On Friday, February 10, 2017 at 6:13:43 PM UTC-5, lakeside bob wrote:
Want to build a gravel screen to sort out over size rocks from sand.
The gravel and rocks would be dumped on grizzly bars on a 40 degree incline and the gravel and rocks would slide down the slope rocks sliding off the top of the grizzly bars, and sand falling between the grizzly bars under the grizzly bars to be picked up and moved to usage area. the rocks moved to waste area. Spacing between bars would be 3 inches.
Question which would bend the least when the gravel and rocks are dumped on the grizzly bars?
Rocks would be up to 18 inches round so about 150 pounds each. Dropped about 18 inches on to the bars.
Size of wheel loader bucket is 1.75 cubic yards so total weight to be slowly dumped on the grizzly bars would be 1.75 x 2800 lbs in yard = 4,900 pounds.
Data
grizzly bars angle 2 inch x 2 inch and 3/8 inch thick.
grizzly bars angle 2.5 inch x 2.5 inch and 1/2 inch thick
grizzly bars 3 inch x 3 inch x 1/8 inch thick square tube
grizzly bars 3 inch x 3 inch x 1/4 inch thick square tube
all 36,000 pound strength steel

thank you for replying it is much appreciated.

The last one will bend the least, by far. The stiffness of the angles will depend on how they're oriented, but neither one is even close to the tubes, no matter how you arrange them.

--
Ed Huntress