Analysis Of Shear Resistance And Flexural Behavior Of Composite Box Girders With Corrugated Steel Webs

The externally prestressed composite box girder with corrugated steel webs is a new type of composite steel-concrete structure. It has gained wide application in Japan and France. Comparing with traditional prestressed concrete, this structure holds specific mechanical behavior, lightens self-weight, increases the capacity of span, shortens construction period, and beautifies the mold. Comparing with composite box girders with flat steel webs, it doesn't need longitudinal ribs to avoid web buckling, and enhances loading efficiency of prestress. In this thesis, a series of experimental researches and theoretical analyses of the flexural behavior including shear and bending resistance relating to this new structure are conducted. The main work is described as follows:(1) This thesis deduces calculating formulas for longitudinal rigidity of the corrugated steel webs. It shows that the contribution of the corrugated steel webs to axial rigidity and flexural stiffness of the cross-section can be ignored.(2) The statically loading test of two model beams indicates that the distribution of normal strain over section depth in composite box girders with corrugated webs accords with the quasi plane assumption: first, normal strain of the corrugated webs is almost zero; next, normal strain of the top and base concrete plate tallies with linear distribution. It can be conservatively considered that the corrugated webs assume full of the shear force over the section and the shear stress is uniformly distributed. Respectively based on elastic and plastic analysis this thesis qualitatively explains its huge advantages of bending resistance.(3) The local and global shear buckling sample can be respectively assimilated to a series of flat rectangular subpanel and an orthotropic plate subjected to shear on four sides. Based on the small deflection theory, the equations for buckling stress of corrugated steel webs under shear are established. Considering both material and geometrical nonlinearities, spatial analyses of the 42 model test girders with corrugated steel webs by Professor Hamilton in America are accomplished. Unavoidable out-of-plane initial imperfections and its effects are primarily discussed. An all stage analysis of buckling performance is also researched. By comparisons between theoretical equations solution, model test results by Professor Hamilton, and spatial analysis, this thesis adjusts some safety factors and then recommends formulas for calculating local and global shear buckling stress.(4) Based on axial force- bending moment–curvature relationship (N-M-φ) of sections, an all stage analysis program for flexural behavior of this structure is established. A destruction bending test for one model beam is accomplished, also. Comparisons between the program solution and model test results are shown to be satisfactory.(5) A mass of parameter analyses are carried out using the program. The influences of secondary effect for the externally prestressed cable, transverse diaphragm at span middle, area of reinforcement in tensile region and span depth ratio on the ultimate carrying capacity of the structure are detailed discussed. By comparisons between the program solution and formulas results using by some completed construction and traditional prestressed concrete, this thesis gives some advice on calculating the ultimate moment capacity in normal section.