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To improve the efficiency of conventional isolation trench and lighten the impact of the excavation on neighbor buildings, a novel high damping isolation trench is proposed. The viscoelastic braces equipped in the high damping isolation trench can dissipate the energy of ground-borne vibration while providing supporting force to ensure the stability of the soil on both sides. According to two actual ancient buildings, two types of high damping isolation trenchs with the plane shape of U and L are designed to solve the potential damages caused by long-term train-induced vibration. First, three-dimensional finite/infinite models based on these two buildings are established, respectively. Then, the energy dissipation characteristics are obtained by experiments. Through calculation, the control effects of the high damping isolation trenchs for these two buildings are investigated. The results indicate that the viscoelastic braces possess high energy dissipation capacity. After setting the high damping isolation trenchs around the structures, even at a small excavation depth, the acceleration and velocity responses of the two buildings are reduced significantly. Furthermore, the selected U-shaped and L-shaped trenches also show superiority compared with the conventional linear-shaped trench in this project.

Magnetorheological damper is a typical semi-active control device. Its output damping force varies with the internal magnetic field, which is a key factor affecting the dynamic performance of the magnetorheological dampers. Existing studies about the magnetic field of magnetorheological dampers are limited to theoretical analysis; thus, this study aims to experimentally explore the complicated magnetic field distribution inside the magnetorheological dampers with multiple coils. First, the magnetic circuit of a three-coil magnetorheological damper was theoretically analyzed and designed, and the finite element model of the three-coil magnetorheological damper was set up to calculate the magnetic induction intensities of the damping gaps in different currents and numbers of coil turns. A three-coil magnetorheological damper embedded with a Hall sensor was then manufactured based on the theoretical and finite element analysis, and internal magnetic field tests under different conditions were carried out to obtain the actual magnetic induction intensities. At last, the magnetic field coupling model of the three-coil magnetorheological damper was proposed by introducing a coupling coefficient to describe the complex magnetic field distribution due to the strong coupling effect of the three coils, and the results calculated by the proposed model agreed well with the finite element analysis and magnetic field test data. The proposed model lays a foundation for the optimal design of the magnetic circuit and the mathematical model of multi-coil magnetorheological dampers.

A new kind of magnetorheological elastomer with the matrix of the bromobutyl rubber is developed. The magnetoviscoelasticity properties of the magnetorheological elastomer specimens are investigated with respect to different magnetic fields, displacement amplitudes, and frequencies under sinusoidal loadings. The experimental results show that the shear storage modulus and the loss factor of magnetorheological elastomers increase with the increasing magnetic field, excitation frequency, and the weight fraction of particles, but decrease with the increasing strain amplitude, and the magnetorheological elastomers have a high loss factor which can reach to 0.682. Then, a microphysical model based on the assumption of the chi-square distribution of the distance between adjacent ferromagnetic particles is proposed, which can eliminate the error generated by the assumption of the uniform distribution and describe the magnetorheological effect more exactly. Based on the proposed microphysical model, the magnetoviscoelasticity parameter model is modified to describe the dynamic properties of magnetorheological elastomers. It can be concluded from comparison between the numerical and experimental results that the modified magnetoviscoelasticity parameter model can describe the magnetorheological elastomer’s performance well.

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) 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.