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 to 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 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.

Research on Reliability of Structural Members Subjected to Snow or Wind Load for Design Working Life of 100 Years in China

“…In the case of design, it should be considered that the factors should include the uncertainty in the material properties, the uncertainty in the geometrical data and the modeling uncertainty [1,[23][24][25][41][42][43]. The suggestion distribution of the resistance of the structure can be defined by a lognormal distribution [27,44]. 14 representative structural members were selected and the statistical parameters for resistance of different structural members under different stress statuses are given in Table 4 [26,45].…”

“…where R d is the design value of the resistance, β is the target reliability index, the recommended values are shown in Table 5, Φ(•) is the cumulative density function of the standard normal distribution, α is the value of the FORM sensitivity factor and for resistance, it may be taken as 0.8. Based on the design value method and the current design expression, for resistance obeys to lognormal distribution [27,44], the partial factor for resistance can be expressed as:…”

“…Reliability-based structural analysis of buildings and constructions made from conventional materials such as masonry, steel or concrete is commonly available in literatures. The theoretical background and basic principles for the reliability analysis and calculations can be found in [17][18][19][20][21][22][23], which already has been applied in several studies [24][25][26][27][28][29]. Peng et al [24] studied the reliability of long span structure under wind and snow loading, and their results indicated that the equivalent extreme-value of element stress of the structure subjected to the dead load and the 100-year return period of wind and snow loads is far less than the allowable value, and the long-span building structure is therefore safe enough.…”

“…Joanna Zięba et al [26] presents an analysis of the reliability of a compressive masonry structure on the example of a wall fragment made of silicate blocks, and the relationship between partial factors applied to actions in various configurations and factors for the compressive strength of masonry was investigated. Considering samples generated by Latin Hypercube Sampling (LHS), the appropriate target reliability levels based on simulations of different scaffold design situations for facade scaffolds were proposed, based on which partial factors are determined [27]. The appropriate probability distribution for annual maximum ground snow loads are studied in detail based on the samples of snow loads on the ground in [28].…”