The nonlinear dynamics of the bidirectional gear-driven friction nanogenerator（TENG）system is modelled by considering the time-varying meshing stiffness，time-varying support stiffness，transmission error，tooth side clearance and bearing clearance. The ode45 function is used to solve the vibration differential equations of system，and the time-varying meshing force diagram，time-frequency diagram，phase diagram，FFT spectrum diagram，Poincaré diagram，bifurcation diagram and three-dimensional spectrum diagram of the system are obtained，to explore the effect of the excitation frequency of the external load on the system dynamics characteristics. In addition，friction nano-generation technology is combined to obtain the output performance of TENG under different parameters，and to investigate the mechanism of the influence of external load excitation frequency and average engagement stiffness on the energy harvesting of the system. The results show that the bidirectional gear-driven friction nanogenerator mechanical transmission system has obvious nonlinear characteristics，and reasonable selection of the external load excitation frequency and meshing stiffness to avoid the control of unstable intervals can improve the mechanical energy conversion efficiency and increase the power generation capacity of TENG.

The axial compression of the landing gear strut can directly lead to the change of system stiffness and rotational inertia，but the effect of strut axial displacement is mostly ignored in existing models of nose landing gear shimmy. A nonlinear dynamic model of six-degree-of-freedom dual-wheel nose landing gear shimmy with axial displacement and longitudinal bending of struts is established. The bifurcation theory is applied to study the effect of introducing axial displacement on the shimmy region，and the maximum compression stroke of the buffer is combined with sliding speed，vertical load，and wheel rotational inertia，respectively. The combined parameters are analyzed by two parameter bifurcation. The fourth order Runge-Kutta method and fast Fourier transform are used to calculate the time-frequency characteristics in the stable shimmy region，and the interaction between the degrees of freedom of torsion，lateral bending，and longitudinal bending of the strut is studied. The results show that under certain conditions，considering the influence of axial displacement of the strut，the areas of torsional and lateral shimmy of the strut have a tendency to shrink. In the bistable region of double wheel nose gear shimmy，when the initial excitation is close to zero equilibrium state，the longitudinal shimmy occurs near 2 times the natural frequency of torsional vibration. When the initial excitation is far from the zero equilibrium state，longitudinal shimmy occurs near 2 times the natural frequency of lateral vibration.

The vibration reduction efficiency of a tuned mass damper（TMD）is closely related to the inherent parameters of the structure and TMD. Accurate identification of the structure and TMD inherent parameters from the response of the structure-TMD coupling system is necessary for the evaluation of the vibration reduction performance of in-service TMD. This paper offers a parameter identification approach based on NSGA-Ⅱ（Nondominated sorting genetic algorithm）that can identify the parameters of‘bare structure’ and‘bare TMD’ from the coupled structure-TMD response in order to solve the issue of state evaluation of TMDs in service. The structure-TMD coupling equation is constructed. It is reduced and transformed into a two-degree-of-freedom system of the structure-controlled mode and TMD coupling. Two objective functions are constructed by means of the system state space matrix. The genetic algorithm is used to find the optimal solution corresponding to the minimum error between the theoretical value and the experimental value，so as to identify the modal parameters of the structure and TMD. The numerical simulation analysis of parameter identification of single-degree-of-freedom structure-TMD coupling system and multi-degree-of-freedom structure-TMD coupling system is carried out. The results show that the proposed method can accurately identify the inherent parameters of structure and TMD from the dynamic system response of the coupling system.

In order to compare the seismic performance of different station-bridge combination systems under transverse seismic action，this paper takes an actual station-bridge separation system as the research object，designs a station-bridge integrated system combined with the actual situation，considers the nonlinear effect of bridge piers and supports，and the nonlinear sliding friction effect between expanded foundation，gravel cushion and metro station roof. A three-dimensional nonlinear dynamic model is established by using the finite element software MIDAS/Civil，and the dynamic response and pier damage of the composite system of two different stations and bridges under the cross-bridge seismic input are studied. The results show that under the unusual seismic lateral input，compared with the station-bridge integrated system，the station-bridge separation system can prolong the structural period and effectively reduce the dynamic response of the pier bottom and the supporting column of metro station. For the two combined station-bridge systems，the internal force response of the supporting column corresponding to the position of the pier is greater than that of other ordinary supporting columns. Under the lateral seismic input of the rare earthquake，compared with the stationbridge integrated system，the station-bridge separation system appears later in the plastic state，the final damage degree is lighter，the time of the support entering the nonlinear stage is later，and the overall deformation of the bridge pier is smaller. The seismic performance of the station and bridge separation system is better under the transverse earthquake action. However，in the actual project，attention should be paid to the increase of internal force caused by the transverse frame effect of the subway support column and the limit of the bridge foundation slip.

In the dynamic impact response analysis of the structure，the dynamic amplification factor（DAF）is usually used to simplify the calculation of the dynamic response of the structure. However，the size of DAF in engineering structures is still controversial. In order to solve this problem，the analytical expression of DAF of multi-degree-of-freedom system（MDOF）is derived in this paper，and the precondition of DAF greater than 2.0 is analyzed. The accuracy of the analytical expression is verified by the single-degree-of-freedom（SDOF）and MDOF example models，and the reason why the DAF of the MDOF is greater than 2.0 is explained. Finally，based on the DAF analytical method proposed in this paper，the DAF distribution law of beam string under cable breaking impact is analyzed. The analysis results show that when the contribution of a first-order modal shape is opposite to the static response，the DAF of the beam string may be greater than 2.0. Even for the damping system，the DAF of the beam string may be greater than 2.0.

Bridge health monitoring data often encounter missing values due to sensor failures and other factors. Existing data recovery methods have not effectively utilized the temporal and spatial correlations in the data. In this paper，a multi-channel recovery method for bridge monitoring data based on temporal and spatial correlations is proposed. The original data is preprocessed using a Kalman filter to eliminate random errors. The preprocessed data is divided into training and testing sets，and training samples are constructed using a sliding window approach with masking. The data recovery issue is formulated as a time series prediction issue. Besides，an end-to-end LSTM network architecture is trained to leverage the temporal and spatial correlations in the historical data of the sensors which enables the recovery of missing data. The proposed method is validated using the measured deflection and cable force data from a suspension bridge，and the performance of single-channel and multi-channel data recovery is discussed. Compared to the traditional RNN models，results show that the proposed method achieves a 22% improvement in accuracy when the data missing rate is 60%. Moreover，the method effectively utilizes the temporal and spatial correlations among different channels，enabling simultaneous recovery of data from multiple channels.

In this paper，we propose a general displacement field function method，which consists of the highly freely chosen basic function and a series of undetermined weighted coefficients to study the free vibration characteristics of GPLs/Al composite plate with an array cutouts. This general displacement field function method can solve the boundary constraint dependence when choosing the displacement field function to obtain the analytical solution in classical plate theory. There is a linear correlation between the weight coefficients. The system of linear equations is constructed based on the boundary constraints，thus the fundamental system of solutions can then be determined. By changing the system of linear equations as well as the fundamental system of solutions，the type of boundary constraint can be easily transferred. This proposed semi-analytic method not only solves the problem of assumed field function dependence on boundary constraints in the classical solution，but also has the superiority of fast conversion of boundary conditions. Meanwhile，by introducing the scatter integral method，a much more efficient and robust method is obtained other than the continuous integral method on the study of free vibration for the structure with an array cutouts. In this paper，we study the free vibration of GPLs/Al composite plates with a single and array cutouts. From the natural frequency and modal analysis，it is found that the generalized mass matrix and stiffness matrix of the open structure decrease synchronously when the cutouts distributed uniformly，and its free vibration characteristics tend to that of the complete plate.

The transverse free vibration characteristics of a two-dimensional nanoplate with axial velocity are investigated based on the nonlocal strain gradient theory. The vibration control equations for the in-plane advection of the system are established according to the generalized Hamilton’s principle，and the intrinsic frequency of the nanoplate is derived by using complex modal analysis in the case of a four-ended simple support. The critical velocity of the system is determined by the equilibrium solution of the control equations，and the real and imaginary parts of the first-fourth-order modal functions are further analyzed for both the sub-critical and the supercritical velocities. The numerical results show that the scaling effect leads to a change in the self-oscillation frequency of the system at the micro- and nanoscale，and the nonlocal and strain gradient parameters have‘softening’ and‘hardening’ effects on the equivalent stiffness of the nanoplates，respectively，which affects the intrinsic frequency and the modal function of the nanoplates. This affects the intrinsic frequency and mode function of the nanoplates，and the higher order frequencies and vibration modes are more significantly affected by the size parameters.

The wind uncovering effect of the roof of a large-span terminal building is one of the important factors affecting its structural safety. Existing studies only consider the benign wind climate and static wind load effects，which are difficult to explain the real wind uncovering pattern and occurrence mechanism of the roof structure under the strong typhoon dynamic load. Based on WRF，CFD and LS/DYNA，this paper carries out the numerical simulation of continuous wind damage of a large-span terminal building under the action of typhoon. The wind field simulation of typhoon "Hegeby" was carried out firstly. The continuous wind uncovering process of the terminal roof under the typhoon was simulated by taking an international airport terminal building as an example，and the wind damage pattern and wind damage rate of the roof cover under different wind angles were compared and analyzed to reveal the wind damage mechanism of the large-span terminal building under the typhoon. The results show that the extreme wind pressure at the windward edge of the terminal roof is higher，and the effect of upward and downward pressure is obvious，and the maximum pressure difference coefficient is 12.41. When the critical wind speed is reached，the windward edge of the roof is partially lifted by the wind，and then the "chain effect" triggers the continuous wind damage of the roof，and the tearing direction of the roof is consistent with the incoming flow direction. The energy failure index K is given based on the law of internal energy change before and after the failure of roof units，which can be used to guide the design of large-span terminal building roofs against wind uncovering.

In order to clarify the collapse mode of multi-span simply-supported beam bridges of high-speed railway，a 10-span high-speed railway simply-supported beam bridge in northwest China is taken as the actual engineering background. Combined with the characteristics of double block ballastless track structure on the bridge，the track-bridge integration research model is established. The collapse mode of this kind of ballastless track bridge in high intensity earthquake zone is studied by using explicit integral method and energy method. The results show that the key parts of the destruction of high-speed railway multi-span simply-supported beam bridge mainly concentrate on the track area of the bridge expansion joint，the concrete area of the support and the support contact surface，and the bottom area of the pier. The energy ratio of the 10-span high-speed railway simply-supported beam bridge collapse discrimination is 89.33%. By coupling the track plate and the groove section at the bridge expansion joint to optimize the structural system，the integrity of the track and bridge connection is improved，so that the track at the bridge expansion joint avoids becoming the key part of the destruction at the early stage of the earthquake. The collapse time of structural system is prolonged by about 45%，and the probability of the beam falling is reduced，so that the overall collapse resistance ability of the bridge is improved.