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RE: Torsion on a steel tube and AISC WINTORQ program

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Jesse, have you contacted AISC yet?  My experience is that they're pretty responsive to questions like that.  Don't know much about that program, sounds good, come across any negatives yet? (besides the issue mentioned below)
 
Brian Tarantino, P.E.
-----Original Message-----
From: Jesse Gobeli [mailto:jgobeli(--nospam--at)jgaeng.com]
Sent: Tuesday, March 18, 2003 9:02 AM
To: seaint(--nospam--at)seaint.org
Subject: Torsion on a steel tube and AISC WINTORQ program

List,
 
I have a question regarding calculating the shear stress in a steel tube.  I have the Steel Design Guide Torsional Analysis of Structural Steel Members and the WINTORQ program from AISC. 
 
Typically, I would calculate the shear stress in a tube using the formula: 
1.  shear stress = T / (2*b^2*t) (from table 4.1 of the Design Guide)
2.  shear stress = T / (2*t*Ao)  for constant T (Design Guide Eq. 4.4)  (This is the method used in example 5.2 of the Design Guide).
3.  shear stress = T / C (from Hollow Structural Sections Connection Manual spec. eq. 6-1, C is tabulated for each shape).
 
Methods 1,2 and 3 seem to give the same result. 
 
The WINTORQ program gives a "wall shear stress" value which seems to come from the following equation: 
4.  shear stress = G*t*theta'   (Design Guide Eq. 4.1)  (theta' from WINTORQ program)
This result can also be obtained using: 
5.  shear stress = T*t/J 
 
The problem is, the results from 1,2 and 3 are somewhat higher than the values from 4 and 5.  Since the Design Guide shows an example based on 2, but the WINTORQ program provides a value based on 4, I am not sure which value to use.  WINTORQ does not give any of the stresses obtained by 1,2 and 3.
 
(By the way, I have worked through the examples in the design guide for Wide Flanges, and along with the  WINTORQ program, they have been a HUGE help in understanding torsion on a wide flange beam.)
 
Jesse Gobeli, P.E.
Dublin, OH