Dear stress fraternity,

In a modal analysis,when we solve an eigen value problem to obtain the natural frequencies of the piping system,should we not use the geometric stiffness matrix instead of stiffness matrix?
Consider a system which is stiff(By "stiff" I mean huge axial forces- of course less than the buckling load for which the "K" becomes Zero). Will the solution employing the geometric stiffness matrix in such stiff systems have a significant effect on frequencies?? Is it employed anywhere?? I have heard of certain aerofoil blades in which the centrifugal forces creates a pull along the axis and increases its natural frequency.
Many high temperature piping calling for minimum natural frequency requirement are mostly stiff.How worst would the huge compressive / tensile forces would alter the frequency?
In the case of piping system, each of the load case may have different natural frequency according to the respective geometric stiffness matrix.
Please help my doubt. Correct me if I am wrong.

Regards

Natural frequency changes due to K-Delta effects ( as mentioned by you) which may be due to the fluid flow effects ( for full derivation refer Flow Induced vibration by Blevins), however the changes are generally not substantial and can be neglected.

Regards