Having a hard time with failure theories. Beam length 20 feet, 6"h x 4"w. sigma yield is 40 ksi. How to calculate the maximum distributed load the beam could carry using von Mises and Tresca failure theories. I have my shear and moment diagrams drawn and know they are right. I found that the max stress will be dead center due to bending. So sigma x= My/I . according to Tresca tmax = sigma yield/2. So how do I make it all relate to find my sigma1 and sigma 2 to plug in to the failure theory equations. Any help would be appreciated.