Research on magnetically levitated rotors has been heavily influenced by studies on slender shaft magnetic levitated rotors. In the study on a certain magnetically levitated flat rotor for a centrifugal pump structure，both experiments and finite element analysis revealed that the support characteristics of the radial permanent magnetic bearings，with the same dual-ring structure，exhibited the significant differences from the known experience when applied to flat rotors. The translational stiffness and torsional stiffness showed substantial variations. This paper analyzes the variations in translational and torsional stiffness of permanent magnetic radial bearings for flat rotors based on changes in the bearing’s structural dimensions. Based on the analysis，a flat rotor magnetic levitation structure is proposed，which can increase and adjust the torsional stiffness of the permanent magnetic bearings，while also allowing for a rational ratio between translational and torsional stiffness. A finite element analysis is used to identify the structural conditions that yield maximum translational and rotational stiffness. The effectiveness of the proposed methodology is subsequently validated.

Based on the Biot’s poroelastic model and the Euler-Bernoulli beam equations，the dynamic response of extended helical pile foundations with multiple helixes is studied. The equivalent stiffness model is used to simulate the helixes on the helical pile. With the utilization of the integral transform，the variable separation methods，and the impedance matrix transfer method，the analytical solution to the dynamic response of helical piles with multiple helixes is derived. Through the comparisons with the simplified analytical solutions and the experimental results，the correctness of the proposed model is justified. Finally，with the presentation of a comprehensive parametric study，some dominant impact factors on the dynamic responses are revealed，and the optimal design scheme is suggested accordingly. The main conclusion of this study can be concluded as：An increase of the extension ratio of helix will increase the complex impedance and resonance frequency at the pile top of the helical pile. An increase of the ratio of helix spacing to width will increase the complex impedance of the pile top，but the effect on the resonance frequency is not significant. An increase of the vertical static load at the top of the pile will significantly reduce the complex impedance and resonance frequency at the pile top. The helix inclination has an optimal range in the effect of complex impedance of the pile top.

In order to achieve rapid construction and reliable connection of precast RC frames，a sleeve-type fully-bolted joint is proposed. The ends of the prefabricated components are reinforced with a steel sleeve-concrete combination. High-strength bolts are pre-built in the sleeve area，and the precast components are rapidly installed using a connection plate. A total of four test specimens were designed for different thicknesses of connecting cover plates. The horizontal hysteresis test study obtained the damage mode，load-displacement hysteresis curve，ultimate bearing capacity，ductility and energy dissipation capacity of this type of joint. The results show that the new joint has a 43% higher ultimate load，70% higher initial stiffness and nearly 50% higher ductility than the cast-in-place joint，and the equivalent viscous damping coefficient is increased by about two times，which shows better seismic performance. Strain analysis reveals that the cover plate at the joints shows a “stress increase”，but the effect on the overall performance is not apparent. As the thickness of the connection plate increases，the squeezing effect of the sleeve on the concrete increases. Therefore，a connection stiffness ratio of 1.6 is more reasonable. Finally，based on the test results，a trifold moment-turning angle model is established，and the calculated results agree with the test values.

Existing bridges undergo time-varying load effects and resistance degradation during service. The complex loads and diverse failure modes make the existing bridges face greater risks in service. Therefore，it is urgent to make time-dependent reliability assessment for the service bridges. The classical time-varying reliability analysis method is more complex and difficult as the number of random variables increases. In this paper，probability density evolution theory is introduced to solve the above problem，which is more advantageous for solving the reliability of complex structures with multiple random variables. The dynamic reliability of the existing bridge in serviceability limit state and ultimate limit state is analyzed by considering the bridge resistance degradation and load effect increase，as well as the time-varying factors such as shrinkage and creep effect of concrete bridges. The accuracy and computational efficiency for this method are compared with the Monte Carlo method，and the effectiveness of the proposed method is verified.

A milling unbalance correction method based on a discrete vector model is proposed to address the issue of poor performance of traditional dynamic balancing methods when the initial unbalance of the micro motor rotor is large. A discrete vector model is established based on the parameters of the milling cutter and rotor，and the corresponding relationship between the equivalent cutting mass and cutting depth under second time cutting is obtained by integrating the discrete points of the edge curve. By comparing with the 3D model simulation data，it is verified that the deviation rate of the model is low. Experimental verification shows that when the initial unbalance on one side of the rotor exceeds 100 mg，a total weight removal rate of over 90% can be achieved，and the equivalent mass of the remaining unbalance on one side can be controlled below 10 mg. All rotors meet the G1 accuracy level. This indicates that this proposed method can improve the dynamic balance accuracy of the micro motor rotor when the initial unbalance of the micro motor rotor is large.

Focusing on a type of cable-bracing inerter system that utilizes positive and negative teeth ball screws to achieve self-balancing properties，this paper explores the prospect of its application in high-rise or super high-rise structures with complex deformation characteristics of bending and shearing. This paper develops a simplified model for the dynamic analysis of bending-shear structures based on the modified Timoshenko beam theory in order to take into account the accuracy and computational efficiency of the simulation of the original structural dynamic characteristics. Three types of cable layout schemes are proposed for the cable-bracing-self-balancing inerter system，and the appropriate cable layouts for the structures with different bending-shear deformation ratios are verified. A quantitative metric is proposed to optimize the anchorage position for structure-specific modal control. The accuracy of the optimization results is confirmed in the time and frequency domains through the application of fixed-point theory for single-modal control. The following conclusions can be derived. The higher the percentage of bending deformation of the structure is，the more effective the vertical connection of the cables will be，and the more effective the diagonal connection will be as the percentage of shear deformation increases. With regard to structure-specific modal control，the optimized anchorage position and fixed-point theory methods can significantly increase the damping efficiency of the inerter system.

Based on the three-dimensional elasticity theory，the smooth stochastic response model of three-dimensional sandwiched cylindrical shells is established by using the unified series method and the pseudo-excitation method （PEM）. The cylindrical shell subdomains are divided according to the interlayer property differences of the sandwich material，and the kinetic energy，strain energy，boundary potential energy and smooth random excitation work of each subdomain are established by using three-dimensional elasticity theory combined with the virtual excitation method. The mechanical coordination conditions between the layered subdomains are converted into coupling condition energies by the coupling penalty function method，and then the overall energy generalization of the sandwiched cylindrical shell is obtained by superposing the energies of each subdomain. The displacement components of each subdomain are constructed using a unified level expression and solved by combining the Rayleigh-Ritz method to obtain the stochastic response of the three-dimensional sandwiched cylindrical shell structure. The correctness of the stochastic response model is verified by comparison with literature and finite element results. Finally，the effects of thickness-to-radius ratio，lay-up angle of laminated-functional gradient sandwich material and power-law index on the random response of three-dimensional sandwiched cylindrical shell are analyzed.

Statistical energy analysis （SEA） is a widely used method for analyzing the high-frequency dynamic response of mechanical structures. The reasonable division of subsystems is one of the critical basises for SEA. In this paper，an automatic identification method of SEA subsystem based on order-reduced modal energy density and hierarchical cluster analysis is developed. First，the structural modal energy densities in the high-frequency band are obtained through the discrete finite element model. Then，the main features of the modal energies are extracted through the proper orthogonal decomposition. The similarity of the modal energy density between different elements is analyzed by hierarchical cluster analysis. Finally，the number of statistical energy analysis subsystems and the corresponding structural elements are identified. The T-shaped plates，I-shaped plates，and engine combustion chamber are taken as simulation models to verify the effectiveness of the proposed method. Simulation results show that the coupling relationship between components，the number of subsystems，and corresponding elements can be automatically identified by the proposed method. Then，the SEA model can be established efficiently and accurately.

Based on a large depot project in Chongqing，the vibration and secondary noise characteristics and human comfort of the over-track buildings induced by metro operation in the depot are studied. The vibration characteristics of the depot are analyzed by field measurement. Combined with the numerical simulation method，the finite element model of the track-soil-depot-over-track buildings is established based on the metro-track coupling theory and the finite element theory. The vibration and secondary noise characteristics of the top buildings under train excitation are analyzed and evaluated. The combined annoyance model of vibration and secondary noise is constructed by combining psychology and fuzzy mathematics to analyze the human comfort，and the annoyance is used as the evaluation index. The results show that under the train operation，the vibration level of the throat area is the highest，and the vibration stability for different areas of the depot is as follows：the inner area > the throat area > the upper cover area. As the lateral propagation distance increases，the maximum Z vibration level of the platform decreases approximately linearly. The vibration peak of each building on the top is 12.5~20 Hz，and the main frequency band of secondary noise is 63~80 Hz. The vibration and secondary noise of each building attenuate with the increase of floors，but the vibration and secondary noise of residential building are amplified after 12 floors. The vibration of each building on the upper cover do not exceed the standard，but the secondary noise exceeds the standard in the commercial building，and the maximum exceeding value is 4.9 dB（A）. The annoyance results obtained by the joint annoyance model are in good agreement with the standard evaluation results，but the annoyance can refine the influence of vibration and secondary noise on human comfort. The model calculation shows that although the first floor of the residential building meets the standard limit，the joint annoyance is above 0.6 at night，and the evaluation using the joint annoyance rate model is more demanding.

The disturbance induced by the rotation of dual axis flex solar wing is the important factor which impacts satellite attitude and pointing accuracy and stability of satellite precise payload. The flexible multibody system method based on recursive formulation is proposed to solve the dynamics problem induced by satellite dual axis flexible solar wing rotation. The satellite dynamics equations are established by considering orbit mechanics，satellite configuration，solar wing flexibility and solar array drive assembly and momentum wheels. As an example of a satellite with dual axis solar wing，the research on multibody dynamics simulation of satellite electromechanical coupling is developed，and the simulated attitude angle and angular velocity of satellite are compared with the corresponding telemetry data. The research shows that the simulated attitude angle and angular velocity of satellite agree well with the corresponding telemetry data，which proves the correctness of the model，The rotation of flexible dual axis solar wing will produce big disturbance torque and attitude angle，the control torque needs to be distributed to momentum wheel assembly for the accurate simulation results，and the disturbance torque of floating satellite caused by the rotation of solar wing was obtained by simulation，which can give the reference condition of ground test verification of solar wing rotation.