| Reactive Powder Concrete (RPC), a kind of ultra-high performance concrete with high strength, high toughness and durability, can overcome many problems in concrete structures effectively. But RPC needs strict production requirements and high production costs. RPC-NC composite beam makes full use of advantages of RPC and ordinary concrete. Due to the continuous social development, modern road and rail transport develop quickly. The increase of traffic volume and the speed improvement lead to increasement of bridge fatigue problems. In view of this situation, the paper studies the fatigue performance of RPC-NC composite beams and relates conclusions:(1) This paper analyses and summarizes the fatigue characteristics and failure pattern of concrete structures. By summarizing the fatigue properties of concrete, RPC and steel S-N curve of different materials are elected and composite beam fatigue analysis methods and process are determined.(2) Based on the railway train fatigue load,32m beam typical fatigue trainsiis determined. We calculate the bending moment spectra by program and the moment ratio spectrum of32m beam is ascertained by the method of rain-flow counting.(3)8group composit beam of different RPC are chosen as the object of study. Concrete and prestressed steel fatigue stress spectrums of Cross-section are calculated by method of theoretical calculation and finite elemente model. Compared the composite beam fatigue lifes, which are concluded based on the theory of materials cumulative fatigue damage, we can know the effect produced by RPC height.(4) Combines related specification and literatures, materials basic parameters of RPC-NC composite beam, which need when reliable indicators are calculated, are abtained based on different materials fatigue stress spectrum under two calculation methods. The parameters include concrete’s, RPC’s and steel’s fatigue strength median, reduction factor and equivalent constant-amplitude cyclic stress median and reduction of three materials. Compared the reliability index of concrete, RPC and steel to conclude the effect produced by RPC height on fatigue properties of composite beam. |
