Borhani, there is a great difference between the material strength values you might find on Woodweb or other sources and the approved design values for construction you will find in the National Design Specification {NDS}. For example, in table 4A, base design values for visually graded lumber, shear parallel to grain in red oak is 85 psi and white oak is 110 psi. No value stated for locust. On Woodweb red oak is 1780 psi and white oak is 2000 psi. My guess is that you should use a much lower design thresshold such as the value for white oak but be aware that most every wood species in the NDS is under 100 psi for shear parallel to grain.