Structural Behavior of L-Type Flange Joint with Various Flange Flatness Conditions

The L-type flange joint is widely used to attach steel tower segments to each other. However, tolerances on the flange surface flatness may occur during its fabrication, leading to a negative impact on the bolt stress distribution. This study evaluates the influences of the flange surface flatness on the behavior of L-type flange joints through numerical simulations. First, the finite element model of a 5 MW L-type flange joint is established, and its accuracy is verified based on comparison with an experimental test. Using the same loading conditions and material properties, the influences of geometrical imperfections (i.e., flange-sided gap, tower-sided gap) on the structural response are investigated. Furthermore, the impact of the flange gap opening length is reported. The results show that the flange-sided gap outperforms the tower-sided gap, resulting in reduced stress concentration in the bolt. In addition, the stresses in flange-sided gapping joints increase with an increase in the opening length.