Replacing damaged lintels in masonry building

[mfstructural]

I am currently looking at a building where our client needs to replace a portion of the lintels. It's a 3 wythe masonry building The original lintel was constructed of a steel WF beam with a plate welded to the bottom. The interior portion of the lintel is intact, with no corrosion. The outer portion of the lintel, including a portion of the bottom flange of the steel plate supporting the outermost wythe of brick is heavily corroded. The plan is to cut off the corroded portion of the plate and also a small portion of the flange that is corroded and place a steel angle across the opening. There are 2 different sizes of openings on the building, 5' and 9'-6". A L5x3 or L6x4 would work for the 5' opening. The issue is with the 9.5' opening. I'm thinking of placing a L6x4x3/8 angle across this 9.5' opening and welding it back to the web of the original lintel with 6" long L4x4 angles at 24" on center. This will prevent the angle from rotating and then I will be able to use the full strength of the angle. There is approximately 5' of brick above each 9.5' opening, except at the parapet where there is about 8' of brick over the opening. Any other recommendations? How have others approached repairing damaged/corroded lintels in the past?
thanks

 

[ACtrafficengr]

We had an over-height piece of equipment tear out the lintel on our vehicle service shop, and had to replace it and all the masonry above it up to the parapet, so your problem is trickier, but not as bad, I suppose.

Could you post a sketch of your proposed repair? I can't quite picture it.

When you cut off the plate and bottom flange, will you have to deal with a stiffness loss causing cracks in the masonry above it?

 

[SLTA]

How old is the original steel? Welding new to old can be messy. It may be simpler to just replace the entire lintel.

Please remember: we're not all guys!

 

[mfstructural]

I did think about replacing the entire lintel, but it gets messing as it's cold out and the interior finishings would be damaged and would rise up the overall cost of the project. If it gets to that point, might have to do that, but for now I'm trying to see if I can get something to work. The building was built in 1915. I've attached a detail of what I'm thinking, I know it's a little clunky. Another alternative is tapping into the steel and installing a rod of some sort

 

[KootK]

I know it's a little clunky.

Yeah. I worry about the flexibility inherent in that daisy chain of angles.

Could you have a new bottom plate welded on, assuming that the existing is weldable?

It would be great if you could corrosion protect the system for the future somehow but I realize that's a tricky thing.

Another thing to consider is that, no matter what you do, pretty much all of the load is likely to remain on what's left of the existing beam. I'm assuming that there's tie courses in the masonry every so often.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[dik]

Can you not through bolt a couple of channels, one on each side over the opening and remove the existing beam and replace it with a W6 or W8, with a bot plate similar to the existing and then remove the channel sections?

Dik

 

[JedClampett]

Don't forget to address the underlying issue, which is probably poor drainage in the gap. If you look at the Brick Industry Association Technical Notes 21B, you'll see details on how to flash the gap and provide weeps between the CMU and the lintel. You can keep water away from the steel, but it takes some picky pain in the neck details.

 

[mfstructural]

Welding a plate to the existing WF would be difficult regardless of steel as there is a window there. Welding too close to the window is also a challenge because many of these masonry buildings have wood framing and a wood timber inserted over window at the inside face of masonry and they are combustible. Yes, I would definitely specify Heckmann type anchors in addition to a header course to tie it together.

dik, how would the load from brick be transferred to the channels temporarily? I'm not picturing it.

As for Jed's comment, adhesive flashing with a termination bar and proper edge flashing and weep blocks will definitely be specified. it's amazing how they never used flashing for water mitigation back then.