Influence of Internal Inward Pressure on Stability of Open-Top Aboveground Steel Tanks Subjected to Wind Loading

Abstract

The results of wind tunnel tests indicate that there is an internal inward pressure induced by wind excitation when open-top tanks are examined, but not when close-top tanks are examined. This internal pressure is considered in many design documents outside of the U.S., however, ASCE-7 and API 650 do not explicitly address this factor. This study examined the effect of this internal pressure by conducting finite element analyses. Open-top tanks with height to diameter ratios of 0.11, 0.2, 0.5, 1.0, 2.0, and 4.0 were modeled using a finite element program. A linear bifurcation analysis and a post-buckling analysis were then conducted to verify the tank's stability when subjected to wind loading in accordance with the wind profiles specified in the selected design documents. To ensure the quality of the analyses, a study on mesh convergence and the load increment of Riks analysis was conducted. It was determined that the presence of the additional internal pressure term has a drastic impact on the buckling capacity of all the tanks examined. As a consequence, it can be concluded that the additional internal pressure generated by the wind on an open-top tank should not be neglected.