Point load on brickwork cracking

[John1967778]

Hi guys,

Are there any limits as to how close you should have openings to point loads on brickwork walls? I've looked through the Australian standards and can't seem to find any information in regards to how close openings in beickwork can be to the 45 degree spread of load from a point load.

I've got a case where large cracks and displacement has occurred besides a door opening to brickwork. Approximately 1meters away the wall is supporting an ibeam which is supporting upper story brickwork and a portion of the flooring and roof (double story house).

At this stage Im thinking the cracks could have been caused by either ground movement or a structural failure of the brickwork. I've attached some photos of the crack. Any thoughts would be much appreciated. Cheers

 

[JoshPlumSE]

There are some discussions in most masonry texts (I would think) about how the spread of load won't occur if your wall is not continuous for a certain length. Essentially, the spread of load also induces a lateral thrust that must be restrained / confined. But, this opening prevents that lateral restraint.

 

[dik]

What sort of support for the brick wall and what is the magnitude of the load?

Dik

 

[oldestguy]

Are there any chances it is due to temperature changes, such as where the sun shines? I'd expect some sort of expansion. Support problems usually have signs of tipping with varying crack width.

 

[John1967778]

The beam is supported on single brick wall with a pier(single brick 110mm thick).

Point load around 50kn

 

[hokie66]

Not answering your question directly, but the movement appears to be lateral, not vertical.

 

[John1967778]

My initial thoughts are is that it has been caused by the lateral thrust produced by the point load. Can't see how it could be ground movement as there are no trees, surrounding soils or water intrusions that could lead to ground movement.

 

[hokie66]

No way to tell without further information about the structure. But single skin brickwork is a very brittle material.

I assume the beam in question is the one on the left of the picture. My guess is that the beam has been rotated by unbalanced loading from above, and that movement has pushed the upper part of the single skin brickwork to the right. Just use a short spirit level on the beam to check my hunch.

 

[John1967778]

Thanks hokie. Wouldn't that be the same as just moving the point load slightly to the rotated point?

 

[hokie66]

Not sure I understand your question. I think you may be focusing too much on vertical point loading. What I am suggesting is that the steel beam may have rotated (clockwise in your photo), and thus the wall it is supporting has moved to the right. You will have to make a determination on site as to whether I am guessing correctly.

 

[dik]

any chance the support has failed?

Dik

 

[John1967778]

Ahhh my apologies Hokie, that steel beam is being supported by the brickwork that has cracked.

Dik, given the proximity of the door opening to the point load, I believe it may be stopping the lateral thrust from forming in the brickwork.

 

[hokie66]

Douglas,
I understand the beam is supported on the brickwork pier. But I doubt the opening has contributed to the movement of the beam and the wall above which is supported by the beam. The opening just defines where the crack started, but the main issue is rotation of the beam. If my theory is correct, neither the beam or the wall above will be plumb.

 

[John1967778]

Thanks Hokie. The beam hasn't rotated ( confirmed with spirit level just now). Getting a plumbing report done for the pipework within close proximity to confirm that there are no leaks with could be causing localised movement to the supporting footings

 

[hokie66]

OK, sorry, that was my best shot. But the movement is certainly lateral. Look at how out of plumb that conduit to the light switch is.

 

[nonplussed]

In my opinion this has nothing to do with the beam load. The beam load is so small it wouldn't have any affect on the brickwork unless it was directly over the middle of the door opening and I don't think the cracking would be in that pattern.

Based on the photo I assume this wall is at the back of the Garage? Therefore I would suspect the cracking is from either:
a) Someone driving their car into the wall. This is most likely the case in my opinion, even if the owner denies it they may be trying to shift the blame onto someone else.
b) If the site is sandy then check for leaking water pipes or stormwater drainage on the outside of the wall. Check compaction along the wall for a length and see if there's a considerable drop in compaction adjacent to the crack. Also dig under the surface to check for moisture.
c) If the site is clay then possibly downwater pipes draining onto the ground adjacent to the crack, or similar problems.

 

[bridgebuster]

I stumbled on to this website a few years ago. It may have some helpful information for your situation:

Link

 

[KootK]

My initial thoughts are is that it has been caused by the lateral thrust produced by the point load.

I also think that there's a plausible story to be told along those lines. Add my sketch below to the idea heap.

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.

 

[haynewp]

It looks like there is a hairline crack above the main one and it looks like it steps up towards the top flange of the beam. I had to lighten the picture to see it. Look one brick above the conduit location at the upper bend. I wouldn’t think the vertical point load caused this movement.

 

[hokie66]

haynewp,
I think that is a TV cable or similar.