Torsional load on clip/lug weld
Torsional load on clip/lug weld
(OP)
When we design the lifting lugs, we usually have to calculate the shear stress in the fillet weld caused by twisting load. Pressure vessel design handbook by Bednar recommends using Sshear = TJ/c, where J is the polar moment of inertia. I believe this is the method that everybody is using. However, Design of weldments by Blodgett pointed out that formula is good only for circular closed sections.Both his book and Roark's Formulas recommends using R(or K) in other types of cross sections. If we follow Blodgett or Roark's, the fillet weld size will be huge, and I never saw anyone using this method to design the lifting lugs. I would like to hear some expert's comments. Thanks.





RE: Torsional load on clip/lug weld
The reason for this position is that the formula T/Jc corresponds to Coulomb's theory for torsion, that assumes the sections remain plane. This is of course true only for circular sections, and is not true especially for long beams where warping of sections (in other words: their departure from remaining flat) is not prevented.
Now it is clear that a beam formed by a fillet weldment around a lug (or also a lug, if it is full penetration welded) cannot be considered as a long beam, and it is quite unlikely that it could display significant warping (though this will depend on the vessel wall thickness).
prex
http://www.xcalcs.com
Online tools for structural design
RE: Torsional load on clip/lug weld
RE: Torsional load on clip/lug weld
I am not doing any lug design right now. The question is just for my personal interest.
RE: Torsional load on clip/lug weld
look at the two different lifting lug calculation on the photo of
www.thill.biz
Leonard Thill
Leonard@thill.biz
RE: Torsional load on clip/lug weld
RE: Torsional load on clip/lug weld
RE: Torsional load on clip/lug weld
WRC 198 has the computer program and the update and revision to WRC 198 IS WRC 448 with update computer program.
http://www.forengineers.org/pvrc/WRC%20Publications%20Catalog%20479.htm
198 (1) Secondary Stress Indices for Integral Structural Attachments to Straight Pipe, by W.G. Dodge; and (2) Stress Indices at Lug Supports on Piping Systems, by E.C. Rodabaugh, W.G. Dodge and S.E. Moore. September 1974 (45 pp) (ISBN #1-58145-197-0) ©¤ $63.00
448 Evaluation of Welded Attachments on Pipe and Elbows by E. C. Rodabaugh, E. A. Wais , G. B. Rawls. ¨C January 2000 (40 pp) (ISBN: 1-58145-455-4) - $96.00