Development of a new design approach for composite dowels positioned close to the concrete surface

Abstract

Composite dowels as shear connectors between steel profiles and concrete sections have been investigated for decades. The long‐term aim is to implement a consistent design concept within Eurocode 4 ‐ covering both, the fields of bridge and building construction. Especially in building construction, where the concrete slabs are dimensioned increasingly slimmer in contrast to bridge construction, the composite dowels are positioned unavoidably close to free concrete surfaces. This causes additional failure modes, leading to the overall failure of the structure, which have not been entirely investigated yet. At University of Kaiserslautern more than 30 push‐out tests were performed within a joint research project in cooperation with RWTH Aachen University. These tests were focused on the resistance of composite dowels close to the concrete surface in dependence of varying influence parameters. Some results showed a significant reduction in shear strength and deformation capacity, mostly accompanied by the spalling of the concrete cover. Simultaneously, numerical simulations were calibrated and utilized to get a deeper understanding of the load transfer mechanisms and to interpolate between existing experimental results. On the basis of experimental measurements and numerical simulations a load transfer model was developed with a corresponding design approach to calculate the theoretical resistance.