steel span

I have an 8"x5" steel I-beam in the basement spanning 30' with a single post in the center supporting one floor and a roof. I would like to move one post to 8' and would like to know how far in from the other end I would have to add an additional post. I'm trying to open up the space for a recroom.
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In a previous post snipped-for-privacy@gmail.com wrote...

Hire a local engineer to evaluate the loads and make recommendations. It won't cost very much and you will be assured of a proper solution.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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On 17 May 2007 08:03:35 -0700, snipped-for-privacy@gmail.com wrote:

saying 5 x 8 steel I beam doesn't tell us enough to give you a meaningful answer. The thickness of the steel in the web, and plates is an important factor.
That said, steel is not as strong as many people think it is. Right now you have two 15' spans if there is a single support in the middle. Were you keep that 15' maximum span (not a good assumption, only an engineer can pinpoint the load points), then were you to move the support to 8 ft from the end, then then next support would need to be at 8 + 15 ft, or 23 ft. Safer might be just to use two: one at 8 ft from each end.
But: get an engineer (as the other poster suggested) to evaluate the situation.
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Frankly, I would be more concerned about what the moved posts are sitting on.
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In a previous post Glenn wrote...

Exactly. Thus the reason for my recommendation to hire a local engineer to evaluate the situation and make recommendations.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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That's a good point. Even with an engineers recommendation, there won't be a proper pier under the new location(s)
--
Steve Barker




"Glenn" < snipped-for-privacy@kc.rr.com> wrote in message
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In a previous post Steve Barker wrote...

If I were the engineer I would specify that a new footing must be placed under any new columns. It generally means cutting a hole in the floor slab, excavating 10-12 inches deep, adding a rebar mat and pouring back flush with the floor. A variation can include hanging the new column from the beam before pouring concrete so that the base plate is buried in the new pour -- no exposed anchor bolts to trip over.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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Good point. Most basement slabs are a flat pour, which should be OK here. But in reality it could be anything, couldn't it? One could do some cores and determine the composition of the slab at each proposed location...
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So the beam is actually two 15' spans.

from the

If the load was uniform then you might expect the beam to be ok as long as you don't create an unsupported section greater than 15' long.
30-8 = 22 which is greater than 15' so you do need another post say 7 or 8 ft in from the other wall. eg A spacing of 8,14,8 would seem possible.
But it's likely the load isn't uniform and there are other factors that must be considered. You absolutly must get this designed by a professional (which I am not).
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Technically, the beam span is closer to 12', time you allow for the point of inflection past the post on either side. So it is carrying a good load.
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As you can see by the answers you have received, it's a costly procedure at best. There are many structural considerations to take into account, not just adding additional steel columns (or lallys).
Your best over all approach might be to reconsider how you could lay out the basement with the existing column in place; perhaps over near a wall or decorated to partially hide it.
If you still want to remove the existing column and add additional ones, you have no choice but to hire a local licensed structural or civil engineer and have him analyze your specific situation. (Remember, even if you sell the home in the future, you would continue to be responsible for this basement. Having an engineer sign off on it places the responsibility onto him as far as the insurance and future lawsuits go.

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In a previous post Dennis wrote...

An excellent summary of the structural issues and future liabilities.
Good show!
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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