Research On The Flexural Behavior Of CSW-CFST-CS Composite Girder

The composite girder with corrugated steel web (CSW), double concrete filled steel tubular chords (CFST) and concrete slab (CS) is a type of newly proposed composite girder, in which the CSWs are utilized as connection components between the CFST members and concrete slab. Compared with the PC box girder with corrugated steel webs, instead of concrete bottom plate with CFST chord, the use of the new composite girder not only further reduces the deadweight of the superstructure, improve the cracking resistance and integrity of the structure, but also enhance the prestressing effect. Moreover, the ultimate load-carrying capacity of the new girder is improved because of the avoidance of joint failure in truss girder with CFST chord and concrete slab. As a new structure, none researches on the experiments and fundamental applying on them have been carried out yet, although there have been engineering examples and the researches of finite element method of the similar structures. Therefore, aiming at understanding the flexural mechanical behavior of this new structure, experimental investigation and finite element study has been conducted in this thesis. The main tasks include:(1) The applications and researches on composite girder with corrugated steel webs, CFST (truss) composite girder and CFST-CSW composite girder at home and abroad had been summarized, which provides references and bases for the study on the mechanical properties of CSW-CS composite girder with double CFST chords.(2) Experimental research on CSW-CFST-CS composite girder has been carried out to offer basic data for study on mechanical properties of this new composite structure. The experimental results demonstrate that the quasi plane section assumption can be applied in the cross section of the composite girder during the elastic stage. Except that bear most of the shear, corrugated steel webs subject to certain bending moment at the same time but the value is significantly smaller than the CFST chords. The bending deformation is evident when the structure damages, which indicate that the new structure possesses good ductility.(3) The finite element program ABAQUS is adopted for establishing entity finite model of CSW-CFST-CS composite girder which can be use for extending parameter analysis because the FEA results agree well with the testing results. The results show that, filling concrete into the steel tube of the negative moment region can greatly improve the compressive strength and stiffness of the chords, reduce the stresses of the steel pipe effectively and lead to higher load carrying capacity. Concrete in the steel tube of the positive moment zone can be contribute to section stiffness. The increase of the thickness of the bottom tube can improve the stiffness and bearing capacity of the structure. The thickness of the corrugated steel webs has little influence on flexural capacity of the composite girder when it is satisfied to avoid local buckling.(4) The trial design on CSW-CFST-CS composite girder continuous bridge has been carried out and compared with Ganhaizi Bridge in which truss girder with single CFST chord and concrete slab is used. The results indicate that the new structure with corrugated steel webs instead of steel truss webs avoid joint failure fundamentally and have a certain application prospects.