Review of API 650 Annex E: Design of large steel welded aboveground storage tanks excited by seismic loads

Abstract

API 650's Annex E, which is an American Standard for designing aboveground steel storage tanks subjected to seismic loads, is reviewed by comparing the design provisions in Annex E with other well-known design documents around the world, including that of New Zealand and Japan. Several limit states such as hydrodynamic hoop stress, uplift, base plate stress, buckling, freeboard, and two stability mechanisms, shear and overturning are investigated. The design provisions for each of the documents were compared for identical tank geometries and seismic parameters for several different tank aspect ratios. The results show that API 650 is slightly under conservative in each of the material failure mechanisms compared to the New Zealand and Japanese design philosophies. The small disparity in results could be due to the fact that the approach in Annex E of API 650 is for tanks of rigid walls and a rigid foundation, whereas the New Zealand and Japanese documents consider tank and foundation flexibility. Despite some marginal differences, API 650 Annex E can be considered to adequately account for all the major failure states when compared to New Zealand and Japanese design documents for design purposes.