Through finite element analysis (FEA) software to study mechanical performance of a bridge structure is currently a commonly used method. The keys to obtain accurate results are to select the appropriate element type and establish a refine mesh model. With the construction of a large number of kilometer-level long-span bridges in practical projects, the time cost of establishing and analyzing a fine mesh solid finite element model (FEM) of a long-span bridge with complex structure can not be ignored. In order to find the balance between accuracy and efficiency, sub-modeling technique can be used to analyze the bridge structure. It is often thought that the sub-modeling technique is only applicable to shell and solid elements, but in fact it is also applicable to plane frame models. Based on two-dimensional (2-D) beam element model, the theory of sub-model was theoretically deduced. Meanwhile the sub-modeling technique was applied and verified by an example of plane frame model. Furthermore, based on the three-dimensional (3-D) solid FEM of a skew bridge, the influence of mesh size on the calculation accuracy was illustrated. Based on sub-modeling technique of nodal displacements, the results of the global model and the sub-model for the skew bridge were compared and studied in terms of stress field and plastic damage of concrete. It is found that the sub-model technique based on nodal displacements is suitable for solid FEM.

Due to the improvement of steel properties, many steel structures with attractive appearance emerge unceasingly. In this article, a new structure of steel octagon-web beam which has the similar appearance with honeycomb beam was presented. The mechanical characteristics of steel octagon-web beam under bending loads were analyzed theoretically. Based on the Vierendeel truss theory in deflection calculation of honeycomb beam, the deflection calculation method of steel octagon-web beam which was validated by finite element method was studied. Two parameters affecting deflection of steel octagon-web beam, such as opening type and expansion ratio, were analyzed. A scale model of steel octagon-web beam was manufactured in order to study bending behavior of the structure. The failure patterns of test specimen under four-point bending test are the buckling of deck and web. A nonlinear finite element model of test specimen whose results were compared with test was established by software ABAQUS 2017. The stresses of slabs under ultimate load have reached yield stress, which shows steel octagon-web beam has good flexural performance.

In this study, a new method of replaceable supporting member within orthotropic steel box girder is proposed in order to reduce stress amplitude and improve fatigue life of orthotropic steel box girder. The component model was established by ABAQUS, and the experiment was conducted to analyze stress amplitude of easily fatigue cracking areas of orthotropic steel box girder with and without the supporting member. In addition, the fatigue life was analyzed and predicted. The comparison results show that the finite element analytical results are in good agreement with the experimental results. The reduced proportion of stress amplitude of U rib, T rib grooves and mid-span of top plate of orthotropic steel box girder range from 40% to 60% and 20% to 40%, respectively. The analytical results show that the stress amplitude of orthotropic steel box girder can be reduced by the similar extent with the addition of the same supporting member under different loading pressure; The supporting member can improve the fatigue life of orthotropic steel box girder pertinently, which is simple in construction and low in cost, and can provide suggestions for solving fatigue problem of orthotropic steel box girder in engineering practice.

The micro-stiffness ratio plays a significant role in the dynamic response characteristics of rock materials when analyzed using particle flow code. In this study, a macro–micro parameter model is developed to relate the micro-stiffness ratio to the macro-Poisson's ratio, revealing the relationships between multi-scale parameters. Large-scale split Hopkinson pressure bar numerical simulations are conducted to investigate the sensitivity of the dynamic mechanical characteristics of limestone to variations in the micro-stiffness ratio. The results indicate that, under impact loading, the force chain gradually concentrates toward the center of the specimen, forming a symmetrical saddle-shaped boundary. As the micro-stiffness ratio increases, both the normal peak stress and elastic modulus decrease, while the normal strain rate and strain acceleration increase. Axial and radial stresses exhibit similar sensitivity to the micro-stiffness ratio. The proportion of axial dissipated energy increases with the micro-stiffness ratio, whereas the proportion of radial dissipated energy decreases. The initiation time of damage evolution is significantly correlated with the micro-stiffness ratio: higher ratios lead to earlier initiation of damage evolution but slower damage accumulation. Consequently, the failure mode transitions from sudden brittle failure to slow and gradual failure.

Steel octagon-web beam (SOWB) is a steel structure girder based on the appearance of cellular beam and assembly concept. In order to study the factors affecting deflection, parametric analysis based on finite element (FE) software ABAQUS 2017 was carried out. The factors include the opening type, expansion ratio (H/d) and height-span ratio (H/L). By analyzing the influencing factors on the structural deflection, a reasonable range of factors or the change rule between the two were obtained. In order to calculate the circumferential stress at the web opening, the web unit is divided into five parts according to the characteristics of the web unit and the Vierendeel truss theory. The calculation method of circumferential stress of each part was discussed, which was verified by comparing with the test results.