Research On Side-mid Span Ratio And Ultimate Span Of Through Type Continuous Beam Arch Composite Bridge With Single Arch Rib

Through type continuous beam arch composite bridge with single arch rib is developed and formed on the basis of the traditional continuous beam bridge and arch bridge,which has the advantages of high material utilization,reliable force,attractive appearance,strong adaptability and has prospective space and opportunities to develop.The research on the side mid-span ratio and ultimate span of single arch rib through continuous beam-arch combination bridge has great significance for bridge span layout and bridge site selection.This paper carries out a theoretical study on the side to span ratio and the ultimate span based on the analysis of the stress and deformation of single-arch rib-through continuous beam-arch combined bridge.The main contents are as follows:（1）Introducing the assumption of membrane tension and adopting the displacement method to deduce the analytical formulae for the support reaction,internal force and mid-span deflection of the single arch rib through continuous beam-arch composite bridge under the action of uniform constant load on the whole bridge and live load on the mid-span Analyze a single arch rib through continuous beam-arch composite bridge based on this analytical formula,and obtain analytical solutions for internal force,reaction force and displacement.Compare the analytical solutions with the numerical solutions obtained by Midas/Civil finite element software.The results show that the error between the two is not large,indicating that the analytical formula is correct.（2）Using the derived analytical formula,the influence of the side-to-span ratio on the support reaction,internal force and deflection of the single arch rib through continuous beam-arch composite bridge is analyzed.The results show that the main beam side support reaction force,vault bending moment,arch foot bending moment,mid-span mid-span bending moment,and side span maximum positive bending moment all increase with the increase of the side-mid span ratioλ.When the beam-arch bending stiffness ratio k_ba=1/80,the left end of the center support and the side support rotation angle both increase with the increase of the side-mid span ratioλ,and the change of the side-mid span ratioλchanges the center support The influence of the bending moment at the right end of the seat and the vertical deflection of the mid-span is small.When the beam-arch bending stiffness ratio k_ba=1 or k_ba=80,the bending moment at the left end of the middle support,the right end bending moment of the middle support and the corner of the side support all decrease first and then increase with the increase of the side-to-span ratioλ.Large,the mid-span vertical deflection of the mid-span decreases with the increase of the side-mid-span ratioλ.（3）By studying the effect of the side-mid-span ratio on the side support reaction,control section bending moment and deflection of a single arch rib through continuous beam-arch composite bridge,three factors that limit the reasonable value of the side-mid-span ratio are obtained,including the support The reaction force is not less than 0,the maximum positive bending moment ratio between the side span and the middle span is not more than 1,and the maximum bending moment ratio between the middle support and the middle span is not less than-2.Through the analysis of three limiting factors of a single arch rib-through continuous beam-arch composite bridge,it is concluded that the reasonable range of the side-to-span ratio is 0.231～0.110.（4）The ultimate span of single-arch rib-through continuous beam-arch combined bridge is theoretically deduced from three control parameters,which include the limit strength of the material,the structural roll stability,and the middle-span deflection of main girder.The analytic formulas for ultimate span under three conditions are obtained,which show that the ultimate span controlled by material increases with the increment of the span ratio k_f.Whereas the ultimate span controlled by stability increases and then decreases with the increment of k_f,so dose the vertical deflection.Through these three control parameters,the ultimate span of single-arch rib-through continuous beam-arch combined bridge is analyzed.It is concluded that when the cross-section of the bridge is determined,its ultimate span is 178m.