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i want to build a 20 x 40 single story structure on spead footings

 

Customer Question

i want to build a 20 x 40 single story structure on spead footings 20 ft on centers. what size i beam or concrete beam could span the 20 ft span. normal residential loading assumed.

 



Already Tried:
nothing this is my first query

Submitted: 290 days and 16 hours ago.
Category: Structural Engineering
Value: $30
Status: CLOSED

Accepted Answer

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Expert:  walkereng replied 290 days and 16 hours ago.


walkereng :

I can help

walkereng :

Elevation
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walkereng :

Can you look at the file I just attached and answer the questions at the bottom of the page? This will give me the information that I need to adequately size a beam for you. Thanks

Customer : the beams would be perimeter beam on top of spread footers, asuming concrete posts above footers 3 ft in height. there would be no center beam. the ceiling joists woould be 1 on 12 engineered joists with a metal standing seam industrial metal roof ( 2" seams).
Customer : location is houston texas. sandy clay soil with 2000 # XXXX. walls to be 2x 6 walls wooden studs 24" centers. structure interior ceiling height 11 ft. outside heights high side shed roof about 14 ft and low side 12'6" assuming truss height at low end of 18"
Customer : floor trusses 20 ft trusses with 16 centers. object is to havecstructure capable of future heit adjustment by jacking up a low corner if ground shifts. upheaval probility low
walkereng :

Before we get started I’d like to point out that a Professional Engineer’s standard of care typically includes a site visit to assess field conditions and get an overall understanding of the structure. This can obviously not be accomplished through the internet. The information provided here is meant for informational purposes only (general sizing and budgeting) and is based on the information provided by you. The only loads considered for this member sizing are vertical loads, no lateral loadings were considered. The information should be verified by a professional engineer who can visit the site to ensure that potentially important information has not been overlooked or omitted.

walkereng :

Will you have roof trusses that clear span the 20' direction?

Customer : got it i am a mechanical engineer checking for calculations and tomguide me on shopping forvsurplus i beams
walkereng :

Great!

Customer : yes spans roof and floor 20 ft. actual builing tombe longer than 20 x20 module, perhaps 20 x 80 unknown at this time
Customer : trying to get to point where i can rouglybcompare floorvsystem cost between up on piers vs a posttesion slab on grade
Customer : sorry about the ipad typing and spelling
walkereng :

Do you have a span length that you are thinking of for your perimeter beam? Thinking of 13.33' spans to make 3 spans on the 40' side.

Customer : no. 20 ft spans all around
walkereng :

OK, let me run some numbers. I was going to try engineered timber beams?

Customer : still need i beam sizes as there are some salvage i beams available
walkereng :

Do you know what I beam sizes you may be able to get? Also what steel grade, 36 ksi or 50 ksi?

Customer : do not know, looking for a place to start calling iron guys on monday
walkereng :

OK, I will size 50 ksi steel beam for you. Hold on a few minutes. Thanks

walkereng :

I can give you a couple of 50 ksi steel beams to span your 20' at your perimeters.

Customer : on the engineered wood i got 5-1/2 x 16" x 20 ft.
walkereng :

You can use a W10x26 (50 ksi) steel beam. The beam is 5.75" wide, 10.375" deep and weighs 26 pounds per linear foot.

walkereng :

You can use a W12x22 (50 ksi) steel beam. The beam is 4" wide, 12.25" deep and weighs 22 pounds per linear foot.

walkereng :

You need to physically connect your floor joists to your steel beams for lateral support.

Customer : thanks any comments on thebwood?
walkereng :

I am running the wood numbers right now.

walkereng :

I can give you a couple of engineered wood options:

5-1/4” x 16” Versa-Lam 2.0 3100 SP

5-1/4” x 16” Versa-Lam 2.0 3100 DF

These are Boise Cascade products and you can go to the following link to find distributors in your area. http://www.bc.com/wood/ewp/distributors.html

walkereng :

As for your footings for your posts, assuming 2,000 psf bearing capacity, you will need a 30"x30" concrete footing that is 15"deep

Customer : Thanks this is very helpful. obviously the whole design looks different when on a slab on grade vs up on blocks
walkereng :

You are correct. This will give you some numbers to budget/plan with.

Expert TypeConsultant
Category: Structural Engineering
Pos. Feedback: 97.6 %
Accepts: 842
Answered: 6/23/2012

Experience: Over 27 years of Structural Engineering experience

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