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Category: Structural Engineering
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Experience:  Structural Engineer
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# I need to calculate the load-bearing capacity of a steel I-Beam

### Customer Question

I need to calculate the load-bearing capacity of a steel I-Beam 6"x6"x1/4", 13'-6" long supported by 9" masonry on each side
Submitted: 5 years ago.
Category: Structural Engineering
Expert:  StructuralEng replied 5 years ago.

StructuralEng : Hi
StructuralEng : I can help with this
Customer:

Thanks

StructuralEng : What grade of steel?
Customer:

Customer:

I know it varies with the grade of steel. This is not a load-bearing beam, just a garage door opening in a masonry wall. What do you suggest?

Customer:

Zoning wants to know.

StructuralEng : Te only load on it will be CMU in the wall? The wall is not load bearing?
Customer:

No load. The roof trusses are 13'-6" apart. This is a one story structure.

Customer:

Putting in a 12' door.

StructuralEng : No load other than the CMU, right?
Customer:

What is CMU?

StructuralEng : What is the height of the CMU above the opening? What is the thickness of the CMU?
StructuralEng : Concrete masonry unit
Customer:

Less that 1'. Maybe 10".

StructuralEng : Really? An you're getting questioned about a beam size? Give me a few minutes to run some numbers
Customer:

PIA zoning guy.

StructuralEng :

You can use a W5x16 or a W6x12. The first number is XXXXX depth in inches and the second number is XXXXX weight of the beam in pounds per foot. Depending on the thickness of the masonry, you might need something bigger just to provide a wide enough bearing surface for the masonry.

StructuralEng :

How thick is the masonry.

StructuralEng :

If you've found my answer helpful, please click the green "accept" button. I'll be happy to answer additional questions on the topic. If you could provide feedback, I would appreciate it.

Customer:

The masonry is about 8" thick I think. Not sure, but I'll stay with that. What kind of load-bearing capacity does that W6x12?

StructuralEng :

The W6x12 can take much more from a strength standpoint. Deflection is controlling the design. ACI 530 requires beams that support unreinforced masonry to be designed for a deflection limit of L/600, which in your case is 1/4"

StructuralEng :

It's only at approximately 50% of the beam capacity from a strength standpoint.

StructuralEng :

The last comment I would have is to make sure the bearing condition is detailed properly to ensure overall stability.

Customer:

Nice and flat, I take it. Do I bolt it down?

StructuralEng :

You can also use a steel tube 7x4x3/8 laid flat. This will give you a nice 7" flat surface to bear the masonry on.

Customer:

Box tube, right?

StructuralEng :

The bearing detail will depend somewhat on what is supporting it, but you'll want it bolted at both ends, but one end needs to be able to move (for thermal expansion and contraction) so you'll want that properly detailed. Also, you'll want full depth stiffeners. And you need to make sure that the masonry is grouted properly at the bearing locations.

Customer:

Thank you for your help. Slot those holes.

StructuralEng :

Correct, the HSS is a steel tube 7" x 4" with a 3/8" thick wall.

Customer:

Thanks again.