Parametric analysis of bolted flange connections of circular monopoles.

摘要

The present study involved the parametric analysis of bolted flange connections of eighteen different circular monopoles. The parameters considered were the number of bolts (8, 6, and 4) and thickness of flange plate [25.4 mm (1.0 in.), 19.05 mm (0.75 in.) and 12.7 mm (0.50 in.)]. These were analyzed under stiffened and unstiffened conditions. Four, two and four stiffeners, 12.7 mm (0.50 in.) thick, were used with 8-, 6- and 4-bolt arrangements. Each finite element model is made up of a small diameter (171.5 mm) circular pipe and a large diameter (327 mm) circular pipe both welded to circular flanges. The outer and inner diameters of the flange plates were 327 mm and 171.5 mm respectively. Each bolt was 25.4 mm (1 in.) diameter and was pretensioned to 227 kN (51 kips); and an external load of 45 kN (10 kips) was applied at the free end of the monopole, 1804 mm (71 in.) from the bolted joint, in the Riks analysis load step of ABAQUS (version 6.3) computer program. From the finite element analysis, it was found that monopoles (8 bolts, 6 bolts and 4 bolts) with unstiffened 12.7 mm (0.50 in.) thick flange plates experienced a large deformation because of the thin flange plate. Optimum solutions to stiffened and unstiffened connections were found to be among those monopoles with minimal gap, deflection and deformation, i.e., 25.4 mm (1 in.) thick flanges with 4 bolts or 19.05 mm (0.75 in.) thick flanges with 6 bolts for unstiffened case; and 12.7 mm (0.50 in.) thick flanges with 8 bolts, 25.4 mm (1 in.) thick flanges with 4 bolts or 19.05 mm (0.75 in.) thick flanges with 6 bolts for stiffened case.; In addition to the parametric study, T-Stub and yield line analytical procedures were also presented with examples; and it was found that the analytical methods provide good preliminary guidance regarding connection parameters when designing bolted flange connections for circular monopoles.