Starting my bridge!!

[scootr]

The mix will have to be real wet for a chute. You may have to push it down the chute otherwise.
hugs, Brandi

Use a vibrator Long chutes are a drag

 

[Doorman63]

Use a vibrator Long chutes are a drag

That’s concrete humor?

I actually have 40’ (4-10’ pieces) of U shaped 22 or 24 gauge sheet metal shrouds for some coiling doors.

 

[EddieWalker]

Interesting build. What type of vehicle are you planning on driving across your bridge?

 

[Doorman63]

Interesting build. What type of vehicle are you planning on driving across your bridge?

Shooting for my Kubota L2501 and/or our 2007 F150 farm truck
Pick up is about 6k

 

[LD1]

Without knowing the wall thickness of the tube.....off the cuff....I'd say the max for that structure is about 2500# presently. Based on the fact that you are spanning a little shy of 20' and deflecting ~1/4" with ~1200# of ATV's.

There is FAR more that goes into engineering calculations.....but for anything but the shortest of spans (where stress/shear become a factor).....L/360 deflection is usually a pretty good rule to follow. That is the length in inches divided by 360.

So say your span is ~18'....thats 216".......and 216/360 is 0.600" deflection MAX. And since you are nearly half that with teh ATV's.....safe to say thats about half the max load that structure will handle.

Then of course you have to have sufficient decking to handle the wheel load of 2.5' crossmember spacing.

Also throw in the fact that the entire weight of the truck or tractor are NOT right in the middle at the same time. A full sized pickup has a lengthy wheelbase. But then you also have to account for dynamic load/stresses of the vehicle moving.

I would forget the aircraft cable and truss it with some rebar similar to whats pictured above but on the BOTTOM so it stays in tension. That will add tremendous strength. But dont just weld the ends at a small point where the rebar comes back to the bridge. Flatten it back out so you get a good 4" or so of weld. Some 3/16 x 2" flat would work too.

Whatever modification you make, slowly work the weight of the load up and keep an eye on deflection. Dont go past 5/8" or so

 

[dodge man]

I don’t think a cable under tension is going to add a lot if any strength.

 

[Lineman North Florida]

How about jetting a pole down mid-span of your bridge on each side to support the weight in the center, we used to jet poles down in water all the time and always found that creosote was far superior than any cca pole in water.

 

[Doorman63]

Without knowing the wall thickness of the tube.....off the cuff....I'd say the max for that structure is about 2500# presently. Based on the fact that you are spanning a little shy of 20' and deflecting ~1/4" with ~1200# of ATV's.

There is FAR more that goes into engineering calculations.....but for anything but the shortest of spans (where stress/shear become a factor).....L/360 deflection is usually a pretty good rule to follow. That is the length in inches divided by 360.

So say your span is ~18'....thats 216".......and 216/360 is 0.600" deflection MAX. And since you are nearly half that with teh ATV's.....safe to say thats about half the max load that structure will handle.

Then of course you have to have sufficient decking to handle the wheel load of 2.5' crossmember spacing.

Also throw in the fact that the entire weight of the truck or tractor are NOT right in the middle at the same time. A full sized pickup has a lengthy wheelbase. But then you also have to account for dynamic load/stresses of the vehicle moving.

I would forget the aircraft cable and truss it with some rebar similar to whats pictured above but on the BOTTOM so it stays in tension. That will add tremendous strength. But dont just weld the ends at a small point where the rebar comes back to the bridge. Flatten it back out so you get a good 4" or so of weld. Some 3/16 x 2" flat would work too.

Whatever modification you make, slowly work the weight of the load up and keep an eye on deflection. Dont go past 5/8" or so

This is why we love this place!!

I have multiple 50’ lengths of 3/8 crane cable (not aircraft cable). 5k capacity turnbuckles aren’t hard to get…..that’s where my cable idea came from.

The rebar/flat stock idea work for me as well……overhead welding isn’t my strong suit so that’s why I was shying away from welding under the bridge.


The decking….I was gonna build a couple different test fixtures to see what will hold the tractor/pick-up.

I was thinking of just throwing some c-channel/tube steel down where the wheels ride and wood plank the rest……this idea has me nervous if someone didn’t drive on the steel.

 

[Doorman63]

I don’t think a cable under tension is going to add a lot if any strength.

A cable under tension bowed down (4 or 6”) in the center should?

 

[Doorman63]

How about jetting a pole down mid-span of your bridge on each side to support the weight in the center, we used to jet poles down in water all the time and always found that creosote was far superior than any cca pole in water.

This is my last resort. I have another bridge with poles/cross bracing/etc in the center. I’m trying to see if it’s possible not to use them.