## Torsion misunderstanding

 Quote by PhanthomJay We seem to have strayed a long way from torsion, haven't we, bro? Anyway, complimentary vertical and longitudinal shears aren't even in the same plane...don't try to combine them! Let's forget the nailed section and look at a solid section b x h with a vertical shear force of V at that section. I is bh^3/12, Q max at the NA is bh^2/8, and the transverse shear stress at the NA is VQ/Ib = 1.5V/bh. There is also a longitudinal shear stress of the same value that acts along the longitudinal axis of the beam. But you don't design the beam for both stresses, just one will do, OK??
I think torsion and shear are similar in behaviour, so i ask about both of them.I jusr reach good point, but why we dont design for both, why we design only for vertical??could you explain??

 I f there is an article to make me understand this it will be better, however i read and in didnt find any answer to my questions
 Recognitions: Gold Member Homework Help Science Advisor If you have a beam that is bending and twisting at the same time, you must design for bending stresses as well as both vertical and torsional shear stresses (they all act on the same plane). If you have a beam subject to bending only due to applied vertical forces, you must design for bending and complimentary vertical and longitudinal shear stresses (those shear stresses act on different planes).