge about the structure of interest. Furthermore, the proposed framework is applicable for designing a variety of active controllers, and different external load types, for example, wind and seismic loads for any desired building. The efficacy of the proposed framework is demonstrated in the context of seismic response control through three numerical case studies. The results confirm that the proposed approach yields significant structural response reductions in the linear and nonlinear regimes. Furthermore, implementation issues such as sensitivity to structural property variations, and time delay are thoroughly investigated.

Multi‐stage superelastic variable stiffness pendulum isolation system for seismic response control of bridges under near‐fault earthquakes

To improve the resilient capability of bridges, a novel multi-stage superelastic variable stiffness pendulum isolator (SVSPI) is developed by incorporating superelastic shape memory alloy (SMA) with the multi-stage variable stiffness pendulum isolator (VSPI), which featured with the favorable adaptability under service conditions and near-fault excitations. Based on OpenSees platform, the numerical model for novel multi-stage superelastic variable stiffness pendulum isolator is created. A fractional factor based design method is suggested for parameter optimization of the multi-stage superelastic variable stiffness pendulum isolator. The example bridges with the novel isolators are designed to conduct the seismic mitigation investigation under near-fault earthquakes. The effectiveness of the novel superelastic multi-stage variable stiffness pendulum isolator and suggested design method is further discussed by case study. Results show that the novel multi-stage superelastic variable stiffness pendulum isolator designed by the proposed fractional factor based design method can perform the dual control of the isolator residual displacement, girder displacement, and base forces in piers for bridges. The effectiveness of the multi-stage superelastic variable stiffness pendulum isolator with the optimal parameters is demonstrated by case study. The technical achievements can provide reliable basis for structural resilience enhancement and potential structural applications.

Deep liquid tanks in seismic response control of asymmetric high-rise buildings

The present work investigates the usefulness of installing deep liquid storage tanks (DLTs) on the roof of high-rise buildings with plan irregularity. The aim is to assess the damping efficiencies of DLTs in reducing responses of high-rise buildings with plan irregularity, considering the effect of their placement and direction of the external excitation. A DLT has a higher liquid depth to tank length ratio as compared to the traditional tuned liquid dampers (TLDs). A 70 m tall, 20-storey reinforced concrete framed building with asymmetry in plan is considered for the numerical assessment. The system coupling facility of ANSYS Workbench is utilized to study the structure-fluid coupled dynamics. ANSYS Transient Structural module solves the structure part using the finite element analysis (FEA), whereas, ANSYS (FLUENT) uses the finite volume method (FVM) to solve the fluid part. The authors [1] developed a practical framework to demonstrate the efficacy of DLTs for symmetrical building, which is extended in the present study for asymmetric building. In this paper, the validity of the framework is presented through an equivalent tuned mass damper (TMD) analogy. It is observed that for an asymmetric high-rise building, eccentric placement of DLT gives better response reduction, both in terms of peak roof displacement and acceleration.

Seismic response control of building structures under pulse-type ground motions by active vibration controller

Active vibration control systems are commonly reported to be the most robust and effective method for vibration control of structures. However, the type of ground motions and the type of analysis may greatly influence their performances. This study investigates the seismic response of building with and without an active controller under pulse-type ground motions. A 20-story non-linear steel benchmark building is considered. Linear and non-linear analysis is conducted to check the effectiveness of the active control system. Active control with a linear quadratic Gaussian (LQG) control algorithm is applied to the benchmark building for seismic control purposes. Initially, some ground motions are selected following earlier studies from the literature concerning the benchmark building. It is found that the LQG control algorithm is quite effective under the considered earthquakes, and the analysis type does not affect the effectiveness of the controller. Thereafter, a set of additional 69 pulse-type ground motions are considered to check the performance of the LQG control algorithm and to find the suitability of linear analysis. It is noticed that under such pulse-type ground motion, the LQG control algorithm is not much effective if the non-linear behavior of the structure is incorporated in the seismic analysis, whereas in case of linear analysis, the LQG control algorithm is still effective. It is concluded that neglecting the non-linear behavior may lead to unconservative estimates of the seismic response when performing seismic analysis and designing structures equipped with active vibration control systems.

Development and performance evaluation of a robust suboptimal H ∞ ‐based proportional–integral controller–observer system with target tracking for better control of seismic responses

Development and performance evaluation of a robust suboptimal <i>H</i> _∞ ‐based proportional–integral controller–observer system with target tracking for better control of seismic responses

Optimum design of a tuned‐mass damper with negative stiffness device subjected to ground excitation

In this study, a negative stiffness device based on the magnetic principle is presented and experimentally tested. Then, a tuned mass damper with a negative stiffness device (denoted as TMD_NSD) subjected to harmonic support excitation is optimized in terms of H∞ optimization criterion, H2 optimization criterion, and stability maximization criterion (SMC). Closed-form expressions for the optimal tuning parameters are derived in terms of both H∞ criterion and SMC, while the optimal tuning parameters are numerically determined in terms of H2 criterion. The control performance of the TMD_NSD is compared with the classical TMD in terms of maximum dynamic amplification factor (DAFmax). It is found that the performance of the TMD_NSD based on these three optimization methods is superior to that of the classical TMD. Besides, the performance based on H∞ and H2 optimization is almost similar, while the performance based on SMC is less than the first two methods. Compared with the classical TMD, the TMD_NSD could significantly reduce the primary system's peak value and broaden the efficient frequency range of vibration mitigation. However, surprisingly, the DAFmax decreases with the increase in the mass ratio of the classical TMD, while the DAFmax for the TMD_NSD increases with the increase in mass ratio. Finally, the effectiveness of optimization methods in seismic response control is examined via time history analyses (THA) under 20 real earthquake excitations. The THA findings suggest that the TMD_NSD is superior to the TMD for seismic response mitigation for the three optimization methods. However, it is noted that the displacement response of TMD_NSD based on H∞ and H2 optimization is comparable but slightly better than that of the SMC method. Nevertheless, in terms of absolute acceleration control, it is shown that TMD_NSD performance based on the SMC method is better than that of the H∞ and H2 methods. Overall, the three optimization methods are validated to be effective for seismic mitigation of the un-damped single-degree-of-freedom (SDOF) primary structure subjected to real seismic excitations.

An adaptive friction isolation system for seismic response control of buildings

This paper proposes an adaptive friction isolation system (AFIS) composed of shape memory alloy (SMA) cables and double friction pendulum bearings (FPBs). Double FPBs with different friction coefficients enable two-level response characteristics that are advantageous at frequent and design basis hazard levels, while SMA cables with initial slack provide adaptive response at maximum considered earthquake hazard level. SMA cables are arranged vertically and they limit excessive isolation displacement by providing hardening effects and additional energy dissipation capacity. They also improve the stability of FPBs under severe earthquakes. Based on the experimental response of FPB and SMA cables, a high-fidelity finite element model of AFIS is first established in ABAQUS. Then, to study the effectiveness of the AFIS in controlling seismic response of structures, a simplified model of the AFIS is developed in OpenSees and nonlinear time history analyses of a seven-story steel frame building isolated with AFIS are conducted. The results show that the AFIS can satisfactorily meet displacement demands under frequent and moderate earthquakes, while it effectively reduces the excessive displacement of the building under severe earthquakes. In particular, the AFIS considerably improves the performance of the isolated building under pulse-like near-fault earthquakes.

Optimization of inerter system for seismic response control based on a modified genetic algorithm with differential crossover strategy

The damping enhancement effect of the inerter system means that its energy dissipation efficiency can be improved with respect to the traditional dampers. Energy dissipation efficiency have been considered as the optimal design principle of the inerter system, however, the solution for optimized key parameters is difficult because of the special mechanical behavior of the inerter. A modified float-point encoding genetic algorithm is proposed in this study to realize the optimal design of the inerter system with maximized energy dissipation efficiency effectively and robustly. A novel and simple crossover strategy termed differential crossover is proposed and applied in the classical genetic algorithm to optimize the inerter system more effectively. The differential crossover strategy means that a new individual is generated based on the difference between two randomly selected individuals in the population. The mathematical expression for the optimization problem of the inerter system corresponding to the maximum energy dissipation efficiency design principle is established. Following the performance-oriented design concept, performance demand is taken as the constrained condition of the optimization problem. Case design confirms that the modified genetic algorithm can successfully solve the optimization problem of the inerter system and perform a better solving ability over the original genetic algorithms.

Seismic Response Control of T-Shaped Porcelain Column Circuit Breaker Based on Shape Memory Alloy Cables

Seismic Response Control of T-Shaped Porcelain Column Circuit Breaker Based on Shape Memory Alloy Cables

Optimum arrangement investigation of LRB and FPS isolators for seismic response control in irregular buildings

The objective of a base isolation system is to decouple the building from the damaging components of the earthquake by placing isolators between the superstructure and the foundation. In this paper, an optimum arrangement of lead rubber bearing (LRB) and friction pendulum system (FPS) is investigated in irregular buildings, and its performance is compared with a regular case. For this purpose, 3 types of irregularities according to ASCE/SEI 7–16 and 3 types of story buildings have been performed. Accordingly, various possible combinations have been applied for the isolators in each model. Afterward, the numerical models have been analyzed using nonlinear time-history analysis. The obtained results show that the application of FPS and LRB isolators in outer and inner columns led to better performance compared to the other arrangements. In this configuration, the inter-story drifts and base shear are reduced, and also the energy dissipation is increased more than in other arrangements. The reason for the superiority of the selected combination is due to the characteristics of FPS isolators in balancing the applied forces with the building’s mass and preventing torsion occurrence in irregular structures. Unlike the irregular buildings, the application of FPS and LRB isolators in inner and outer columns, result in better performance by reducing the story drifts in regular structures.

Resilient active seismic response control of structural systems

This paper proposes a dissipative resilient observer and controller (DROC) design for a network controlled system (NCS) that handles faults, implementation errors, or cyberattacks that can be modeled as bounded controller or observer gain perturbations. It presents linear matrix inequality (LMI) conditions for the robust stability of the system in the presence of bounded perturbations in the observer and controller. Furthermore, a new LMI-based time-delay control (TDC) algorithm that mitigates the effects of perturbations due to time-delays in the NCS is introduced. The robust methodology is applied to active control of a scaled model of a structural system equipped with an active mass driver system. The results demonstrate that the proposed methodology is robust and ensures stable system response due to various types of earthquake base excitations.

Seismic response control of modal building using shape memory alloy tension sling damper

Seismic response control of modal building using shape memory alloy tension sling damper

Seismic response control of base-isolated structures with fluid inerter damper

Seismic response control of base-isolated structures with fluid inerter 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.

Seismic response control of modal building using shape memory alloy tension sling damper

Seismic response control of modal building using shape memory alloy tension sling damper

Optimal design of tuned viscous mass damper for acceleration response control of civil structures under seismic excitations

The tuned viscous mass damper (TVMD) is one of the effective inerter-based systems for vibration control of civil structures. TVMD is composed of an inerter, a spring, and an energy dissipation element (EDE). Although the optimal design of TVMD has already been well investigated, the research findings focusing on the TVMD design for acceleration response control of the primary structure under seismic excitations are sparse. In this study, three closed-form solutions of TVMD optimal design parameters are proposed under the hypothesis of harmonic and white noise seismic excitation to mitigate the acceleration response of the undamped primary structure. Numerical analysis results indicate that the proposed closed-form solutions can still provide a good estimating of the TVMD optimal design parameters for the lightly damped primary structure whose damping ratio is less than 0.05. The control performance of TVMD is regarded as the effective damping ratio added to the primary structure, and the analytical expression of the effective damping ratio of TVMD is therefore derived. Further, a novel concept of effective damping ratio enhancement (EDRE) effect is proposed to explain the better control performance of a TVMD than a bare EDE with the same damping coefficient. It is found that TVMD designed by the proposed closed-form solutions (with the hypothesis of white noise seismic excitation) can ensure its better control performance than a bare EDE with the same damping coefficient. The control performance of three TVMDs (named as TVMD1, TVMD2, and TVMD3, respectively) designed by the proposed closed-form solutions is eventually corroborated by twenty sets of real seismic ground motions. The results show that TVMD2 is the most economical and efficient control scheme for structural seismic response control. Combining with the restricted condition for the proposed closed-form solutions, TVMD1 is still recommended in the case of mass ratio in the range of 0.25 to 0.50. If the higher control performance of TVMD is expected with its damping ratio larger than 0.125, TVMD3 is a better choice.