Tributary Area method 1

[Usman3301]

Hi there,
I am a trainee and was assigned a task of designing wall footing. My senior told me to use "Tributary area method" for load calculations for this specific task. He gave me a list of formulas for various cases such as transfer of load from slab to "Exterior shorter beam, Exterior longer beam, Interior Shorter beam and Interior longer beam". For rectangular and square slab section, these formulas are quite easy to use. But in cases where slab section isn't rectangular anymore, I don't know how to distribute load in order to get approximate results.
I have attached a pic below, in which I have to design wall footing, for bath walls as well. Kindly help me in understanding how this method works.
I have highlighted walls for which I am having difficulty understanding load distribution.
Here's the link

https://files.engineering.com/getfi...7c80-41f6-a8cb-badde53da141&file=eng-tips.png

 

[r13]

I assume the drawing shown is the first floor plan, that shows wall discontinuous at (door) openings, and you need to calculate the wall load transferred to the (strip) footing below. The linked sketch shows how the wall/strip footings would look in the plan. You should modify to fit the actual layout. Link

 

[BAretired]

The walls outlined in blue are probably non-bearing walls (or partitions) and probably don't have a footing under them. Ignore them and use an appropriate partition allowance in your dead load for each floor.

@retired13,
looks like your link has expired.

BA

 

[r13]

BA,

I stored files on cloud services, have no clue why it will "expire". I think is the access problem, and have to find another way to do it.

 

[r13]

Usman,

Don't let the door openings fool you, all walls are continuous right below the roof deck, and most likely can be assumed continuous on the load calculation for footings.

 

[BAretired]

retired13,

The following is what appears on my screen when I click on your link.

This XML file does not appear to have any style information associated with it. The document tree is shown below.
<Error>
<Code>AccessDenied</Code>
<Message>Request has expired</Message>
<X-Amz-Expires>300</X-Amz-Expires>
<Expires>2020-04-12T21:07:45Z</Expires>
<ServerTime>2020-04-12T22:26:13Z</ServerTime>
<RequestId>1BB55E450536DB25</RequestId>
<HostId>
mmvQRFc2ZOtrRrOHJbjc+qLz2jW63FBUSMg6n3qz/WViC8C73UnsakAXzCpOBJaQJpQS22Dos60=
</HostId>
</Error>

BA

 

[r13]

BA,

Thanks. I need to find another way to store files on the web without limits on public access.

 

[r13]

BA,

Thanks. That site is awesome. It seems more and more people have the same problem. Just see JoshPlum on another thread complaining the upload.

 

[msquared48]

Great idea BA!

Mike McCann, PE, SE (WA, HI)

 

[Usman3301]

Thank you so much "Retired13" and "BAretired" for your response.
@retired13
I can't access the link you attached as a reference. As mentioned by BAretired, I am getting the same error.
So what approach should I take? If I am to consider bath slab to be depressed 6 inches, then I can't consider master-bed slab and bathroom slab as one panel. And this is where I am having problem.
I am attaching preliminary foundation plan and section as well. Kindly help me out in understanding this load distribution. And it would be great if you can give insight to how to handle these situations better or any better alternatives, I am all ears.
Foundation-

https://files.engineering.com/getfi...ce-4add-a350-b398a1209010&file=foundation.JPG

Ground floor-

https://files.engineering.com/getfi...-97b7-845b3c2a4a8b&file=Ground_floor_plan.JPG

Section-

https://files.engineering.com/getfi...-1ad8-4692-ada4-0b89da367686&file=Section.JPG

 

[r13]

Usman,

Sorry for the bad link, try this one. Please follow the simplification on the foundation plan to calculate tributary floor load to the walls. Note for the irregular areas shown, distribute the total area load to the total length of the border wall. Due to aspect ratio, you might get some trapezoidal areas instead of all triangles as shown. Link

 

[Usman3301]

Thank you Sir for helping me out in this. I am grateful to you for being so helpful.
Your markings on the plan have simplified the whole problem for me.
Have a nice day

 

[r13]

Glad to be helpful.

In the future, do not afraid make simplifications, such as make walls with small offset a straight line, draw 90° lines in places of round corners, or chamfers. The important thing is all floor areas are accounted for, and distributed to the nearest wall, or support. The rewards of simplicity is increased efficiency, and making fewer mistakes

Also note, ignore non-load carrying partitions (walls stop below the upper level slab) in floor load distribution, but include these partitions' weight as concentrate load on the walls they attached to.