What is Liberal stress?

B31.3 allows stresses to be calculated in 2 ways. One of these is typically refferred to as "Liberal". I suggest you do a search for the word "liberal" as this subject has been discussed before.

Read the B31.3 (2006) Code section 302.3.5d and equation 1b. Although the Code does not use the word, this is the 'liberal' allowable stress.

You should learn to use the search function to look for answers to frequently asked questions.

You first need to understand the meaning of "Allowable Stress RANGE". This is NOT a single static stress state.

It may help you to read this discussion of "liberal allowable stress range"

http://www.coade.com/ubb/Forum1/HTML/000057.html

Regards, John

John P.,

If you take time to read a little bit of what you want to know you will get your answers. Here is what you could have read if you could have tried to search for answers.

A conservative formulation of the allowable expansion stress range for many codes in CAESAR II is calculated from:

f ( 1.25 Sc + .25 Sh )

When the user requests that the "Liberal Allowable" be used, the difference between Sh and Sl, provided Sh > Sl, will be added to the term inside the parenthesis, i.e.

SA(Liberal) = f[ 1.25 Sc + .25 Sh + ( Sh - Sl) ]

The liberal expression will only be employed when there is at least one sustained stress case in the load set. If there is more than one sustained stress case in a single problem, then the largest of Sl, considering all of the sustained cases, for any single element end will be chosen to subtract from Sh. Because the sustained stress varies from one pipe to another, the allowable expansion stress will also vary.


Cheers!

Liberal is a CAESAR II term. It is relative. Once upon a time everyone used Eqn 1a because it was easy to calculate - but is was conservative. Computer software made Eqn 1b practical. It made sense for us to call it "liberal" but that means liberal with respect to Eqn 1a. Actually, we should call it "more accurate and less conservative".