The Testing And Research On The Working Stress Of RC Columns

In the stress test of structural behavior, there is not a reliable testing method to obtain the concrete stress in a RC structure. After consulting a large number of references and data, the boring-electrical test method is proposed in this paper to test the working stress of RC columns. The study mainly includes the following contents:Ten RC columns are tested and the main influencing factors of testing results are analyzed. The variety of the release strain at the edge of a hole with different aperture and different sticking style of resistance strain gauge are tested and investigated. The results show the strain at the edge of a hole increases with the magnification of the aperture, but almost keep changeless with different sticking style of strain gauge. Also it proves that the boring-electrical test method can be used to measure the working stress of practical RC columns.The stress distribution along the edges of the hole in the testing columns with axial compression and eccentric compression are analyzed by ANSYS program, and the strain in the position of strain gauge is calculated. The stress distribution and stress concentration factors at the edges of the hole with different aperture in the columns with axial compression are studied. Moreover, the relationship between the stress concentration factors and the depth of the hole are investigated. The results indicated that the stress concentration factors under axial compression and eccentric compression have great difference. The maximum stress along the edges of the hole under axial compression increases with the magnification of the aperture, but the stress concentration factors does not do. The stress concentration factors are greatly affected by the depth of the hole. It increases with the depth, but gently when the ratio of depth to diameter of the hole reaches 1.2, and at the moment the surface release strain of the test columns can be tested completelyThe strain is calculated using the release ratio from finite element analysis, and the concrete stress is obtained by the physics equation of the space problem. Furthermore, an approximate calculation formula is proposed to calculate the working stress of RC columns measured by boring-electrical test method. In the end of the paper, the key steps to test the release strain in RC columns by boring-electrical test method and the noticeable proceeding in practical projects are summarized.