Based on the condition of static equilibrium and the equivalent law of shearing stress of an infinitesimal segment, this paper provides a strict derivation of the general formula for shearing stress in a nonuniform box girder with corrugated steel webs in the elastic stage. The derived formula is applied to investigate the stress distribution in concrete flanges and corrugated steel webs. Additional shear stress was found to be caused by the bending moment, and the axial force should be included in calculations from the effect of variable cross sections, which are quite different from that of the uniform cross sections. Moreover, because the additional shear stress of the bending moment is self-balanced, the shear force distribution can be adjusted between the concrete slabs and steel webs. Research shows that shear stress decreases markedly in the webs, whereas the shear stress apparently increases in the inclined bottom flange in the action of the bending moment. This study also found and explai...

The determination of a suitable strut-and-tie model (STM) of a number of disturbed three-dimensional (3D) domains is a challenging task. To overcome this problem, this paper presents a performance-based ground structure optimization method for automatically generating optimal STMs in 3D concrete structures. In this method, first, a new microtruss element in which each internal node provides equal opportunities for transferring loads is proposed. Then, an equivalence mode between the microtruss element and the continuum element is introduced to ensure a realistic and precise simulation of actual structures. Finally, several examples are used to demonstrate the capability of the proposed approach for revealing the true mechanisms of the load transfer in 3D concrete structures. The numerical results indicate that the developed algorithm can generate optimal STMs that are supported by design specifications and previously existing solutions and can be used in practice, especially in complex disturbed concrete structures for which STMs cannot be obtained by general optimization methods. Generally, the procedure presented in this paper is limited to homogeneous material with linear constitutive laws.

Despite the construction of several curved prestressed concrete girder bridges with corrugated steel webs (CSWs) around the world; their shear behavior has seldom been investigated. Accordingly, this paper substitutes the lack of available information on the global elastic shear buckling of a plane curved corrugated steel web (PCCSW) in a curved girder. This is based on the equilibrium equations and geometric equations in the elastic theory of classical shells, combined with the constitutive relation of orthotropic shells. Currently, the global elastic shear buckling process of the PCCSW in a curved girder is studied, for the first time in literature, with an equivalent orthotropic open circular cylindrical shell (OOCCS) model. The governing differential equation of global elastic shear buckling of the PCCSW, as well as its buckling strength, is derived by considering the orthotropic characteristics of a corrugated steel web, the rational trigonometric displacement modes, Galerkin’s method and variational principles. Additionally, the accuracy of the proposed theoretical formula is verified by comparison with finite element (FE) results. Moreover, the expressions of the inner or outer folded angle and radius of curvature are given by the cosine theorem of the trigonometric function and inverse trigonometric function. Subsequently, parametric analysis of the shear buckling behavior of the PCCSW is carried out by considering the cases where the radius of curvature is constant or variable. This parametric analysis highlights the effects of web dimensions, height-to-thickness ratio, aspect ratios of longitudinal and inclined panels, corrugation height, curvature radius and folded angles on the elastic shear buckling strength. As a result, this study provides a theoretical reference for the design and application of composite curved girders with CSWs.

The optimal strut-and-tie models (STMs) of two typical irregular concrete deep beams were constructed using evolutionary structural optimization and compared with those of previous studies. The reinforced concrete deep beam specimens were cast according to the reinforcement designs guided by different STMs. Eight irregular concrete deep beam specimens were experimentally investigated under stepped loading, and the differences in the amount of steel used, the load-carrying capacity, and the failure pattern of the different specimens were analyzed. The results show that the optimal STMs proposed in this study have significant advantages in terms of cost-effectiveness and can simultaneously ensure the load-carrying capacity, delay the crack propagation of irregular concrete deep beams, and reduce the amount of steel used in structural members. Therefore, they have an important engineering application value for the reinforcement design of irregular concrete deep beams.

This paper presents a practical method for automatically generating optimal strut-and-tie models (STMs) in anchorage zones. In the proposed approach, a new microtruss element pattern is created to build ground structures. In certain conditions, the approach could also be improved by combining the microtruss grids with solid elements. Furthermore, the formula for the cross-sectional areas of bar elements in the microtruss grid is deduced for the purpose of replacing the continuum structures built by solid elements with discrete structures built by truss elements. Then, three examples are illustrated to demonstrate the capability of the proposed optimization procedure to find the optimal STMs of anchorage zones. The existing solutions and numerical experiments indicate that the proposed approach accurately reflects the actual load-transfer mechanism in anchorage zones. The method can be used in practice, especially in the design of some disturbed regions (D-regions) in which optimal STMs cannot be obtained by traditional optimization procedures. It should be noted that at present, the application of the proposed model in this paper is limited to homogeneous material with linear constitutive laws.