The Breakroom > The Water Cooler

Building a Bridge

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naffsharpe (Nathan):
Nice job Steve, I love the speed warning sign! Does the central section allow some "spring" to the deck when the running sections are loaded or does it aid drainage (or both!) . Nathan.

vtsteam:
Thanks guys, sorry I haven't been able to participate here much lately, still preparing for winter...

There are two wear strips which I guess technically divides the bridge deck itself into three sections. The wear strips do what they say in their name, but also, being 3" deep, spread out the loads further across the main deck planking, which runs cross-wise. And of course they in turn spread the loads across the four steel deck beams and add additional stiffness. As mentioned the deck is made up of 2x6's on edge. The wear strips add 3".

Drainage has not been a problem -- the corners and ends drain. There hasn't been any standing water despite all the rain we've had -- seems to rain every other day.

The wear strips are at the level of the tops of the concrete abutments, so tires neither drop onto the bridge, nor bump up onto it at vehicle entry and exit. I figured, it's best not to have every 20,000 lb axle load acting like a hammer twice per crossing. Driving across it feels very smooth. There is no bump.

The strips are quite wide so compact cars and wide axle trucks alike will stay on the treads, rather than fall off the side onto the bridge deck. Not that it would hurt anything to do that, but it might make for a disconcerting moment for a small car. I've crossed the strips on purpose while maneuvering my tractor into position for auguring holes for posts at the ends, but I hardly noticed it.

There are no regulations about road signage on private property, but I do want people to slow to 5 mph when crossing. Especially my in-laws! I'm sure it can handle much higher speeds, but why subject it to that? Besides in winter, I don't want anybody slipping into the rails, etc. 5 mph is an intelligent speed then.

I've also posted it at 30 tons, since I had a few delivery trucks balk at crossing un-posted and their drivers walk packages up to the house. Thought I'd save them some time and trouble! They were used to no bridge here.

Nathan, there just isn't any perceptible spring when big loads cross. 35 tons of loaded dump truck was only 1/8" over 16' And rainwater just drains naturally off the ends. We did a good job of leveling the deck apparently, and last I checked nothing had changed with use.

Almost a quarter million pounds of concrete, plus a few truck loads of 6" crushed rip-rap stone is keeping it pretty stable.

krv3000:
brill

tom osselton:
I always thought that it could help in handling frost as being colder it would roll off to the lower area. The Incans had agriculture set up like that crops raised to protect against frost!

vtsteam:
Thanks Bob.  :beer:
Tom, could be. Coincidentally we had our first frost this morning. I didn't notice it on the bridge though, when I walked my daughter to the road for school bus pickup. 

The bridge does get sun during the day in winter. When snow gets here, the wear strips will definitely dry first after shoveling. I'm planning to set up a sand barrel nearby.

Another advantage of having a bridge and driveway is bringing in sand. After every icing I used to hand carry it in and spread it along all 600 feet to the house. Even then, we routinely wore ice grippers in the walk to the cars, and back, carrying groceries and heating fuel.

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