Transfer of End Reaction of Beam to a Load Bearing Wall

[sithlord382]

Hi All,

I think this is bit of an easy one but could definitely use some advise.

What is the correct way to take into account/ calculate the transfer of a load from a beam, onto and down a load bearing wall and subsequently into a foundation?

I have a steel beam with an end reaction of 25kN, this beam is sitting on a load bearing wall which is 3m high. What is the best approach in allowing for that end reaction of 25kN in my wall load take down calculation when working out the load exerted onto the foundations? Theoretically I am fully aware that the 25kN end reaction will transfer into the load bearing wall and down in a 45degree line. However it doesn't just disappear into the wall and not get transferred down into the foundation. When I am calculating the size of the foundation based on the loads from above, how to I allow for the beams end reaction?

Also what approach would you take for a higher load eg. 200kN or a higher wall eg. 8m?

Kind Regardss,

S

 

[phamENG]

Depends on the wall. Is it a wood stud wall? Cast in place concrete? Masonry? If masonry, is it stack bond or running? Each has different load distribution characteristics.

 

[sithlord382]

Hi phamENG,

The wall in question is a 100mm thick blockwork wall so i have assumed a dead load of 2.4kN/m^2, which I have multiplied by the height of 3m to work out the load take down of the wall itself.

Its more about including the end reaction of 25kN which I am stuck on.

Thanks,

S

 

[jayrod12]

Agree with phamENG, it really depends.

To elaborate on his list:
Wood wall - load transfers straight down so you need to provide a column in the wall and something below it at the foundation level

CIP Concrete - Load spreads as it goes down and gets added to the total load at the bottom of the wall. For concrete walls with no openings load spreads at roughly 45 degrees, therefore in your current example at the bottom of the wall the point load adds approximately 4.2 kN/m.

Masonry wall - depends on stack bond or running bond, stack bond goes essentially straight down. Running bond you get a load spread as indicated in your applicable masonry code.

Higher loads, higher walls, etc. all need to be addressed in a case by case but the basic concept is the same. Just note that often masonry codes have a maximum width of spread regardless of stack bond or running bond, so a tall masonry wall doesn't necessarily allow you to spread the load significantly further than a shorter wall.

EDIT: I see you indicated masonry, so the next question is stack bond or running, then which masonry code. Take a look in your masonry code for load spread. Also with masonry pay attention to the bearing stress since how the load is delivered to the wall could affect the allowable bearing capacity.

 

[sithlord382]

Hi jayrod12,

Many thanks for your reply. Following on from my previous response I can confirm that the masonry wall will be running bond and I am looking to use 7.3N/mm^2 blockwork.

Forgive my ignorance but I have been using BS-6399 Part 1 for working out load chase downs. I take it I need to have a read of BS 5628

Thanks,

S

 

[jayrod12]

No problem. I am completely unfamiliar with those codes, but I would assume somewhere in there is something about concentrated loads on masonry walls.

 

[JoshPlumSE]

This is actually a great exercise for young engineers. It's a simple load path issue, but it requires them to really think about it and how their though process changes for different materials.

For Concrete (or fully grouted masonry), I spread it out in 45 degrees or so. Then it gets turned into a distributed load where the centroid of the distributed load coincides with the load point. My tendency is to do this with a running bond as well (even if it's ungrouted). But, I'd want to review the code sections on load spread first.

For Cold Formed or Wood Walls, I make sure there is a stud directly below the load point which takes it all the way down to the next floor or the foundation. If the load is not that high, I probably could spread it out a little at each floor level. But, if it's a large load, the I make sure there are studs all the way down.

 

[dik]

A 4" wall with a height of 10' might be pushing it a tad...

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

-Dik

 

[KootK]

1) I do the 45 degree spread with running bond too. Obviously, it's not super scientific.

2) Spreading out point loads in this way such that they present themselves as line loads at the foundation is a common thing to do to avoid the need for discrete, isolated footings. It's a particularly useful technique when dealing with renovations and existing footings.

3) With masonry, be cognizant that there maybe vertical construction / contraction joints present in the masonry. The presence of such joints will affect your assumption about the load distribution in some cases, particularly if you're being aggressive with it.

4) Like dik said, a 4" wall is not exactly a beefy element. In addition to the wall capacity, you might give some thought to whether or not you can really make a robust connection between the wall and the beam. At 4" thick, and likely solid units, you won't be able to grout in anchor bolts or anything like that. And it probably won't be feasible to bolt a connection to the face of the wall. My guess is that you'll want to run the beam through an opening let into the wall and grout that opening in solid and/or make use of a padstone to distribute the beam reaction a bit locally.