A powerful methodology in concrete fracture research is the cohesive crack model with a bilinear softening law, where both the energy and the stress ratios play important roles. Here a direct numerical approach based on the intrinsic cohesive crack model was employed in fracture analysis of normal-strength and high-strength concrete specimens. The best-fit energy ratio is found to be consistent with that reported by Bazant and Becq-Giraudon while varying over a narrower range. The best-fit stress ratio is found to be larger than all of the results from the inverse analysis. It is recommended that the softening law for high-strength concrete had a larger stress ratio.
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