Unreinforced Brick Masonry Opening

[Rweave]

I am working on this building where they exposed the existing steel lintels that is supporting 12" wide unreinforced brick masonry x 4' high x 6' span opening. The existing steel lintels need to be replaced, so I am working on trying to come up with a plan to support the brick above the window while the lintel is removed and replaced.
Does anyone know about this unreinforced deep beam anaylsis? I figured why not use what we have on site and anaylize the brick to carry its own weight at the opening. I am very limited on time/material I can bring into this project. Since this wall is 12" thick there are (2) 8" beams side by side spanning this opening currently. But when the contractor went to remove the outer steel beam/lintel to confirm the condition of the interior lintel, he said that the exterior one slid right out like it wasn't even loaded. So this is telling me there is something else going on with the nature of the brick over this opening currently. So therefore I was looking into any input on this unreinforced deep beam anaylsis and if I can use this approach or not?? Thank you.

 

[concretemasonry]

You cannot use the job site reviewed performance of the existing structure.

You probably saw the "real" arching strength of masonry in a building that was sound for years and performed well without distress. Just the single half of an over-built (probably for appearance and convenience). One of the beams was carrying the majority of the loads for some time.

You will forced to make a redesign of the lintels according the the current methods even if the wall is not loadbearing.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[XR250]

I have never seen any contractor put temporary shoring on an opening of this size when cutting a new one or replacing lintels.
Certainly risky, but it is done commonly.
If you are worried about it, you can bolt a steel channel to the outside of the opening.

 

[Rweave]

Concretemasonry - I am replacing the existing lintels with new lintels for sure, that is not the situation. The situation is trying to come up with a solution to shore up the existing structural brick Masonry. That is what I was asking about using the Deep Beam anaylsis to count on the Brick to carry its own weight during the removal and replacement of new lintels.

 

[JAE]

If you have adequate masonry on either side of the opening, then you may be able to count on arching action of the brick during lintel replacement. There might be some brick directly above the center of the lintel span that would come loose and fall (the underside of the "arch") but those can be replaced once the new lintels are in place.

If you don't have adequate masonry on the sides of the opening (to resist the lateral thrust of the arch) then you would need to come up with a way to support the masonry above. We've used channels (per ExcelEngineering's comment above) and bolted them across the face of the brick on each side of the wall. We've also used straps hanging down from the channels with cut-in angles to help grab the masonry.

 

[concretemasonry]

In addition to JAE's good comments, determine if you have enough there to justify "arch action". This may make a difference in your design and construction controls of the new masonry above the new lintels. Since it is new construction, you may have to stamp the revision drawings.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[Rweave]

Thank you JAE and CONCRETEMASONRY for your replies. I will keep this information for the future for sure. It just so happened for this project after revealing the adjacent windows masonry above the lintels there seems to not be consistant running bonds. There was some misc infill brick and stacked bond masonry. So therefore I don't think I am allowed to take in account the arching action anymore. I am now looking into how to make this brick above the window into a composite section.

 

[concretemasonry]

Rweave -

If you look at the most recent masonry standards there is a mention of the term "running bond" that is now considered "other than stack bond" and it defines the typical amount of bonding to be considered to be "running bond" and ultimately get arch action.

In masonry, the structural element in not any of the individual materials or products and the WALL is the structural element.

The basis is because masonry testing and research for many decades has been based on wall assemblies, so the standards (ACI 530) are conservative and based on a myriad of different materials of different strengths and properties. Obviously, a rubble wall with high strength mortar and extremely strong will be difficult to define but the difference between different patterns (random, quarter bond, third bond, half bond) can be recognized.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.