The Incremental Core Drilling Method to Determine In-Situ Stresses in Concrete

Abstract

The incremental core-drilling method (ICDM) is a nondestructive technique to assess in-situ stresses in concrete. In contrast to other available methods of in-situ stress measurement in concrete, the ICDM can quantify stresses that vary through the thickness of the concrete member under investigation, such as those due to bending or eccentric prestressing. In this method, a core is drilled into a concrete structure in discrete increments. The displacements which occur locally around the perimeter of the core at each increment are measured and related to the in-situ stresses by an elastic calculation process known as the influence function method. This paper presents the analytical and numerical techniques necessary for practical use of the ICDM, as well as results from experimental tests in which simple concrete beams were subjected to controlled loads and insitu stresses measured via the ICDM were compared to known stress distributions. The ability of the technique to accurately measure a variety of different stress distributions is demonstrated, and practical considerations for an ICDM investigation are discussed.