Steel beam design where brick wall is removed. 8

[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.

 

[PEinVA]

No. The E does not change for the grade of steel used. It looks like your stuck around L/420 huh? If you can use a 10" deep member you will definitely have no problem getting it to work.

Try designing your own beam made of plates maybe?

The masonry is existing right? Is your L/600 load include the brick? Where does the 2220#/ft come from?

RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[jike]

Tell the Architect that a soffit would really look nice at the lintel!

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.

 

[PEinVA]

Not sure what of your load is DL and LL but, you only need to count LL for L/600 limits. In our office, we've also used a maximum limit of 0.3", but that is for longer spans. Maybe if you only counted your LL, a W8x67 (a column section) would work.

civilperson. He stated it was in place of an 8" wall. If you look at the W8 sections, you wouldn't be able to fit 2 beams into this area next to each other. What is the steel beam connecting too? Or is it just bearing in a pocket? You may be able to count on some stiffening from the connection and this may also reduce your deflection.

If you are a member of AISC you can search for papers about this topic.



RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke

 

[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?

 

[tngolfer]

The 0.3" deflection limit is from ACI 530 (masonry code). It will control for spans over 15'. This will be your limit, not L/600, so you actually need a higher moment of inertia than you originally thought.

 

[tdsull]

Can you install 2 beams that are independent of one another. Make the stiif one carry all the exisitng brick and a second to handle the new load with your normal deflection criteria.

 

[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.

Mike McCann
MMC Engineering

 

[tngolfer]

Is the composite section shown in the attachment an option?

 

[csd72]

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

 

[fasboater]

You could have your beam cambered..

 

[ronster]

"You could have your beam cambered.."

A cambered beam beam will deflect as much a a non cambered beam, just starting from a different point. Also a cambered beam will initially only support the brick wall at the mid point. I would not recommend it.

 

[ronster]

Any reason why the beam can not be upset so that it is above the second floor? If it has 8" of brick above the entire length of beam you should be able to go above the floor depending on the low roof condition/detail. Or you might want to consider adding a seperate beam to pick up the second floor load.
What keeps the water from running down the 8" brick exterior bearing wall and going into your new room? Also, it will be difficult for the contractor to shore the wall to install the beam. You might want to consider removing the entire brick wall and replacing with a stud bearing wall with brick veneer above the beam.

 

[csd72]

how can the beam be upset if it doesnt have any feelings?

 

[ronster]

"Not sure what of your load is DL and LL but, you only need to count LL for L/600 limits"

This not true. You do not need to include any load applied to the beam before the brick is installed including the beam weight but any weight including the weight of the brick should be used towards the l/600 calculation.

 

[whir]

I agree with csd72. The masonry will distribute loads to the supports of the beam. Then, the load that the beam is carrying will be that applied within a triangle from support to support half the height of the beam span.

 

[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.