In order to solve the problem that it is difficult to fully consider the dynamic characteristics （amplitude-phase frequency characteristics） requirements in the PID parameter design of electromechanical servo system，a PID design method for dynamic characteristics is proposed. The 9-order Transfer Function （TF） model of electromechanical servo system is established based on dynamic equation. The relationship between Routh criterion and TF coefficient is used to supplement the stability constraint of the system and the compatibility constraint of TF coefficient to ensure the stability of the system and the compatibility of TF coefficient in the PID design process. On this basis，based on the idea of parameter identification，the rational fraction orthogonal polynomial method is used to identify the coefficients in the TF model，so that the PID parameters are quickly determined，which improving the design efficiency，and multiple groups of controller parameters that meet the original index can be identified by adjusting the index data. The simulation results show that the designed PID parameters not only meet the requirements of dynamic characteristics，but also take into account the compatibility of system stability and TF coefficient. The design results are in good agreement with the simulation experiments.

The problem of load identification denotes identifying loads based on the measurement of structural responses，which is the inverse problem in structural dynamics. A load identification method based on time-delay neural network is proposed in this paper，and numerical examples based on simulation and experiments are provided to show that the method overperforms normal back-propagation neural network in accuracy of identification. Additionally，statistic pooling is introduced on the basis of the method，and it is proved that the method performs well in noisy environment compared with BP neural networks. based on the load identification methods mentioned above，a sensor placement optimization based on particle swarm optimization algorithm is proposed，and the optimal sensor placement is able to reduce the error of identification by 90% compared with the random sensor placements，meanwhile the minimum spacing of installation among sensors is also ensured during the optimization.

Sparse regularization has been proven to be effective in addressing the ill-posed problem in moving force identification （MFI）. However，existing methods often neglect frequency characteristic disparities between static and dynamic components in moving loads，thereby limiting the identification accuracy. Therefore，an MFI method integrating response prior information and weighted dictionary is proposed. A linear relationship between vehicle-induced bridge responses and moving vehicle loads is established in bridge-vehicle system. Once frequency domain analysis is separately performed on bending moment and acceleration responses，the obtained frequency prior information is then employed to construct weighted dictionaries that correspond to both static and dynamic load components. Subsequently，the static and dynamic components of moving loads are individually solved by alternating direction method of multipliers （ADMM）. The effectiveness of proposed method is demonstrated through numerical simulations on a real bridge，and a series of MFI experiments are conducted in laboratory. Results show that the weighted dictionaries considering response prior information significantly improves the accuracy of force identification and enhance its robustness to noise.

The key to damage pattern recognition lies in digging and classifying damage features from the response data of civil structures. To this end，a stack auto-encoder network with several auto-encoder hidden layers and a Softmax classification layer is built for analyzing frame structures. A hybrid learning mechanism is adopted to combining unsupervised and supervised learning strategies. Finite element analysis is used to generate the transmissibility function samples corresponding to different scenarios of a frame structure. The transmissibility samples are then divided into training，validation，and test sets. The parameters of the auto-encoder hidden layers，such as the weights and bias，are determined by a pre-training strategy in order to avoid the phenomenon of network over fitting. A fine-tuning step is employed to adjust the pre-trained network parameters，and the network hyper parameters are further adjusted based on the validation set. The measured transmissibility data are input into the network to evaluate the damage of the frame structure. The analysis results show that the proposed method can effectively extract and classify the damage features. Both the single and double damage scenarios at the frame joints were identified with higher accuracy and better anti-noise ability than the traditional shallow neural network.

Vortex shedding and drift are key characteristics around the bridge girders during VIVs，and therefore it is necessary to reveal VIVs mechanisms of bridge girders from the perspective of vortex dynamics. A simplified vortex model was constructed from the perspective of aerodynamic work. Taking a typical streamlined-closed box girder as an example，a simplified wortex model was constructed from the perspective of aerodynamic work. Combined with the aerodynamic time-frequency characteristics of the bridge girder from wind tunnel experiments and the flow field characteristics around the girder based on numerical simulation method，the above model was verified and then the multi-order VIVs lock-in range mechanisms of the girder were revealed. The results indicate that the Strouhal number of the separation vortex characterizes energy effects of the vortex aerodynamics，which can be expressed as a positive integer multiple of the ratio of vortex-drift velocity to oncoming flow velocity，implying that a separation point can excite multiple VIVs lock-in ranges. There were 3 order lock-in ranges of vertical VIVs for the girder. Both the 2nd and 3rd lock-in ranges are excited and sustained by the large-scale separated vortexes separating at the leading edge and periodic drift in the drift distance between the separation point and the trailing edge. Especially，it takes about 2 and 1 vibration cycle for the separation vortexes to traverse the drift distance in the 2nd and 3rd order VIVs lock-in ranges，respectively. Therefore，they are dominated by the 2nd and 1st order simplified-vortex modes originating from the leading edge，respectively. This study verifies the rationality of the simplified-vortex model to deduce the vortices evolutionary characteristics around the bridge girder and provides a new methodology for VIVs mechanism of the bridge girders.

Impact load is a common load，but it is also very special. Compared with other persistent loads，impact load has the characteristics of short duration and large output energy，leading to the transient vibration which may affect the system’s operation safety. In this paper，the active magnetic bearing （AMB）-flexible rotor was installed on an elastically supported base. The vibration characteristics of the elastic supported base under five types of impact loads，including double half-sine wave，half-sine wave，sine wave，triangle wave，and double triangle wave，were investigated. The influence of different impact load parameters on the acceleration of the base was obtained. In order to suppress the rotor vibrations，relative to the base induced by impact loads，a transient vibration compensation control strategy based on the base acceleration was derived. The theoretical and experimental results indicate that the elastic supported base and the AMBs-flexible rotor system installed on it both exhibit obvious impact characteristics under impact loads. These impact characteristics vary with different types of impact loads. The effect of base shock excitations on the rotor vibration can be effectively suppressed by the proposed algorithm.

The traditional additional acoustic black hole （ABH） structure is mainly designed for vibration suppression of plate structures，but it is difficult to be applied to pipe structures that are widely available in engineering. In order to solve the vibration suppression problem of pipe structures，a new additional ABH device，‘Circular Spiral ABH Damper （CSABH）’ is proposed to be applied to pipe structures. By designing the ABH area in the form of a spiral，the modal density of the damper is increased，and a better coupling with the main structure is achieved. The results show that the CSABH has good wave aggregation characteristics and can achieve a vibration suppression of 20~5000 Hz for the pipe. Besides，when the pipe constraints and temperature conditions are changed，the CSABH with the same parameters can still play a good wide frequency damping effect，showing the robustness of the damping. The wide frequency，high efficiency and high robustness of CSABH in the vibration control of pipeline structures are verified experimentally.

The existing shell model is accurate in the frequency band of 0~500 Hz，making it highly suitable for tire vibration analysis. However，the modal properties of the tire belt cannot be obtained separately and the freedom as well as the number of parameters required by the model increases，because the shell model couples the tire belt and sidewall. Therefore，this shell model was improved in this paper. The shell model for simulating the tire belt remained unchanged，whereas，by using the method for approximating the sidewall used in the ring model and plate model of tire，the two-dimensional shell model for simulating the tire sidewall was replaced by an elastic foundation to simplify the boundary conditions of the tire belt and reduce the number of parameters related to the tire sidewall. The solving method for the improved shell model was developed to calculate the modal frequency and the modal shape of the tire belt. The validity of both the improved shell model and its solving method was demonstrated by an experiment.

In order to improve the climbing ability of rack vehicles，the gear-rack system is added to the traditional rail vehicles. Aiming at the problem that there are many kinds of gear-rack systems in the world at present，and the diversity of gear-rack systems equipped with them leading to the dynamic characteristics difference of rack vehicles，this paper considers the impact of gear-rack meshing on the basis of analyzing the generation mechanism of gear-rack meshing excitation，the rack vehicle coupled dynamic models with two kinds of Strub system，double row teeth Abt system and Locher system are established，and experimental verification on the model are carried out； Based on the model，the gear-rack meshing behavior of rack vehicle running at different speeds on the engagement section of the ramp is analyzed，and the influence of track irregularities on the gear-rack meshing center distance error is explored； On this basis，the wheel/rail action and car body acceleration of the rack vehicle are studied，and the rack vehicle safety are analyzed as well as stabitity. The results show that there are significant differences in the dynamic characteristics of rack vehicles with different gear-rack systems，and the Locher system has the best dynamic characteristics； The gear-rack meshing behavior of coaxial Strub system and double row teeth Abt system is poor and affected by the track irregularity obviously. The maximum impact value of the gear-rack contact force is 20.3 kN，and the meshing center distance error is 3.73 cm； The safety of coaxial Strub system and double row teeth Abt system is poor，and the maximum wheel/rail vertical force of double row teeth Abt system is 51.7 kN； The car body stability of the differential shaft Strub system is the worst. The maximum car body acceleration is 0.033 m/s²，and the stability index is 1.27. The conclusions offer theoretical support for the design，safe operation，and maintenance of mountain rack railways in China.

Aiming at the problem that the effectiveness and computation cost of the maximum second-order cyclic stationarity blind deconvolution （CYCBD） algorithm are affected by parameter setting，the crest of the harmonics spectrum （HSC） was used as an evaluation index to determine the length of the CYCBD filter adaptively，and the calculation cost of the optimization process was balanced by the method of encoder time series reconstruction. The bearing fault order is calculated and the cycle frequency is set according to it. The pulse number of time series reconstruction is determined according to the fault order. The central difference method （CDM） is used to calculate the instantaneous angular speed （IAS） of the reconstructed signal. The filter length of CYCBD was adaptively selected with the HSC as the evaluation index using the equal-step search strategy. The spectrum corresponding to the maximum HSC is calculated to achieve fault feature extraction. The simulation and experimental data analysis results show that the proposed method can adaptively select the filter length，which has an obvious effect on reducing the cost of the CYCBD algorithm，and is effective for rolling bearing fault feature extraction.