Reliability assessment of deflection limitation methods in reinforced concrete beams

Abstract The depth of reinforced concrete (RC) beams and slabs is typically governed by the limitation of deflections. The minimisation of beam and slab depths thus notably reduces the material cost of RC structures. Semi‐empirical slenderness ratio methods to initially size member depths are often simplified for ease of use, time efficiency and due to the limited knowledge available at preliminary design stage. These methods often contain considerable uncertainty and the serviceability limit state (SLS) reliability performance implied by using these methods is currently unknown. This research aims to quantify and compare the SLS deflection reliability performance of slenderness ratio (also called span‐to‐effective depth or ) methods to other analytical methods. A database of experimental samples from existing research is used to determine model factors for the methods. The SLS reliability performance of each method is evaluated for a simulated database of beams, considering both hinged and partially restrained supports. Analytical methods were found to achieve satisfactory reliability, whereas slenderness ratio methods produce conservative reliability values and especially so for longer beams. The preferential use of analytical over slenderness ratio methods may therefore promote a more sustainable use of materials and reduce structural costs while still providing adequate SLS reliability.