An Alternative Perspective to Resolve Modelling Uncertainty in Reliability Analysis for D/t Limitation Models of CFST

Abstract

For the design of Concrete-Filled Steel Tube(CFST) columns, the outside diameter D to the steel tube thickness t ratio(D/t ratio) is limited to prevent the local buckling of steel tubes. Each design code proposes the respective model to compute the maximum D/t ratio using the yield strength of steel or and the elastic modulus of steel E. Considering the uncertainty in and E, the reliability index for the local buckling of a CFST section can be calculated by formulating the limit state function including the maximum D/t models. The resulted depends on the maximum D/t model used for the reliability analysis. This variability in reliability analysis is due to ambiguity in choosing computational models and it is called as modelling uncertainty. This uncertainty can be considered as non-specificity of an epistemic uncertainty and modelled by constructing possibility distribution functions. In this study, three different computation models for the maximum D/t ratio are used to conduct reliability analyses for the local buckling of a CFST section and the reliability index will be computed respectively. The non-specific will be modelled by possibility distribution function and a metric, degree of confirmation, is measured from the possibility distribution function. It is shown that the degree of confirmation increases when decreases. Conclusively, a new set of reliability indices associated with a degree of confirmation is determined and it is allowed to decide reliability index for the local buckling of a CFST section with an acceptable confirmation level.