This paper develops a free vibration model of rectangular microplates including three material length scale parameters and two displacement field variables using the modified strain gradient theory and a refined higher-order shear deformation theory, and presented the related governing differential equations. The analytical vibration frequencies of a four-edge supported rectangular microplate were obtained via the Navier method. Combining the Gauss-Lobatto quadrature and differential quadrature rules, a four-node seventy-two-DOF differential quadrature finite element was constructed to solve the free vibration of rectangular microplates with general boundary conditions. Through typical numerical examples, the effectiveness of the present model was established, and the effects of boundary conditions, material length scale parameters, aspect ratio and length-thickness ratio on the vibration frequencies and mode shapes of rectangular microplates were revealed. The results indicate that the vibration frequencies and some mode shapes of rectangular microplates exhibit significant size effect, and its intensity is associated with the boundary conditions and geometric dimensions.

Large flexible appendages of flexible spacecraft are characterised by their large scale and low stiffness, resulting in vibration of large flexible appendages that can seriously affect the attitude precision of the spacecraft. Information fusion preview control is combined with fuzzy control to construct the attitude controller. According to the information fusion theory, the spacecraft's desired trajectory and system dynamics information are fused, the optimal preview control law is derived. The optimal preview control law can be easily obtained due to the information fusion control has a simple design process and low computational burden. In real engineering, the control torque generated by the actuator is limited. The fuzzy controller is employed to adjust the parameters of the control law on-line in order to satisfy the requirements of limitation. Simulation results show that the designed control strategy with high control performance can effectively suppress the vibration of the flexible appendages, and the attitude angle can reach the desired value accurately and quickly. The proposed control strategy can be served as a reference for the engineering application of large flexible spacecraft attitude control.

Against the characteristic of large deformation for reinforced concrete（RC）frame, RC frame-frame truss composite wall（FTCW）structure was proposed, and two reinforced concrete（RC）frameframe truss composite wall（FTCW）specimens with a scale of 1∶2 were implemented for cyclic loading test. The seismic performance of bearing capacity, ductility and stiffness degradation were analyzed by the test phenomenon, hysteresis curves, backbone curves and stiffness degradation curves. The simulation of cyclic loading test was conducted by ABAQUS software, and the results were compared with the test results. The influence of the amount of infill FTCW, rebar ratio of RC frame columns, axial compression ratio, concrete strength, embedded angle steel and the layout direction of FTCW were analyzed. The test behav-iors showed that a multistage energy consuming system that FTCW worked before RC frame and the internal diagonal struts worked before the outer frame inside the FTCW, forming a multistage energy consumption system for the design purpose of earthquake resistant structures. The numerical analysis results showed that the most effective way to improve the bearing capacity of RC frame-FTCW was to increase the amount of filled FTCW, followed by increasing the rebar ratio of frame columns, and the improvement of increasing the concrete strength or adding angle steel for the internal diagonal struts were smaller. The improvement of axial compression ratio on the bearing capacity was unnoticeable. In addition, the layout direction of FTCW was significant, and the number and position of FTCW should be symmetrically arranged.

In order to investigate a structure with better mechanical properties, this paper proposes a square honeycomb lattice sandwich cylindrical shell structure, which combines metal thin-walled tubes and honeycomb structures. The mechanical behavior of the sandwich cylindrical shell structure with a square honeycomb as the core under radial compressive loads is studied by experimental and numerical methods. By comparing the results of two research methods, the accuracy of the finite element model is verified, and the deformation mode of the structure under radial compressive loads is analyzed, and the reinforcement mechanism of the structure is discussed. The results show that the rectangular honeycomb lattice sandwich cylin-drical shell structure will undergo three deformation stages:elastic stage, plastic stage and collapsibility stage under radial compression load. Compared with the simple superposition of single-layer cylindrical shells and cores, the load-bearing and energy absorption of the square honeycomb lattice sandwich cylindrical shell are greatly improved. The structure is mainly coupled and reinforced by the formation of plastic hinges and the debonding between the square honeycomb core and the inner and outer cylindrical shells.

The anti-yaw vibration devices currently used in high-speed trains are hydraulic dampers, whose damping characteristics cannot be adjusted according to the changes in the vehicle's operating state and environmental conditions, resulting in poor ride quality and stability for the vehicle. A semi-active damper based on magnetorheological technology combined with intelligent control technology can solve this problem. In this paper, a three-coil magnetorheological damper has been developed with adjustable damping characteristics based on the technical specifications of the anti-yaw damper. The multi-physical field of the damper is simulated, and damping performance of the damper is tested under different excitation currents, amplitudes, frequencies, and coil combinations. The results show that the magnetic circuit design of the damper is reasonable and complies with the technical requirements for anti-yaw dampers, with a maximum output force of 46 kN and an adjustable dynamic coefficient of 28. In addition, an analysis is conducted on the magnetic field distribution at varying coil spacings. The findings indicate that a critical distance exists between the coils, and the critical distance of this damper is 0.69 times the width of the coil, beyond which the magnetic field distribution becomes non-uniform. The change in magnetic flux density at the effective damping channel will stop when a certain part of the magnetic circuit reaches saturation.

In order to enhance the seismic performance of reinforced concrete columns, a method of embedding steel wire mesh to strengthen concrete columns was proposed. A total of six specimens including reinforced concrete column, four steel mesh-reinforced columns, and one stirrup-reinforced column were designed and poured. Constant axial pressure was applied to the specimens and horizontal quasi-static cyclic loading was carried out. The failure patterns, crack distribution, hysteretic characteristics, ductility, and energy dissipation capacity of each specimen were tested. The seismic performances of steel wire mesh-reinforced specimens and stirrup-reinforced specimens with the same equivalent stirrup ratio were compared and analyzed, and the effects of steel mesh layers and configuration height range on the seismic perform-ance of members were discussed. The research results show that the proper configuration of steel mesh can effectively restrict the formation and development of column sectional crack and“diagonal crack”, and transform the bending-shear failure mode of the specimen into bending failure mode. Therefore, compared with the reference specimen and stirrup-reinforced specimen, the wire mesh-reinforced specimen shows greater initial stiffness, better ductile deformation and cumulative energy dissipation capacity. The research results preliminarily clarify the relationship between the number of wire mesh layers, height range and ductile deformation capacity, stiffness degradation, and energy dissipation capacity of specimens, and the related results can provide reference for the design of embedded wire mesh-reinforced concrete columns.

In steel-concrete composite structures, due to the existence of certain interface slip and web shear deformation, the assumption of flat section is no longer applicable. In order to scientifically study the effects of shear deformation and interface slip on the deflection and interface slip of composite beams, this paper adopts Goodman's assumption and Timoshenko beam's double generalized displacement assumption, introduces the strain relationship of composite beams and element microsegment mechanical equilibrium, and derives the elastic bending differential equation of double inverted T-shaped steel-concrete composite beams considering shear deformation and interface slip. Then based on the equivalent spring model and the equivalent rod spring model, a theoretical calculation formula for the elastic shear stiffness of the embedded web connection is derived. By using the known deformation and constraint conditions of the composite beam, we obtain the analytical solution of deflection and slip of the simply supported composite beam under concentrated load in the span and verify it through the experimental results of four double inverted T-shaped steel-concrete composite beams with different parameters. The results show that the deflection and slip values obtained from theoretical calculations are in good agreement with the measured values, and the correctness of the theoretical calculation formula for the elastic shear stiffness of the embedded web connection is verified. In the deflection deformation of double inverted T-shaped composite beams, the deflection value caused by bending accounts for about 56% of the total deflection, the deflection value caused by interface slip accounts for about 36% of the total deflection, and the deflection value caused by shear deformation accounts for about 8% of the total deflection. This article comprehensively considers the effects of shear deformation and interface slip on the deflection and slip of composite beams, and makes a significant improvement compared to the model structure that does not consider shear deformation and interface slip.

In order to determine the influence of aggregate irregularity on the mechanical properties and failure morphology of concrete, Python programs were developed to generate randomly distributed aggregate models with different sharpness in ABAQUS, and the 0-thickness cohesive element and variable-thickness solid interface transition zone（ITZ）were established respectively. First, the reliability of model was determined by changing mesh size and friction coefficient between the loading pad and concrete compared with the experiment. Then, the quality of two ITZ modeling methods was analyzed. Finally, the uniaxial compression mechanical behavior of the three-dimensional meso-concrete model was analyzed from the aspects of stress-strain curve, fracture propagation, and energy dissipation. The simulation results show that the 0 thickness cohesive ITZ and the solid thickness ITZ model can predict the compressive strength of concrete, and the stress-strain curve and failure morphology of the ITZ model with solid thickness are more consistent with the experiment. The fracture propagation of concrete is obviously affected by the shape parameters of aggregate. The interior and surface of the spherical aggregate model are penetrating cracks. The strain energy of polyhedral aggregate model is larger, and there are many micro-cracks in the concrete, the possibility being compressed and destroyed into more fragments is higher. With the increase of aggregate irregularity, the compressive strength of concrete increases slightly, but the peak strain is not affected.

In the past decade, approximately one-third of civil aviation safety incidents have been related to landing, with hard landings comprising one-fifth of these landing-related incidents. Hard landings not only damage aircraft structures but also can lead to aircraft destruction or loss of life in severe cases. However, statistical data on hard landings remain limited. This paper systematically analyzes hard landing criteria through a review of quantitative standards, simulation analysis, and machine learning techniques. It also conducts a statistical examination of 53 typical hard landing incidents of mainstream aircraft such as Boeing-737 and Airbus-A320 over the past decade, offering a detailed exploration of common structural damage patterns associated with hard landings. Results show that heavy landing incidents often cause damage of different degrees to the aircraft's landing gear, fuselage, wings, and other key components. Moreover, the extent of damage differs significantly among various types of heavy landing incidents.

In this paper, the effects of doping elements（Re and Ru）content on the stability and occupancy orientation of a Ni-Al binary model nickel-based single-crystal superalloy are studied by using first-principles calculations. The results show that the total energy of the system decreases gradually with the increase of the content of Re and Ru elements, which suggests that the stability of the system is improved. The system using Ru to replace Ni has the lowest stability, while the stability of system is the best by using Re to replace Al. Therefore, Re and Ru are more inclined to replace Al, which is consistent with the previous experimental results. Meanwhile, compared to other contents of Re and Ru, when Re and Ru with the content of about 1.4% are used to replace Al, the substitution formation energy is the lowest. Furthermore, two different stacking fault modes are obtained by deleting a layer of atoms in the Ni-Al binary model. Research on these two stacking fault modes indicates that replacing Al with Re and Ru can improve the stability of the systems, and systems containing Re are more stable, which have lower substitution formation energy compared to replacing Al with Ru. However, for different stacking fault modes, when replacing Al with Re and Ru, the content of Re and Ru is different for the best of a stable system and the lowest of substitution formation energy and stacking fault energy. Replacing Al with Re results in a better stability in stacking fault systems, but the content of Re in the most stable system depends on the selected stacking fault mode.