| Because of its excellent performance, concrete has been widely used in hydropower dams and other hydraulic structures. However, there are lots of crack in many concrete dams in our country, which is the reason why people say "no dam without crack". Some of them seem to due to lower strength and stiffness than actual requirements. But actually, the reason is insufficient fracture toughness if analyzed from the view of fracture mechanics of concrete. Before building concrete dams, fracture toughness should be considered as one of the important performance indicators for the design of concrete anti cracking, in order to prevent the occurrence and expansion of cracks.Based on the production of the dam, the concrete three-point bending fracture is used to test the double-K fracture parameters. Strain gage method for monitoring the Pini of concrete specimen is applied to get some rules of the crack propagation. The strain field near the crack tip is analyzed by using digital image correlation method, so as to get a warning for the instability and failure of the specimen. It is a worthwhile study for the concrete since brittle failure is easily to happen.Besides, because of high stress cyclic loading the structure of building could change greatly, which is very easily to cause fatigue damage or failure. Study on fatigue property of hydraulic concrete can ensure the hydraulic structures run a long period safely and stably. The dam concrete beam is tested on the MTS 810 TestStar material testing system with the fatigue loading. According to the damaged situation of concrete the overall life of specimen is estimated, and compared with the final actual life span. The (CMOD, n/N) relationship curve with a certain degree of reliability is obtained in the study based on (CMOD, n/N) data statistical distribution of the reliability. |
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