×
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

Torsional Fixity

Torsional Fixity

Torsional Fixity

(OP)
I'm writing a stiffness matrix program and including fixity numbers for each end of 0 to 1 for both flexure and torsion. (0 = pinned, 1 = fixed)

For flexure it's fairly obvious to me, but for torsion I'm having trouble understanding what the fixity means.

A fixity of 1 means warping constrained, and a fixity of 0 means warping unconstrained, correct?

However, a fixity of 0 will still have the torsional stiffness of GJ/L at 100% (only St. Venant's), correct?

For a ball and socket joint, there would be no torsional stiffness at all. Would this be classified as free rather than pinned?

And, theoretically, couldn't you have a ball and socket joint that restrains warping?

RE: Torsional Fixity

Yes, fixed end torsional constraint means the cross section cannot warp. Pinned (or free) means it is unrestrained to warp (however a free end can rotate while a pinned or fixed end cannot).

RE: Torsional Fixity

I am not sure I understand your question. Each end has 6 degrees of freedom, 3 for translation and 3 for rotation. Doesn't the ball joint have the 3 translational degrees of freedom constrained and the three for rotation unconstrained? A free end has no degrees of freedom constrained.

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!


Resources