Study On Fatigue Damage Behavior Of Prestressed High Performance Concrete Beam

High performance concrete(HPC)is a kind of new conception concrete put forward by western countries in the 1980 s.It has been paid much attention by engineering circles for its excellent workability,durability and volume stability.With the development of economy,the problem of structural fatigue becomes more and more prominent with the characteristics of large span and high frequency of contemporary bridge structure.The safety accidents caused by fatigue of bridge structure are threatening the people’s life and property.Considering the superior performance of high performance concrete,it is worthy of study to improve the fatigue performance of the structure in modern bridge structure.Although it has been popularized,the research on the development law of fatigue damage of high performance fly ash concrete And the amount of fly ash is strictly controlled.This paper designs the prestressed high performance concrete model beam based on the similarity theory and studies the fatigue of the high performance concrete through the fatigue test,static load test and finite element software.And the effects of fly ash content and concrete strength grade on the fatigue performance of high performance concrete simply supported beams are studied.The main work and conclusions are as follows:(1)The characteristics of fly ash were summarized and analyzed,and the mechanism of fly ash incorporation into concrete was discussed.(2)The similarity theory is introduced in detail,and the similarity theory is used to derive the size and reinforcement of the model beam.The test load scheme and test content of the model beam are briefly introduced.(3)The fatigue damage development law of high performance concrete was qualitatively studied by collecting the deflection of the cross section of the five model beams,the strain and the residual strain of the cross-section concrete,and found that under the loading condition Fatigue load 2 million times)fatigue damage development to cycle load 200,000 times as the dividing point,the first stage of rapid development of damage,the second phase of the development of slow injury.The fatigue cumulative damage of high performance concrete basically presents a two-stage development law.(4)Based on the test results,the effects of fly ash content and concrete strength grade on the fatigue performance of high performance concrete beams were studied.It was found that the addition of fly ash in a certain range was beneficial to improve the fatigue performance of concrete Concrete strength grade is not obvious;high-performance concrete fatigue resistance and stability,can be used in the bridge structure.(5)The finite element analysis software ANSYS and NCODE Designlife were used for static analysis and fatigue analysis respectively.The fatigue point of the fatigue design was calculated as the research object,the fatigue damage cloud image and the fatigue life cloud were calculated,and the fatigue Cumulative damage was in two stages of development,consistent with the experimental analysis.