Stress Measurements in Concrete Structures with Modified Doorstopper Technique

This paper presents the use of the modified doorstopper technique for measuring both absolute and relative stresses in concrete structures. The equipment, the field procedure, and the stress calculation model are presented and are followed by the results of some stress measurement campaigns in concrete structures. The polytechnique stress meter (PSM), a stress-meter designed for monitoring the very low stress variations found in civil engineering concrete structures such as dams, is also described. Results from both laboratory tests and a 7-month field monitoring period show the stability and sensitivity that can be attained with the new stress-meter. The stress calculation model for both absolute and relative stresses requires no hypotheses concerning the principal stress orientation or magnitude and can take into account the heterogeneous, anisotropic, and eventually nonlinear behavior of concrete found at the measurement scale.