Reliability of beams according to Eurocodes in serviceability limit state

To achieve a relatively consistent probability of failure for structural elements, most design codes apply reliability based code calibration process. Such approaches commonly focus on the strength of the structural members, which is related to the ultimate limit state (ULS). However in the design of beams the performance of the structural elements is often limited by the serviceability requirements, which are related to the serviceability limit state (SLS) using different load combinations than applied in the ultimate limit state.The current study aims to investigate the reliability for serviceability design for flexural members made of different materials (steel, concrete and timber) according to the specifications of the Eurocodes. Second-order reliability method (SORM) is applied to determine the reliability index for different design situations for beams subjected to bending. The probabilistic models of basic variables for time invariant analysis have been taken from the JCSS Probabilistic Model Code. The characteristic, the frequent and the quasi-permanent combination of actions are investigated and compared. The differences in service reliability for different materials are discussed. The results show that there are differences between the achieved reliability indices in the serviceability state between different materials and that for the given load combinations in the Eurocode the reliability index is often below the one given in the code.

► The reliability of Eurocode specifications for serviceability limit states for office floors is investigated.
► The excessive deflections of simply supported beams made of steel, concrete and timber are considered.
► The loads, material properties and the deflection limits are modeled as random variables.
► We found that the reliability for serviceability is not consistent for different load ratios and materials.
► We found that the reliability for serviceability is generally below the target value of the code.