Assessing characteristic value selection methods for design with load and resistance factor design (LRFD) — design robustness perspective

Abstract

An important step in load and resistance factor design (LRFD) is the selection of the characteristic values of uncertain soil parameters, which can be quite subjective despite the simplicity of LRFD. This paper assesses five statistical methods for the selection of characteristic values for design with LRFD, focusing on the design robustness. A framework based on the consideration of safety, cost, and design robustness is proposed for assessing these selection methods. This framework is illustrated with an example, the design of a drilled shaft in sand using LRFD, in which the best overall method for selecting the characteristic values is suggested. The implication of the outcome of this study is quite significant in geotechnical engineering practice, as it provides guidance on the selection of the characteristic values for design with LRFD.

Probability of Failure for Fixed Offshore Structures Determination: An Analysis of a Braced Monopod and 4-Legged Platforms with Respect to Industry Standards

“…Since these events (success and failure) are complements, the following is true where reliability is equivalent to 1the probability of failure (POF). Failures occur where loads and strength models overlap each other (Chandrasekaran & Nagavinothini, 2020;Rao, 1992;Salgado & Kim, 2014;Shen et al, 2019). An alternate for the probability of failure (POF) can also be expressed as presented in Equation ( 4) to Equation ( 6);…”

On characteristic values for calculating factors of safety for dyke stability

“…Engineering practice often uses characteristic soil property values, which are meant to account for (among other things) the spatial nature of soil variability with respect to the extent of the failure mechanism, and partial factorsfor example, as in Eurocode 7 (EC7) (CEN, 2004). Although EC7 gives only limited guidance on determining characteristic values, several simplified approaches have been proposed (Shen et al, 2019). However, a more rigorous approach is the random finite-element method (RFEM) (Fenton & Griffiths, 2008), which combines random field theory with the finite-element method within a Monte-Carlo framework (Griffiths et al, 2009;Hicks & Spencer, 2010).…”

On characteristic values and the reliability-based assessment of dykes

“…Various approaches have been proposed for selecting the characteristic values of soil properties; for example, as reported by Orr (2017) and Shen et al (2018).…”