Fatigue Failure of Concrete in Tension

Concentric tensile and flexural tensile fatigue tests were carried out on plain concrete specimens. The effects of pulsating tensile loadings as well as of alternating tensilecompressive loadings were studiep. The results of the constant-amplitude tests have been presented in S-N diagrams and a Goodman diagram. From these results it emerged that fatigue life was strongly reduced by alternation of the stress from tension to compression. Furthermore the number of cycles to failure for wet specimens was lower than for dry ones. It was also found that for equal load signals applied, flexural tests resulted in longer fatigue lifes than concentric tests, probably because of the possibility of redistribution of stresses. The longitudinal strains of the concentric tests were analysed. This resulted in a strong relation between strain rate and fatigue life. The concentric tests were continued with program-loading tests in order to check Miner's rule. Based on strain rate Miner's rule could be verified and Miner's number, M = 1, at failure turned out to be safe in general.