Design Temperature Consideration

[marchieV]

Hello.

I just need some opinion regarding the design consideration of beam in a piperack. Do you always consider the load at Minimum Design Temperature for the design/sizing of beam?

Actually, the Minimum Design Temperature that I used in the Stress Analysis was only an assumption at 0degC but the generated support load is very high that is why I was doubting if the design of the beam (Structural Engr.) will be over design. The Maximum Design Temperature and Operating Temperature loads is not that high as compared to Minimum Design Temperature.

Please I need your support and enlightenment.

Thank you in advance.

Sincerely,

marchie

 

[BigInch]

What do you mean?

Have you calculated the loads to be used for design of the pipe rack structure with the pipe temperature set at 0[°]C?

Was the structure also at 0[°]C?

 

[europipe]

Is the temperature of a piperack an issue?
Where is it, Mars?

 

[racookpe1978]

Are you concerned about the residual structural steel strength at 0 deg C - and why, or the load ON the pipe structural steel at 0 deg C when the pipe cools down that much and shrinks from it operating temperature?

What fluid, what operating min and max temperatures, and what other conditions are you using?

 

[marchieV]

Actually all the loads generated by CAESAR II will be used by structural engineer. I usually consider Operating and Design Conditions in the generated report that I will give to them.

I am more concern on the generated load at Minimum Design Temperature because it always gives a very high load (NOTE also that 0degC is only my assumption).

Sincerely,

marchie

 

[uaepiping]

Take advice from marchieV.
As per line list (providing design minimum, maximum and operating temperatures) do the analysis by designing proper supports.
Provide the restrain summary to structural engineer for his considerations/calculations.

 

[BigInch]

You should give all loading conditions to the structural engineer. All loads, with all possible values and directions such loads can take. It is not your job to try to decide what load represents the worst load for structural design.

A minimum or maximum load in all but the most simplistic definition (the largest load in the downward direction, placed on a horizontal beam) has no meaning, especially to a structural engineer. What is the meaning of minimum and maximum loads, first algebraically, and the meaning of a minimum or maximum load to a structural engineer? Which is worse for a structure, -1000 lbs, or +10,000 lbs? 1000 lbs up, 10,000 lbs down? 5000 lbs left, or 2 lbs right. The structure must be desinged to take all. It must also be designed to withstand moments created from such loads, which depend on a beam's length of span between supports, for example. A 10 lb load at the center of a beam with a 20 ft span creates a 50 ft-lb bending moment, the same bending moment as a 5 lb load on a 40 ft span.

A minimum load of -1000 lbs (downward) may define the worst case load for a concrete beam or floor, whereas +1000 lbs (upward) may also define an equally bad case for a concrete beam or floor. A downward load to a concrete beam will create tension on the bottom of the beam, so requiring sufficient reinforcing steel to be placed in the bottom region of the beam. If the load were upward, tension reinforcement would need to be placed at the top of a concrete beam. If the beam was steel, perhaps there would be no difference in the steel beam selected, if the selected beam was a standard WF, because in a standard WF beam there is just as much negative moment resistance as positive. That might not be true, if the beam was specially made up from steel plate, or cut from wood. Load type and direction, or structural geometry and materials and method of resistance the structural engineer will use for design of the structure can have far more influence on what load is actually worse, rather than what happens to be the simple smallest, or biggest magnitude of the load.

 

[MikeHalloran]

I have lived in places where -40C is not unusual in winter.
Your management, or your customer, or your AHJ should have already specified a minimum design temperature; you just need to find it.


Mike Halloran
Pembroke Pines, FL, USA

 

[LittleInch]

I don't know a lot about structural design of the rack, but in general you find that design allows different safety factors for occasional events compared to normal or sustained events.

Otherwise everything would be horrendously over designed.

Therefore I would look for the lowest temperature which can be normally expected, coincident with other forces such as the pipe being full of product. This is your sustained load on the structure. Then do a min design temp and provide this as an occasional load on the structure, but also check if it could only happen if there is e.g. nothing in the pipe.

Min design temp is normally a bit extreme, with a margin below what might be expected in any set of circumstances.

Assuming 0 Deg C is dangerous. It might be higher, it might be even lower (e.g. cold gas venting). This should be data provided to you in the line list, piping specification or design basis.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.