Hi,
The failure envelope used by Caesar in only based on r < 1.
How do we get the failure envelope when r >1.
i have going through the Code stresses document in the Caesar help menu and found all the failure envelopes are for r < 1.
Can someone explain this.

I am assuming that you are talking about plain pipe.

If you use CAESAR II online help (F1 key) for the field al(0:1), it says "The ratio of theses strengths r, called bi-axial stress ratio, can range between 0.5 and 0.75 for plain pipe, depending on winding angle and specific pipe type." This is directly quoted from ISO 14692-3:2002(E) (on page 21).

In CAESAR II, al(0:1) should be less that al(2:1), which means r < 1, as you already have known.

Thanks for your response.
1. Let us discuss about the plane pipe first , if you refer to ISO 14692-3-2002(E) section 7.11.32 page 20,in the first paragraph itself it is mentioned "If r is greater than 1,eg.hand lay up pipes,7.11.3.3 applies.".
So there can be case when r > 1 for plain pipe.

2. Also if you use help (F1) for qualifying stress it says," In CAESAR II qualified stress joints
σ qs, for plain pipe is not directly required, although users should be aware that
(σqs)pipe= σ shl(2:1), and σ shl(2:1) is required input for plain pipe."
Now my point is in ISO-14692 i did not come across the equation which equates
(σ sqs)pipe= σ shl(2:1).I dont understand the background of this equation.

3.For plain pipe value of σ a,sum and equation used in CAESAR II is different from that given in ISO -14692.3-2002(E).(equation 21,22 page 21 for r<1).
Can someone esplain this discrepancy.
Regards