Point Load Distribution in Overhang Slabs: Effects of Model Complexity and Load History

Abstract

Understanding the distribution of point loads in overhang slabs is crucial for improving design and assessment of reinforced concrete bridges. The concept of an effective width allows shear forces and bending moments to be evaluated at critical sections and used in the dimensioning of the slab. While linear Finite Element (FE) analyses generally provide conservative and sufficiently accurate results, they may not fully capture the structural behaviour. Non-linear FE analyses offer a more realistic representation, but at the cost of increased computational effort and complexity. Finding a balance between accuracy and efficiency is therefore a key consideration. This Master’s thesis investigates the load-bearing capacity and force distribution re sulting from concentrated loads using analysis models of varying complexity, aligned with current regulations. A series of load cases and geometries were analysed using conventional hand calculations, linear FE models, and non-linear FE models. Findings reveal a significantly higher load-bearing capacity in non-linear analysis due to force redistribution following reinforcement yielding. Furthermore, the edge beam has little effect on the load-bearing capacity in linear models, while in non-linear analysis it significantly improves both capacity and force distribution. Hand calculations and linear analysis are conservative, simple, and relatively quick to perform, making them suitable for an initial evaluation of load-bearing capacity. However, if a higher capacity needs to be verified, non-linear FE analysis can be used to provide a more refined and potentially less conservative assessment. The non-linear FE model was also subjected to a loading history, where the cantilever slab experienced sequential point loads at multiple locations, resulting in increased per manent deflections and cracking. However, the prior loading had low effect on the ultimate load-bearing capacity. Its main influence was observed in the serviceability limit state, where both deflection and crack width were increased