Topic: Green House Design

[theluck19]

Hello,

I’ve been asked to design and cost estimate a green house of 20m x 20m (Span 5m). It’s a steel structure with Double layer polyethylene film covering it. I initially prepared a sketch with Structural I columns in the perimeter and MS Posts in between the spans with MS Truss for roofing. How ever my PM asks me to remove the Structural Columns as it is expensive. I have my doubts about providing just MS Posts all around. This Structure has to with stand winds of upto 60 Km/Ph & there is the load of the maintenance guy on who climbs the structure to clean the polyethylene film.

Anyone who has done this type of structure please help me out. I am an RCC  guy and don’t know much about Structural Steel or PEB Structures.

Cheers,
Theluck19

[Krushert]

The building has to be design and built to your current building code.  That is a minimum.  And you can not design a structure that is unsafe.   You need to involve a structural engineer in the design to verify what the PM is asking for.  He is right that the Steel Columns are expensive.  But something has to pick up that load or it has to be directed to somewhere else which is not easy.

However, you built your proposal/fee on a certain type of design that is of a  typical construction.  Your fees do not cover an unconventional design and this change is additional services.   Have a sit down with the PM to discuss the above and say this will cost extra. 

[theluck19]

Hi Krushert,

And you can not design a structure that is unsafe.   You need to involve a structural engineer

I suggested this & the reply I got was do it as per the picture. I have attached the picture. I guess he is just trying to find out the cost per square foot of a green house so that he can pitch to customers. I did some research about the wind condition, topography of the area etc.. guess I am over thinking it. Might as well prepare a detailing drawing like the snap, prepare a BOQ & add the rates. My knowledge is very limited when it comes to Steel Structures let alone Green House which is a completely new concept for me. By the way the PM is a Landscape guy and not an engineer or an architect.   

[Krushert]

By the way the PM is a Landscape guy and not an engineer or an architect.   

Enough said.   

[MP]

I <snip> don’t know much about Structural Steel or PEB Structures <and> the PM is <snip> not an engineer or an architect.

[dgorsman]

We are the Knights who say... NO. 

[CAB]

You can't be serious.
Remove the interior columns & that structure would collapse.
The bar joist would need to be significantly taller (you can just make them out in the photo).
All the load the interior columns would now be transferred to the exterior columns.
That means much larger columns & a moment force added to that connection.
Now you need to consider wind loads and the racking forces the exterior columns would
need to withstand from the wind. The resulting design would be much more expensive than the cost
of the columns removed.
Make sure your name is not on the drawings!

[MP]

You can't be serious. <snipped good summary analysis> Make sure your name is not on the drawings!

Times a million.

[Greg B]

Or design it out of PVC pipe and put a disclaimer on it.  Not to be built in location that has wind or people can breath on it.

[mjfarrell]

or start asking for facts:

http://greenhouseplanning.com/wp-content/uploads/2014/07/Greenhouse-Planning-Worksheet.pdf
  and other details:

https://www.ars.usda.gov/ARSUserFiles/50820500/Publications/ManualforVirtualGrower1.1.pdf

http://edis.ifas.ufl.edu/pdffiles/CV/CV19500.pdf

That should keep Mr. landscape designer busy until July.

[BIGAL]

Given the brightness in the image I would suggest its all made out of aluminium, basically there is no way that if using plastic sheeting for roof that it can have person even breathe on it. Let alone lay on it.

I drive past some cheapo Greenhouse's and they are pvc tubes in a full arc then a plastic sheet pulled over and no doubt anchored to the ground obviously no vertical sides. But small scale commercial greenhouses.

I do not want to be the bearer of bad news but its the type of structure that a company will specialise in and just be able to go 20x20x5 is $$$$ fully installed. I would try to be the middle man and be the project manager and source a company take a small cut. Do all the other design stuff and get paid for that.

Check out greenhouses in Holland they are acres in size.

A quick google trying to find one near me, found what you want in a couple of minutes company specialising in large scale green houses plus all the goodies, misters, conveyors etc.

Do you have any nearby ? Knock on their door they will probably tell you who built it.

Its like car sheds you could never design one compared to the price of a off the catalouge.

[theluck19]

Make sure your name is not on the drawings!

I ain't signing S#!T

its the type of structure that a company will specialise in and just be able to go 20x20x5 is $$$$ fully installed. I would try to be the middle man and be the project manager and source a company take a small cut.
Do you have any nearby ? Knock on their door they will probably tell you who built it.
Its like car sheds you could never design one compared to the price of a off the catalouge.

I found a vendor through a friend of mine. He is prepared to give me the shop drawings if I promise to get him the job. I think after seeing how he does it, I will have an idea to proceed on future jobs.

That should keep Mr. landscape designer busy until July.

I don't think I will be here that long. Its one thing to work with an ignorant colleague but to work under an boss who has no engineering qualification or experience is just not worth it. Hoping to get back into residential and commercial design and detailing, but the job market here in Chennai is not so good.

Anyway thanks guys!!