Standardization of Testing Method for Tension Softening Diagrams of Concrete through Inverse Analysis and Applications

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In this study, we intended to establish a testing method for determination of tension softening diagrams of concrete based on discussions with researchers in the world. We evaluated the properties of steel fiber reinforced concrete and recycled aggregate concrete using the determined tension softening diagrams. In addition, the bond properties of concrete were also evaluated through the diagrams.The program of Finite Element Inverse Analysis for the accurate determination of the tension softening diagrams from experimental load- displacement curves of concrete beam specimens has been proposed in the report of the subcommittee on size effect (chairman : K.Rokugo) under JSCE concrete committee. The preferable conditions for the shape and size of beam specimens and for the measurements of displacement were indicated. An example of the loading apparatus for the stable measurement of load- displacement curves was also shown.The international workshop on the establishment of testing methods for the diagrams and applications was held in Gifu in October 1998. It was agreed in the workshop that the applicability of the tension softening diagrams is superior. to other fracture mechanics parameters and that the simplification of the diagrams should be taken depending on the applications. It was recommended that a technical committee on the standardization of the testing methods for the diagrams should be made in RILEM as well as JCI in Japan.It was found in this study that the diagrams were effective for the performance evaluation of steel fiber reinforced concrete differing in sorts of fibers, fiber contents and mortar matrix strength. It was pointed out that the shape of the diagrams did not depend on the specimen sizes, when the fiber content was less than 2 % by volume. The flexural fracture behavior of recycled aggregate concrete could be well distinguished through the shapes of the tension softening diagrams.