The discussion centers on the use of average shear stress (V/A) over maximum shear stress (VQ/It) when determining the safety factor for structural members, specifically in the context of Finite Element Analysis (FEA) and hand calculations. Participants highlight that average shear stress is often sufficient for bolts and pins in direct shear, while maximum shear stress is more applicable for beams under shear and bending. The conversation also emphasizes the importance of considering contact stresses and bearing stresses in conjunction with average shear stress for accurate assessments. Additionally, resources for advanced theories of ductile fractures are sought by participants.
PREREQUISITESStructural engineers, mechanical engineers, and students involved in FEA, as well as professionals focused on the safety and performance of bolted connections and structural integrity assessments.
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:
