Reliability analysis of shear design provisions for cold formed steel sections

Abstract

This study focuses on the structural reliability analysis of cold-formed steel (CFS) sections under the ultimate limit state of shear. It considers two design models: the EN 1993-1-3 standard and its recent modification proposed by a previous study. The bias and uncertainty in these models were calibrated by comparing the design models’ prediction to 67 experimental results. Reliability analyses for the CFS beams, designed according to both models, were conducted using Monte Carlo Simulation (MCS) and the First Order Reliability Method (FORM). This analysis incorporated the model uncertainty and other parameters describing these models into the stochastic description. The 10% fractile of the reliability values for beams designed using the existing EN 1993-1-3 provisions showed values that were more conservative than those of the modified EN 1993-1-3 provisions, compared to the reliability target of 3.8. A FORM sensitivity analysis identified the yield strength of steel fyb and the resistance model uncertainty ΓR as the main positive drivers of uncertainty in the computed reliability indices of the design models. Additionally, a multiplicative modification factor was proposed for both the existing and modified versions of EN 1993-1-3, ensuring that these models optimally meet the specified reliability targets of 3.8 and 4.3 for Eurocode reliability classes 2 and 3, respectively. The proposed modifications maintain the partial factor γM0 at 1.0, as stipulated by the EN 1993-1-3 provisions for the resistance of the cross-section.