Fatigue life assessment of concrete members under variable amplitude loading: An analytical approach

Abstract

As structural design and analysis become more refined there is an increased demand for fundamental information on the performance of concrete under loads other than static. Apart from the application of different types of loading, the material behaviour of concrete is highly heterogeneous and complex in nature due to the occurrence of extensive micro-cracking and toughening mechanisms. In this work, an attempt has been made to estimate the crack growth in concrete members under the action of fatigue loading considering complex material behaviour. In addition to the dependency of size and shape of the member on fatigue behaviour, the effect of loading history under the action of varying amplitude load cycles with sudden overload is important and has been considered in this work. Further, the effect of loading frequency on crack growth and fatigue life has been demonstrated through thermal diffusion coefficient. The mathematical formulation for the prediction of crack growth rate has been derived on the basis of theoretical arguments utilizing the concepts of self-similarity and intermediate asymptotic. Available experimental data on concrete fatigue has been taken up from the literature and are used to determine the unknown coefficients in the formulation. The predicted results based on the proposed formulation are found to capture the effects of loading history, sudden overload, and loading frequency in addition to the effect of structural size. The proposed model is then solved using higher-order numerical integration techniques enabled by surrogate modelling followed by a sensitivity analysis. Loading frequency and energy release rate due to overload cycle are found to be less sensitive on the fatigue life prediction.