Question on masonry load spread angle

[Josha456]

Hi,

I have a question regarding the general angle that should be taken to distribute loads through masonry for the purpose of designing structure lower down the wall. I have looked online but cannot find a specific reference to this, EC6 6.1.3 shows a 60° spread below a concentrated load, however this is a specific case that refers to determining the stress used to design the wall panel for buckling, in BS 5628 section 30 a 45° angle is used to perform the same calculation. This leads me to suspect that these angles are refering to this specific check rather than a general load spread.

The angle would appear to be either 60° or 45°, i wonder if the particular bond used is the determining factor (spreader bond might be 45° but english bond 60° to account for the header course)? this is just a guess.

I would appreciate your advice.

 

[dik]

There are several textbooks that show the 45deg (I don't know how to get the symbol) with one of them referencing the actual angle approaches 30deg from horiz. If you want confirmation, then this might be a time for a quick FEM model just to show the influence.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Agent666]

For specific point loads applied to the face of the wall from say an incoming steel beam, my local code suggests reviewing the axial and bending interaction over a wall length of 4 times the thickness (2t either side of the load).

But in terms of general load spread I very much feel this is left up to an individuals judgement. If uou were to model taking into account stiffness the spread may be much more than you think, which probably justifies simple angular estimates. Personally I think 45 degrees sounds reasonable and is in line with the arching action you might get on deeper lintels and the like.

https://engineervsheep.com

 

[WARose]

The Masonry Designer's Guide suggests a angle ranging from 30 to 45 degrees (off the vertical). I've typically used 30 (especially at the bond beam level) for vertical loads.

 

[Josha456]

Thanks for the advice

 

[JLNJ]

These angles are all for walls without interruptions. If you are near an opening or a corner, then the distribution needs a closer look.

 

[phamENG]

If you are near an opening or a corner

Don't forget expansion joint. Those interrupt it, too. Which is a reason they should be called out on structural drawings, but that's another discussion.

 

[Josha456]

If the masonry turns the corner without creating a vertical joint, how would this affect the angle?

 

[phamENG]

In reality it would wrap around some - if it didn't, then the walls would have to create a joint (crack) and deflect separately. In practice, any extra from that is ignored. I'm not sure that anyone has ever quantified it.

 

[Josha456]

not quite sure i understand why the load would not spread around a continous corner, would it not be similar to load spreading into the wall from a beam bearing on a nib?

 

[phamENG]

Like I said - it would. But for a number of reasons, we tend to ignore it. One, it's easier and faster. Two, it's conservative. Three, if you don't put a joint at or near the corner intentionally, the building will likely put one there for you.

I have no idea what a nib is. I see you're in England, so it's probably a regional thing.

 

[JLNJ]

If it “spreads around a corner” the resultant force will be in a different plane than the applied load.

 

[BAretired]

This could be of some help. Looks like an unsolved issue to me. Conservatism may be the best policy when determining the spread angle.

http://canadamasonrydesigncentre.com/download/10th_symposium/2c-4.pdf

BA

 

[HTURKAK]

This snap from BS 5628-1

And this is from BS-EN -1996-1

This snap is from Institution of Structural Engineers manual...showing the load path..

Regarding the load distribution at continuous corner, it would be similar to load spreading from corner to the both walls ..

My suggestion will be the use of angle producing conservative effect..