Abstract
Stress relief techniques for measuring stresses have only been recently applied to concrete structures. The release of stresses due to either hole-drilling or slot-cutting are normally measured by surface strain gauging. A new technique is proposed in which an instrumented cylindrical inclusion is inserted inside a small hole in concrete to measure the stress relief due to overcoring. This thesis describes an experimental development of the proposed technique for in-situ stress measurement in concrete structures. The analysis, design and fabrication of the instrumented inclusion is described and a programme of calibration experiments is also described. Two types of instrumented inclusions of biaxial and triaxial configurations were used for bi-dimensional and tri-dimensional stress measurement respectively. Field trials using the inclusion technique were performed with limited success on three reinforced concrete bridges. Results of the field testing showed that the technique provides an extension of the existing stress relief methods for stress measurement by surface gauging. The potential use of the inclusion technique for in-situ stress measurement in existing structures is recognised but further refinement of the method and analysis is also recommended.