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Using Strip Analysis to calculate Moment on a simply supported concrete slab bridge

Using Strip Analysis to calculate Moment on a simply supported concrete slab bridge

Using Strip Analysis to calculate Moment on a simply supported concrete slab bridge

(OP)
I am getting some crazy results on my strip analysis of a simply supported concrete slab bridge and I think I don't understand the application of the Live load.

AASHTO H20 Specify 32,00 pounds on the rear axle and 16,000 pounds on one wheel. The wheel foot print amounts to 10” x 20” which creates a load of 16,000/10/20 or 80 psi, (11,520 psf).

I have been assuming that since the strip analysis uses a 12” wide strip the length of the bridge span, this 11,520 psf should be used in the calculation of the Moment. But doing so results in the requirement of a 46 inch thick slab.

How does one apply the H20 loading in the strip analysis of a concrete slab bridge?

Thanks

RE: Using Strip Analysis to calculate Moment on a simply supported concrete slab bridge

What is your span?

Are you doing a uniform loading of 11,520? I think you need to do point loads.

Also, here is a link to TxDOT's standard details for pre-stressed slab beams. They come in 4ft and 5ft widths. You can compare your design loads to them to see if you are in the ball park.

Have a look at the 'Optional Design' section. There is an 'Ultimate Moment Capacity' for Strength 1.

For example, a 24ft wide roadway with SB15 (slab beam 15" thick) spanning 25ft has a capacity of 551 kip ft.

Link

ftp://ftp.dot.state.tx.us/pub/txdot-info/cmd/cserv...

RE: Using Strip Analysis to calculate Moment on a simply supported concrete slab bridge

You cite H20, I'm assuming that you're following the standard specification. Look in Chapter 3, you can distribute the load over a wider section. Look for the distribution factor for slabs with main reinforcement parallel to traffic.

RE: Using Strip Analysis to calculate Moment on a simply supported concrete slab bridge

(OP)
JoelTXCive,

The Span is 18.5' the width is 20'.

The 18.5' includes the 2' wide abutments on each end. So the unsupported span is 14.5'

It is for a driveway entrance to an orchard. It crosses an irrigation canal, (12.5' wide)

Bridge Buster,

Thanks for the info. I will check that out.

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