A Rapid Analysis Method For Fatigue Damage Of Concrete And Its Application On Ballastless Slab Track Of High Speed Railway

As a common construction material,concrete is often subjected to long-term cyclic loading.Under the action of cyclic loading,the micro-cracks and micro-holes inside the concrete could easily extend and expand with time,eventually leading to the degradation of the mechanical properties of the concrete.This phenomenon is called fatigue failure of concrete.The fatigue evolution of concrete usually occurs in a long time span with unique mechanism,which has been a difficult problem in the field of concrete.In engineering,it is only possible to estimate the fatigue life of concrete members by empirical formulas.In order to complete the fatigue analysis of concrete quickly and accurately,research is carried out in several aspects,including concrete constitutive model for fatigue,numerical analysis and acceleration algorithm.The main content of this article is briefly explained below.(1)Based on the double-scalar elasto-plastic damage constitutive model,a further research is carried out on concrete fatigue problem.With the help of double-scalar elasto-plastic damage constitutive model,the fatigue damage evolution rule and fatigue plastic evolution rule proposed by Marigo and Liang Junsong,several numerical calculations,including concrete compression,tension,repeated tension and compression,four-point bending of concrete beam are completed on ABAQUS,the results of which are in good agreement with the experiments,which proves the accuracy of the fatigue damage constitutive model.(2)In order to shorten the time for fatigue calculation,an acceleration algorithm is built on MATLAB,which combines fine calculation with explicit extrapolation.This algorithm is based on the idea of Cycle Jump Method proposed by Cognard,Ding Zhaodong and so on.By controlling the calculation process of ABAQUS,the computing time could be significantly shortened.By comparing the calculation results before and after using the algorithm,it can be found that the algorithm can greatly improve the calculation efficiency without affecting the calculation accuracy.Furthermore,several programs are proposed for algorithm optimization.With the help of these programs,the calculation efficiency of acceleration algorithm can be further improved.(3)Finally,the damage constitutive model,combined with acceleration algorithm,is used to analyze the high-cycle fatigue problem of reinforced concrete ballastless slab track.By comparison,the result is close to the experiment,the predicted fatigue life is similar to theexperiment fatigue life,and the calculation time is only a few hours.At the same time,the damage distribution map of the slab track at different fatigue development stages can be obtained through calculation,which is important to further study on fatigue evolution law of the slab track.All of these results come to a conclusion that the calculation system proposed in this paper can quickly and accurately analyze engineering problems.At last,the influence of fastener stiffness and elastic modulus of concrete on the fatigue life of the slab track is studied,and their recommended value is given according to the study.