Sensitivity of reinforcement spatial variability in concrete slabs for deflection serviceability

Reinforced concrete (RC) structures can be affected by unpredictability in design, loading, modelling assumptions, geometric deviations and construction errors. The aim of this study was to analyse the impact of construction-related imperfections – specifically slab geometry variation and reinforcement placement – on the safety and performance of solid RC slabs. These imperfections were treated as random variables. The sensitivity of slab deflections to parameters arising from both material properties and construction variability was evaluated. The methodology used incorporated spatial variability of reinforcement through stochastic fields, analysed using the finite-element method. Simulations were performed using Ansys software, in which concrete was modelled using the Drucker–Prager criterion and reinforcement was modelled using a bilinear elastoplastic model with isotropic hardening. The behaviour of slabs with perfectly placed reinforcement and slabs with irregular placement was compared. The results show that the compressive strength of concrete and the geometric dimensions of the slab were the most influential factors on deflection. Variability in reinforcement placement produced behaviour similar to that of ideal placement, suggesting minimal impact on final deflections. These findings highlight the critical role of concrete strength and slab geometry, while minor deviations in reinforcement positioning appear to have a negligible effect on the overall structural performance of slabs.