is max bending stress the same as the yeild strength

i dont know whether to use the yeild srength or allowable stress to determine section sizes of a beam please help me :)

thank you.
 PhysOrg.com science news on PhysOrg.com >> Ants and carnivorous plants conspire for mutualistic feeding>> Forecast for Titan: Wild weather could be ahead>> Researchers stitch defects into the world's thinnest semiconductor
 You should use the allowable stress which is a percentage of yield stress (e.g 60% of yield stress).
 Thanks for your reply you are very kind So I use allowable my factor of safety is 3 but I thought that meant the allowable divided by three not the yield how would I determine the allowable if that is the case. Or is it just my yield divided by three equals the max allowable and safe load?

is max bending stress the same as the yeild strength

 Quote by engtobe Or is it just my yield divided by three equals the max allowable and safe load?
Yes, this is correct.
 thanks mate :)
 is it possible to calculate the width and thickness of a plate that is helping to support a beam when you have values for shear and bearing stress, a diameter of to bolts and the load it carries. i have tried using bearing stress = load/diameter*t and then rearanging for t but the answer is wrong.
 Bearing stress is one of many modes of failure. Do you have a sketch of your bolting arrangement?
 yes i have attached it to this post Attached Thumbnails
 You should check failure in both the hinge pin and bolts. In addition to the bearing stress consider: 2) Tensile failure = 2 X La X plate thickness where La is the distance from the edge of the hole to the edge of the plate. 3) Pin push block out = 2 X d X plate thickness, where d = distance from hole edge to part edge.

 Tags beams, design, statics, steel