Structural safety of pultruded FRP profiles for global buckling. Part 1: Approach to material uncertainty, resistance models, and model uncertainties.

This two-part paper proposes a resistance format and partial factors for the global buckling of FRP profiles based on reliability analysis and partial factor calibration. Most current recommendations for the design of structural members made with FRP materials are not grounded on reliability concepts and this poses questions concerning safety and economy. Part 1 of this paper presents the resistance format proposed, the approach to the variability of material properties, the resistance models, and the design equations for the following global buckling modes: (i) flexural, (ii) flexural-torsional, and (iii) lateral-torsional; all of them refer to well-known formulations available in the literature. Probability distributions for the model uncertainties of the resistance models are defined based on all trustworthy experiments collected by the authors from the literature. In general, the three resistance models proposed provide estimates of the critical buckling stress with good accuracy when compared to the observed (tested) buckling resistance, resulting in an average bias close to one. The coefficient of variation of the model uncertainties varies between 11% (flexural buckling) and 19% (flexural-torsional buckling). Preliminary partial factors are proposed in this part and their reliability-based calibration is presented in Part 2.