Reliability-based calibration of partial factors for the design of temporary scaffold structures

Abstract

In this work, partial factors for the design of temporary scaffold structures are calibrated based on reliability calculations. Scaffolds are commonly designed in accordance with the rules in standards (e.g. EN12811, EN12810) and information found in codes of good practice. However, there is no clear proof that these design procedures result in an appropriate and consistent safety level for scaffold structures. The present study proposes appropriate target reliability levels for façade scaffolds, based on which partial factors are determined. The results are based on simulations of different scaffold design situations, considering samples generated by Latin Hypercube Sampling (LHS). The results of these simulations are processed by applying FORM analyses for buckling and yielding of the scaffold elements. As such, the inherent reliability corresponding to current design practice is determined. Based on the inherent and target reliabilities, partial factors are calibrated using two methods: the Adjusted Partial Factor Method and an optimisation procedure based on least-square averaging. Concluding, annual reliability indexes in the range 2.5–3.5 are found. These lead to partial factors lower than or equal to those used in current design practice. Hence, there is an optimisation possible in the design of temporary structures compared to current practice, leading to more economical scaffold designs.