The Research Of Structure System Safety Under The Suspender Failure Of CFST Arch Bridge

Because of the complex stress state of the suspenders and the influence of corrosion,fatigue and other factors make the suspenders fail. Failure of suspenders will cause thesuspenders internal force redistribution. So in the design of Arch Bridge, failure of suspendersfor increasing safety calculation is very necessary. It not only can be explicitly calculated theinfluence of suspender, arch and beam stress state and the influence of stability of arch bridge,but also has very important significance to improve the safety of the whole bridge.Whether failure of suspenders is safe for system of the structure or not, researching theeffect on bottom-through arch bridge in case of failure of suspenders is carried out. In thispaper, the bottom-through arch bridge of the Middle Route Project of South-to-North WaterDiversion in Wei Gang Pu north across the canal of the1section of Yexian County in Henanis taken as the research object. First, the error between theoretical calculation of cable forceand measured value after calibrating the K value is analyzed by the vibration frequencymethod under the different boundary conditions of both ends of the suspender rod. The resultsof the analysis indicate that cable force by equivalent hinge method is closed to cable forceafter calibrating K value and the error is within5.5%that can meet the engineeringrequirements.Secondly, the mechanical properties and dimensional stability of the Arch Bridge iscalculated by using the finite element analysis software MIDAS/CIVIL.In static security, when a single suspender fails, the maximum stress, stress amplitude ofthe remaining suspender and stress state of the bridge structure can satisfy the requirements ofdesign and specification. Failure of single suspender having small effect to static response ofbottom-through arch bridge and failure of single suspender is fail-safe. When there are threepairs of successive suspenders failing, it will lead the bridge structure to appear tensile stressof certain position, large displacement causing partial cracking of concrete. What is more, itwill cause chain failure of suspenders, and then cause serious injury to the bridge structure,even collapse.In dynamic safety, vibration of this arch bridge mainly includes out of plane vibration ofarch rib, the vertical vibration of the arch bridge and torsion vibration. Out of plane stiffnessof arch rib is relatively small and the in-plane vibration appears later than the out of planevibration. The suspender is arranged so that the vertical vibration of bridge deck performancesfor the overall vertical vibration of the arch bridge. Failure of suspenders has little effect onnatural frequency of transverse vibration of the bridge, while has great effect on the verticaland torsion vibration. Failure of suspenders will lead vertical and torsion vibration frequencyto reduce. Therefore, safety of arch bridge suspender is important to the safety of arch bridge. In stability, stability coefficient of first order under each condition corresponding to thebridge structure ranges from4.85to5.26that meets requirement. The stability coefficient isgreater than or equal to4in the construction and operation period according to the designexperience of concrete filled steel tube arch bridge in our country. Failure of suspenders haslittle effect on low order stability safety coefficients of the arch bridge, that is to say failure ofsuspenders influences on the structural system is failure-safety. The forms of instabilitymainly perform for the arch rib lateral surface instability.