High-Performance Materials in Composite Construction

Scope of the investigations was the fatigue behavior of different shear connectors like headed studs and the puzzle-strip, which is a continuous shear connector in high-strength concrete (HSC). 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 × 10 6 applying 40–50% of the static resistance as a maximum amplitude and R = 0,45. The residual strength after 1,0 × 10 6 load cycles was reduced by about 25% in comparison with the static push-out strength. The continuous shear connectors were tested with two different stress amplitudes (R = 0,54 and R = 0,42). None of the test specimens failed in the fatigue tests with up to 2,0 × 10 6 load cycles. Moreover, there was no reduction in residual strength in the tests with the smaller stress range (ΔP/Pu,0 = 0,2). One test with a stress range ΔP/Pu,0 = 0,25 showed a recuction in residual strength of 24%. The cyclic beam tests with headed studs show that the prediction of the fatigue failure according to the current standards is not satisfactorily. 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 manufactoring process, the state of the cutting-induced heat treatment of the surface material and the surface roughness. For the tested connector geometry, a threshold value for the crack propagation was determined.