Research On Fracture Behaviors Of Dam Concrete And Wet-screened Concrete In Direct Tension

The design, construction and safety assessment of a dam all require to study thefracture behaviors of dam concrete deeply and systematically.To determine properly the mechanical properites of dam concrete is very importantto construct a safe, reliable and economic dam. Testing the mechanical properites ofdam concrete is often restricted by the specimen size, testing machine and testingmethod and so on, so it is very difficult. There are limited experimental data availableconcerning dam concrete. The standard-size wet-screened concrete specimens aregenerally employed to test the mechanical properties of dam concrete at home andabroad. The performance indices of dam concrete are evaluated by those ofwet-screened concrete. The wet-screened procedure is to remove from fresh concrete allaggregate particles large than certain size-40mm. However, there must be somedifferences between them. It is necessary to determine the relationships between themby tests. To simplify the test job, the performance indices of dam concrete can bepredicted by those of wet-screened concrete.The tension softening curves were determined and the fracture behaviors werestudied based on a lot of direct tension tests data of dam concrete and wet-screenedconcrete. In addition, a database was presented to predict the softening curves of damconcrete.(1) Analyze and process experimental fracture test data of11groups directtension specimens. Obtained their stress-strain curves in direct tension which start fromthe original point. (2) The tension softening curves (stress-crack width curves) of dam concrete andwet-screened concrete were obtained by employing the principle of concrete fracturemechanics based on the above stress-strain curves. Correspondingly, the ralativestress-crack width curves and fracture energy were also achieved.(3) The mathematical expressions of dam concrete and wet-screened concretewere identified.(4) Established a database by artificial neural network to predict the tensionsoftening curves of dam concrete in a certain range of mixture. With such a database,softening curves can be predicted without performing the tests only when the mixture isknown..(5) The influences of concrete strength and aggregate size on the softening curvesof dam concrete and wet-screened concrete were studied. The relationships between thesoftening curves of dam concrete and those of wet-screened concrete were alsoinvestigated.