cattle grate help

[MMW]

One of my customers wants to install a cattle grate in his driveway & asked me if I want to build it. I know what they are & what they look like but don't know the sizes of material commonly used. His contractor quoted him $14,000 installed for one 14' by 10' or 12'. That's all the info I have at this time. I was thinking 4" sch 40 for the top pipes but not sure about I-beam sizing. As far as I know there is no natural span to cross. I get that this creates it's own span.

I know I need more info to build it but trying to get an idea on material to ballpark it.

Two I-beams running across the drive & maybe five running with the drive with the pipes on top with 4" openings? Maybe 10" beams?

[JSFAB]

Over the years, I have built 20 or 30 cattle guards. Standard design is 8' (going with the road) x 10' or 12' (going across the road). We would frame it all around with 8" channel, then have six more 8" channels running in line with the road. All the outside channels had flat surfaces facing out, internal channels were notched and welded all around. Normally left a 3 or 4 foot gap between the middle channels, no way would any truck weight bear on this.

On top, simply 1" rebar, welded every 4" on center. Second rebar from each end, was bolted in, sandwiched between two flats, double flats were welded on each side, and also on the center two channels. This allowed removal for cleaning underneath if necessary.

With proper spacing of the internal channels, these were always strong enough to handle 80,000 # truck and trailer combinations.

The customer would normally have pre-cast concrete beams to set these on, backhoe or excavator would just have to dig it out, set the beams down level, and then set the cattle guard on top, backfilling all around. The design is strong and rigid enough, you could do just as well setting on RR ties.

I think I posted pictures years ago, search under "calweld" both this board and on Hobart.

[Don52]

Attached is a picture of one with side wings.
Prefabricated ones are available from:

http://www.livestockshed.com/c-115-sioux-steel-cattle-guards.aspx

[Sandy]

You really need to come to an understanding of what traffic is going to be passing before you can even start with the sizing of materials. Just mamma and her Mercedes, cattle trucks, concrete trucks, combines, those things. Does he have a by-pass for the heavy stuff? The problem with by-pass gates is that no-one ever uses them.

[Bodybagger]

Using the AASHTO H20-44 design vehicle, a 20 ton truck with a front axle weight of 8,000lb and a rear axle weight of 32,000lb with an axle spacing of 14 feet, the highest bending force due to live load occurs when the rear axle is centered over the 14 foot span and is weight x span /4 = 112,000 ft-lbs. Using two beams, each beam centered under the wheel path, each beam experiences half this, or 56,000 ft-lb. Using the LRFD load factor of 1.6 times live load, you're looking for a beam that can withstand 89,600 ft-lbs of bending force. Looking through table 3-10 of the AISC Steel Construction Manual along the axis corresponding to a 14' unsupported length (since lateral torsional buckling may be an issue), some beams listed above the 90ft-kip line include the W12x26 and W10x30. That example was simplified and does not include the dead weight of the beams and the grid which will increase the design requirements, and this design vehicle is NOT an overloaded cement truck.

[JSFAB]

Normally, the smaller dimension is in line with the road, wider is across the road, just to accommodate turns, bad truck drivers, etc. Most cattle guards back in the 50s and 60s were 4' or 5', they only started increasing when we started introducing Brahma blood into the mix. They are like jackrabbits, I have seen myself a brahma cross clear a six-foot high fence, just hitting his hind leg on the top rail.

Current standard is, 8' in line with the road, width is whatever is necessary so the trailer follows if in a turn.

Properly located, 8" channel, stood upright, notched to fit and welded all around, with 1" rebar on top, is more than enough to take a 80,000 pound truck and trailer load without distorting or breaking.

Before steel prices started going over the top, I was building 8 x 10 and 8 x 12 cattle guards for $2000 each, and clearing close to $1000 each. The good old days.

[MMW]

I looked at many photos & have settled on using 2.5" sch 40 pipe for the top. The customer also likes the look of pipe vs. bar.

One question I do have is most of the ones I have seen have the end channels leg in. I would think leg out would lock it into the ground/drive better. Is this mainly for ease of install/removal on an already completed drive?

I will be making it in two panels 14' wide (across drive) x roughly 7' long so about 14' long when installed. Each section will have a removable section for cleanout. Using six 10" x15# i-beam for the runners with 10" x 15.3# channel ends. Openings between pipes will be a little less than 4". Customer is going to install himself on compacted stone & then the paving co. will do the drive after it is installed. It has been an existing drive that is being redone so settling should not be an issue.

[Broccoli1]

need to put them in front of some of the bars around here :0

[MMW]

Here is the finished product. Before paint, since two will be placed together I added pipes sticking out that go into corresponding holes so if any settling occurs they will stay closely level with each other. In primer with the cleanout section removed. Finally one painted & out the door while I finish the second one.

[B&M Welding Inc.]

That's nice work! Looks like you get into the heavy work too!

[Type]

Nice, what side of tube is that?

[MMW]

2.5" sch 40 (2-7/8" od)