Sensitivity analysis of design parameters in L-type wind turbine tower flanges

This study systematically quantifies how six key design parameters of an L-type ring flange connection joining wind turbine tower segments (bolt circle diameter (DBCD), flange thickness (Tflt/Tfl), flange width (Wfl), neck shell thickness (tsh), number of bolts (N), and bolt size) affect the extreme and fatigue verification ratios and the final cost of the connection. A one-factor-at-a-time (OFAT) sensitivity analysis was carried out: each parameter was varied individually while the others were held at a converged reference design, and at every step the extreme verification ratio, fatigue verification ratio, geometric verification result, and final material/manufacturing cost were computed, amounting to 73 design scenarios in total. The analysis reveals two distinct optimization trends: the optimum occurs at the upper bound of the acceptable region for DBCD, and at the lower bound for tsh, Tflt, Wfl, N, and bolt size. Among these, flange width (Wfl) shows a disproportionately large effect on the fatigue ratio: a change of only 49 mm (0.112–0.161 m) drops the ratio from over 200 to below 1.0. By translating this analytical framework into quantified parameter trends and bounds for a representative case, the study provides a practical, illustrative roadmap for preliminary flange design in tower sections of broadly similar scale and loading. Because this is a single-case OFAT analysis with representative loads and a simplified cost model, case-specific verification, validation of parameter interactions, and further experimental confirmation remain necessary before adoption in a specific project (see Section 4).