Foundation Impedance Functions: Theory Versus Experiment

Abstract

Forced‐haimonic‐vibration tests, using an eccentric‐mass shaker, were conducted on two small but different concrete foundations. One foundation (Cholame 1E), located in central California, consisted of a 4‐in.–(10‐cm‐) thick, 50‐in.‐ (1.27‐m‐) square slab with corner piers embedded in moderately stiff alluvial deposits. The other foundation (Station 6), a 6‐in.‐ (15‐cm‐) thick, 48‐in.‐×45‐in.‐(1.22‐m‐×1.14‐m‐) rectangular slab, rested directly on softer deposits in the Imperial Valley of southern California. Experimental foundation‐impedance functions, computed from the vibration‐response data, were similar to theoretical predictions for Station 6; however, significant differences were observed between the experimental and theoretical impedance functions for Cholame 1E. These differences probably resulted from overestimation of the shear‐wave velocities of the top layers of soil directly underneath the Cholame IE foundation, and to a lesser extent from the use of a simple embedded disk to model the founda...