Hello Stressers,

With the new technology of FEA Tools, SIF's & K's is automatically inserted in Caesar II for Non-code components such as bend with trunnions, D/T>100, etc..

My question is, is Caesar already capable of handling K factor for bends in the inplane and outplane direction (Ki and Ko)? or it takes the highest value of the two?

Many Thanks,
Cheers!!!!

CAESAR II accepts only one value for bend flexibility.

Thanks Dave. Is there a plan to modify the matrix architecture of Caesar II to include two flex factor "K" or one is enough to evaluate piping systems?

Many Thanks,

Hello Mr. Borzki.

For me, it's the first time to hear that flexibility factor is also different in in-plane and out-plane direction.

Do codes line ASME B31.3/B31.1 or Section VIII talk about the different values in in-plane and out-plane direction?

Thanks

Hello...

Refer to Appendix D of ASME B31.3..The flexibility factor is given as one value only (this will apply for both in-plane and out-plane).. This is also to simplify the "stiffness matrix" for bends/elbows. Most "beam element software" such as Caesar II is programmed to this "stiffness matrix for bend/elbow". Which has been the practice ever since. But with the advent of FEA software, this limitation can be overcome but it's not practical for general piping system to employ. If you have a very critical piping system then that's the time you can employ FEA. But do note that FEA is not easy as it seems technology. Unlike "beam element" which has a closed-form solution, FEA is an approximation of a continuous system. That's why FEA is always correlated to physical testing. It's a good calibrating tool to minimize prototypes and number of testing required. This is where FEA tool can be very helpful. That's why you can see some and most FEA developers/consultants for a certain system have physical testing labs to calibrate their software.

Cheers!!!

I see that our bend stiffness matrix can accept an in-plane and out-plane flexibility factor but until a standard publishes differing terms, I believe we we'll continue to use a single value.
One interesting point...
Even though CAESAR II is a stiffness method (as is most every piping package), the Codes offer only a "flexibility factor" for these bends. So we first build a flexibility matrix for bends and then invert them for use in the system stiffness matrix.

Thanks Dave for the info...For the meantime, we can try both values taken from FEA output.. Usually, the higher value is taken since it's more stiffer.. Engineering judgment will come into play into a case by case basis.. But if it's within the Code range (D/t<100), then it's not practical to run each bend using FEA.. This is why FEA Tools was developed to streamline the process for out of Code components, in terms of productivity and efficiency..