Cumulative fatigue damage of plain concrete in compression

The thesis reports an investigation carried out on more than two hundred and fifty prismatic specimens to study the cumulative fatigue damage of plain concrete subjected to constant and variable amplitude cyclic compressive stresses. Pulse velocity measurements and strain characteristics were used to indicate the extent of progressive fatigue damage. At a given percentage of the life the amount of damage of a specimen is dependent on the stress level. Prismatic specimens were also subjected to repeated compressive stresses according to various load programmes in which the maximum load was varied between two limits the minimum load being kept constant throughout. The results were interpreted according to the pulse velocity measurements, the physical appearance of fractered specimens together with the phenomenon of progressive fracture itself. Palmgren-Miner hypothesis was found to give conservative or unsafe predictions of the fatigue life depending on the load programme. Factors affecting the accuracy of the hypothesis are discussed and an empirical design chart is presented.