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Viscoelastic (VE) dampers are one of the most promising techniques for reducing vibration in engineering structures caused by earthquakes and wind. This work aims to develop a kind of high-...

This paper aims to develop viscoelastic dampers, which can effectively suppress vibration in a wide frequency range. First, several viscoelastic materials for damping performance were selected, and different batches of cylindrical viscoelastic dampers were fabricated by overall vulcanization. Second, the dynamic mechanical properties of the cylindrical viscoelastic dampers under different amplitudes and frequencies are tested, and the hysteretic curves under different loading conditions are obtained. Finally, by calculating the dynamic mechanical properties of the cylindrical viscoelastic dampers, the energy dissipation performance of these different batches of viscoelastic dampers is compared and analyzed. The experimental results show that the cylindrical viscoelastic damper presents a full hysteretic curve in a wide frequency range, in which the maximum loss factor can reach 0.57. Besides, the equivalent stiffness, storage modulus, loss factor, and energy consumption per cycle of the viscoelastic damper raise with the frequency increasing, while the equivalent damping decreases with the increase of frequency. When the displacement increases, the energy consumption per cycle of the viscoelastic damper rises rapidly, and the equivalent stiffness, equivalent damping, storage modulus, and loss factor change slightly.

Viscoelastic dampers are a kind of energy-dissipation device with good damping performance. They are also extensively utilized in earthquake mitigation for structures in civil engineering. ...

Viscoelastic dampers are a kind of classical passive energy dissipation and vibration control devices which are widely utilized in engineering fields. The mechanical properties and energy dissipation capacity of the viscoelastic damper are significantly affected by ambient temperature. In this work, dynamic properties tests of the sandwich type viscoelastic damper at different environmental temperatures are carried out. The equivalent fractional Kelvin model which can characterize the mechanical behavior of the viscoelastic damper with varying frequencies and temperatures is introduced to describe the dynamic properties and energy dissipation capability of the sandwich viscoelastic damper. The self-heating phenomenon of the sandwich viscoelastic damper is studied with a numerical simulation, and the dynamic properties and energy dissipation variation of the viscoelastic damper with self-heating processes are also analyzed. The results show that the dynamic properties of the viscoelastic damper are significantly affected by temperature, excitation frequency and the internal self-generated heating.

The viscoelastic material is one of most popular shock absorbing materials for mitigating vibrations of building structures due to earthquake. Its dynamic performance is affected by the temperature, the excitation frequency and the excitation amplitude. Therefore, in order to study the non-linear dynamic performance of the viscoelastic materials, a hybrid test system using the electric exciter is proposed, in which the electric exciter is the actuator, MATLAB is used for the simulation of the numerical substructure and the communication between the upper computer and the lower machine, and STM32 single-chip microcomputer is used to control the work state of the electric exciter. Based on the equivalent force control method and the incremental PID control algorithm, a controller is designed to make sure the electric exciter produces accurate control forces to the non-linear test component in the physical substructure. It can be shown from the test results that the developed whole hybrid test system is feasible and effective.

The magnetorheological (MR) damping material is a kind of smart shock absorption material, and it can be made into MR dampers for reducing the vibration or dynamic response of structures. During the vibration mitigation control of structures with MR dampers, the displacement and acceleration responses are always concerned firstly because the displacement responses determine the safety of structures and, at the same time, the acceleration responses determine the comfort level of the human body staying in structures. That means, the control currents choice of MR dampers during the vibration process is a multi-objective optimization control problem. In this paper, the particle swarm optimization (PSO) algorithm is developed to control the displacement and acceleration responses simultaneously. Numerical analysis for a five-floor steel frame structure with one MR damper installed on each floor is carried out. Simulation results of the PSO control structure are compared with those of passive control (including the ON-control and the OFF-control) structures and the uncontrolled structure. Analysis results demonstrate that the PSO algorithm can reduce the displacement responses of the structure obviously and, at the same time, it can reduce the acceleration responses of the structure to a certain extent. Furthermore, the PSO algorithm reduces the seismic responses of structures more effectively than those of passive control structures.

Viscoelastic dampers are one of the most popular earthquake mitigation devices for building structures with a large number of applications in civil engineering. The seismic performance of viscoelastic dampers is greatly affected by viscoelastic materials. The present paper addresses the theoretical and experimental studies of the viscoelastic damper. The regular polyhedron chain network models for viscoelastic materials are proposed based on the molecular chain network microstructures and the temperature–frequency equivalent principle. Several dynamic property tests for the viscoelastic damper at different temperatures, frequencies, and displacements are carried out, and the proposed models are verified by comparing the numerical and experimental results. The comparisons show that the viscoelastic damper has perfect energy dissipation capacity, and the regular polyhedron chain network models can well describe the mechanical properties of the viscoelastic damper at different environmental temperatures and excitation frequencies.

Performance tests of magnetorheological (MR) dampers show that the hysteresis curves generally show an obvious force–lag phenomenon, which is due to the presence of trapped air in the working chamber of the damper. However, the force–lag phenomenon is barely considered in existing studies, and its influence on the seismic performance of MR damped structures is still unclear. In this paper, experimental and theoretical research have been carried out to analyze the force–lag phenomenon and its influence. Firstly, a specially designed MR damper was manufactured so that MR fluid can be poured into the damper successively for several times until the working chamber was filled, and performance tests were carried out correspondingly with different MR fluid perfusion densities (a parameter introduced in this paper to describe the volume fraction of MR fluid in the working chamber). The mechanical properties of the MR damper under different MR fluid perfusion densities were compared to reveal the influence of the force–lag phenomenon. Then, the effects of excitation properties on the force–lag phenomenon were discussed by comparing experiments results under different currents, frequencies and displacement amplitudes. Further, a force–lag mathematical model was proposed by considering the variation of the force-lag part with MR fluid perfusion density to reflect the force–lag phenomenon with different volume fractions of trapped air, and then verified based on the performance test data. Finally, numerical analysis of MR damped structures with different MR fluid perfusion densities was performed using the proposed force–lag mathematical model. Results show that the damping effect of MR control systems will be weaken due to the force–lag phenomenon, and with the increase of the MR fluid perfusion density, the seismic performance of MR damped structures will gradually improve.

Magnetorheological (MR) damper is a semi-active control device designed by utilizing the instantaneous fluid-solid conversion characteristics of MR fluid, thus the microstructure of MR fluid fundamentally determines the mechanical properties of MR dampers. In order to study the influence of MR fluid microstructure on the macroscopic mechanical properties of MR dampers, a micro-macro mathematical model for MR dampers was proposed to describe the dynamic properties of MR dampers affected by the microstructure of MR fluid. Firstly, the micromodel of MR fluid was brought into classic quasi-static model and the double-Sigmoid model to propose a mathematical model, which considers the MR fluid microstructure by expressing the yield force parameter in the traditional double-Sigmoid model with the microstructure parameters of MR fluid. By analyzing the data of the performance test of a single-coil MR damper, the parameters of the proposed mathematical model were fitted. The proposed micro-macro model for MR dampers was verified by comparing the results calculated by this model with the performance test data. Based on the proposed micro-macro mathematical model, the nonlinear hysteretic curves with different MR fluid microstructure parameters can be numerically analyzed and compared. Finally, the influences of the volume fraction, size, and coating thickness of ferromagnetic particles on the mechanical properties of MR dampers were revealed and discussed. The research can provide guidance for the preparation and formulation optimization of high-performance MR fluid.

To truly reflect the influence on structural seismic response control using viscoelastic dampers with strong nonlinear properties and reduce the cost and difficulty of experimental research, a new user-programmable hybrid simulation platform is developed. The core implementation details of this platform, including the core architecture, software system, and testing setup, are described. To better realize accuracy and stability of the hybrid simulation experiment, methods for solving the equivalent force equilibrium equation for hybrid simulation experiments on viscoelastically damped structures are proposed. Then, the mechanical properties of the experimental substructure (viscoelastic damper) are tested under different temperatures, amplitudes and frequencies, and the mathematical model parameters of the experimental substructure are identified. A seismic response comparison of viscoelastically damped structures obtained by the hybrid simulation experiment and the time history analysis verifies the robustness and reliability of the hybrid simulation platform to test nonlinear systems. Lastly, a series of hybrid simulation experiments for viscoelastically damped structures under different temperatures, seismic intensities and seismic waves are implemented using this hybrid simulation platform for the first time. The experimental results reveal the influence on structural seismic response control by viscoelastic damper under different temperatures, seismic intensities and seismic waves.

In this chapter, design and parameters optimization on intelligent control devices are introduced. Magnetorheological (MR) damper and MR elastomer are designed optimally as examples of semi-active control devices. The active control devices are also designed based on the control force optimization.

The basic principle of semiactive intelligent control method is introduced firstly, and then the commonly used semiactive control devices, such as magnetorheological (MR) damper, electrorheological damper, piezoelectricity friction damper, semiactive-varied stiffness damper, semiactive-varied damping damper, and MR elastomer device, are introduced in detail including basic principles, construction and design, mathematical model, analysis and design methods, test and applications.

The analytical method of the structures incorporated with magnetorheological (MR) dampers, including the elastic analysis and elasto-plastic analysis, is introduced. In this chapter, taking the building structure with MR dampers as an example, the models of the structure and dampers will be discussed. Finally, the dynamic response analysis method based on SIMULINK is introduced.

The control algorithm and theoretical dynamic analysis method of the intelligent controlled structure have been presented in detail in the previous chapters; this chapter will focus on the specific numerical examples. The building structure with magnetorheological (MR) dampers, the bridge with MR dampers, and the platform with MR elastomer devices are chosen to evaluate the control effects of the semiactive intelligent control devices. The building structure with active tendon system is taken as an example to verify the control effect of active control.

The intelligent vibration control strategies are applied to real structures through the intelligent controller, thus the hardware design of the intelligent controller is very important to the effectiveness of intelligent control of civil engineering structures. In this chapter, the intelligent controller of magnetorheological dampers is taken for example to introduce the hardware design method of intelligent controllers, and then experimental study is carried out to verify the effectiveness of the intelligent controllers.

The fuzzy control technology is a kind of intelligent control method, and it has strong robustness. The fuzzy control strategy is used to choose the control currents of MR dampers in this paper. In order to illustrate how to design the fuzzy controller, three kinds of the fuzzy controller having different membership functions and fuzzy rules are designed. A five-floor MR structure using the designed different fuzzy controllers is simulated. Analysis results show that for the MR structure, it is not best that MR dampers provide the maximum forces to the structure, so the displacement and acceleration responses of the structure must be weighed at the same time to make MR dampers provide reasonable forces when the membership functions and fuzzy rules are designed.

The control strategy is very important for semi-active control or active control systems. An integrated intelligent control strategy for building structures incorporated with magnetorheological (MR) dampers subjected to earthquake excitation is proposed. In this strategy, the time-delay problem is solved by a neural network and the control currents of the MR dampers are determined quickly by a fuzzy controller. Through a numerical example of a three-storey structure with one MR damper installed in the first floor, the seismic responses of the uncontrolled, the intelligently controlled, the passive-on controlled, and the passive-off controlled structures under different earthquake excitations are analyzed. Based on the numerical results, it can be found that the time domain and the frequency domain responses are reduced effectively when the MR damper is added in the structure, and the integrated intelligent control strategy has a better earthquake mitigation effect.

Magnetorheological (MR) damper is a prominent semi-active control device for earthquake responses mitigation of structures. The most important topic for the intelligent MR structures is choosing the control current of MR dampers quickly and accurately. The typical control strategy is on–off control strategy, i.e. bi-state control strategy, while inherent time-delay and coarse control precision lie in this strategy. This paper proposes neuro-fuzzy control strategy, in which the neural-network technique is adopted to solve time-delay problem and the fuzzy controller is used to determine the control current of MR dampers quickly and accurately. Through comparison between the bi-state control and the neuro-fuzzy control strategies and a numerical example about a three-story reinforced concrete structure, it can be concluded that the control strategy is very important for semi-active control, the neuro-fuzzy control strategy can determine currents of MR dampers quickly and accurately, and the control effect of the neuro-fuzzy control strategy is better than that of the bi-state control strategy.

The magnetorheological (MR) damper, a shock absorption device, can be used to reduce vibration or dynamic response of controlled systems. Its parameters can be adjusted in real-time by updating its control current, therefore, it is critical to determine the control current of the MR damper accurately and quickly. This study proposes a fuzzy control strategy based on a neural network forecasting model of the building structure with MR dampers, in which a neural network forecasting model is developed to predict dynamic responses of the system with MR dampers and a fuzzy controller is then designed to determine control currents of MR dampers. A five-floor steel structure with MR dampers using the proposed fuzzy control strategy is simulated by using Simulink. Simulation results of the fuzzy control system are compared with those of the bi-state control system, the passive-on control system, the passive-off control system, and the uncontrolled system. Analysis results demonstrate that the fuzzy control strategy can determine control currents of MR dampers accurately and quickly; furthermore, the fuzzy control strategy reduces seismic responses of structures more effectively than the passive-on control strategy, the passive-off control strategy, and the bi-state control strategy.

Magnetorheological (MR) dampers are one of the most promising devices for mitigation of vibration of engineering structures due to earthquakes and wind excitation. In this paper, a compact two-column model of an MR fluid is proposed in order to formulate a general solution for calculation of the yield shear stress of an MR fluid. The magnetic induction intensity in the damping gap, which is the key parameter of the compact two-column model, is determined through simulation of the magnetic circuit of the MR damper. To verify the effectiveness and significance of the proposed model, damping forces calculated based on the proposed model and the traditional single-chain model are compared with the experimental data. Results show that the proposed compact two-column model is more accurate and that it can describe the rheological properties of the MR fluids very well.

Magnetorheological (MR) damper has a potential use in the vibration control of large structures due to its lower energy input and fine earthquake mitigation ability. A key problem for controlling structure with MR dampers is choosing the control current quickly and accurately. In order to solve this problem, a new method by using fuzzy controller, namely fuzzy full-state control method, is proposed. Dynamic responses under different inputs of fuzzy controller are compared. At the same time, dynamic responses of the traditional bi-state (BS) controlled structure and the passive full-current (PFC) controlled structure under different earthquake waves are compared with those of fuzzy full-state controlled structure. Through a numerical example about a three-story reinforced concrete structure, it can be concluded that fuzzy control technique can realize choosing of currents of MR dampers quickly and accurately and have good control effect.

Semi-active control of buildings and structures with magnetorheological (MR) dampers for earthquake hazard mitigation represents a relatively new research area. In this paper, the Bingham model of MR damper is introduced, and the formula relating the yielding shear stress and the control current of MR dampers is put forward that matches the experimental data. Then an on-line real-time control method for semi-active control of structures with MR dampers is proposed. This method considers the time-delay problem of semi-active control, which can solve distortion of the responses of structures. Finally, through a numerical example of a three-storey reinforced concrete structure, a comparison is made between controlled structure and uncontrolled structure. The calculated results show that MR dampers can reduce the seismic responses of structures effectively. Moreover, the on-line real-time control method is compared with the traditional elastoplastic time-history analysis method, and the efficacy of the on-line real-time control method is demonstrated. In addition, the Levenberg–Marquardt algorithm is used to train the on-line control neural network, and studies show that the algorithm has a very fast convergence rate.

Magnetorheological (MR) damper, a kind of intelligent vibration mitigation device, can be used to reduce the vibration or dynamic responses of structures. Its damping forces can be adjusted in real-time by updating control currents of the MR damper according to the state parameters of the structure. In this paper, a single-chip microprocessor (SCM) for MR damper coupling sensing and control is developed. The SCM has three main functions: the first one is that it can collect the acceleration responses of the structure by using the acceleration sensor in real-time; the second one is that it can use the segmented control strategy to decide the control currents of the MR damper according to the collected acceleration information; the third one is that based on the PWM technology it can realize to accurately supply power for the MR damper. The developed SCM is tested through experiment. The analysis results of the simulation and experiment show that the SCM can collect the state information of the structure in real-time and realize to choose the currents of MR damper accurately to control the damping forces of the MR damper.