EXPERIMENTAL STUDIES OF VARIABLE-AMPLITUDE FATIGUE OF CONCRETE IN BIAXIAL TENSION-COMPRESSION AND TRIAXIAL TENSION-COMPRESSION-COMPRESSION LOADING CASES

摘要

Experimental studies of two and three grade variable- amplitude fatigue of concrete in biaxial tension- compression and triaxial tension-compression- compression loading cases are carried out. After reaching the experimental result, fatigue damage analysis is presented, including linear fatigue damage analysis and nonlinear fatigue damage analysis. The results of the analysis of fatigue residual strain in constant and variable-amplitude fatigue processes, show that residual strain of concrete in tension-compression and tension- compression-compression loading cases is connected with relative fatigue times and stress ratio, and it is not affected by the loading course on the whole. Corresponding ultimate residual strain can be used as the criteria of fatigue damage. Moreover, through this analysis, relative residual strain is defined as damage variant, the damage evolution equation is given, the fatigue damage model in tension- compression and tension-compression-compression multiaxial loading cases is established. The damage model in this paper is reasonable after contrasting the theoretical calculation result and the experimental observation result. This model may also be used to forecast the residual fatigue life of concrete. Tests carried out in this paper fill the blank of variable-amplitude fatigue test in tension- compression and tension-compression-compression multiaxial loading cases. This item is subsidized by the doctor fund of Beijing Institute of Civil Engineering and Architecture.