Analysis of measuring existing stresses in concrete structure by hole drilling core surface strain gauge method

The hole drilling core surface strain gauge method for measuring existing stresses in concrete structures has been discussed. First, the release detection process of hole drilling has been simulated using nonlinear three-dimensional finite element method, based on the concrete damaged plasticity theory. The technique of element birth and death has been used to simulate the drilling process. Laws of stress measurement described by stress release rates and h/d (where h is the depth of hole and d is its diameter) have been studied. Second, experiments have been carried out to prove the efficiency of this method. Compared with numerical results, the experimental stress release rates are obviously lower than simulation results. Finally, normal stresses have been loaded on the cylindrical surface of the concrete core to simulate the influence of core bit swaying, and the results of modified numerical data analysis have been obtained. The results indicate that the rules of stress measurement by hole drilling release which have been represented by stress release rates and h/d, are widely used.