Comparable in Steel

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  #1  
Old 02-28-13, 12:05 PM
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Comparable in Steel Beam

I am doing some work in my 7' high basement (actually trying to make some more useful space) and am in a situation where there are 3 3x10 joists together 20' long holding up the 8" floor joists above. There is also a brick column in the center so in actuality its like they span 9' on each side. I want to do away with this obstruction by cutting the supported floor joists with 3/4 space and install a T or a beam with one flange cut off so that the wood joists now sit on the flange, is this something that is done or am I looking for trouble?

I was thinking about using a a W8 x 40 or W8 x 48 wide flange beam(with the top flange cut off) giving the wood joists about 4" to sit on. Is this overkill? What would have the same strength in steel, to the 3 3x10 wood beams sistered together?

All comments, help and suggestions are appreciated.
 

Last edited by zizanio; 02-28-13 at 12:37 PM.
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  #2  
Old 02-28-13, 12:39 PM
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Can't determine the feasibility until we know a few more things, such as the applied loading, and the length of the proposed steel beam (perpendicular to the 20' joist span). And keep in mind it will require a serious effort to snake a W beam into position, making an access hole in a foundation wall and coming in from one end--even just a 12-footer will weigh almost 600 lb. If you're asking the steel to span a considerable distance, you may well need something stouter than a W 8 x 48. Don't even think about making a T-beam by removing the top flange of a W-beam--an inverted T-section, while much easier to lift into position from the bottom, would typically not be strong enough to resist heavier loads without excessive sagging (unless the flange was built up with an adequately-sized cover plate).
 
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Old 02-28-13, 12:50 PM
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Thanks BridgeMan45

The length of the proposed steel beam I need is 9 feet. The applied loading I am not sure of but as I said earlier, there are 3 3x10 wood beams there now.

Can't determine the feasibility until we know a few more things, such as the applied loading, and the length of the proposed steel beam (perpendicular to the 20' joist span)
 
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Old 02-28-13, 01:03 PM
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Often times these issues are best addressed by having a structural engineer on site.
 
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Old 02-28-13, 01:28 PM
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All right. After reading your initial post again, I think I see what you want to do (but still am slightly confused). What you initially called "joists", composed of triple 3 x 10s, is actually a beam running the full 20' length, supporting joists above it. Presently supported at mid-span by a brick column. Which you want to eliminate, yes? Or do you, because that would mean your new steel beam would need to be the same length as the total run of the built-up wooden member presently in place. That being 20', not the 9' you just mentioned.

Am I close to being on the right track?
 
  #6  
Old 02-28-13, 01:37 PM
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Yes Bridgeman45, you are almost on the right track.
Lets just say I want to replace a 9' (not the whole 20') long wood beam composed of 3 3x10 wood beams running perpendicular to the floor joists above by installing a heavy wide flange steel beam with the top flange cut off for easier installation.
 
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Old 02-28-13, 02:22 PM
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If you are determined to use an inverted T for the replacement beam (despite my best efforts suggesting that you don't), you should give serious thought to purchasing a rolled section of the required section modulus, in that configuration, rather than trying to cut off the top flange of a W beam. The reason being that significant distortion of the remaining member will occur when you try burning off the flange. The contraction taking place following flame-cutting will warp and twist it, and will also cause significant sag in the finished product. Unless you possess heat-straightening skills far greater than the average DIY-er, you will be in for a head-ache of nightmare proportions.
 
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Old 02-28-13, 03:47 PM
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Rolled section?
I dont understand. What do you mean by rolled section? Do they sell a wide flange beam with one of the flanges already sawed off? How can I make the one flange beam stronger to fit my application?
 
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Old 02-28-13, 05:09 PM
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I'm referring to structural tee sections, produced in rolling mills by cutting a W-beam exactly in half, longitudinally along the web. I suspect most mills currently use plasma cutting, which generates very little heat and practically no distortion. Not sure about availability, as I think the demand for same has gone down considerably, from when they were more common.

As others have suggested, hire an engineer to design the member you need before you start shopping around. He/she can come up with the most economical size, along with designing a cover plate that won't require out-of-position welding.

But I still don't understand how you plan to replace just 9' (with steel) of a 20' wooden beam--web splices? Another thing to consider would be using an LVL beam, full-length. I suspect using one would be less expensive than going with steel, especially since you wouldn't need an engineer to design it for you.
 
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Old 03-01-13, 02:40 AM
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But I still don't understand how you plan to replace just 9' (with steel) of a 20' wooden beam--web splices? Another thing to consider would be using an LVL beam, full-length. I suspect using one would be less expensive than going with steel, especially since you wouldn't need an engineer to design it for you.
I am sorry if I am making it a bit difficult to understand, lets try this one more time.

I have 3 3x10 wood beams joined together (so its like having a 10"x10" wood beam) that are 20 feet long running perpendicular, under the floor joists on the 1st floor.

In the center of this 20 foot run, is a 2' brick column that was built so now whatever load there was on the 20' long span just got divided into 2 sections of 9' each, right?

Here's the good part.
I am building a cmu wall underneath this long 20' 10x10 wood beam to support all but about a 9' section and being that it comes down 10" from a short basement ceiling, I want to to replace the 9' 10"x10" wood beam section with a steel T inserted in between the 2 sides of floor it supports. I will support both sides of the floor joists above, cut about 3/4 of an inch, and slide the steel T in, then remove the suppports.
So my question is, and as the title of this post reads, what would be comparable in steel to the 9' long 10"x10" wood beam? How strong is a 9' 10"x10" block of wood? What is comparable in a steel T? All posts here are much appreciated.

I have added some pics to clarify things.
 
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Last edited by zizanio; 03-01-13 at 03:07 AM.
  #11  
Old 03-01-13, 11:30 AM
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I just got another idea.
Why not, instead of cutting the top flange of a wide angle beam, get 2 8x4 x 1/2" or better yet 8x4x3/4 inch angle irons back to back, and bolt them together after I install them one at a time?

Less waste than asking the supply house or fabricator to cut a flange off the i-beam, I would wind up paying for the cut peice anyway and pay for the cutting.

If I do the angle iron idea, all I need to do is have the supply house punch 4 or 5 3/4" holes into the 9 or 10 foot span and then bolt them together once i install them.

As always, all comments are appreciated.
 
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Old 03-01-13, 11:44 AM
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Finally. Ten posts into the thread before sharing with us the CMU wall you are building (to support the wooden beam on either side of a new steel member in the center). Better late than never, I guess.

Guessing your beam is composed of some decent material (pix look like solid, old growth), I assumed a unit bending stress of 1600 PSI. Computing a bending moment for that over a 10' span (another assumption, thinking you will have 9' clear opening), it works out to a tad more than 171,000 in.-lb. Assuming you'll use a mild steel member with allowable bending stress of 24 kips per sq. in., you'll need something with a section modulus (S) of 7.13 cu. in. The AISC steel manual shows a WT 7 x 54.5 will work, with an S of 7.56 cu. in. Good luck in getting it up and in there, as it will weigh 545 lb., and the bearing ends of your new block wall are going to be in the way.

Also, you should give some serious thought to removing the rats nests of loose wires you have hanging everywhere--good chance of self-strangulation one of these days.
 
  #13  
Old 03-01-13, 12:40 PM
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Thanks for the post bridgeman, I am now starting to seriously consider the 2 angle iron idea for more strength and ease of installation. Also, I never said anything about a wooden beam on either side of a new steel member in the center, I am looking to remove the 10"x10" wood beam.
 
  #14  
Old 03-01-13, 12:50 PM
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The AISC steel manual shows a WT 7 x 54.5 will work, with an S of 7.56 cu. in.
Also, whats a WT 7 x 54.5, I cant find it on the steel beam specs anywhere?
 
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Old 03-01-13, 06:34 PM
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It's a structural tee, made from exactly half of a W 14 x 109, by cutting the web as I described earlier. Look on Page 1-58 of the AISC Manual, 8th edition, or Page 1-62, 9th edition.

Regarding your comment in Post 13, I'm not sure what you're smoking, but I suspect it's not legal. In Post 10, you said "I am building a CMU wall underneath this long 20' 10 x 10 wood beam to support all but a 9' section . . . ." To me that means a wall is going to be built under the wooden beam, yes?

"Angle iron" won't work, as it's too soft (you'd need 1000-lbs. worth), and also is no longer available. A double steel angle would work, but not 8 x 4, as 8" legs are too tall to fit at the sawn ends of your 8" joists (unless they are true 8", and not 7-1/2"). A double 7 x 4 x 3/4 has a combined S of 16.8 cu. in.
 
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Old 03-01-13, 10:44 PM
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I never said anything about a wooden beam on either side of a new steel member in the center, I am looking to remove the 10"x10" wood beam.
That wood beam is holding your house up, and has been for as long as it's been up. Why would you want to remove it?
 
  #17  
Old 03-02-13, 01:39 AM
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That wood beam is holding your house up, and has been for as long as it's been up. Why would you want to remove it?
Yes, you are right, its been sitting on top of the original stone rubble foundation wall for about 100 years.

One of the reasons I want to replace it with steel is to get more headroom, this wood beam protrudes 10 inches from the 7 foot ceiling. Another reason I want to replace, it is because it does not sit square in the room and we are finishing the basement and will be spending time there, there is a 19" difference in a 20 foot span.

For the headroom. I want to replace it with steel that is installed something similar to a header, not underneath the floor joists. After the installation I don't want to have any protrusions from the ceiling. I figured installing steel and having the floor joists sit on the flange would be less work than installing an lvl beam and nailing joist hangers.
 

Last edited by zizanio; 03-02-13 at 02:33 AM.
  #18  
Old 03-02-13, 03:27 AM
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In Post 10, you said "I am building a CMU wall underneath this long 20' 10 x 10 wood beam to support all but a 9' section . . . ." To me that means a wall is going to be built under the wooden beam, yes?
The wooden beam will be removed, the floor joists cut about 1 1/2" and a tee or more than likely a double steel angle (8x4) will be installed using the 4" leg for the joists to sit on. I like the angle steel idea better because I wont waste any steel.

I just measured the unsupported span again to be closer to 100", thats a bit over 8'.

"Angle iron" won't work, as it's too soft (you'd need 1000-lbs. worth), and also is no longer available. A double steel angle would work, but not 8 x 4, as 8" legs are too tall to fit at the sawn ends of your 8" joists (unless they are true 8", and not 7-1/2"). A double 7 x 4 x 3/4 has a combined S of 16.8 cu. in.
I meant to say angle steel. The joist are 8" and not 7 1/2", if I use the 8 x 4 x 1/2" angles, I have a 7 1/2" sitting height and that looks to be good.

If I use double 7 x 4 x 1/2 angles, the center would be 1" thick and the legs 1/2" thick, would the 1/2" leg thickness be adequate or would I need a cover plate?

Will the 4" leg that the floor joists be sitting on strong enough or will I need to have a plate welded to the bottom, I think its called a cover plate?

If I decide to do the 8 x 4 angles, is the 3 1/2" sitting area where the wood joist will sit enough? I'm thinking yes because wood hangers have less sitting area.

Also, don't the double angles need to be joined together mechanically and/or by welding? And if so, how where would they be bolted and welded?

Another question I have is how much steel needs to be sitting on foundation?

I've attached some pics of the holes that were sawed open when they built the house 100 years ago about 2 feet away from the foundation where the wood beam sits to pass 1 1/2 inch heat pipes, they measure over 3" maybe 3" big, didn't this affect the strength of the wood beam? If the holes were not opened could they have gotten away with less of a beam?

Thanks everyone for the postings, I really appreciate it.
 
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Old 03-02-13, 07:35 PM
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I never said anything about a wooden beam on either side of a new steel member in the center, I am looking to remove the 10"x10" wood beam.
One of the reasons I want to replace it with steel is to get more headroom, this wood beam protrudes 10 inches from the 7 foot ceiling.
Here's the good part.
I am building a cmu wall underneath this long 20' 10x10 wood beam to support all but about a 9' section and being that it comes down 10" from a short basement ceiling, I want to to replace the 9' 10"x10" wood beam section with a steel T inserted in between the 2 sides of floor it supports.
Originally Posted by BridgeMan45
I'm not sure what you're smoking, but I suspect it's not legal.


Would you like to clarify your plan?
 
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Old 03-02-13, 10:21 PM
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Why not simply cut the ends of the joists to create a gap just wide enough
to slide three 2x10 glulam beams up in between and then install joist hangers?


.
 
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Old 03-02-13, 11:32 PM
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Would you like to clarify your plan?


I want to do exactly what Halton is saying and is shown in the photo below, except instead of using the three wood 2x10 glulam beams as he is suggesting, I want to stick a double steel angle in there.



Why not simply cut the ends of the joists to create a gap just wide enough
to slide three 2x10 glulam beams up in between and then install joist hangers?
 
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Old 03-03-13, 10:19 AM
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Why do you want to replace the entire length of the existing beam instead of just the part where you will have the walk-through? Is that because the beam isn't exactly square to the space?
 
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Old 03-03-13, 11:36 AM
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Why do you want to replace the entire length of the existing beam instead of just the part where you will have the walk-through? Is that because the beam isn't exactly square to the space?


Because it hides some of the natural light that comes from the window behind it.
Because it protrudes 10"+ from the ceiling.
Because it is not square to the room.
Because there is wood sections rotting.
Because I feel brave enough to do it.
Because I found a steel supply store near me to buy at wholesale prices.
Because I found a steel fabricator even closer (walking distance) that can cut, weld, punch holes and do any other preparation I need for peanuts and they will sell the steel at supply house prices.
Because I am remodeling the whole basement (first time in 100 years) and I don't want to regret that I didn't do it after I finish.
 
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