Elastic buckling strength of T-section transition ringbeams in steel silos and tanks

A ring is generally provided at the intersection between the cylinder and the cone of an elevated storage silo or tank to resist a large circumferential compressive force at the intersection (the transition junction). This ring is a main structural member and is often referred to as a ringbeam (in contrast to relatively light rings as stiffeners on shell walls). A common cross-sectional form of this ringbeam is a T-section. Previous studies by the authors have led to simple strength approximations for the elastic buckling of T-section ringbeams which are either simply-supported or clamped at the inner edge. This paper is aimed at establishing a simple elastic buckling strength approximation for these ringbeams with elastic (i.e. semirigid) rotational restraint as is generally provided by the adjacent shell walls in a silo or tank. This is achieved by a suitable interpolation of the buckling strength approximations of the two limiting cases mentioned above, and using the effective section method to relate the loading on a silo or tank to the circumferential compressive stress at the inner edge of the ringbeam. An existing interpolation formula previously developed by Jumikis and Rotter for annular plate ringbeams is found to be satisfactory for T-section ringbeams as well. The developed elastic buckling strength approximation can be used in practical design directly.