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#71101 - 02/20/18 09:22 PM PVELite Tower Deflection
xinquan Offline
Member

Registered: 05/17/00
Posts: 8
Loc: Singapore
Hi Ray, it seems that PVELite does not combine the input horizontal forces applied to the tower with the wind forces to derive the tower deflection. How can we combine both forces to derive the correct deflection? Your help is urgently needed. Thank you.

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#71106 - 02/21/18 07:30 AM Re: PVELite Tower Deflection [Re: xinquan]
Ray_Delaforce Offline
Member

Registered: 01/02/03
Posts: 743
Loc: Houston, TX
Hello xinquan,

Calculating the deflection of simple cantilever such as a uniform beam, one have a uniform section throughout its length, can be accomplished with a simple equation. This is one of the first things we learn at engineering school. However, a tower is made up of courses of varying thicknesses and diameters, so that a simple equation can no longer be used. We have to take a different approach.

We use the method set out in the paper by C.E. Freese which used a numeric integration method. When numeric integration is applied, ideally, the tower should be made up of short sections for greater accuracy. So the accuracy depends on the lengths of the individual sections.

Now, if forces are applied to a tower, does PV Elite take them into account? If you build a tower in PV Elite, you will that the programme does take the external forces into account.

Why doesn't PV Elite show the calculation of the deflection in the output? Remember it is an iterative routing. If we went through the process, it would take up many pages of paper.
_________________________
Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM

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#71107 - 02/21/18 08:14 AM Re: PVELite Tower Deflection [Re: xinquan]
Scott_Mayeux Offline

Member

Registered: 12/23/99
Posts: 347
Loc: Houston,TX,USA
Hello Xinquan,

I can confirm that applied global loads are considered in the tower deflection calculation. If you are expecting the results to differ when you enter in nozzle loads, there will be no difference.

You must enter a lateral force in the X or Z direction in the Force/Moment dialog at the appropriate elevation to see a difference in the tower deflection calculation.
_________________________
Scott Mayeux
CADWorx & Analysis Solutions
Intergraph Process, Power, & Marine

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#71108 - 02/21/18 08:30 AM Re: PVELite Tower Deflection [Re: xinquan]
Ray_Delaforce Offline
Member

Registered: 01/02/03
Posts: 743
Loc: Houston, TX
Hello xinquan,

I forgot to mention what Scott said. I apologise.
_________________________
Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM

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#71109 - 02/21/18 07:38 PM Re: PVELite Tower Deflection [Re: Ray_Delaforce]
xinquan Offline
Member

Registered: 05/17/00
Posts: 8
Loc: Singapore
Hi Ray/Scott,

Thank you very much for the prompt reply.
PVElite did the deflection calculation for the applied force separately from the wind load. See attached output results, the deflection due to the applied force is 130.037 mm and that due to wind load is 487.542 mm, these two deflections are not superimposed.


Attachments
9902-E_PipingNPlatform.pdf (911 downloads)


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#71115 - 02/22/18 08:29 AM Re: PVELite Tower Deflection [Re: xinquan]
Ray_Delaforce Offline
Member

Registered: 01/02/03
Posts: 743
Loc: Houston, TX
Hello xinquan,

They should be added together in the deflection report.
_________________________
Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM

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#71116 - 02/22/18 09:21 AM Re: PVELite Tower Deflection [Re: Ray_Delaforce]
xinquan Offline
Member

Registered: 05/17/00
Posts: 8
Loc: Singapore
You mean we have to manually add these two deflections?
I am curious why is it not done in the PVELite since they are supposed to be added up?

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#71117 - 02/22/18 09:35 AM Re: PVELite Tower Deflection [Re: xinquan]
Ray_Delaforce Offline
Member

Registered: 01/02/03
Posts: 743
Loc: Houston, TX
Hello xinquan,

Just look at the deflection report in the output.
_________________________
Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM

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#71118 - 02/22/18 06:41 PM Re: PVELite Tower Deflection [Re: Ray_Delaforce]
xinquan Offline
Member

Registered: 05/17/00
Posts: 8
Loc: Singapore
My question is since both the deflections due to the applied force and the wind load are supposed to be superimposed, why didn't PVELite just added them up to show the final combined deflection?
This will mislead the user to interpret that the deflection is still within the allowable but in actual fact it already exceed the allowable.
In my case, the total deflection is 130.037 + 487.542 = 617.579 mm which already exceed the allowable(=489 mm) deflection.

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#71125 - 02/23/18 07:43 AM Re: PVELite Tower Deflection [Re: xinquan]
Ray_Delaforce Offline
Member

Registered: 01/02/03
Posts: 743
Loc: Houston, TX
Hello xinquan,

At the moment, this is the way the programme works requiring you to add the deflections together.

We are cognisant of your concern, and we are considering changing the programme to reflect the total deflection.
_________________________
Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM

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