Ermüdung von Verbunddübelleisten in UHPC unter zyklischer Pull-out-Beanspruchung

Fatigue of composite dowels in UHPC under cyclic pull out loading

Composite dowels can be used as a powerful alternative to headed studs for the efficient combination of ultra-high performance concrete (UHPC) with high-strength steel in modern steel-concrete composite structures. Besides sufficient shear resistance, the composite dowels have to ensure the transmission of tensile forces in the composite connection in order to prevent lifting of the concrete slab. In particular, in the very slender concrete slabs of high-strength composite beams, in which the composite dowels have very small embedment depths, this can lead to structural problems. While initial findings concerning the structural anchorage behavior of composite dowels under static loads already exist, studies on the fatigue of composite dowels under cyclic pull out loading are still lacking, so far. The present paper presents static and cyclic pull out tests of composite dowels in UHPC slabs. While the influence of different embedment depths as well as the use of a transverse reinforcement have been investigated in the experiments under static loading, the cyclic tests particularly focused on load-dependent parameters (upper load level and load range). Finally, an approach to estimate the lifetime of composite dowels in UHPC under cyclic pull out loading is proposed.