Stress at elbows

Back in the old days, I thought that I had learned that piping elbows were less flexible than the pipe itself... something about the SIF or Stress Intensification Factor of the elbows. While viewing one of the SPED (Society of Piping Engineers & Designers) videos recently, it was stated that elbows are more flexible than pipe. Is this true?

Thanks,
Bob

I believe that, in reality, some flexibility credit can be given to temporary deformation of the ell in terms of going from a circular cross-section to an oval one and back again. However, this flexibility is not given credit in piping codes and we must pretend that it does not exist...

Or maybe this flexibility is from the directional change perspective. Elbows by providing change in direction give you the flexibility e.g. in expansion loops, which pipe does not have.

I had never thought of flexibility in those terms, Shrivallabha... thank you.

Bob