Failure Envelopes for Ring Foundations Resting on Tresca Soil under Combined Loading

Ring foundations are used to support tall and heavy circular onshore structures such as chimneys, cooling towers, storage tanks, and silos and offshore structures such as wind turbines and annular platforms. The present study focused on developing failure envelopes for ring foundations subjected to the combined loading of vertical (V), horizontal (H), and moment (M). Parametric three-dimensional finite-element limit analyses were carried out for circular and ring foundations resting on the surface of cohesive soil following the Tresca criteria. The failure envelopes were generated separately under V:H, V:M, and H:M loading combinations. Variations in the ring foundation geometry (R-i/R-o) of 0.2, 0.4, 0.6, and 0.8 and linearly increasing soil heterogeneity values (k(B)/s(um)) of 0, 1, 2, 3, 6, and 10 were considered in this study. The results indicated variations in failure loci with a variation in R-i/R-o and k(B)/s(um). The typical contours of failure loads under the combined loadings and three-dimensional failure surface patterns are presented for the ring foundations with R-i/R-o= 0.2 and 0.8 to understand the shape of the failure surfaces. (C) 2022 American Society of Civil Engineers.