Hi everybody,
I'm checking a Caesar's file, and I am not sure I am on the right track with the concept of modelling in Caesar the differential & individual pile displacements. The geotechnical and structural design of the support structure predicted a maximum seismic deflection of the top of each individual pile to be 105mm. The maximum differetial pile deflection (using SRSS method)was determined to be 150mm. The way how these facts were used into the analysis are as follows: when only one pile deflects from its neutral state its top end can only move a maximum of 105mm. However,when two neighbouring supports deflect in opposite directions simultaneously the total relative movement between them cannot exceed 150mm. A large number of combinations of pile displacements were considered in order to gain a better understanding of the effects of various probable scenarios. Consequently two separate files were created: one for the individual pile displacement and one for the diferential pile displacement.The new piping design utilises only two types of pipe supports, simple rest and Rest+Guide, therefore,since the fuel oil line is only restrained laterally, by means of guides, the piping stress analysis only considered the lateral (transverse)displacements of the piles relative to the centreline of the piping. Although the simple rests will be expected to move as well, the frictional forces between the pipe and rest will be easily overcome without significant effect on the state of piping stress. Therefore,the rest displacement were not considered in the design.
In the Case #1(individual pile displacement) the guide diplacements were assumed to be equal to the maximum pile displ. of 105mm.In the Case #2 (differencial pile displacement)the guide displ. was assumed to be equal to max. differential pile displ. of 75mm. The stress ranges due to the effects of both thermal and imposed mechanical displ. were assessed in the line with the provisions of section 319.2 of ASME B31.3 Code. My question is: would these two files have the right approach in modelling & checking the stress range. How close to reality are they? From structural point of view I personally understand that the maximun inertia occurs at the maximum differential displacement. Please bring some light into the darkness..Thank you in advance for taking your time...

Do I have this right? Maximum absolute, individual guide deflection is 105mm and maximum differential deflection between neighboring guides is 150mm.
If so, I would guess that the highest loads/stresses due to these deflections, on individual straight runs, each with several guides would follow something like this:
Here are seven guides along a straight run and elbows on both ends:
-1-2-3-4-5-6-7-
Let -4- move its maximum = +105mm
To develope the maximum bending, then -3- & -5- would be the maximum opposite or = -45mm
But then what to do with -2- & -6-? I figure a bending reversal would be the worst case. That means these two guides move back to +105mm and likewise -1- & -7- would return to -45mm. I might also confirm that -2- & -6- at -105mm and -1- & -7- at +45mm would not be as large.

Of course all this is highly dependent on what's going on beyond those elbows on either end and the spacing between these guides. I would try to select the stiffest straight run to run this test.