Hi Arun,

If you specify either (and) X, Y or Z restraints the appropriate (as specified) translational (linear) movement of the pipe will be stopped (it will be made zero in the model) and the applied force(s) (reaction) that is (are) necessary to stop the movement will be calculated by CAESAR II and the force will appear in the "restraint" report. Similarly, if you specify either (and) RX, RY or RZ restraints the appropriate (as specified) rotational movement of the pipe will be stopped (it will be made zero in the model) and the applied moment (reaction) that is necessary to stop the rotation will be calculated by CAESAR II and the force will appear in the "restraint" report.

What your colleagues here are telling you is that it is very difficult to design a "real world" restraint that will absolutely restrain (stop) a moment (RX, RY or RZ). More commonly, we will locate a PAIR of translational restraints (X, Y or Z), such that the moment that we wish to diminish (control) will be broken-up into a force couple of opposite signs. It is much easier to design restraints against forces than it is to design restraints against moments.

Arun, we piping engineers often see cases where an uninformed "analyst" will "solve" a problem of excess loadings on a piece of equipment by placing a rotational restraint (RX, RY or RZ) in his/her analysis model. The resulting calculated numbers will look quite "nice", but the truth is it is usually the case that it is impossible to actually fabricate the restraint. Remember, we typically fabricate restraints from structural steel shapes and plates that are in fact elastic (i.e., they will deflect under loading). They will NOT result in the moments being completely restrained (stopped). Sometimes problems are "solved" on paper (in the computer) but the resulting design does not protect the equipment that the piping is attached to.

Look at the list of references provided on the COADE web site and try to obtain one or more of the books that address structural design and analysis of piping systems. Also, ask your colleagues for help and/or review of your restraint designs.

Regards, John.