Triaxial Theoretic Analysis And Application Research Of Steel-Concrete Composite Box Beams

Steel-concrete composite box beam is a new type of structure based on the development foundation of the steel structure and the reinforced concrete structure. The composite box beam may make use of the advantage both the steel box beam and the reinforced concrete slab. The steel-concrete composite box beams have been used for many years and have recently been becoming more popular in China, and most curved composite box beam in China were designed especially in special-shaped overpass bridge structure. studies for both structure behavior and operational performance of composite steel-concrete beams have attracted considerable attentions. Because of the new structure for the steel-concrete composite box beam,studies in this field is still in primary development period at home and abroad, and the studies for analytical theory of the steel-concrete composite box beams are lagging behind the engineering application. Compared with traditional reinforced-concrete box beam structure, there are a lot of issues that need to be solved in field for analytical theory of the steel-concrete composite box beams. To investigate the structural behavior of the steel-concrete composite box beams and application performance better, according to elementary beam theory, by increasing the degree of freedom analytical method, slip, deformation, space displacement model, elastic behaviors, shear lag effect, restrained torsion, distortion angle and distortion warp are studied. The main research achievements are summarized as the following.The nonlinear problem for interface of the steel-concrete composite box beams are carried out easily according to Goodman elastic interlayer assumptions, and it can be conveniently dealed with any kinds of connection mode between steel box girder and reinforced concrete slab; the relationships between loading and slip, deformation are analyzed by introducing function of axis deformation rotation displacement; differential equations of the steel-concrete composite box beams include deformation and torsion angle are presented, expression of general solutions was derived, and computational expressions considering interface slip and curvature include distortion angle, axis deformation rotation displacement, and deflection corresponding were obtained; on the basis of the computation expressions above, internal force, deformation, internal force in interface between steel box girder and reinforced concrete slab, and interface slip were conducted under concentrated loading and uniform loading respectively. In addition, based on finite element program ANSYS and this theory, analyses for the slippage effect of the steel-concrete composite box beams were carried out respectively, and the comparison results between this theory and the numerical analysis were obtain.Based on slab-beam model, Vlasov's thin-walled beam theory, Timoshonko's beam theory, and composite beam theory, by generalized coordinate analytical principle and increasing the degree of freedom analytical method, a new composite curved beam segment element was used, and the composite curved beam segment element include seven extra degrees-of-freedom over the normal six degrees-of-freedom beam formulation, to take into account the shear deformation, shear lag effects, torsional warping, distorsion angle, distortional warping, slip and slip strain; stiffness matrix of the composite curved beam segment element was derived, and the composite curved beam segment element include thirteen degrees-of-freedom of every node, to take into account the extension, flexure, torsion, torsional warping, slip, distorsion, shear deformation, shear lag effects and interaction between the longitudinal and transverse deformations. According to the generalized coordinate analytical principle, the arbitrary point displacement of the composite beam cross section is equal to the multiplication both generalized displacement and generalized coordinate respectively. In this paper, the generalized displacement u, Vb, vs, w,θ,θ,φ, (?)are taken as fundamental variables to describe arbitrary point displacement on the composite beam cross section. By variational principle, precise expression of element stiffness matrices and equivalent nodal load vector are obtain under local coordinate system.In the present calculating formula, the effects of eccentricity between shear center and centroid of cross section are considered, and code a finite element procedure. The comparison results of the theory analysis and the numerical simulation demonstrate that the proposed spatial composite curved beam segment element is correct and efficient.Torsional analysis model of the composite box beams was presented according to structural characteristics of the composite box beams, and two different materials of the composite box beams are taken into account in the present formulation. According to thin-walled structure theory, torsional analysis of the composite box beams was carried out, and the analytical method and calculation formula were presented corresponding. In addition, dynamic differential equation of composite box beams was derived, dynamic parameter analysis for the composite box beams is carried out according to general finite element program ANSYS and this theory respectively.Meanwhile, a typical Y-shape composite box beam bridge was selected from existing Y-shape composite box beam bridge as the model for the study to investigate service performance in the structure application, and the static and dynamic analysis for the typical Y-shape composite box beam bridge are conducted based on the finite element program ANSYS. Multi-direction parameter analysis for the typical composite box beam bridge are carried out, and some points for the application performance of the composite box beams are presented to provide theoretical basis for design and structural analysis of the special-shaped composite box beam bridge. Calculation model for the composite box beam segment element analysis of the special-shaped composites box beam bridge and some noticeable problems of the structural anlysis are proposed based on space beam grillage analytical method. Finally, the elementary assumption of its application in cable stayed bridge, partially cable-stayed bridge, self-anchored suspension bridge and continuous rigid frame bridge is proposed.