Cutting hole in existing CMU wall

[JStructsteel]

Cutting an opening thru a wall, replace with wide flange beam. Bearing checks out on wall, will have them reinforce cells at the end. As for the strip footing, how much would you let it spread out? Even though the wall is removed to the left of the new edge, obviously the remaining wall will transfer load down. Customary 45 deg conservative? I know a point load on top of a masonry wall will transfer load down over an opening, why not to a footing?

Obviously the load to the right of the new opening will still be there, so have to make sure my new load does not over stress that portion too.

Hopefully you can follow what I am saying!
Thanks

 

[KootK]

I've no doubt that the load will distribute to some degree but I think that it's a more complicated animal than it is when the load is able to distribute symmetrically. Obviously, the centroid of your soil pressure needs to coincide with the controid of your applied loads. Otherwise, it's hard to lay a claim to the whole "engineering" thing. I'd be inclined to study the nature of the adjacent wall system, including the location of any control joints, and then apply some judgment from there. Another approach would be to see if the wall segments on either side of the opening could lean into one another for stability, putting the remaining block over the opening into axial compression. Along with that would come the usual considerations for equilibrium and thrust resistance.

 

[msquared48]

If you know the size and shape of the strip footing and any stem wall, you may be able to span out the end loads of the wide flange further than 45 degtees if you know the reinforcing in the strip footing, just using beam theory. May also be able to increase the allowable bearing pressure locally with input from a Geotech.

If all else fails, underpin.

Mike McCann, PE, SE (WA)

 

[JStructsteel]

Thanks, the loads are not huge, and there is excess bearing capacity. The stem wall is about 3' deep, so distribution is likely. Also, as Mike said, the beam bearing will distribute down the wall too even more than I assume.

 

[XR250]

Def. alot of judgement required here as KootK intimated. The flanking walls will act as a rigid body and tend to turn the point load into a triangular footing pressure. I also agree that the masonry above the opening will tend to prevent this from occurring.
In my experience, masonry performs alot better than the numbers would indicate.