| The steel-concrete composite girder bridge combined the advances of greatmechanical property, long span ability and great deck pavement performance. Whilethe slender web design appeared as the span grown, and web stability had becamethe important factor of steel-concrete composite girder bridge design. Thedepth-span ratio of girder is1/20~1/25, when the span passed100meters, the heightof the web will reached9~10meters. While the design code of china can’t fulfill theweb design at present, which give rise to the design problem of the web in long-spansteel-concrete composite bridge.The concrete deck and steel girder was connect each other with the shear stubs,the concrete deck, shear stubs, stifferener and steel flanges restrained the webboundary rotationally, and effect the buckling characters of the web. The stabilitytheory supposed that the boundary condition of webs were simplied or clampedsupported, which didn’t matched the real web structure boundary conditions. Focuson high web, large ratio of height to thickness characters web, boundary uncertaintyand complicated loads of long-span steel-concrete composite bridge, This paper usedelastic plate theory, Ritz energy variational method, finite element simulation andmodel test, considering the rotational restraint of concrete deck, shear studs, stiffenerand steel flanges, an effective buckling theory model of high web based on theelastic rotational restraint boundary in long-span steel-concrete composite bridgewas obtained. Then a calculation method of critical buckling stress of high webunder the composite loading of bending and shear considering the elastic rotationalrestraint boundary is obtained. Finally, the optimization design method of stiffenerfor the stability design of high web in long-span steel-concrete composite bridge ispresented. The research have breaks a new path for the high web buckling andoptimal design of the web longitudinal stiffeners. Main works in this paper isfollowing:(1) Solved the elastic rotational restraint coefficient χ of web in steel-concrtecomposite bridge. Coefficient χ denotes the ratio of rotational sifferen to webbending rigidity. Based on the elastic plate buckling theory, considering the anglechanging of flange and web equaled with each other, the rotatioal stifferen Czof composite flange was found and elastic rotational coefficient x of steel-concrete-composite-flange was solved.The formula shown that, the exsitance of shear stubs and concrete deck increased the elastic rotational restraint coefficient x.(2) xt and xo denoted the topper and lower flange boundaries of web in steel-concrete compostie girder. Supposed the buckling deformation function w(x,y) of web under bending was combined harmonic and polynomial, based on Rayleigh-Ritz variational method a buckling coefficient of web subjected to bending stress considering the boundary rotational restraint was obtained:In the formula, coefficient A1-A7had included the elastic rotational restraint coefficient xt and xo, when the coefficient x=0, it signifed that the boundary is simplily supported; the web critical buckling stress increased as the elastic rotational restraint coefficient x. When the coefficient xt and xo passed20, the web critical buckling stress tended to a constant, it signified that the boundary condition is clamped supported. The results show that a good agreement between finite element computation and theoretical analysis.(3) Supposed the buckling deformation function w(x,y) of web under shear was double trigonometric series, based on Rayleigh-Ritz variational method, a shear critial buckling stress matrix was found: Supposing the det of matrix equaled0, and an explicit critial buckling stress of web subjected to shear stress Tcr considering the boundary rotational restraint was obtained. The results show that a good agreement between finite element computation and theoretical analysis.(4)Then a girder experiment including7steel-concrete composite beams which subjected to shear loading was carried out to research how the different shear stubs distribution effected the critical buckling coefficient of the web in steel-concrete composite beam. The parameters of composite girder were:lenghtX height of girder was3200mm X900mm, width X height X thickness of web was1300mm X800mm X6mm, thickness of concrete deck was80mm, width X thickness of toper flange was400mm X5mm, width X thickness of lower flange was600mm X10mm; in order to research the different shear stubs distribution effect on the elastic rotationally restraint coefficient of steel-concrete composite flanges, seting the shear stub parameter was φ10mm X40mm, longitudinal spacing varied from200mm to500mm, transverse spacing varied from30mm to150mm; The results shown a good agreement with the theory model found by this paper, and the error range is1.2%-11.6%.(5) Parameter study was carried out to investigated how the elastic rotationally restraint coefficient of flanges, ratio of shear-bending, bending stress gradient and aspect ratio effect the web plate local buckling. Then a bending-shear interaction equation of plate with flanges restrained was built:The equation results are good agreement with the experiment results of Hongkong-Zhu Hai-Macau steel-concrete composite bridge girder, and the error was2.5%.(6) Web plate buckling of Hongkong-Zhu Hai-Macau steel-concrete composite bridge was analyzed. Acorrding to the bridge construction stage, web plate buckling in15kinds of the conditions were analyzed, the results shown that:the stability of the web plate in negative moment region of Hongkong-Zhu Hai-Macau steel-concrete composite bridge were satisfied the demand of the design code.(7) Based on Rayleigh-Ritz variational method and elastic plate buckling theory, a method of longitudinal stiffener optimal distribution of high webconsidering the boundary rotational restrainted was formed. Researched on howlongitudinal stiffener imperfection affect the critical buckling coefficient. |
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