I have one urgent query regarding the restraint loads reported by restraint and restraint summary.

As an example, at a particular node there is rest support (+Y) with friction and guide support (X) with 3mm gap.

If I extract the restraint report, the loads on rest and guide will be reported differently say,

(Rest)+Y Fx=300 Fy=-3000 Fz= 250
(Guide)X Fx=800 Fy=0 Fz= 0

If I extract the restraint summary report, the loads on rest and guide will be combined,

Fx=1100 Fy=-3000 Fz=250


I am not able to understand why this happens and which one is the actual load on guide support.

My purpose is to provide loading on supports for support design.

Please provide guidance.

It looks to me as if you specified mu=.13 on the +Y support and no friction on the X guide.The +Y support carries 3000 pounds (or Newtons?) which generates a friction load of 390 pounds. The gap on your guide closes and the pipe loads the guide with 800 pounds.

As I understand it, the structures people want to see your normal load and they will design in the effects of friction on their own.

Hello Dave,

The loads I specified are just random figures I used for example. They are not actual figures from CAESAR output.

So, What I understood from your explanation is that for giving loads to design supports we should not use restraint summary report. The restraint report gives the actual piping load on guide due to expansion and displacement of pipes (friction force is not included).

Please correct me if I am wrong.

I have included some actual CAESAR output figures-

Below is the snapshot of the model where a +Y restraint with friction factor 0.3 is specified along with guide restraint with 3mm gap.




Below is the output from Restraint report.

http://s13.postimg.org/tjyzruo2f/image.jpg


Below is the output from Restraint summary report.

http://s23.postimg.org/xromsc1yj/image.jpg

Your statement does not reflect what I said.

Dave, I have edited my post above with actual CAESAR output. Please explain the reason for two different Fx values in the two reports.

From my understanding, when you view the Restraints report, you are reviewing the loads due to each restraint definition.

So if in your input, you defined +Y with friction coefficient, the Restraints report shows you the FY, and the FZ&FZ due to friction coefficient multiplied by FY.

And in the same report, the X restraint at the same node would only show FX if you don't define friction with the X restraint definition in your input.

Restraint Summary report would report the total loads at each restraint node point. So that's why you're seeing the sum of the force/moment in each direction.

As far as what you should give to structural, maybe you can check with your structural engineers or company procedure on which way to go. If they would calculate the friction forces based on your normal loads, maybe you don't need to include the loads due to friction when you give it to them. Or maybe it doesn't matter if you feel like the difference is insignificant.

Hello Faizal,

As u can see in the caesar output I posted above, the FY load is 13749N which when multiplied by friction coeff (0.3) the values for Fx shall be 4124N where as CAESAR output shows 1566N. This happens everytime in all cases.

So that means the loads in horizontal directions on rest support are not only due to friction but have other effects also.

FY = -13749N
Ff = 13749N X 0.3 = 4127.7N = sqrt(FX^2 + FZ^2)
The FX and FZ above are due to friction only.

The distribution of FX and FZ due to friction is based on the displacement vectors if I remember it right. I bet that the ratio DX:DZ=1:2.44.

Please review the discussion on "friction" in the User's Manual. Mu*Normal_Force is the limiting (maximum) friction load. The force at that point could be less than this limiting load, which is interpreted as "not sliding". If the load at that point is equal to the limiting load, it is interpreted as "sliding".

Faizal,

If we provided two restriants at one node say +Y & Z (Guide stop)with mu=0.3.

Then how to calculate friction load in X direction for individual restraints +y and z(guide)

The restraint report will display a line for each restraint vector, in your case, one for the +Y and one for the Z. Each of these lines will show the normal load for your restraint direction, other values on that line will be friction for that restraint vector.

Thanks Dave for your information