Performance Study On Long Span Beam-arch-frame Composite Bridge

Beam-arch-frame composite bridge is a new bridge structure form, in which rigid frames and arches are rigidly connected to bear the load together. this kind of bridge has many features, such as reasonable stress,high utilization ratio,beautiful shape and easy for construct. through the engineering of Zhuzhou Honggang Bridge,we have researched and resolved many aspects based on performance study, and obtain some conclusions as follows:(1)With the FEM results of suspender forces under the uniform load, the result assumed that all the suspender forces were almost equal, and the suspender forces could be regarded as filmy ones. The beam-arch-frame composite bridge was departed into beam-arch-frame body and filmy suspender. Through the deforming balance equation at the midpoint, the practical formulas of filmy suspender forces, deflections at the midpoint were acquired. Then verified the formulas by a single span beam-arch-frame composite bridge and Zhuzhou Honggang Bridge. To analyzed the reasons of inaccuracy and to revise. Next , the paper presented the expressions on ratio of load sharing and ratio of moment sharing between beam and arch. Moreover ,the influence about ratio of beam-arch-frame sectional flexural rigidity, ratio of suspender arch equivalent flexural rigidity, ratio of rise to span, influence coefficient of axial deformation were discussed.(2)Through summarizing the methods of determine the reasonable status of completed bridge, and combining stress feature of rigid beam-soft arch beam-arch-frame composite bridge, Ordered the axial force of arch as objective function. Based on the formulas of filmy suspender forces, combined with the envelope diagram of upper limb and lower margin stress of arch under live load, used the formulas of stress control requirement to solve the filmy suspender forces. Then the suspender forces can be sure.(3)Introduced the content and meaning of simulation calculation in the construction process,fundamental principle and design procedure. Build the finite element model by using the MIDAS. Computing the model by forward-iteration method, analyzing the stress,moment,displacement of V-pier,beam and arch under the worst operating condition.(4) Have done research on stability analysis of Honggang bridge. the paper derived the safety factor under the worst operating condition and the status of completed bridge . we can see that either in under the worst operating condition or the status of completed bridge, the bridge has good stability. Moreover, the parametric research on the influence of different factors on the stability of the main arch was analyzed,such as the arrangement and stiffness of the 1ateral brace, inclined angle of arch ,the rise-span ratio etc.