Coupling effect and its correction on experimental results of three-point bend

Coupling of flexure and shear exists in three-point bend beams. The coupling coefficients of flexure and shear were introduced，and the coupling equations of flexure and shear were deduced based on Tsaicriteria. The coupling effect of flexure and shear was analyzed quantificationally，and the modification method of the experimental results was presented. It was shown that the experimental results of three-point bend were influenced obviously by the coupling of flexure and shear. The flexural strength error from the coupling effect increased with the flexural-shear strength ratio，  whereas the shear strength error decreased with it. For the given coupling coefficients of flexure and shear，the test errors were determined by the division of span-height ratio into the flexural-shear strength ratio. The experimental results were modified by the modification methods，and the correctional results of three-point bend on different span-height ratios became more comparable. The inherent properties were reflected by the correctional results.