Partial load factor for self-weight of slabs in multiple-floor buildings

In building design, the partial load factor (PLF) for the self-weight of slabs is independent of the number of floors. This is in contrast to variable actions, where the load may be reduced for higher buildings. This simplified approach, with a typical value of γG = 1.35, has an impact on the estimated internal forces in columns and foundations, and has strong financial and material consumption implications (particularly detrimental for concrete slabs with larger significance of self-weight than alternative floor systems). For high-rise buildings, the construction sequence (only some floors propped during casting) becomes relevant for determining internal forces. In addition, the aleatoric component of some uncertainties (such as thickness of slabs) may partly compensate from floor to floor. Therefore, a constant PLF (independent of the number of floors) may lead to an uneven level of safety. In this paper, a semi-probabilistic analysis is performed, considering modelling errors and levels of correlation between floors. As a result, tailored values of the PLF are determined consistently with the level of refinement used for structural analysis. A case study of a concrete building with flat slabs is presented, showcasing the earlier findings and demonstrating that considering the evolutive construction sequence allows considering lower values of the PLF (γG ≈ 1.20).