Zur konstruktiven Durchbildung des Decke-Stütze-Knotens in Flachdecken aus Elementplatten

Construction of slab-column-connections in semi-precast flat slabs

Due to the high degree of prefabrication, semi-precast flat slabs are gaining importance. In this context, the construction of the slab-column-connection has a safety-related significance. In daily engineering practice, the joint widths between semi-precast slabs as well as the joint widths between semi-precast slabs and the column's vicinity is constructed differently. The European Technical Approvals of different punching shear reinforcement systems limit the minimum joint width between semi-precast elements to 4 cm. Following these provisions, the joint widths between semi-precast slabs and the column's vicinity is constructed with 4 cm in some cases. An advantage of this approach is the possibility to adjust dimensional and positional tolerances at construction site. However, a disadvantage is the additional formwork for the joint from the soffit.
A systematic test series with special lattice girders as punching shear reinforcement showed no reduction of the punching shear resistance for smaller joint widths between semi-precast slabs and the column's vicinity. To confirm these test results, two punching shear tests with double headed studs and lattice girders as punching shear reinforcement were conducted at Institute of Structural Concrete (RWTH Aachen). In the tests, the influence of the joint width between semi-precast slabs and the column's vicinity as well as the influence of column height tolerances were investigated. Based on the results of the tests, this article gives recommendations for the construction of slab-column-connections in semi-precast flat slabs.