Allowable load on steel road plate

[Daves10]

I am looking for some help in determining the proper temporary steel plate to allow the passage of a 12,000 wheel load over an 8 ft span.
Thanks

 

[Ron]

An 8-foot span is awfully long to try that. A plate would have to be about 3 inches thick for a 4-foot wide section to resist that kind of load. Most road plates only have 2 or 3 foot spans. You might want to consider something else.

 

[JStephen]

You can sum moments about one of the centerlines and find the average moment in the plate & solve for thickness. I get around 1" doing this. You might find more accurate 2-way formulas in "Formulas for Stress and Strain" or other references. The answer could vary some depending on your allowable stress and design assumptions.

Seems like some larger cities have standard tables for plates used to cover holes in pavement- make sure you're not overlooking something there.

 

[JStephen]

(The 1" thickness is based on a square plate- 8'x8', by the way). That 3" sounds too high.

If this is only supported at the ends, not at the sides, you may have sizable deflection as well.

 

[apsix]

1" is OK for strength for an effective width of 8', but static deflection is about L/100 and an 8' effective width is optimistic. What if the wheel load is on the edge of the plate, or if there are 2 wheels on the 8' wide plate?

You need to start with what size plate is available and proceed from there. Also, as mentioned above, check if standard tables are available.

 

[mrMikee]

There are a few plate calculations available on the following site that may be of use:

http://www.xcalcs.com/

Also try Roarks "Formulas for Stress and Strain" as mentioned above by JStephen. I'd check several formulas to get consistent results, some solve for peak stress and other solve for an average stress across a section. It depends on whether your needs are for a long term installation where peak stress is important or if it is for temporary use where the basic strength is adequate. However an 8' plate is probably going to have considerable deflection.

-Mike

 

[JStephen]

Apsix, I was actually assuming the plate was supported on all sides, so critical load is in the center, although that was not stated.

 

[Tomfh]

How wide is the span, and is it supported on the side edges too?

 

[apsix]

JStephen
True, I should have read your second post properly!

 

[mrMikee]

To satisfy my curiosity I solved case 1b in Roark and got for a 1" plate:

stress = 24900 psi
deflection = 0.467 inches

This is for a square plate 96" each side with simple supports and the load applied on 6" circle in center of the plate.

-Mike

 

[minorchord2000]

Don't forget the code required impact on that 12k.

 

[bridgebuster]

Here's a link to CalTrans. They give plate thicknesses for trenches up to 5'-3" wide; after that it has to be designed.

http://www.dot.ca.gov/hq/traffops/developserv/permits/pdf/manual/updates/Steel_Plate_(TR-0157).pdf

 

[bridgebuster]

here's two more, both are about the same as CalTrans

http://www.ci.austin.tx.us/development/downloads/backup03_18.doc

http://www.springsgov.com/units/traffic/Web_TrControl_05.pdf