Sustained loading effect on the fatigue life of plain concrete

The sustained loading effect on the fatigue properties of concrete was investigated. First, flexural sustained loading tests on plain concrete beams were conducted to establish a fundamental relationship between sustained stress and sustained time. A corresponding formula for calculating the equivalent damage under cyclic lending is also proposed Based on these relations, the fatigue equation previously proposed by the authors is modified to account for the sustained loaning effect. The modified fatigue equations agree well with previous experimental results at high stress ratios.