Under-supported Railway CFST Arch Bridge’s Suspender Force Analysis

In recent years, CFST arch bridge is adopted widely in the building bridge. It is one of the most competitive power bridges between the span of60-200meter. As the vital supporting component in bottom-supported tied arch bridge, The Suspenders Tension has great impact to the stress state of the tie-beam and the arch rib. Because of the design theory of suspender is not standardization in the initial design; the fatigue corrosion problem of suspender is overlooked. The structural factors which impact to the stress of suspender are not system researched. At present, the safe stress problem of suspender has becomes the key problem which impact to the working of CFST arch bridge.This article takes an actual project as the example. The finite element model of the through CFST arch bridge is established, this engineering model is analyzed by MIDAS CIVIL.According to the fatigue damage of suspender, this article analyses several key factors which impact its force. These factors include temperature changes, concrete shrinkage and creep, the wind and rain vibration problem of suspender, bridge vibration problems and the connection form of suspender etc. It is found that the reasons of suspender’s damage are various, they include the complicated additional shear force and additional shear force which suffered by itself, suspender is long-term in the high-frequency vibration and the corrosion of materials etc, the fatigue force is not only the reason for suspender breaking.According to the force balance method, the suspender tension is confirmed, the dead load moment of the arch rib and the tie beam are ensured sensible distribution and the suspender force is uniform. For the construction phase of the initial tension, the reverse method is using for solving it. To sensible regulation the suspender tension, the tie beam control parts and the internal force of the arch rib will be distributed rationally. Comparing the change of suspender force before and after building the bridge, the result show that the live load increases the tension of the suspender suffered, the increase of suspender force is basically the same, the suspender is greatly affected by the live load.By changed the structural system elements, the influence of suspender force is analyzed and compared. The calculated data show that:Maintain the appropriate suspenders spacing (generally5to10m) is beneficial to the fatigue force of the suspender itself and the whole force. Too large or too small spacing will bring the problem of the arch bridge construction or force aspects. The fatigue force of the1/4span and the span crowns is the most serious, we should pay for more attention in design. The change of rise-span ratio Arch span in the arch bridge is not obviously affected to the suspender force. The stress and the stress amplitude of the suspender increase with the stiffness ratio of the arch beam increases, and the side-suspender is the most affected. The distance’s change of the side-suspender to the arch foot only impact greater on the side-suspender force, while impact little on the other suspender.