Reinforcing existing Beam 2

[rfd23]

I have existing W8x18 beam. I need to reinforce this beam due to change in span. I did some research on welding of plates to wxisting beam. Most of the time we weld horizontal plate on bottom of bottom flange or weld a vertical plate along web, welded to undrside of top flange and top of botom flange.
Can I use two vertical plates on both sides of web and welded to web. depth of plates would be to suit welding and k of beam.
All thoughts are greatly appreciated.

 

[csd72]

Simplest solution is to put a new channel in on either side.

Welding adjacent to the timber joists is a potential fire hazard.

 

[rcd445]

The most effective solution that I found was to weld a plate to the bottom flange and a pair of angle to the underside of the top flange. Use a bottom plate wider than the flange so that the weld can be from the top instead of overhead. The angles should be placed so one toe is against the bottom of the top flange and the other toe is against the wide flange's web. You may have to clip the hoizontal toe if the beams flange is too narrow and it may help to clip the vertical leg in order to use a thick angle and get more mass near the top flange.

 

[kslee1000]

rcd445:

The weak appeal of adding angle to bottom side of flange is its back corner (right angle) against the round fillet of rolled beam. It is feasible only if the angle is attached to a plate, as thick as the fillet, that is welded prior. Then, it is a lot of field weld.

 

[rcd445]

Place the angles with vertical legs to the outside to avoid welding near the fillet. A section through the composite beam would appear to have two hollow tubes as the top flange.

 

[rfd23]

Thanks every body.
BAretired, At this moment Column is a 3.5'' dia post with a thin cap plate. it is welded to bottom flange. what do you think is it a secure connection. To me it sounds secure. what is your opinion.

 

[BAretired]

rfd23,

Hopefully the cap plate is not too thin. It is almost assuredly adequate but it never hurts to check it. Consider the column spanning vertically between the floor deck and the grade slab. Apply a horizontal load, H = 0.02*Cf where Cf is the compressive force in the bottom flange. The moment at the cap plate is then Hab/h where a is distance from cap plate to floor deck, b is distance from cap plate to grade slab and h = a + b.

Since you are making the steel beam continuous, you will have inflection points each side of the column. Please note that inflection points are not braced points, so in addition to bracing the top flange, it is a good idea to brace the bottom flange of the beam at or near each inflection point.



BA

 

[kslee1000]

rfd23:

How many spans in direction of the continuouse beam? Span lengths?

Is there a beam in parallel to the above beam on each side. How they will be handled? Will they be made continuous as well, with columns alinged? Or they are remain in present condition?

I think you need to provide broader information on layout to get feed backs on the whole, rather than piece by piece.

 

[rfd23]

Ok.
Let me scan/draw the plan and then we can discuss.
actually.
BAretired,
Cap plate appears to be very thin. May be 3 to 5 mm.

 

[BAretired]

rfd23,

If the cap plate is 150 x 100 x 5 and is welded to the exterior edge of the beam flange, it is too thin to develop the required moment. You would have to add support under the plate.

At one point, you said the simple span moment is 32'k. You later said the continuous moment is 20'k. That seems like too much difference for the effects of continuity. Please check it again.

To arrive at a simple span moment of 32'k with a 10.35' span, the total load on one span would be 24.7k or about 2400 pounds per lineal foot. How is it possible to get so much load into the beam with 2 x 6 joists? Is there a bearing wall above? It doesn't sound right.

Please include a cross section through the beam when you post the plan.




BA

 

[rfd23]

BA retired,
attached is plan for the house.
yes this beam is carrying GF, First floor and Roof load. There is a bearing wall on that beam.
In my plans I am proposing 2 new posts, but client did not want any of them. in this way I have to reinforce existing footing, psot and beam. Existing footing is very thin. it is 3ftx3ftx4 in thick. it is only 4 in thick. How I can reinforce this kind of footing.
please advice.

 

[BAretired]

I have never run into a four inch thick footing. It is difficult to understand how such a footing would have been approved by the authorities in the first place. I would suggest that the existing footing be replaced with a properly designed foundation. Meanwhile, the structure must be suitably supported.

BA

 

[kslee1000]

It looks like the latest scope is to remove the 2nd column from the right, thus double the span length from 8'-1" to 16'-2". The column pads are 3'x3'x4", the beam has bearing wall directly on top.

Ok, you are facing least 2 immediate problems:
1. As BA point out - inadequate footings.
2. It would take some effort to simply BEEF-UP the beam (make the 2 8'-1" as a single 16'-2" beam), if possible. Then, how about the columns?

You may include the following in your action plan:
1. Replace the inadequate footings, or do strengthening.
2. Check the capacity of the columns, replace or strengthening.
3. Replace the beams (2 @ 8'-1") with stronger shape to span 16'-2" (simply supported at columns). Or, make the existing beams (4 @ 8'-1", 1 @ 6'-3") continuous, and beef up the beam at the longest span, if feasible.

 

[BAretired]

kslee,

The drawing is a little hard to read, but I believe there will be a span of 10'-4" with a 3'-0" cantilever each end.

BA

 

[kslee1000]

BA:

He stated the owner does not want additional columns in his latest response that was addressed to you. I could be wrong though.

 

[rfd23]

Yes, Ksle
Owner want middle span to be 16 ft 3 in.
Final spans would be 8-1, 8-2, and 16 ft-3 inch.
Attached plan is my proposal which owner does not agree.
just ignore my propsal.
I checked W8x18 even with additional w8x18 at bottom flange does not work for 16 ft span.
Udl on beam is 2.35k/ft.
Max. moment is approximately 60K-ft.
Please advise.

 

[BAretired]

Anything can be done if the owner has the budget and the headroom for it.

BA

 

[kslee1000]

A quick cal indicates you need at least a W8x48. However, I have problem with the load you provided, looks like the original design load was higher than that. I will double check tomorrow and let you know my finding.

But, as pointed out by BA, $$$ is the main issue here (not me, the owner .

 

[kslee1000]

More questions here.

1. Is there a column above to column that is to be removed.
2. What is material of the bearing wall?
3. What the bearing wall supports, roof structure, or another floor?

Be prepared, this project is not simple. Everything has to started from ground (Foundation) up.

 

[rfd23]

kslee,
let me scan my background load calculations and put on this forum.

 

[rfd23]

find attached file for basic load calculations.