The discussion revolves around the use of average shear stress versus maximum shear stress in the context of determining the safety factor for structural members, particularly in applications involving bolts and pins. Participants explore the implications of these different approaches in finite element analysis (FEA) and hand calculations.
Participants do not reach a consensus on the superiority of average versus maximum shear stress, with multiple viewpoints presented regarding their applications and implications in structural analysis.
The discussion highlights the complexity of shear stress calculations, including the influence of geometry and loading conditions, as well as the need to consider additional factors such as contact and bearing stresses. There are indications of unresolved assumptions regarding the applicability of different stress calculations in various scenarios.
When a bolt or pin is in direct shear, average V/A shear stress is used. Maximum VQ/It shear stresses are used for beams subject to shear and bending. But often in a Wide Flange beam average shear stress is used by using the area of the web and not the flanges, and you get close to the same result as the max shear stress formula. Even the max shear stress hand calculation is an approximation, because there are variations in shear stress not only top to bottom, but often left to right as well,as FEA might show. The safety factor has it covered. Nothing tops the good old fashioned hand calcs.chad mcelroy said:
besides checking for shear stresses in bolts or rods (using average V/A shear stress calculations when bolt or rod is subject to shear and not bending), you must also check for bearing stresses in the bolt and plate at the contact area between the bolt/rod and the connected plate hole wall. Most codes allow for some deformation and yielding at the bearing contact areas. I haven't done much research in ductile fracture theories. Shear tear out in the plate must also be checked for holes near edges.chad mcelroy said:
