Structure analysts for bending moment

[neaveyoung]

Recently I want to calculate the base moment of one barrier. But I have some doubt find out the bending moment at the fix end for 1kN/m2 infill load. The object is standing 10 meter high with the length of 8 meter. Kindly assist for this simple structure analysts. Attached the sketch.

Many thanks.

 

[manstrom]

A is correct. There is a factor of 8 missing in B. You should be able to figure it out.

Back to basics. Turn the area load into a point load at the midpoint of the load. Solve for the moment.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[msquared48]

Just remember that this is the overturning moment at the base of the wall, not at the bottom of the footing, where you should compute it for the footing overturning.

Mike McCann, PE, SE (WA)

 

[CANPRO]

I don't think B is missing a factor of 8. In B he is solving moment in a 1m strip. A and B are basically identical...one is for the full 8m and other is 1m strip. Both are correct.

 

[BAretired]

I agree that both are correct.

BA

 

[freddyjnr01]

for B you considered a meter width. Which isnt the case. The actual width is 8m. thanks

 

[msquared48]

I also agree with CANPRO.

Mike McCann, PE, SE (WA)

 

[freddyjnr01]

CANPRO is right though but the question neaveyoung wants to solve is an 8m width barrier and not a meter width.

 

[IDS]

Both are correct answers to the question asked, with the correct units.

You can design the wall for the full 8 metres width using A, or a 1 metre wide strip using B, and get almost exactly the same answer.

When the footing is included using the metre width (with the moment adjusted for the increased lever arm) would be slightly conservative, because it doesn't take account of the additional distribution width.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[thenley]

I agree with CANPRO as well, as far as the sketch is drawn.

However, if I'm understanding the description correctly, this is basically a retaining wall, yes? If so, you wouldn't have a constant 1kN/m² load over the whole face, you'd have a linearly varying pressure from 0kN/m² at the top to X at the bottom, where X = (material density in kN/m³) * 10m. This will also change your moment calculation. But if X happens to be 1kN/m², then your approach is conservative.

 

[BAretired]

Where were we told that it is a retaining wall? Could be a free standing wall exposed to wind pressure.

BA