Analysis Of Torsional Performance Of Double-box And Single-chamber Steel-concrete Composite Beams

Compared with traditional reinforced concrete beams and steel beams,steel-concrete composite beams are a structural type developed on the basis of steel structures and concrete structures.Therefore,it has also been widely used in engineering,and is developing in the direction of large span and width.A double-box single-chamber steel-concrete composite beam structure with a span of 60 m is studied,and the torsional characteristics of this kind of double-box single-chamber steel-concrete composite beam structure are analyzed with both theoretical analysis and numerical simulation.The research contents are as follows:(1)Using the equivalent principle of stiffness and displacement,the steel roof and floor with stiffeners and the web are equivalent to an isotropic orthotropic plate structure;based on the principle of energy variation method and Umansky’s second torsion theory,a double-box single Constrained torsion control differential equation of chamber steel-concrete composite girder bridge,the initial parameter method is applied to obtain the solution of the constrained torsion control differential equation;the cross section of double-box single-chamber steel boxconcrete composite girder bridge under mid-span concentrated torque and full-span uniform torque is deduced,and the calculation formulas of torsion angle,warpage deformation coefficient,constrained torsion double moment and total torque are compared with both theoretical and the finite element results by numerical method to verify the correctness of the calculation formula.(2)The calculation formulas of the shear flow and torsional moment of inertia of the double-box and single-chamber steel box-concrete composite girder bridge are derived and obtained by using the film comparison method,and the calculation formula of the double-box and single-chamber steel box-concrete composite girder bridge is established The finite element model is used to analyze the distribution law of characteristic parameters such as section torsion angle,warping deformation coefficient,and restraint torsion double moment along the longitudinal direction of the bridge,and further analyze the horizontal distribution law of top and bottom plate normal stress and web shear stress under the coupling of torsion and distortion..(3)The constrained torsional frequency formula of the double-box single-chamber steel box-combined girder bridge under the free vibration state were derived through theoretical derivation.The correctness of the calculation formula was verified based on the finite element method.The influence of parameters such as the thickness of the base plate and the height of the composite beam on the restraint torsion frequency were also analyzed with numerical methods.(4)Based on the finite element method,symmetrical loads and eccentric loads are applied to the mid-span of a double-box single-chamber steel box-concrete composite simply supported girder bridge,and the eccentric load side of the tenth point section of the main girder and the connection of the steel web are extracted.The normal stress corresponding to the lower edge of the steel floor and the shear stress at the center node of the steel web are calculated,and the stress amplification factor is valuated;the effect of different height-span ratios,widthspan ratios,web thicknesses and base plate thicknesses under symmetrical and eccentric loading is analyzed.