Fatigue Strength of High Strength Concrete under Cyclic Loading

The interest in the fatigue of concrete began more than a hundred years ago with the development of reinforced concrete. The technological development in high strength concrete (HSC), has led to construction of modern complicated structures of considerable height and span. However, HSC is more brittle than conventional concrete, so, an alternative method to enhance ductility is to add fibers into the concrete matrix thus fiber reinforced concrete is made. Nowadays, the fatigue behavior of fiber reinforced concrete is getting more and more attention due to frequent application of cyclic loads as shown in figure 1. The aim of the present study is to investigate the fatigue strength of conventional HSC. The M60 grade concrete has been designed as per ACI-211.4-R based on trial mixes. Four concrete beams were cast of reinforced conventional HSC. All the beams have been tested under three point loading using 500 kN servo controlled actuator. The stress ratio in the range of 0.7-0.9 with an interval of 0.1 was incorporated for cyclic loading of beams. From the experimental data obtained, a relationship between S-N has been developed. An equation has been proposed to predict the fatigue strength of conventional (without fibers).