A novel method for nonlinear force reconstruction has been developed to reproduce the stick-slip friction contact behaviors of joint interface. Nonlinear substructure modeling is employed to simplify the complex jointed structures into the linear substructures and nonlinear joints. An inversion technique has been developed to eliminate the singularity of transfer matrix，extracting only the transfer relationship between the degree-of-freedoms of nonlinear joints and measuring locations. The harmonic balance method is used to directly apply the measured nonlinear dynamic responses of the linear substructures to reconstruct local hysteresis nonlinear contact forces of the bolted joint interface. Numerical simulations and experimental investigations of a lap-type bolted joint beam system have been performed to verify the nonlinear force reconstruction process，and to investigate the effects of stick-slip friction contact at the bolted joint interface. The good agreement between the comparison results validates the proposed nonlinear force reconstruction method，and the reconstructed nonlinear virtual excitation can be further used to detect the loss of bolt preload effectively.

In this paper，the analytical model of the vibration characteristics for the composite double-layer spherical shell and annular plate coupled structure under different boundary conditions is constructed using the spectral geometry method based on the first-order shear deformation theory，and the boundary conditions of the coupled structure are simulated by the artificial virtual spring technique. The coupling relationship between the sub-structures is simulated by arranging the coupling spring simulator according to the connection relationship. The Hamiltonian principle is applied to derive the characteristic equations of the composite double-layer spherical shell and annular plate coupled structure，and the inherent characteristics and steady-state response of the coupled structure are solved. The results obtained are compared with the results of finite element method to verify the correctness of the calculations. The effects of geometric parameters，material parameters on the vibration response of the composite double-layer spherical shell and annular plate coupled structure are analyzed.

Complex multi-mode signals can be decomposed into single mode components using time-frequency decomposition technology. This allows for the use of a simple and reliable single mode identification method to identify the complex modal signals of mechanical structure. Empirical wavelet transform (EWT) method can effectively decompose the modes, and some revised methods even can overcome the strong noise. However, when reconstructing the modes, the reconstructed mode could be distorted due to overlapping filters and closely spaced components. Focusing on the problem of mode decomposition and reconstruction, this paper analyzes the problem of distorted reconstructed mode of EWT method, proposes a revised method based on the Iterative Truncated Singular Value Decomposition (ITSVD) method, and applies this new method to both the synthesis signal and the experimental signal from the vibration response of a mechanical structure model with a joint surface. The results suggest that the proposed ITSVD-EWT method is more effective in mode decompose and reconstruction.

At present，traditional Braille books have had difficulty meeting the needs of the blind，this paper proposes a new type of ultrasonic resonant Braille display cell based on the squeeze film generated by ultrasonic vibration. The Reynolds equation which determines the aerodynamic characteristics of the squeeze film is derived theoretically，the mechanical model and approximate solution of the output buoyancy are obtained by using the “piston effect” of the squeeze film，the vibration characteristics and output performance test of Braille display cell were tested using the built experimental platform. The results show that the resonant frequency of the Braille display cell is 30.8 kHz，when the peak-to-peak value of the excitation voltage is 130 Vpp to 200 Vpp，a stable squeeze film with certain buoyancy can be formed. The theoretical calculation results are basically consistent with the experimental results. In the experiment，three kinds of samples can be lifted from 13.92 μm to 47.71 μm，Braille display cell has sufficient output performance.

Recursive Least Squares algorithm is widely adopted in the field of micro-vibration adaptive control because of its simplicity and speed. Due to the particularity and complexity of the disturbance environment in the micro-vibration active control application，the robustness of the parameter adaptive algorithm used in the micro-vibration control needs to be considered. For the Multiple-Input Multiple-Output （MIMO） active vibration control system，this paper presents a MIMO robust parameter adaptive algorithm based on an Infinite Impulse Response （IIR） filter. This robust parameter adaptive algorithm takes advantage of the dead zone and normalization. The deducing process and convergence analysis of the robust parameter adaptive algorithm are illustrated in detail. A 3-DOF real time micro-vibration control experimental platform has been constructed. Comparison are provided with sine disturbance，double sine disturbance and broadband disturbance. Experimental results confirm the feasibility and robust of the proposed algorithm.

Soilbag，with the advantages of high bearing capacity，high damping ratio and low cost，is a kind of base isolation material which is suitable for the low- and mid-rise buildings. The relationship between shear stress-shear strain，dynamic characteristic parameters and shear strength of stacked soilbags were analyzed and discussed through a series of laboratory cyclic simple shear tests. The variation of dynamic shear modulus and equivalent damping ratio of stacked soilbags under different vertical stresses and shear strain amplitude was further investigated. And the influence of number of load cycles on the dynamic characteristic parameters and shear strength parameters was also studied. The test results show that the peak shear stress and dynamic shear modulus increase while the equivalent damping ratio decreases with the increasing number of load cycles under small-strain condition； when the shear strain is large enough，the interface slippage and the strain softening occur on stacked soilbags. The peak shear stress （shear strength） decreases with the increasing number of load cycles. And the variation of dynamic characteristic parameters is totally opposite to that under small-strain condition. The internal friction angle of the shear strength parameters of stacked soilbags gradually decreases with the increasing number of load cycles while the additional cohesion force increases and tends to be stable during the test. The energy is dissipated through the shear deformation of soil particles inside bags and the interlayer slippage of stacked soilbags under high shear strain amplitude.

This paper introduces a method of structural modal parameter identification based on visual vibrometry. For continuous and long time sampling video，this method ensures the accuracy and resolution of measurement results by setting local “virtual” measurement points and enlarging video slices，and significantly improves the data processing efficiency. It includes several steps： recording a video of the test structure under external excitations； Setting a series of “virtual measurement points” at the edge of the structure by using edge detection algorithm； Extracting apparent motions of “virtual measuring points” using optical flow methods，and then identifying natural frequencies and modal damping ratios using the stochastic subspace method； Estimating the full-field operational mode shapes of the structure by applying motion magnification to cropped videos. Two real-life tests are conducted to validate the procedure： firstly，vibration test of a model aircraft excited by a single sinusoidal input is used，where the response peak appears in the same frequency with the known-input. Secondly，operational modal analysis of a cantilevered beam is conducted using visual vibrometry，in which the first five modal parameters are estimated and compared to the measurement results using a Scanning Laser Doppler Vibrometer. It is shown that the maximum relative discrepancies of the natural frequencies and damping ratios are only 0.35% and 14.6%，respectively，and the modal shapes are also observed in excellent correlation.

Directed at the proposed earthquake reduction system，named the tuned tandem mass dampers （TTMD），the optimized analysis of the multi-degree-of-freedom （MDOF） structure-TTMD system has been investigated in frequency domain by the particle swarm optimization. The seismic simulation of the MDOF structure-TTMD system has been established under earthquakes. Considering different types of seismic records，the control efficiency of TTMD for the structural seismic responses was analyzed in the time domain and compared to that of the tuned mass damper （TMD） with the equal total mass ratio. Further taking into account the structural stiffness of the -10% and -30% degradations，the earthquake reduction behaviors of TTMD were scrutinized for the seismic responses of the structure with the stiffness degradation. It is found in terms of numerical results that the TTMD outperforms the TMD in seismic performance and robustness. Likewise，the TTMD has a drastically reduced damping demand，thus being an enhanced earthquake reduction system.

To enhance the seismic mitigation performance of conventional damped outrigger （CDO） system，this study investigates the seismic performance improvement of inerter-negative stiffness damped outrigger （INSDO） system，which is based on the three-element passive mitigation system consisted of inerter，stiffness and damper. The Clough-Penzien spectrum model is adopted to simulate stationary stochastic seismic excitation，and the motion equations of the structure-damper-excitation system are then expressed utilizing augmented state space method. The root-mean-square （RMS） of the structural response under stochastic excitation is calculated via the solution of Lyapunov equation，and optimal parameters of INSDO system are determined by multi-objective optimization method based on maximum harmful inter-story drift and acceleration control. The seismic performance of INSDO system under typical natural seismic records is further evaluated. Results indicate that compared with the CDO system，the optimum INSDO system can reduce the bottom average story drift RMS by 57.97% and the top average absolute acceleration RMS by 36.99% under El-Centro and Kobe excitations，which further verifies the effectiveness of multi-objective optimization method. Compared to the introduction of inerter or negative stiffness element alone，the combination of two kinds of element can further amplify the displacement of the damping element，and realize the seismic performance enhancement of INSDO system by improving the energy dissipation ratio of damper and seismic input energy.

It focused on the test and simulation study on the longitudinal load transfer law under the coupling shock condition of a roadrailer. The bogie of this type of the vehicle contains the towing plate and the yaw damper device，which are oriented in the longitudinal direction. Therefore the load transmission path and its value need to be investigated for further strength evaluation of the structural component. In the test，force sensors were installed on the key components. In the simulation，a comprehensive whole vehicle dynamic model，which contains 3 carbodies and 4 bogies，was established based on the theory and method of the rail vehicle and multibody dynamics. Meanwhile the collider is simplified to a mass considering its mass and speed to simulate the locomotive. Besides，it gave the modeling details of the yaw damper device and the towing plate. By the SIMPACK solver，the results demonstrate that the forces on the hook and the yaw damper device both increase with the impact speed increasing. Furthermore，the simulation results were slightly smaller than the test results，but the law is nearly the same. Under these conditions，the yaw damper had no effect. Therefore，the transmission path is only through the towing plate，which is useful for further strength evaluation.