Determining an Equipment load behind reinforced concrete wall
Determining an Equipment load behind reinforced concrete wall
(OP)
I am designing a reinforced concrete wall. I would like to design it to ensure it may withstand the maximum operating equipment load behind the wall. The area is paved behind the wall. ASCE code recommends a minimum of 250 pcf for tractor trailer and fire lanes, but how do I analyze a load for a loader having an operating weight of 100,000 pounds?
Is it reasonable to view the pavement as bearing the weight of the loader and treating it as a surcharge load, using the area between the center of the tires? Example, if the loader has an operating wt of 100,000 lbs, a 15' long wheel base and 12' wide axle length between tires, would it be unreasonable to call this a 555 psf surcharge behind the wall? My gut feeling is this is not an acceptable design procedure.
Is it reasonable to view the pavement as bearing the weight of the loader and treating it as a surcharge load, using the area between the center of the tires? Example, if the loader has an operating wt of 100,000 lbs, a 15' long wheel base and 12' wide axle length between tires, would it be unreasonable to call this a 555 psf surcharge behind the wall? My gut feeling is this is not an acceptable design procedure.





RE: Determining an Equipment load behind reinforced concrete wall
BigInch
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http://virtualpipeline.spaces.msn.com
RE: Determining an Equipment load behind reinforced concrete wall
A normal highway truck has an axle load of about 32,000# or 16,000# on 2 adjacent tires. The loader would have significantly more load on a single, but larger, tire.
RE: Determining an Equipment load behind reinforced concrete wall
For this condition, I would use 4 point loads at the tire locations. configure it as close to the wall as it will get. Loaders, like most heay equipment are not loaded evenly and weights are quoted w/o payload. With a full bucket, the load will go up substatially. as much as 2/3 of the load may be on the front tires. If the bucket is empty, The back tires probably carry considerably more weight than the front.
Find the most critical alignment (often this can be done by inspection) use 4 point loads for the tire contact points and compute the load. If the alignment is symetrical, you can use 2 points and double. Rember that for lateral pressure diagrams the theoretical load in the wall is twice the calulated value.
RE: Determining an Equipment load behind reinforced concrete wall
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: Determining an Equipment load behind reinforced concrete wall
Book called Soil Engineering by Spangler and Handy, Third Edition, pg. 567, eq. 22-23, has the following equation:
P= applied truck-wheel load, lbs
x= horizontal distance from wall to load, ft.
y= lateral distance from point to load, ft.
z= vertical distance from point to load, ft
R= sqrt (x squared + y squared + z squared)
hc= horizontal unit pressure at any point on the wall, psf
Equation: hc= P (x squared * z)/ (R to the 5th power)
To find the maximum load to the wall, I would assume you would write a excel program or trial and error to find the depth below grade having the maximum applied load. Then use that depth below grade in your moment calculations.
Sorry I can't use upper/lower case letters here. This is the best information I've found yet, and appears to give reasonable results.
RE: Determining an Equipment load behind reinforced concrete wall
This book has many examples for analyzing soil stresses for many situations. The book also contains a disc with DOS-based software for formulating stress distributions for many different situations. Even though the software is very simplistic, it's also very useful.
Alternatively, you could determine stress distributions using the Boussinesq techniques or others.
RE: Determining an Equipment load behind reinforced concrete wall
RE: Determining an Equipment load behind reinforced concrete wall
That's a good point. I retract my statement.
RE: Determining an Equipment load behind reinforced concrete wall
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com