Extracting sensitive damage features from structural response signals is crucial for damage identification methods based on pattern classification. To this end，a hybrid network that combines a deep belief networks （DBN） and a long-short term memory （LSTM） network is proposed through a hybrid learning mechanism to utilize the merits of both networks in the aspects of extracting high-order abstract features and considering data sequence correlations. First，transmissibility data from response signals are sequentially input into the DBN to achieve the initial data compression and feature extraction，reducing the redundant information in the responses. Then，the extracted feature sequences are input into the LSTM network to consider the correlation between the different responses for acquiring the relevant sensitive damage features. Finally，a classification layer with the Softmax function is used to classify the features output by the LSTM network. Thereby，different structural damage patterns can be identified. The damage identification results on a three-dimensional experimental steel frame demonstrate that the hybrid learning mechanism can better train the network parameters，and the fine-tuning on the whole hybrid network contributes to the subsequent damage feature classification. Under the pollution of numerical or measured noises，the hybrid network can still effectively perform the data compression，feature extraction and classification. The various damage scenarios of the experimental frame are well identified.

Milling vibration problems can increase tool wear and reduce part machining accuracy，the suppression of which is a hot research topic in the field of milling. In order to suppress forced vibration in milling and enhance the stability of the machining system，a spindle-tool system is proposed based on electromagnetic actuators technology. The electromagnetic actuators are mounted in the spindle-tool system and acts on the toolholder position，using its controlled electromagnetic force for vibration suppression. Firstly，the structure and working principle of the system is described and the milling dynamics of the system is modelled. Secondly，based on the working principle of electromagnetic actuators，a PD controller is designed and the dynamic model and controller are simulated and verified. Finally，machine vibration signals are collected and external excitation experiments are carried out on a rotor test bench simulating tool process. Simulation and experimental results show that the spindle-tool system based on electromagnetic actuators under PD control law can effectively suppress the forced vibrations during the milling process.

The rod string is a thin rod string composed of a coupling and a rod connected by threads. The research on the dynamic behavior of the sucker rod string is the basis to prevent the failure of the sucker rod string and reduce the operation cost of the oil well. In view of the coupling vibration of rod string，it is proposed that the torsional torque generated by the friction force between the rod and tubing is the excitation of torsional vibration. Considering the influence of friction force on the coupling vibration of rod string，a simulation model of the coupling vibration of rod string in one directional well with initial bending is established under the conditions of displacement excitation at the top，load excitation at the bottom，trajectory excitation at the curved hole and tubing constraint. The four-order Runge-Kutta method is used to solve the simulation model and to simulate the dynamic behavior of the rod string. The simulation results show that： both longitudinal and transverse vibration simulation results are affected by the coupling vibration of the rod string. The effect on longitudinal vibration is not obvious. The contact force between the rod and the tubing in the inclined section of the oil well is high，and the collision in the compressed section of the rod string is serious. Hence，the inclined section of the oil well and the compressed section of the rod string are dangerous points for eccentric wear. Under normal preload conditions，the torsional vibration of the rod string is not sufficient to cause the rod string to trip. However，when the preload force of the coupling drops below the maximum torque of the rod string，torsional vibration may cause the rod string to trip. The research provides a theoretical basis for analyzing the failure mechanism of pumping rods，improving the working life of pumping rods and optimizing the design of pumping rods.

The star-shaped negative Poisson’s ratio structure is used as the core of sandwich panels. The dynamic model of a sandwich plate is established，and the equivalent elastic parameters of sandwich layer are derived. The equations of motion of sandwich plates are derived based on Hertz theory，first order shear deformation theory and Hamilton principle. Then，the equations of motion are solved by navier method. The contact force of the impact model is obtained through the spring-mass model with two degrees of freedom，and the lateral displacement of the sandwich plate after impact is calculated by Duhamel integral. The predicted results of plate contact force and lateral displacement are compared with the published papers to verify the accuracy. Meanwhile，the low-velocity impact response of star-shaped negative Poisson’s ratio sandwich panels is also compared with the negative Poisson’s ratio concave hexagonal honeycomb sandwich panels，and the influence of the parameters of sandwich panels is also discussed. When the impact velocity increases，the maximum contact force and the maximum lateral displacement of the sandwich plate also increase，while the duration of the impact response decreases. The greater the thickness ratio of the sandwich plate is，the better the impact performance of the sandwich plate will be. The smaller the side length ratio of cell is，the better the impact performance of sandwich plate will be. The increase of the cell concave angle enhances the impact performance of the sandwich panel. This study can provide some reference for the study of impact resistance of negative Poisson’s ratio metamaterial structures and sandwich panels.

Tianjin Metro Line 6 is adjacent to Beiyangyuan Campus of Tianjin University，and the train operation may cause adverse vibration effects on important infrastructures of the campus. In this paper，the National Facility for Earthquake Engineering Simulation of Tianjin University，which is close to the line，is taken as the research object. Firstly，the site vibration test is carried out on the sites distributed along the line and the adjacent constructions，through which the vibration attenuation law along the site and the vibration level of the control points in the constructions are studied. Furthermore，a whole process finite element model of tunneling-site-facility constructions is established，and the vibration simulation analysis of site and facility constructions is carried out considering whether the protected river exists or not （actually there is a protected river）. The vibration isolation efficiency of the protected river is emphatically discussed. The research shows that the vibration impact of the operation of Tianjin Metro Line 6 on the large-scale earthquake engineering simulation research facilities of Tianjin University meets the limit requirements of the code. Affected by Tianjin soft soil and the protected river，the vertical acceleration attenuation of the site is significant，and the attenuation rate reaches 97.33% from 0m to 80 m. The design of the mass concrete foundation of the facility and its bottom pile foundation is helpful to the vibration control of the foundation itself. Due to the presence of protected river，the amplitude of the site and the large shaking table foundations was reduced by 40.87% and 27.97%，and the frequency spectrum of the site showed obvious “double peak” phenomenon in 0~20 Hz and 40~80 Hz bands.

To establish a 3D metro train-FST coupling model in the frequency domain，the key problem of the rail displacement at each moving wheel-rail contact point caused by all moving wheel-rail forces needs to be solved firstly. The matrix of the TFC establishes the relationship between them. Based on the established 3D discrete supported floating slab track model in the frequency domain，a method to calculate the TFC is put forward in this paper. Based on the relationship between the fixed and moving coordinate systems，the TFC to a moving point on FST can be written as the integration of the rail displacement response at a fixed point in the frequency domain caused by a moving harmonic load. After calculating the TFC of the 3D FST，some conclusions are obtained. At each excitation frequency，the TFC of a moving wheel-rail force to each wheel-rail contact point is the largest at the point of the force itself. Due to the moving of the wheel-rail force，there is a certain difference between the TFC of the front axle wheel-rail force to the rear axle wheel-rail contact point and that of the rear axle wheel-rail force to the rear axle wheel-rail contact point. In the same bogie，the TFC of the left wheel-rail force of the front axle to the right wheel-rail contact point of the same axle is similar to the TFC of that force to the left wheel-rail contact point of the rear axle. It is advisable to use a 3D model to finely analyze the dynamic characteristics of floating slab tracks.

Aiming at the problem of the multi-order modal vibration of flexible wind turbine tower，a self anchored damping cable is designed in this paper，which converts the angular displacement of tower bending vibration into linear displacement，and drives the damper to dissipate energy and reduce vibration. Firstly，the tower-damper-cable vibration equation is established，and the analytical solution of the additional damping ratio provided by the damper cable for the first two-order bending vibration of the wind turbine tower is obtained. Then，the relationship between the damper viscosity coefficient and the additional damping ratio provided by the damper cable for the first two-order modal vibration of the wind turbine tower is analyzed through model experiment. The results show that the damping cable can provide a large additional damping ratio for the first two-order bending vibration of the tower，and the analytical solution of the additional damping ratio is in good agreement with the experimental results. Finally，based on the theoretical calculation formula of additional damping ratio，the influence of parameters on the damping performance of damping cable is analyzed.

This article investigates the optimization problem of a novel base isolation system by introducing a passive network consisting of one damper，one spring and one inerter and a grounded element with negative stiffness. The dynamic equations of the system are established and the frequency response function in the dimensionless form is derived. Since it is found that the amplitude-frequency response curves pass through four fixed-points，the extended fixed-point method is utilized to solve the parameter optimization problem. The explicit expressions of the optimal inertance-to-mass ratio，the optimal natural frequency ratio，and the optimal corner frequency ratio of the system are derived by adjusting the four fixed points to the same height. The expression of the optimal damping ratio is calculated by letting the amplitudes of the three invariant frequencies among the four fixed points to the same amplitudes as those of the four fixed-points. A necessary and sufficient condition for the system with optimal parameter values to be stable is derived by utilizing the Hurwitz stability criterion. Compared with other three optimal isolation systems，the optimal isolation system in this article can provide better H_∞ performance and better output responses in the multi-storey building vibration system.

Vehicle transport is an important part of logistics transport. It is of great significance to study the response of cargoes in the process of vehicle transport. Considering the coupling effect between cargo and vehicle bottom，an 11-degree-of-freedom vehicle-cargo coupling model is established. The relationship between three-way response is compared，and the influence of different road levels and cargo-related parameters （load，stiffness，damping） on the system response is taken into consideration. The results show that the coupling effect of vehicle-cargo significantly affects the system response. The influence of rotation in transportation cannot be ignored. The vibration response of cargo increases with a decrease of load，stiffness and damping. The worse the road condition is，the bigger the vibration response of cargo and vehicle bottom will be. The research results are of great significance and value for the design of vehicle-cargo transportation system.

In order to solve the problem of seismic design of continuous beam bridge in which the longitudinal seismic inertia force is only carried by the fixed pier，the seismic potential of the movable pier is fully exerted with the same section as the fixed pier. Based on the principle of wrap rope，the mass rotation wrap rope device excited by additional mass inertia force is developed to realize the cooperative force of fixed pier and movable pier and limit the relative displacement of beam end. Based on the working principle and structural characteristics of the device，the restoring force model of the device is proposed，and through a 3-span regular continuous beam bridge，the finite element model of the whole bridge is established. The effects of additional mass，friction coefficient and initial relaxation coefficient on the vibration reduction performance of continuous beam bridge are systematically analyzed. The results show that the effect of mass rotation wrap rope device on reducing the seismic response of fixed pier and lifting the movable pier to participate in the longitudinal whole cooperative force of continuous beam bridge is obvious. The influence of parameters of different seismic wave input characteristics is slightly different，but reasonable design parameters of the device will produce a more obvious effect of shock absorption.