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walkereng
walkereng, Bachelor's Degree
Category: Engineering
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Experience:  Over 30 years of comprehensive experience
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We are building a home in Mexico an the drawing states that

Customer Question

We are building a home in Mexico an the drawing states that I need a 19" high concrete beam to support the wooded pergola. The span is 5.66M between the 12" columns. Can we add steel to reduce the size of the beam?
Submitted: 1 year ago.
Category: Engineering
Expert:  StructuralEng replied 1 year ago.

How much do you want to reduce the size?

Customer: replied 1 year ago.
Down to 12". My wife is concerned with the roof being too high and thus limiting the amount of shade by the pool.
Expert:  StructuralEng replied 1 year ago.

You would have to double the amount of steel just for strength and deflection will be an issue

Customer: replied 1 year ago.
The drawing doesn't specify the width of the beam. The builder just says that he can reduce the size but I will look funny. Its sounds to me like they spec'd the beam size purely for aesthetic reasons. What should the width be?
Expert:  StructuralEng replied 1 year ago.

We don't determine beam sizes for aesthetic reasons. I can't size a beam without loading and deflection criteria.

Customer: replied 1 year ago.
you are saying that we need a 19" deep reinforced concrete beam to support what....its own weight plus a few smaller wood beams? Here is a picture of a pergola from the area with a 30' span. He used an 8" steel beam wrapped in cedar. Can you tell me what size of concrete beam and amount of rebar would be compareable?
Customer: replied 1 year ago.
is that it then?
Customer: replied 1 year ago.
OK so the span is 5.66M, the maximum deflection would be 18.87mm. The load will be around 7 kips/squ.ft.
Customer: replied 1 year ago.
Are you going to answer ?
Expert:  StructuralEng replied 1 year ago.

7 kips/sq ft is not in any universe a realistic load.

Customer: replied 1 year ago.
OK, your the engineer. Tell me how to figure it out. 5 beams sitting on it with one end attached to the house. Each beam weighs 200 lbs. So 500 lbs resting on each span.
Customer: replied 1 year ago.
Are you an actual engineer?
Customer: replied 1 year ago.
Answer me or close the conversation so I can rate you.
Expert:  StructuralEng replied 1 year ago.

I'm going to opt out. You've provided no information to help me answer this question. I want to help, but I'm not a mind reader and neither photo that you've send shows a concrete beam.

Customer: replied 1 year ago.
Oh, so what you need is a picture of a beam that isn't built yet. Maybe you are an engineer. You can probably figure out the square root of a pickle jar but you would starve to death trying to get one out. By the way that was a joke. Thanks for nothing
Customer: replied 1 year ago.
Please opt out.
Expert:  StructuralEng replied 1 year ago.

You've given 0 criteria to design a beam other than the span.

Customer: replied 1 year ago.
I gave you all a real engineer would need. Here is a tutorial as well. This should helphttps://www.youtube.com/watch?v=9Vd_q1KHIRo

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