×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*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.

# PDELTA QUESTION CLARIFIED

## PDELTA QUESTION CLARIFIED

(OP)
Thanks CV and NO KNOW for response. Let me clarify. Guide to Stability Design Criteria for Metal Structures suggests Pdelta as one among three procedures for determination of strength of frames designed using Allowable Stress Method(item 15.12,1976),suggesting K=1 and direct use of second order moments. Edward L. Wilson in his book "3D static and dynamic analysis of Str." page 11-11 also refers to this procedure. In K methods, compressive strength is divided by a factor of safety dependent on K-based slenderness. In moment magnification actual compressive stress is divided by "allowable" Euler stress which is also K-based.

My question is we have two points here: Allowable Compressive Strength and Moment Magnification due to axial load level. Will blindly putting K=1 work or are there extra considerations?.

Merry X-mas to all fellow engineers

Replies continue below

### RE: PDELTA QUESTION CLARIFIED

I think Compressive Strength is itself and Moment magnification comes from the displacment of nodes and bow efect between nodes.  If the FEA have both PDelta ( displacment of nodes ) and Pdelta ( bow efect ) then we are near the real behaviour of the model.  I think the only thing and the most important is to load the model by steps of load and not suddenly, to give way to the update of the geometric matrix.

Regards

CV
carlosvalinhas@netcabo.pt

#### 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.

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:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!