Theoretical formulation of the core drilling method to evaluate stresses in concrete structures

Abstract

The hole drilling method is an ASTM Standard Test Method that is used to evaluate residual stresses in isotropic linearly elastic materials. In civil engineering, the method is often used to evaluate stresses in metal structures. However, the method is not applicable to concrete because the heterogeneous composition of concrete prevents strain measurements from being made over small gage lengths. This paper presents the theoretical formulation of a modified hole drilling method that is applicable to concrete structures. This modified method is referred to as the core drilling method. Potential applications of the method include the determination of insitu stress in a variety of reinforced concrete, prestressed concrete, and steel-concrete composite structures, including bridges, buildings, dams, retaining walls, tunnels, shafts, and containment vessels. Equations are derived to relate the displacements caused by local stress relaxation as a core hole is cut into a structure to the magnitudes and directions of the in situ stresses. Several practical stress states are treated in the formulation. Numerical examples are presented to verify the theoretical formulation and to further explain the method.