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ANSWERED on Sat 10 Oct 2009 - 4:08 pm UTC by redhoss

Question: I beam size for 22 ft span residential. need help ASAP

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Fri 9 Oct 2009 - 4:51 pm UTC

Question

dave k.
Customer

I am remodeling a house and would like to figure the size of steel I beam.
the house is 44x24 single level with truss roof. I would like to remove the existing wooden beam that runs the lenght(44ft) it has steel posts every 9 ft.
I would like to span two 22ft  steel I beams, with one end on each of the existing poured concrete foundation walls( 8")and install new footing and concrete pillar in the center to carry the other ends of each beam.
I would like to keep each of the 22ft spans free of posts if possable.

the floor joists are 2x10, 3/4 T&G decking. over one 22ft span is an open floor plan with living room and kitchen.  over the other 22ft span is two bedrooms and bath.

Im dont know what the loads are and not sure how to figure them.
please help me!!

Dave K.

 
 

Fri 9 Oct 2009 - 5:06 pm UTC

Comment

dave k.
Customer

Also would like the new beams to be of wide flange style and keep them in the 8 to 10 inch height range.

 

Sat 10 Oct 2009 - 11:13 am UTC

Uclue Researcher Request for clarification

redhoss
Researcher

Hello Dave, I can help you. But I need to clear something up first. As I understand the roof trusses are supported by the walls and the beams you need support only the floor loading. Let me know if I am correct and I can get you an answer.

 

Sat 10 Oct 2009 - 2:16 pm UTC

Comment

dave k.
Customer

yes redhoss, you are correct.  the total roof and ceiling load is carried thru the trusses to the exterior walls to the foundation.

 

Sat 10 Oct 2009 - 4:08 pm UTC

Uclue Researcher Answer

redhoss
Researcher

Okay, we should use a live load of 40 psf and a dead load of 20 psf. The formula we need is:

I = 5 x w x L^4 / 384 x E x D

Where:

I = moment of inertia
w = 60 psf x 12' = 720 #/ft
L = 22'
D = allowable deflection = 22 x 12 / 360 = 0.73"
E = 30,000,000 psi

Plugging in the numbers, we get a required I of 174 in^4

A good choice in a 10" beam would be:

W10x39

In an 8" it would be:

W8x48

In case you need it, the reaction at your center column is 15,840#.

Please ask for a clarification if you have any questions. Good luck with your project, Redhoss.

 
 

Sat 10 Oct 2009 - 9:59 pm UTC

Comment

dave k.
Customer

Redhoss, you have really helped me out on this project, also would you have any recmondation on what size footing i should put under the center pillar?  and would you recomend a concrete pillar or steel post
Thank you very much
Dave

 

Sun 11 Oct 2009 - 7:07 pm UTC

Accepted and rated

dave k.
Customer

Redhoss, would like to thank you for your help, it was very prompt and to the point.  Even tho the beam is bigger than i had figured it to be (my math wasnt quite rite) The project is moving foward, beams should be in place within a week or so.

I did alot of research trying to find the loads on steel beams, and that is how i found you and this site....  What a great thing that you are doing for people. I will use you again... 

I always try and figure things out on my own first, but always want to ask a pro to verify awnsers...

again thank you for your help

Dave K.

 

Sun 11 Oct 2009 - 10:07 pm UTC

Uclue Researcher Answer clarification

redhoss
Researcher

Thank you Dave. It makes an old man feel good to have anyone value his opinion. As to your question on the footing. I have no idea what your soil bearing strength might be and you probably don't either. Here is a good guideline:

http://books.google.com/books?id=JgNZFrqXl3UC&pg=PA66&lpg=PA66&dq=average+unconfined+compressive+strength+soil&source=bl&ots=riiP7JvTcQ&sig=XUhVScklpcbi-19p6OZ-DA9Efrg&hl=en&ei=hFDSSo-KMoSGtge4qO3vAw&sa=X&oi=book_result&ct=result&resnum=4&ved=0CBsQ6AEwAw#v=onepage&q=average%20unconfined%20compressive%20strength%20soil&f=false

If you assume a strength of 1,000 psf, a spread footing would require an area of:

15,840/1,000 = 15.84 ft^2

This would mean your footing would need to be about 4 ft square. You can adjust this number down if you feel your soil strength is greater.

You could likely get another engineer to use allowed reductions and come up with a lighter beam. However, I have yet to kill anyone (that I know of) and enjoy sleeping at night. I look forward to helping you again.

 

Sun 11 Oct 2009 - 11:51 pm UTC

Comment

dave k.
Customer

Redhoss,

Thanks for your insight on the footings, in my research on the footings i found that a 3.25 x 3.25 would be good,  funny thing is,between me asking you and you giving your opion on the footing. I had already cut a 4x4 area and was planning to use that size. Just as you on the beam  my thoughts were alittle extra never hurt anyone...  I would rather not downsize the beam.... This is my home and I would like to make it the best possible the first time around..and becides i dont want to wake up in the basement anytime soon!!!

Thank you again,you have given me back alittle faith in mankind and the willingness for one to help another...
I hope that I may do the same at some point in my life..

Thank you
Dave

 

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