抄録
Diagonal shear failure could lead to the serious damage in concrete structures due to earthquakes. However, mechanisms of diagonal shear failure in reinforced concrete (RC) beams have not been completely clarified yet. Generally, the diagonal shear failure occurs, depending on the ratio of the shear span to the beam depth. In the case that the ratio is smaller than or equal to 2.7, the shear failure occurs as the diagonal tensile failure. In this study, diagonal shear failure in RC beams is investigated, applying acoustic emission (AE) method. AE method is one of nondestructive testings for concrete structures with a high capacity for diagnostics and health monitoring. Presently, it is known that fracture mechanisms are identified by AE waveform analysis. The moment tensor analysis of recorded AE waveforms can identify cracking kinematics of location, crack-type and crack orientation. The analysis is implemented as SiGMA (simplified Green's functions for moment tensor analysis) procedure. Prior to testing RC beams, theoretical waveforms were calculated in order to determine location of AE sensors. Theoretical waveforms were synthesized by introducing the dislocation model and Green's functions in a half space. Then, cracking mechanisms in the experiments are investigated by applying the SiGMA procedure to detected AE waveforms. Since classification of crack mechanisms can be analyzed by AE parameter, the results of AE parameter analysis and those of SiGMA analysis are compared and discussed.
