This paper presents a reliability-based code calibration procedure aimed at determining optimal partial safety factors to be employed in design rules for pultruded glass fibre-reinforced polymer (pGFRP) I-section beams, susceptible to web-crippling, namely under end-two-flange (ETF) and interior-two-flange (ITF) loading cases with unfastened flanges. Following a comprehensive state-of-the-art literature overview regarding web-crippling of pGFRP beams, the description of a direct strength method (DSM)-based resistance model for the two web-crippling loading cases is presented. Next, attention is turned to the detailed description of the (structural) reliability-based code calibration procedure for both loading cases. This includes detailing all the necessary steps and pertinent data, encompassing the adopted probabilistic models for material properties, loads, geometrical dimensions, and resistance model uncertainty. Then, the results obtained through the application of the code calibration procedure are presented, validated, and discussed. Lastly, the paper closes by presenting relevant concluding remarks, which include recommendations for the partial safety factors to be applied in the resistance model for pGFRP I-beams under ETF and ITF loading cases.