Stability design of axially loaded stringer-stiffened moderately-thick cylindrical shells in steel tubular transmission towers

Abstract

Steel tubes internally stiffened with stringers are promising structural members of long-span transmission towers, but the study on its stability design remains insufficient. To gain insight into the inelastic buckling behavior of the tubes, compressive tests of 33 specimens are conducted. Using the test results, finite element (FE) models are first established and validated. Then, the adequacy of an equation in the literature for predicting elastic buckling stress is investigated via FE analysis (FEA), and a correction coefficient is proposed to diminish the discrepancy between the predicted and the FEA results. Afterward, the FE-based inelastic analysis is performed, wherein the initial imperfections including the local dimples, out-of-roundness, and residual stress were considered in the FE models. The effects of the imperfections on the ultimate strength are investigated. Further, the effects of the length to diameter ratio, diameter to wall thickness ratio, and stringer’s number and size on the reduction factor are investigated. Comparatively, the effect of the diameter to wall thickness ratio on the reduction factor is the most significant. The test and FEA results show that the axial ultimate strength is insusceptible to the initial imperfections. In addition, to achieve an efficient design, the restriction of the height to thickness ratio of stringers is suggested to avoid the stringer instability. Finally, the corresponding formulas for design are presented.