Interesting question.

Doubtless Rich Ay will give you the real CAESAR II answers that you are looking for. I would like to offer some food for thought. Perhaps it will stimulate some more discussion.

A piping system is an irregular space frame. If it is in equillibrium, it will be connected to some supporting structure(s). The total load must be transferred to the supporting structure(s) to keep it in equillibrium. The total load includes live weight (including e.g., contents, ice, large birds that land on it, etc.), dead weight (pipe, in-line components (e.g., valves, strainers, flange sets, etc.)) insulation (and cladding), hanger hardware, accumulated debris, external loads (e.g., wind), thermal expansion/contraction thrusts, and other stuff that doesn't readily come to mind. The summation of all these loads and the supporting reactions equals zero. If anything changes, a redistribution of forces (e.g., weights) is compelled to occur. The distribution of forces is a classic "beam 3 moment" distribution problem. The obvious change is the one that occurs in thermal expansion/contraction when the length of the piping changes and thermal thrusts are imposed on (at least) the terminal points (i.e., "anchors"). It is clear how this forces a change in the force (load) distribution. Of course the operating case has a thermal component and will include terminal equipment movements. Hanger angularity associated with thermal (and wind) loadings will also transfer thrusts to the terminal points ("anchors"). Perhaps less obvious is the various effects of pressure.

Pressure stiffening will cause slight changes in the stiffness matrix if it is turned on. Bourdon effect only comes into effect in pipe with a large D/t ratio and significant pressure. Small diferences in pressure can affect the weight distribution though.

Be careful of those "structural guys". They say "dead load" when they really mean total load. Include the loading of the "sprung" and "unsprung" hanger hardware weight. Hope that when "Bubba" walks along your pipe, he treads lightly. And just when you think you got it right the electricians will hang a bank of conduit from you pipe. There is a special place in hell for "pipers" who hang their new piping from somebody's existing (well designed) piping system.

Consider the rather significant change in load distribution that occurs when the cold pipe heats up (and the opposite)due to the reduced modulus of elasticity. Piping will sag noticeably if the hangers are too widely spaced (then fluid may collect in the "low points"). If you do a sustained load run with cold Young's modulus then do it again with hot Young's modulus you will see diferences,

What else should be said, my estemed colleagues?

Best regards, John.