Report No.: CCEER-01-5

Title: Performance of A Full-Scale Two-Story Wood Frame Structure Supported on Ever-Level Isolators

Authors: M. Saiidi, A. Itani, I. Buckle and Z. Cheng

Date: October 2001

Sponsoring Agency: Ever-Level Foundation Systems, Inc.

Performing Organization:
Department of Civil Engineering/258
University of Nevada, Reno
Reno, NV 89557


A full-scale two-story wood frame building supported on base isolation devices developed and patented by the Ever-Level Foundation Systems, Inc. (ELFSI) was tested. The device consists of a ball and socket segment and an elastomeric pad. The ball and socket part of the isolator accommodates foundation rotation while keeping the structure level and reduces the stiffness below that of the elastomeric bearing alone. The objective of the study was to evaluate the performance of the isolator under simulated earthquakes and to assess the effectiveness of the ELFSI device in reducing earthquake forces. The earthquake simulations were conducted using one of the shake tables at the Large-Scale Structures Laboratory of the University of Nevada, Reno, with the primary motion being the El Centro 1940 record.

The structure was subjected to motions in its strong direction and was tested in three modes: (1) fully isolated, (2) semi-isolated, and (3) fixed base. Relative displacement histories and absolute acceleration histories at different floors were recorded and evaluated. The results showed that the ELFSI device withstood over four inches of relative displacement while maintaining its integrity. The fixed base story shear forces were reduced by 40 to 50 percent when the model was supported on the ELFSI devices.