Wayne Whitney wrote:
On 2010-06-22, Phil wrote:

Plan 1: 2 columns (4 and 20 feet) under ground-floor columns with
steel U supporting the beam's gap

Plan 2: single column @ 16 feet with beam replacement. (this post was
about this plan)

[Also, from previous posts, there is a column coming down at x = 4
feet carrying half the load from a 16 foot span of floor joists for
the second story.]

The only difference between these two plans is the column carrying
the second story floor joists. The load from the first story floor
joists is the same in both case, 16 feet of span. But in Plan 1, the
ground floor column is above your basement column, while in Plan 2,
the ground floor column hits the basement girder 4' from the basement
column, imposing extra bending moment on the girder.

By my calculations, which I am not qualified to do, that extra point
load increases the maximum moment in the basement girder by a factor
of 25/16, or plus 56%. [Assuming the floor joist loads for the first
and second story are the same.] So unless your steel flitch plate
solution for Plan 1 is at the edge of what is feasible, I would expect
it to be possible to do Plan 2 the same way using more or thicker
flitch plates.

Of course, there may be other irregularities not presented, or there
may be a difficulty in making the connections properly in Plan 2.
Your structural engineer should be able to tell you.

Sounds about right. My thinking, (again, w/o _any_ calculations )
while a little more installation effort, was to extend the side plate
the full or nearly the full distance and beef it up to 3/8" or even
1/2". I'm pretty confident that would handle the deflection pretty
easily if the vertical loads are on the columns, wherever he chooses to
end up putting them.

But, he's got an enganier who's gettin' the big bucks and my
registration ain't no good anywhere but TN and here and I'm not working
anyway (other than farming again, that is)...

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