CDLD
Structural
- May 20, 2020
- 215
Hello,
After reviewing the requirements of AISC Appendix 6, I understand that for a torsional brace to prevent LTB of another beam there must be adequate strength and stiffness of the bracing system.
On of the stiffness requirements, is web distortional stiffness which is particularly critical when the torsional brace is located at one of the flanges of the braced beam. In fact the AISC equation for web distortional stiffness was derived from this critical case.
Bsec = web distortional stiffness
Part of the equation calculates the moment of inertia of the braced beam's web; which is taken as an effective strip of 1.5 * ho wide.
The force requirement of the brace is the following:
Should the web of the braced beam have the flexural strength to transfer this brace torque to the flanges?
If so, does it seem reasonable to calculate the flexural strength of the web using the same effective web width as used in the web distortion equations above (ie. 1.5*ho wide)?
I ask this because in the worked example by Yura below, the web flexural strength is not verified - I wonder if this was an oversight?
minute - 1:25 approximately
Thank you and sorry for the long post
After reviewing the requirements of AISC Appendix 6, I understand that for a torsional brace to prevent LTB of another beam there must be adequate strength and stiffness of the bracing system.
On of the stiffness requirements, is web distortional stiffness which is particularly critical when the torsional brace is located at one of the flanges of the braced beam. In fact the AISC equation for web distortional stiffness was derived from this critical case.
Bsec = web distortional stiffness
Part of the equation calculates the moment of inertia of the braced beam's web; which is taken as an effective strip of 1.5 * ho wide.
The force requirement of the brace is the following:
Should the web of the braced beam have the flexural strength to transfer this brace torque to the flanges?
If so, does it seem reasonable to calculate the flexural strength of the web using the same effective web width as used in the web distortion equations above (ie. 1.5*ho wide)?
I ask this because in the worked example by Yura below, the web flexural strength is not verified - I wonder if this was an oversight?
minute - 1:25 approximately
Thank you and sorry for the long post
