what will be diff between +Y OR Y using in caesar..

when you restraint in +Y , this means element is free to move in +Y but fixed in -Y .

hi
if you are using +Y restraint it will act just like a simple rest
if you are using Y restraint it will act on both directions (+Y,-Y)
just like (REST+HOLDDOWN) support

If there is any uplift in the support
If You use +Y - No load on the Restraint
If you use Y - A positive load on the HOLDDOWN support will come.

This is a good question. I've seen many debates as to when Y used vs. +Y. In our office, we have only a couple of senior level engineers who have been using Caesar for a while, and they have different opinions:

- For rod hangers, we have one engineer who insists that the proper Caesar support is the Y. Yet, another engineer (who I tend to agree with) will only use a +Y for a Rod Hanger. His reasoning is we want it clearly called out if there is uplift at this node, so we can correct that. The engineer #1 insists that the rod hanger can actually take a bit of uplift, and that he checks each rod to see what the upward force is, and somehow determines what the movement of the pipe would be if not held down by the rod. If the movement up is less than 1/16" he 'waves' it off, with the idea that "realistically, this won't move up, and the rod will remain in tension.

This seems a little risky to me. Anyone else have some thoughts?

Thanks,
Gary

I think we all could think up situations where +Y is correct or Y is correct. But we can confirm the validity only by reviewing the results.
Input is not absolute. Initial focus in the output processor should be the confirmation of the input. (I cringe when I see people go directly to the stress report!) Use the "results" to check you model and update your model accordingly.
I would suggest noting all the model uncertainties while building the model and using this list to check/confirm your model's fidelity before proceeding through the output.

hi dave,

IAM DOING STATIC ANALYSIS AND TO CHECK DISPLACEMENTS PIPING THAT IS INLET CONNECTED TO ONE STACK HEAT EXCEHANGER SYSTEM AND THE OUT LET CONNECTED TO ANOTHER HEAT EXCHANGER SYSTEM.

MY DOUBT IS

1.) ONE OF SENIOR ENGINEER TOLD ME TO DEFINE DISPLACEMENTS AT A NODE IN VERTICAL PIPE RUN AND PUT RESTRAINT AS +Y.

IN THE SYSTEM I DESINED FOR EXAMPLE @ NODE 120 RESTRAINT +Y

AND DISPLACEMENTS AS DY1=1.2MM AND DY2=1.2MM

HOW THESE DISPLACEMENTS HAS BEEN DEFINED. PLS HLP ME TO UNDERSTAND

A displacement and a restraint are both boundary conditions. A "Y support" the same thing as a displacement of DY=0.

However, you can't model a "+Y" with a displacement. A displacement fixes the node in both directions for the displaced Degree of Freedom.

So in your example above, when you include "Displacement Vector 1" in a load case, node 120 will move up 1.2mm - period, end of story. The same will happen if you include "Displacement Vector 2" in a load case (because both DY values are the same).

HI RICHARD,
THANKS FOR YOUR SUPPORT.

IAM WORKING WITH AN SENIOR ENGINEER JUST HE TOLD ME TO PUT AT NODE 120, DEFINE DY1=1.2MM AND DY2=1.2MM


SO, ACTUALLY MY DOUBT IS THAT HOW THESE DISPLACEMENTS AT NODE 120 DY1=1.2MM AND DY2=1.2MM.


CAN YOU HELP ME

Using the defined data, at node 120 you have:

(Predefined) Displacement Vector 1 with
DY1 = 1.2mm

This means node 120 will move up (assuming Y is vertical) 1.2mm in any load case in which you include "D1" in the list of loads. You didn't say anything about the other 5 DOF (DX1, DZ1, RX1, RY1, RZ1)? If you leave these blank they are free. If you're modeling a nozzle then these other DOF are not free and you should specify 0.0.

Similarly since the above data indicates DY2=1.2mm, both (predefined) displacement vectors appear to be the same.