Investigation of stress level on fatigue performance of plain concrete based on energy dissipation method

Abstract

Fatiguefailure is one of the most common failure modes for concrete structures. When subjected to fatigue loading, which may be induced either by vehicle load or by wind load, the damage of concrete would develop gradually due to the evolution of internal micro-cracks. Once the damage value exceeds a critical threshold, the concrete will lose its loading capacity. Therefore, knowledge aboutthe fatiguedamage evolutionof concreteis crucial for evaluatingits time-dependent deterioration as well as establishing the fatigue life prediction model of reinforced concrete structures. This paper dealt with an experimental research of stress level on fatigue performance of plain concrete based on the energy dissipation method. The developments of strain, stiffness degradation and energy dissipation were discussed in accordance with the obtained experimental data. Moreover, the parameter of effective area ratio, e.g. the ratio between the area of matrix and the area of concrete at the same cross section, was proposed to describe the fatigue damage as well as its evolution during the cyclic loading process. The results show that the developments of strain, stiffness degradation and fatigue damage can all be divided into three stages: (i) an instable and relatively brief stage due to the initiation of material original micro-cracks; (ii) a linear developing stage because of the propagation of internal micro-cracks; (iii) a rapid and unstable stage as a result of the growth and coalescence of cracks. In the linear developing stage, the value of strain rate remains constant approximately, irrespective of the stress level. In addition, the fatigue damage and stiffness degradation of concrete are closely linked to the stress level. With the increase of stress level, the fatigue damage enhances. But onthecontrary, the stiffness degradation reduces when the stress level rises. The average value of single-cycle energy dissipation per unit volume in the second stage Ed,V increasesexponentially due to the increasing of the stress level, and a fatigue life prediction model was developed by means of energy dissipation method. It is demonstrated that the fatigue life decreases with the absorbed energy of concrete and there is a linear relationship between the logarithmic fatigue life and Ed,V.