Overlooked Assumption in Nonconstrained Post Embedment

Abstract

In the traditional formula for determining the required embedment depth for nonconstrained posts it is assumed that shear and moment at grade have the same algebraic sign, as is the case for determinant structures that are free to translate laterally (flag poles or billboard signs). This article demonstrates that in an indeterminant lateral force resistive system, which consists of a combination of embedded posts and structural diaphragms (many buildings), the shear and moment at grade most often have opposite algebraic signs. In this case the traditional formula should not be applied. This article presents an alternate method for checking embedment depth based upon the calculated lateral soil bearing pressure.