Structural safety of pultruded FRP profiles for global buckling. Part 2: Reliability-based evaluation of safety formats and partial factor calibration

This two-part paper presents a study about the structural safety of pultruded fibre-reinforced polymer (FRP) profiles with respect to global buckling phenomena, which often govern their ultimate limit states design: flexural buckling, flexural-torsional buckling and lateral-torsional buckling. The first part [1] presented the resistance models for those buckling mechanisms, the probability models for model uncertainties of resistance, and a preliminary set of partial factors related to the model uncertainty, all consistent with the Eurocodes. Aiming at validating the resistance format proposed and that set of partial factors, this second part presents explicit reliability analyses of pultruded FRP profiles designed for the different global buckling failure mechanisms, so that the design equations proposed comply with the target reliability index recommended in EN 1990 for common structural elements. The reliability-based calibration followed similar methodology of documents that assessed the reliability of design with the Eurocodes, including the stochastic modelling of loads and geometry. Partial factor calibration was made through iterative reliability analyses on representative structural elements defined from the proposed design equations. This calibration process allowed defining (i) recommendations for partial factor γ Rd and (ii) the representative material property used to define γ m for each buckling mechanism. The final part of the paper includes recommendations for future research, towards the validation of assumptions made in this study and the standardization of FRP materials.