×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Combined Shear and Torsion - Compression field method

Combined Shear and Torsion - Compression field method

Combined Shear and Torsion - Compression field method

(OP)
In earlier versions (pre 2005) of AASHTO LFRD Bridge Design Specifications, torsion was included in the determination of beta and theta in the "resistance" equations for epsilon_s. In the most recent Bridge Specs (2012), torsion was not included in the calculation of epsilon_s (Eqs 5.8.3.4.2-1, 5.8.3.4.2-2 and 5.8.3.4.2-3). However, in the current Canadian Standard, also using compression field method, torsion was included in similar equations.

Why are these two standards, both using the same method, treating combined shear and torsion differently ?


RE: Combined Shear and Torsion - Compression field method

The LRFD 2012 and CSA S6-06 (Oct 2011) approach looks consistent with epsilon referring to longitudinal strain. I can't speak for pre-2005 LRFD.

Both Canadian and US have sections on combined Shear and Torsion as well as you probably know.

HTH

VoD

RE: Combined Shear and Torsion - Compression field method

(OP)
The commentary of LFRD 2012 seems to suggest that the shear contribution from torsion is not to be considered in the calculation of the longitudinal strain. In CSA S6-06, this shear contribution is included in calculating longitudinal strain. If my interpretation of the LFRD commentary is correct, then these two codes are not consistent in the calculation of the longitudinal strain.

RE: Combined Shear and Torsion - Compression field method

Have a look at this paper: ASSESSMENT OF THE NEW AASHTO DESIGN PROVISIONS FOR SHEAR AND COMBINED SHEAR/TORSION AND COMPARISON WITH THE EQUIVALENT ACI PROVISIONS

krex.k-state.edu/dspace/handle/2097/7011

CSA S6 Cl.8.9.3.19 formula appears on page 24.

VoD

RE: Combined Shear and Torsion - Compression field method

(OP)
Thank you VoD. I have read this paper before your posting.

In Canadian CHDBC 2006, Clause 8.9.3.19 requires the shear contribution to be included in the calculation of the longitudinal strain. In AASHTO 2012 (6th Edn), the commentary on page 5-59 states "A stress limit for principal tension at the neutral axis in the web was added in 2004. This check requires shear demand, and not the resistance, to be modified for torsion". This seems to suggest that the shear contribution from torsion is not to be considered in the calculation of the longitudinal strain in AASHTO 2012. I have also come across an example from an American road authority for a bridge related structure which show shear contribution not included in the calculation of the longitudinal strain.

The key question is:
If using AASHTO 2012 for combined shear and torsion, should the shear contribution be included in the calculation of the longitudinal strain ?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close