CHARACTERISTICS OF SECONDARY FLEXURES IN UNIAXIAL TENSION TEST OF CONCRETE

摘要

In the uniaxial tension test of concrete, inevitably some secondary flexures occur. However the characteristics of the secondary flexures are not well understood among others because of the complexity of performing the uniaxial tension test without the flexures. In this paper the uniaxial tension test in which secondary flexures are minimized, by a specially developed device, are compared to the tests where secondary flexures are left to develop freely. Experimental results and theoretical calculations are shown for the influence of secondary flexures on load-deformation curves, tensile strength and strain energy of the specimen. Plural flexures which grow finally plural cracks were also analyzed concerning to an experimental result. It is concluded that secondary flexures should be minimized, because they produce considerable error to the load-deformation curve and tensile strength. Furthermore, secondary flexures should be controlled continuously during the test because the minimized state is an unstable equilibrium of strain energy in the specimen. And the flexures can only be minimized by using a notched specimen because plural flexures occur in an un-notched specimen.