Design Forces for Punching Shear Verification in Thick Raft Foundations with Special Regard to Partial Safety Factors

The thickness of raft foundations for buildings is usually dimensioned in regard to the punching shear resistance of punctual loads. The punching shear verification can hereby be performed according to Eurocode 2, which considers an isolated part of the slab. The rotation of the slab, however, is not explicitly regarded in this calculation, even though the rotation of the slab has significant impact on punching shear from a mechanical perspective. In this paper a comprehensive numerical analysis of the entire slab behaviour is aimed. A central aspect is the regard of realistic soil behaviour through geotechnical analysis and the direct consideration of the settlement troughs of the entire structure in the investigation. This approach enables a clear distinction between forces due to external loads and forces due to imposed deformations. Simulations with imposed settlement troughs show a significant reduction in the effective punching shear force and enable more sustainable dimensions of raft foundations.