anindya am talking about loads on restraints, so definitely it is compressive. my question is if we use scalar combination the loads on the rest (+Y)is getting reduced in some cases and increasing in some cases due to the change in wind direction.(i.e -x,x or z,-z).if we use absolute combination the loads are just increasing and also the restraint load is in (-Y) direction.
for sus+wind cases:
guide loads are properly reflected in scalar combination and not in absolute.
rest loads are properly reflected in absolute combination and not in scalar.
i need a clear explanation of why is this so?

Arun,

You should have put this information in your previous post, so the whole discussion could be followed in a single thread.

From the CAESAR II Help:

Short Explanation
Scalar - signed combination disp./force/stress level
ABS - unsigned combination disp./force/stress level


Detailed Explanation
Scalar - Combine the displacement vectors, the force vectors,
and the stress scalars.

Displacements are the algebraic combination of the
displacement vectors.

Forces are the algebraic combination of the force vectors.

Stresses are the scalar combination of the stress scalars.

The Displacements and Forces of an ALG case and Scalar case
are equivalent. There may be variation at the stress level,
since in an ALG combination the stresses are calculated and
in a Scalar combination the are combined. For example:
Load Case 1: Bending stress = 100 psi, due to X-moment
Load Case 2: Bending stress = 100 psi, due to Z-moment
Algebraic (vectorial) sum = sqrt(100*100 + 100*100) = 144 psi
Scalar sum = 100 + 100 = 200 psi

Scalar would typically be used to sum (SUS + OCC) code
stresses.

ABS - Combine the ABSolute value of the displacements, the
ABSolute value of the forces, and the ABSolute value
of the stresses.

Displacements are the sum of the absolute value of the
displacements of all cases included in the combination.

Forces are the sum of the absolute value of the
forces of all cases included in the combination.

Stresses are the sum of the absolute value of the
stresses of all cases included in the combination.


So, what you're seeing makes perfect sense.

Arun,
Besides Richard Ay's explnanation, which is self explanatory, pl. note that SCALAR ADDITION ( as I have mentioned before , you should ponder why SCALAR and not ALBEGRAIC)is for code stress check for SUS+OCC only. Code does not recommend, how you need to add the restraint loads for different combinations.

The tensile / compressive I referred to was for "pipe stress only".When you are mentining "loads on restraints, so definitely it is compressive", are you referring to the compressive loading on the restraint ? What has pipe stress got to do with it ? Are you designing the piping or the supporting structure?

Pl. don't think I am trying to teach you or anything that way. I only feel that you need to study the code requirements and the intents in a better way.

Regards

Design of piping systems is separated into two distinct categories - the structural response of the system (in terms of restraint loads and pipe displacement) and the strength of the pipe measured as stress. Most any mechanical engineer will be familiar with the former but the parochial rules of the latter are unique.

That's why you (usually) don't look at stress in the operating case and you don't review restraint loads in the expansion stress range case. I would also question any use of the restraint report from the sus+occ case. But I'm glad you are asking questions about the reports. Keep in mind that you can probably develop your own answer by simply running a small job that tests your question. Varying one piece of data (such as summation technique) will show what happens.

Arun,

There is a post by SAM ( I cannot recall which post, just search by name and you will get it). The post has an excellent discussion and some sample load cases, which will give you some food for thought as to what you need to do for Restraint loads.

Regards

thanks richard, anindya and dave for ur answers and comments.

Dear Richard Ay,

For wind occasional load case, is it correct that for linear loadcase the OCC code stress = SUS + OCC (SCALAR combination method) while for non linear loadcase the OCC code stress = SUS + OCC (ABS combination method)?

The piping Codes do not make a distinction between linear and non-linear jobs in the application (usage) of the stress equations. I suggest the "scalar" combination method is to be used for SUS+OCC load cases.

Thanks Richard for the explanation.