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 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.

The classic fiber model based on Euler-Bernoulli beam theory overlooks the influence of shear deformation on the section of the beam. In order to establish a more accurate creep analysis method for reinforced concrete fiber beam elements, this paper proposes a fiber beam element considering shear effects based on Timoshenko beam theory. The stiffness matrix of the fiber beam element is derived, and the finite element equation for the equivalent nodal force of creep analysis based on concrete creep analysis initial strain method is obtained. Finally, a finite element method for creep analysis of reinforced concrete fiber beam elements is established. A computing program is developed in FORTRAN language, and elastic analysis for normal beam and reinforced concrete beam, and creep analysis for reinforced concrete beam are conducted. The results are compared with analytical solutions, commercial software and other literature, indicating that the proposed method can accurately consider the shear effects and clearly define the behaviors of steel and concrete in the creep performance of reinforced concrete beams. Moreover, including steel in the creep analysis model can effectively improve the accuracy of the results.

The objective of this paper is to study the mechanical characteristics of the interface between loess and geosynthetics, in hope of providing targeted suggestions for the design of reinforced loess projects. A large-scale interface shear apparatus was used to conduct direct shear tests on the geogrid-loess interface to study the effects of the moisture content and compaction degree of loess on the shear stress-shear displacement relationships, shear strength indices, and thickness of shear band of the geogrid-loess interface. The mechanism of the effects was analyzed, and the constitutive model of the geogrid-loess interface was discussed. The test results show that as the moisture content increases（not exceeding the plastic limit）, the shear stress-shear displacement curves of the geogrid-loess interface change from softening type to hardening type. The interface cohesion and friction angle significantly decrease with the increase of the moisture content, and thus the interface shear strength decreases accordingly. The thickness of shear band increases with the moisture content. The compaction degree of loess has little influence on the shear strength of the geogrid-soil interface, but it affects the thickness of shear band significantly. The thickness of shear band increases greatly when the compaction degree reaches 90%. Hence, the compaction degree of the backfill of reinforced loess engineering should not be less than 90%. The thickness of the shear band of geogrid-loess interface decreases continuously along the shear direction, with a maximum thickness of 3 cm approximately. This indicates that the shear band between the reinforcement and soil is the thinnest at the facing column in reinforced loess retaining walls. Hence, a flexible or integral facing column is recommended to be used in reinforced loess retaining walls. The hyperbolic interface constitutive model can effectively reflect the shear behavior of the geogrid-loess interface.

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.

To study the effect of double circular holes on the mechanical properties of rocks and the crack extension process, a uniaxial compression model for rock specimens containing double circular holes was constructed, and the correctness and rationality of the numerical model were verified based on the comparison of the macroscopic mechanical parameters obtained from experiments and simulations. In addition, the crack extension process of specimens containing double circular holes and the evolution of the stress field around the circular holes were analyzed. The results show that the numerical simulation results are in good agreement with the experimental results；the initial tensile crack first sprouts at the upper and lower ends of the circular hole, and with the increase of axial stress, structural weak zones are usually formed at the left and right sides of the hole wall. The sprouting direction of the initial tensile crack is in the axial load-ing direction, independent of the orientation angle α, but the damage pattern of the specimen is influenced by the orientation angle α. The initial tensile crack is generated in the tensile stress concentration area；the tensile stress concentration area at the upper and lower ends of the circular hole moves and dissipates accordingly with the expansion of the initial tensile crack. The compressive stress concentration area of the stress component σ_yy is located on the left and right sides of the circular hole, while a shielding area of compressive stress is formed at the upper and lower ends of the circular hole, and the smaller the distance from the vertical center line of the circular hole, the stronger the shielding effect and the weaker the compressive stress.

The roughness of the interface between new and old concrete is one of the key factors that affect its shear performance. In this paper, the roughness of the new and old concrete interface is characterized and quantified based on fractal theory. Different fractal dimension interfaces of new and old concrete random aggregate geometric models are established using the Monte Carlo method and aggregate grading theory. By simulating the mechanical behavior of rough interfaces using zero-thickness cohesive elements locally embedded in the model, the effects of mesh size, random distribution of aggregates, fractal dimension, normal pressure, and interface material parameters on the shear performance of rough interfaces between new and old concrete are analyzed. The results show that the model's mesh size and random distribution of aggregates have no significant effect on the shear performance of the interface between new and old concrete. As the fractal dimension increases, the interface shear strength first increases and then decreases, and the fractal dimension corresponding to the maximum shear strength decreases as the normal pressure increases. Under the same fractal dimension, the shear strength increases linearly with the normal pressure. The normal pressure has a more significant impact on the interface shear strength compared to the fractal dimension. As the fractal dimension increases, cracks are more likely to propagate deeper into the old concrete area, and increasing the strength and fracture energy of the new and old interface can effectively improve the shear performance of the interface.

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.

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.

The modeling of the passive dynamic walker of flexible legged rimless wheel is studied, and the influence of damping coefficient on system dynamics is analyzed. According to the geometric characteristics of the walker, the independent generalized coordinates are selected to describe the position of the system, and the second kind of Lagrange equation is used to establish the dynamic model of the passive dynamic walker of flexible legged rimless wheel. By analyzing the structure and physical properties of the flexible leg, it is concluded that the impact occurs in the tangential direction of the telescopic leg and the impact force is not transmitted between the leg and the ground in the radial direction during the impact stage, and a state jump model under the assumption of partial impact is proposed. The numerical simulation of passive dynamic walking of flexible legged rimless wheels using different damping parameters verifies the effective-ness of the proposed method. When a larger damping coefficient is selected, the double-limb support period of periodic walking accounts for 77.6% of the whole walking cycle, while the single-limb support period accounts for 22.4% of the whole walking cycle. The periodic walking can be achieved when the slope angle is in the range of 0.1-0.7 rad. The slope angle of the flexible legged rimless wheel that can passively and dynamically walk on decreases as the damping coefficient decreases.