IS CAESAR SUITABLE FOR LINES OF DIA 90" OR MORE AND WITH WALL THK OF 6 TO 8mm.ALSO I WANTED TO KNOW WHETHER SIF HAS TO BE INPUTED MANUALLY OR THE PROGRAM WILL DO OF ITS OWN.

Caesar II uses infinitely thin Stick elements, that is it does not understand the concept of volume.This is something you must understand and remember.

For restraint reactions and element stresses use of CAESAR II is no problem.As you must be aware the code SIFs ( I am referring to B31 codes) should be used with caution for D/T >100 , so CAESAR II will only issue a warning, but compute as per the flexibility characteristic per the element geometry.But for 90 " dia and 6-8 mm thk. wall you should resort to rigorous FEA to arrive at the SIF ( and flexibilty values)values and do the manual input.

Regards

B31.3 code calculates sif for D/T<=100 and if it is more than 100 we have to calculate sif using FEA software as per the advise of Mr.Anindya.

SWORDFISH,

As Anindya says, Caesar 2 uses beam theory and the beams are represented as centerlines to which inertial values are assigned for the purpose of calculating forces, moments and bending stresses. Caesar 2 can be used to model a duct system as you describe and it may provide some useful data. You should use that data with caution and always keep in mind the context. If you want to calculate the local membrane and bending stresses in the wall of your ducting, you will have to apply Finite Element (or shell theory) methodology. Look at the Paulin Research website for further discussion.

You may not (should not) use the stress intensification factors calculated by applying the equations from the B31 Pressure Piping Codes to your duct system. Perhaps it would be useful to you if you review exactly what a B31 SIF really is and understand that when you use B31 SIF's within the D/t limits prescribed by the Codes (look at the notes in Appendix "D") you will be calculating a stress that is really about one half of the actual elastic stress. Remember that the Code SIF's came from fatigue testing on pipe and fittings that were NPS 4, schedule 40, carbon steel - these data were extrapolated down to NPS 1/2 and up to NPS 72 but obviously at the extremes of this range the accuracy will have diminished.

Please read the AWWA M-11 Manual to find more useful information for the design of large tubular structures. References such as this will also give you some guidance on designing appropriate supports for ducting. Remember that duct sections with large D/t ratios will tend to assume an oval shape at support locations (sometimes the section will "go oval" laying on the ground (or on a truck), loaded only by its own dead weight). When the "round" duct section becomes oval, it will become a beam that has a "strong axis" and a "weak axis". Caesar 2 will not know that the section properties have changed in a straight length of "ovalized" duct section and so it will apply the section modulus of a circular section pipe in the calculations. It is important to stiffen the duct sections at support locations (and sometimes between supports) to assure that the duct section retains a near circular cross section.

Regards, John.