Seismic horizontal pullout capacity of vertical anchors in sands

Abstract

The problem of finding the horizontal pullout capacity of vertical anchors embedded in sands with the inclusion of pseudostatic horizontal earthquake body forces, was tackled in this note. The analysis was carried out using an upper bound limit analysis, with the consideration of two different collapse mechanisms: bilinear and composite logarithmic spiral rupture surfaces. The results are presented in nondimensional form to find the pullout resistance with changes in earthquake acceleration for different combinations of embedment ratio of the anchor (λ), friction angle of the soil (φ;), and the anchor-soil interface wall friction angle (δ). The pullout resistance decreases quite substantially with increases in the magnitude of the earthquake acceleration. For values of δ up to about 0.25–0.5φ, the bilinear and composite logarithmic spiral rupture surfaces gave almost identical answers, whereas for higher values of δ, the choice of the logarithmic spiral provides significantly smaller pullout resistance. The results compare favorably with the existing theoretical data.Key words: anchors, earthquakes, failure, limit analysis, sands.