Simplified Earthquake Analysis of Structures with Foundation Uplift

TLDR

The study develops simplified analysis procedures that account for foundation‑mat uplift when computing the earthquake response of single‑degree‑of‑freedom structures. The procedures model the foundation as a rigid mat on either rigid or flexible soil represented by two spring‑damper elements (Winkler or viscoelastic), and compute the maximum base shear and deformation directly from the response spectrum. The simplified procedures yield maximum base shear and deformation estimates that are sufficiently accurate for practical design.

Abstract

Simplified analysis procedures are developed to consider the beneficial effects of foundation‐mat uplift in computing the earthquake response of structures, which respond essentially as single‐degree‐of‐freedom systems in their fixed‐base condition. These analysis procedures are presented for structures attached to a rigid foundation mat, which is supported on rigid foundation soil or flexible foundation soil modeled as two spring‐damper elements. Winkler foundation with distributed spring‐damper elements, or a viscoelastic half‐space. In these analysis procedures, the maximum earthquake‐induced base shear and deformation for an uplifting structure are computed directly from the earthquake response spectrum. It is demonstrated that the simplified analysis procedures provide results for the maximum base shear and deformation to a useful degree of accuracy for practical structural design.