Research Of Multiscaling Fatigue Failure Behavior Of Suspenders In A Half-through Arch Bridge

With the rapid development of bridge construction, the problem that how to prolong the service life of a bridge has been increasingly highlighted. As an important component of the bridge, the suspenders of a bridge he bridge structure loads as well as the traffic loads, environmental corrosion, and so on. Therefore, the suspenders would inevitably suffer the destruction while the structural resistance would decrease accordingly. This would result in the fatigue failure of bridge suspenders. The fatigue failure problems of steel wires in the bridge suspenders attract more and more attentions in the bridge engineering field. The influence factors for the fatigue failure of steel wires are discussed one by one based on the results of numerical analysis. A macro/micro trans-scale fatigue crack growth model is adopted in this work. First, the model is verified by the fatigue test data. By using the commercial software Midas/C ivil, a FEM analytical model of Maocaojie Large Bridgeis established. Using the macro/micro fatigue crack propagation model, the fatigue behaviors of steel wires are analyzed in details.This work is based on the macro/micro trans-scale fatigue crack growth model by using thre restraining stress zone. The fatigue behaviors of steel wires are investigated. The main influence factors are addressed. The completed work can be concluded as follows.(1) The fatigue failure problem of 40CrNi2Si2MoVA low alloy and high trength stee l material is studied. By using the fatigue test data of smooth specimens, two materia l fatigue parameters are determined. Then, the fatigue lives for the notched specimens are predicted. The theoretical results are in good agreement with the test data. This indicates that the the proposed model can describe the whole fatigue process from micro-scale to macro-scale.(2) AFEM analytical model o f the Maocaojie Large Bridge is established. By consideratio n of the relaxation and tension effects and under the different loading cases, the tensile stresses in the steel wires are calculated in details. The results will be used in the next fatigue analysis for the steel wires.(3) By using the trans-scale fatigue crack growth model, he fatigue failure behaviors of stee l wires in the suspenders of Maocaojie Large Bridge are calculated. A group of a~N curvesunder different loading cases are obtained. The different influence factors are discussed. The results show that the microscopic effects have a large influence on the fatigue behaviors o f steel wires.