Fatigue Behavior of Shear Connectors in High Performance Concrete

The paper deals with the fatigue behavior of headed studs and continuous shear connectors in high strength concrete. For both types of shear connectors cyclic push-out tests as well as large-scale beam tests under cyclic loading were carried out. The headed studs failed after a mean lifetime of 2.3-106 applying 40% to 50% of the static resistance as a maximum amplitude and R = 0.45 and 0.65, respectively. The residual strength after 1.0-106 load cycles was reduced by about 25% in comparison to the static push-out strength. The continuous shear connector, which is called “puzzle strip”, did not fail in the fatigue tests with up to 2.0-106 load cycles, and there was no reduction in residual strength at all. The cyclic beam tests with headed studs show that the prediction of the fatigue failure according to the current standards is not satisfactory. A good prediction of the crack propagation (thus fatigue) can rather be accomplished by using an approach based on the crack-slip relationship. For the continuous puzzle strip the fatigue behavior depends on the state of the cutting-induced heat treatment of the surface material and on the surface roughness. For these connectors a threshold value for the crack propagation could be determined.