Steel beam design where brick wall is removed

#1

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QUESTION

BRENDANF
I am opening up an existing 8" brick exterior wall to 16’-6" for a room addition. I need to keep the ceilings flush and the depth of the floor joists above is 9.25", so I am limited to about 9" for the new steel beam depth. I am figuring the load on the beam to be to be 2220 pounds/foot. The question is if I use A-50 steel instead of A-36 steel does the “E” number, 29,000,000 change between the 2 different grades of steel? I am having problems with deflection–l/600 for masonry

REPLIES

jike
How about using an W8 with side plates? or a W8 with cover plates?

BRENDANF
The loads come from, 300# from the floor above, 630# from the brick wall above the beam, 550 from a new flat roof, 540# from the pitched roof above the second floor, and 180# from the attic above the second floor.

I’m thinking I can change the direction of the new flat roof rafters and I can omit their load from the beam design. If I do that I’ll have a design value of I of 288 in4. Additionally, if I install a 4x12x1/2" steel tube on the existing exterior of this 8" brick wall and a 4x8x1/2" steel tube on the interior of this brick wall with a 1/4"x12" steel plate shop welded to the bottom of the 4x8x1/2" tube, I can then field weld the 1/4" plate to the 4x12x1/2" steel tube.

I am thinking that this would make the installation of the beam relatively easy. What do you think

civilperson
Two beams will have double the I of one beam. Pair up the supporting beams and cut deflection in half.

faromic80
First I would try using a cover plate and see how close to L/600 or .3 I could get.

tngolfer
I wouldn’t count much on the connection. I keep your pin-pin design going. I tried checking a W8 with a C8 welded to both the top and bottom flanges since you have 9" of depth to work with. You could use the transformed section but the largest beam you could use is a W8x21 (bf=5.27") to fit into a C8x18.75 (T=6.13").

What if you installed a beam at a floor above to relieve some of the load on the lower floor?

msquared48
What about adding an HSS section to either side of the web of the beam - like an HSS 6X3X1/4 - one that would fit between the flanges, and calculating the composite section I to reduce the deflection ratio? Doesn’t sound like you need much more at L/420 already.

csd72
Have you taken brick arching into account from the floors above? This may reduce your loads somewhat.

BRENDANF
This opening is happening at a corner of the building. The extertior walls are 2 story, 8" brick walls with furring and plaster. Can I still do the arching effect of the masonry? Or only consider arching on one side of the beam? Thanks, your responses have been enlightening.

KootK
You can probably do one sided arching if you’ve got some meat on that side of your opening.

I’ve used a slick detail using two channels. Place on on either side of the brick above the opening, through bolt them together, and connect the bottom flanges with a steel plate (continuous or intermittent). That way you don’t use up any soffit depth.

Of course, the channels will be exposed to view so you’ll need architectural approval for that. You might also neeed to find a way to deal with water migrating in from outsite. I think it looks cool. I’m hardly impartial though…

ronster
You can not have arching on one side of the beam. Arching causes an equal lateral outward thrust on both sides over the opening. You need masonry beyond the opening on both sides to resist it. Also any windows could interfere with arching. I would not depend on arching on such a large opening at the end of a wall.

I often use the double channel Adam suggested. If you cut a horizontal groove into the the brick you can turn the channel leg in towards the wall into the cut and have the channel directly support the wall without need for shoring.

Make sure you alert the architect to the water problem as it will be a problem.

BRENDANF
I took the new flat roof load and the floor load off the beam, and plan on using a W8x48 with at 1/2" steel plate welded to the bottom of the beam.

Thanks for your help!

#3

I’d typically use a couple of 10" channels x 20’ through bolted on either side of the wall as a needle beam. I would then install a W8 lintel after cutting out the masonry below the needle beam. I’d grout in bearing plates at each end. I’d limit live load deflection to L/720 and place the new W8 with the natural camber upwards and weld it to the bearing plates. Patch and grout as required…

Done like a turkey…

Dik