Strain-based fatigue failure criterion for steel-fiber reinforced concrete

摘要

This work proposes a new strain-based failure criterion for compression fatigue in steel-fiber reinforced concrete. It is based on the Spark and Menzies' relationship between the logarithm of the secondary strain rate per cycle and the specimen life expressed as the logarithm of the number of cycles until failure. This relationship permits calculating the critical strain at the failure of the specimen as the sum of two terms. The first one is the maximum strain in the first cycle due to the maximum compression stress. The second term is the increase of strain due to the remaining cycles until failure. Thus, failure occurs when the strain reaches a critical level during fatigue loading. On the contrary, the material continues resisting while its accumulated strain is lower than the critical one. This criterion is validated against a series of low-cycle fatigue tests in five types of concrete with different amounts of fiber that share the same concrete matrix. Besides, the experimental results show that the fibers delay the deformation and deterioration processes caused by fatigue. They also show that there is an optimum fiber content that maximizes fatigue life.