Friction stiffness

Pipe stiffness refers to the pipe’s ability to resist deformation and maintain its shape under external forces. In other words, the greater the stiffness of a pipe, the less it deforms, and the stronger its resistance to external forces.

For more details, refer to section 6.6.2 in the book on pipe stress engineering. The general idea is that friction is a nonlinear factor; whether friction is present depends on whether there is relative displacement between the pipe and the supports, yet the magnitude of frictional force in turn affects this relative displacement. Therefore, the calculation of friction involves assuming that the frictional effect corresponds to a horizontally constrained support, and then performing calculations. If the error between two such calculations is less than a certain value, the software considers the result to be converged. The stiffness of the assumed horizontally constrained brace is the friction stiffness; the larger its value, the more accurate the calculations, but convergence becomes more difficult. The smaller its value, the greater the calculation error, but convergence is easier.

Can it be assumed that for C2, a default high stiffness value is set (which is inaccurate in reality); if static friction applies based on this stiffness value, then the software considers the calculation of the static friction force to be complete. Since the friction stiffness remains constant when calculating friction force in C2, C2 uses a simplified method to replace the actual forces. The stiffness value set for C2 depends on practical engineering considerations; for example, the frictional stiffness of pipes laid in ducts can be set quite high, but it is 0 if the pipes are placed on hangers