Effect of Foundation Width on Subgrade Reaction Modulus

摘要

Structures are subjected to vertical and horizontalloads. Vertical subgrade reaction acts on the foundation bottomsurface, and in the case of an embedded structure, horizontalsubgrade reaction acts on the embedded part. The subgradereaction is obtained by multiplying the displacement of thefoundation by the Subgrade Reaction Modulus (SRM). Inpractice, SRM is calculated using an equation that incorporatesthe negative power relationship of the Foundation Width (FW). Ifthe structure is evaluated to be poorly seismic resistant, it isnecessary to widen FW. However, when the FW is widened, thedesign value of SRM decreases. In this case, it is not possible toexpect an increase in the subgrade reaction proportional to theincrease of FW. Therefore, when the inertia force is very high,the FW has to be very wide. However, underestimating SRM canlead to structural overdesign. In this study, the relationshipbetween SRM and FW, for a structure in which vertical andhorizontal load act simultaneously, was analyzed. Compared withthe design practice assumptions, the horizontal SRM was foundto be highly dependent on FW while the vertical SRM was shownto be less dependent on FW.