MECHANICAL ANALYSIS AND OPTIMAL DESIGN OF ASYMMETRIC INNER-AND-OUTER RIGID FLANGE CONNECTIONS

The symmetric inner and outer rigid flange connection structure, with an equal number of bolts, is commonly employed in the design and construction of transmission towers. However, due to discrepancies in the circular radius and circumference of the inner and outer flange bolts, this symmetrical configuration often gives rise to processing and installation challenges in practical engineering applications. To address ease of manufacturing and on-site installation, this study introduces a design concept for an asymmetric inner and outer rigid flange connection structure with varying bolt quantities. Utilizing the commercial finite element software ABAQUS, the stress analysis of this asymmetric rigid flange connection structure is simulated under axial tension, bending, and combined loading conditions. The investigation explores the impact of bolt distribution and geometric parameters on the flange connection structure. In the context of this study's design, the axial tension of the inner and outer bolts serves as an indicator for evaluating the structural performance. The findings reveal that under tension loading, the ratio of forces on the inner and outer bolts correlates linearly with the distance ratio from the main pipe wall, achieving equal tension on both when the distance ratio is 0.925. Similarly, under bending moments, the ratio of maximum bolt forces on the inner and outer rings exhibits a linear relationship with the distance ratio, resulting in equal maximum forces on both rings at a distance ratio of 0.832. Under combined loading conditions, the bolt forces represent a superposition of those experienced under pure bending and pure tension. Furthermore, this study examines the influence of the stagger angle of inner and outer flanges and bolt pre-tension on bolt forces. The research indicates that while the former has a minor impact on bolt forces and can be disregarded in design considerations, the influence of the latter diminishes gradually with increasing external loads. Consequently, this study offers theoretical guidance for optimizing the design of asymmetric inner and outer flange structures.