An alternative practical solution to identify the base level location of tall buildings

One of the topics that are always disputed by the structural engineers in the design of the buildings with underground stories is the location of the base level. Regardless of the complex approach of considering the interaction of soil and structure, generally most guidelines propose a qualitative approach to determine the position of the base level. Unfortunately, this qualitative approach is generally binary and proposes only two locations for the base level: on the top of the foundation or on the top of retaining wall. But in tall buildings or buildings with a significant number of basements, this binary qualitative approach can create a significant difference, even in the design of upper stories. In this article, an alternative practical solution has been proposed to obtain a quantitative method for determining the location of the base level, using the main concept of the base level, i.e. where the seismic displacement of the building is insignificant compared to the surrounding soil. The method has been applied and discussed in a real project for the design of a high-rise building in Tehran.