Shear Deformation And Shear Buckling Of Non-prismatic Beams With Corrugated Steel Webs

The PC box girder with corrugated steel webs (CSWs) is a new type of composite steel-concrete structure, which can bring strength of each material itself into full play. And this structure can gain a satisfactory economic benefits and superior behavior through reasonable and effective combination. As a new kind of load-carrying member, the PC box girder with CSWs have wide application prospect in the field of bridge engineering. Large span PC girder bridges with CSWs exhibit some following structural characteristics: 1) non-prismatic cross section; 2) cantilever construction; 3) CSWs with concrete encasement near the supports. The mechanical behavior of the non-prismatic beam is very different from that of the prismatic beam owing to the effect of variable section. These computational assumptions are not applicable any more in the non-prismatic beams with CSWs, for example, it is not proper to assume the CSWs bears all the vertical shear in section due to the Resal effect of a non-prismatic beam. Many scholars have focused on the global and local buckling of prismatic I- or box girders with CSWs, studies on the basic mechanics properties of non-prismatic box girders with CSWs remain insufficient. Researches on the shear behaviors of non-prismatic beams with CSWs are experimentally carried out for the first time. The main contents of this thesis are as follows:(1) Based on the condition of static equilibrium and the equivalent law of shearing stress of an infinitesimal segment, this thesis provides a strict derivation of the general formula for shearing stress in a nonuniform box girder with CSWs in the elastic stage by Timoshenko beam theory. The derived formula is applied to investigate the stress distribution in concrete flanges and CSWs. 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, the additional shear stresses caused by the bending moment and the axial force have been proven to be selfbalanced.(2) This study found that it is improper to use equivalent flat concrete webs which bear all vertical shear force in the section to replace CSWs in some design software. To reflect the mechanical performance difference of CSWs in different directions, a more precise theoretical model, the assimilated orthotropic plate, is presented to simulate CSWs based on orthotropic plate theory.(3) To make these formulas applicable to nonprismatic beams, the idea of the equivalent inertia moment of beams with variable cross sections is presented in this thesis based on the the Simpson integral, therein providing the basis for a united calculation formula for the bending deformation of non-prismatic and prismatic beams. Additionly, based on the concept of isoparametric mapping, a generic approach for investigating the bending and shear deformation in a non-prismatic elastic beam with CSWs was presented in this study.(4) Several available methods of calculating the shear buckling strength of CSWs are presented by considering the factors of inelastic buckling and shear yield stress.The reliability and practicality of these methods are verified by comparing with the existing 101 groups of experimental results.(5) Supported by the Natural Science Foundation of China (grant No.51478107),researches on the shear behaviors of two groups of the non-prismatic beams with CSWs are experimentally carried out for the first time. Based on the riks algorithm,the whole loading process simulation of the test beams from elastic deformation to concrete cracking to CSWs buckling or yield to plastic deformation after buckling or yield are realized by the use of ABAQUS software.