Thermo-Mechanical Characterization of a Full-Scale Energy Foundation

Abstract

This paper documents the thermo-mechanical characterization of an energy foundation constructed as part of a new single-story building at the U.S. Air Force Academy. During a 39-hour heating test, the foundation increased in temperature by 21.7 °C, while the sandstone subsurface only increased in temperature by less than 1 °C at a distance of 1.22 m from the center of the foundation. The distributions in thermal axial stress and displacement in the foundation were calculated from the measured thermal axial strain values, and a maximum compressive thermal axial stress of 5.2 MPa was observed near the middle of the foundation and a maximum upward displacement of 1.55 mm was observed at the head. The thermal axial stresses and displacements measured were well within acceptable limits for structural elements.