This paper evaluates the solutions of stress intensity factor K adopted in BS 8571 (2014) through a comparison with existing numerical results of K that were obtained using the finite element analysis for clamped single edge notched tension (SENT) specimens. BS 8571 adopted two K solutions for thicker and thinner specimens, respectively. One is an analytical K solution obtained by Ahmad et al. (1991), and the other is a numerical solution obtained by CanMet. Comparison shows that the analytical K solution is correct only for crack length to specimen width ratio a/W≤0.6, but incorrect for a/W>0.6. It is found that Ahmad et al. made mistakes in their mathematical deviations of the K solution for deep cracks of a/W>0.6. In order to obtain accurate K solutions valid for clamped SENT specimens over a wide range of a/W, a reinvestigation is performed using the crack compliance method proposed by Marchand et al. (1986). Based on a set of available simple K solutions for single edge notched specimens in pure bending and in pure tension, a corrected analytical solution of K for clamped SENT is obtained using the exact integration method. On this basis, a closed-form analytical solution of K is obtained using curve fitting and the accuracy is within 1% for crack sizes up to a/W=0.98. Comparison shows that the proposed closed-form solution of K agrees well with the available solutions of K for clamped SENT specimens.

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