Crossing a unknown bridge with equipment

[Builder]

New customer. Has an older bridge about 14' long. I don't fully trust it. I am being asked to add ~100 tons of stone beyond bridge, so dump truck must cross bridge. Triaxle is out of question at 74,000lbs. Considering 33,000lb single axle and don't really feel good about that, either. It will cost a lot more in time/labor to drive M-7040 buckets of stone across bridge. Many, many trips.

Bottom line. I'm asking Customer to sign "waiver" for damage to bridge.
Question: Would Customer's H/O insurance cover damage if I bend a steel beam or otherwise damage his bridge if i cross it with single axle stone delivery?

 

[jbarker855]

I believe there is great variation between individual homeowner insurance policies. Most cover nothing .
I would hazard a guess that homeowner insurance would not cover his bridge.
I will be very interested in other replies though, as we own a 90 foot bridge built from old railroad flatcar, and many companies are hesitant to cross it. I have just presumed that homeowner's insurance wouldn't cover our bridge, but I never asked them.
-Jay

 

[LD1]

How deep of a drop is it that the bridge is crossing?? I would be more concerned with damage/injury to the one crossing the bridge thean the bridge itself.

Do you have any pictures. 14' is not a very big span. If you can give pics and some basic dimensions on how it is constructed (eg. 2 ibeams x" high by y" wide by z' appart etc, etc) maybe we can determine how much weight it should hold.

Another suggestion, if it is not too deep, would be to come up with some sort of temporary support underneath at the mid point, shortning the spans to 7'. This could be done with concrete blocks, big wood blocks, jack posts, or whatever else you can come up with.

 

[beenthere]

Seems you need to be concerned about your equipment being covered as well as the bridge.
I'd think a contract that includes the customer coming up with an insurance policy (short term rider) that covers bridge and your equipment on his property if the bridge should fail. Otherwise, I wouldn't think you would take the chance. Seems it is his problem, not yours to solve.

 

[CurlyDave]

I would be at least as worried about my life as my equipment.

 

[Egon]

Either decline the work or set it up so the loads crossing the bridge are within it's capacity. Charge for the work accordingly.

A waiver for damage would also be a good idea.

 

[DanD78]

If the banks are not very tall dig it out and make a water crossing. Fill it back in when done. Do you have an engineer friend or know the township or county road guy that could look and advise a weight limit.

Dan

 

[Builder]

can't do anything dramatic to beef-up the bridge- not that kind of profit in the job. 100 tons of modified spread out on a couple hundred feet of driveway ain't gonna make me the next millionaire. :laughing:

However, it's a new customer and they need a LOT of future work. If I don't do the driveway, someone else WILL and they may get all the future work (if they don't destroy the bridge).

Maybe I should just take the stone across in tractor buckets as originally I thought, but that's a ton of wear & tear on my machine and it will take a lot more time. OR, I could use my backhoe. It has a larger capacity bucket than my M-7040, but still weighs <20,000lbs. I think that will be fine crossing the bridge.

 

[tommu56]

At least get them to sign a damage waiver.
Whats on the other side if it is a house can a fire truck (read 30-60,000 lbs) go across what will they do in an emergency?
How do you know it will take the weight of the loader and load?
What do they drive across it regularly?
drive you empty dump across and measure the deflection then go by the seat of your pants.

What is the structure made of I drive over a skidder bridge to my cabin and it is just made of 2x8 laminated but the span is only about 10' and it is solid as a rock.

Quote them a new bridge :laughing:

tom

 

[tommu56]

rent a roofers conveyor
one dump on it and in to a dump on the other side

tom

 

[Builder]

Wish I still had my small dump......
Biggest known truck to cross bridge is propane delivery truck. I gotta think it's a 33K truck. The difference is that we'll be crossing it at least 10 times in 2 days, but it's gonna be ~33K same as propane truck.

I'm 95% sure it'll be fine, but if I damage it, I don't want to be the party to blame. I thought maybe some thick 12" wide planks temporarily fastend to the bridge planks might help distribute some more weight.

 

[Lt CHEG]

I think the backhoe is probably a good idea for this one. It'll move more material but still not be as heavy as a loaded dump truck. Another option might be to dump the load on the near side of the bridge and use the backhoe to pile it up on the other side of the bridge. You could then drive the empty dump truck over the bridge and load it up with the material. Then drive the dump truck to where the material needs to be and tailgate spread it, etc. It certainly isn't as quick as just driving the dump truck over the bridge but if the material has to go any distance from the bridge then it is probably much quicker than just taking a bucket load of material at a time.

 

[LD1]

If you have any idea at all...I'd still like to know how/what the bridge construction is made of.

And how deep is the creek/gourge it is spanning. If you are considering 12" planks attached, wouldn't it be easier to form a temporary support at mid span and just drive the dump over it?

 

[Transit]

Have you looked at the underside of the bridge, what condition is it in? planks will distribute the weight but do little for the deflection of the span. If the local fire department will not cross the bridge that's telling you something.

 

[Builder]

It crosses a small stream. There's enough room under it to crawl under-maybe 5' high. I'm pretty sure the beams are ~ 10" high I or c channel on about 30" centers, but I'll have to take another look. Bridge deck looks like true 3x8's. Some are a little suspect looking. Concrete walls on both sides look pretty good.

 

[LD1]

I wouldn't have a moments hesitation about crossing it. Provided the planking and concrete is sound.

You said that you would be crossing in a 33k truck. That puts roughly 25k over the rear axle.

Using l/360 deflection limitations, (14 x 12)/360 =.46. That means the bridge would be allowed to flex .46" in the middle without doing any damage, collapsing, or staying bent permanetly.

Using a W10 x 19 I-beam (which is at the low end of the 10" beams) it would take 14000 lbs to be at the .46" limit. @ 30" centers I am assuming there are at least 5 beams which would make a 10ft bridge.

With 5 beams it would take 70,000lbs plus, right in the middle, to make the bridge deform. Of course the load wont be evenly distrubuted but the L/360 aldready has a good bit of safty factor built in and if the decking is solid, I wouldn't worry none. And with only 14' to cross, your front should be off the bridge before the rear's enter.

If they are heavier than a 10 x 19 beam, that is just icing on the cake. A 10 x 19 only has 4" flanges and a .250 web and would hold up. If you knew all the measurments of the beam, I could give you more info.

I don't think you have anything to worry about, but as others mentioned, a waiver is a good idea. Or maybe even suggest to the owner that HE have an engineer come out and rate the bridge. Did you ask him if he had an engineer design the bridge, if so, it should have a max rating. If is is a homemade bridge, maybe he'll foot the bill to get it rated.

 

[MarkV]

Call the fire department and see if someone would come out and say it they would cross it. If they will not you should not and you have a good reason to tell the customer why it will cost more to move it by tractor rather than truck.

MarkV

 

[Builder]

I wouldn't have a moments hesitation about crossing it. Provided the planking and concrete is sound.

You said that you would be crossing in a 33k truck. That puts roughly 25k over the rear axle.

Using l/360 deflection limitations, (14 x 12)/360 =.46. That means the bridge would be allowed to flex .46" in the middle without doing any damage, collapsing, or staying bent permanetly.

Using a W10 x 19 I-beam (which is at the low end of the 10" beams) it would take 14000 lbs to be at the .46" limit. @ 30" centers I am assuming there are at least 5 beams which would make a 10ft bridge.

With 5 beams it would take 70,000lbs plus, right in the middle, to make the bridge deform. Of course the load wont be evenly distrubuted but the L/360 aldready has a good bit of safty factor built in and if the decking is solid, I wouldn't worry none. And with only 14' to cross, your front should be off the bridge before the rear's enter.

If they are heavier than a 10 x 19 beam, that is just icing on the cake. A 10 x 19 only has 4" flanges and a .250 web and would hold up. If you knew all the measurments of the beam, I could give you more info.

I don't think you have anything to worry about, but as others mentioned, a waiver is a good idea. Or maybe even suggest to the owner that HE have an engineer come out and rate the bridge. Did you ask him if he had an engineer design the bridge, if so, it should have a max rating. If is is a homemade bridge, maybe he'll foot the bill to get it rated.

That's what I'm thinkin'. My dump is a long wheelbase (170") by the time the front axle gets to the other side, the rear axle will only be just getting on the bridge. However, I'm having the stone delivered and it will be a stubby dump-probably a 2' shorter wheelbase.

 

[Transit]

Good analysis LD1. We have some unknowns; how old is the bridge, how often has it been maintained, has it ever been rated? A five foot drop is not much; then again when you have 30k+ pounds strapped to your butt you have to add in the pucker factor. You are not dropping a wheel into a pothole, truck rolled over on the drivers side and tons of stone on you.
I can understand your need for the business in these times, but sometimes its better to go down the road. Look carefully and look twice more from every angle.

 

[LD1]

Even a shorter wheelbase isnt going to change that much. The highest stress on the bridge will still be when the rears are at dead center. A 2' shorther WB would give it a 12' overall wheelbase. With the front 1' from being across and the rears only on by 1' wouldnt stress the beams by near as much as ust the rears in the center.

I was just also pondering your suggestion of driving the BH across 1 bucketload at a time. This may even be more dangerous than the dump, but I dont know for sure.
With a weight of roughly 8.5 ton, and maybe another ton in the bucket, that is almost 20k itself. It has a much shorter WB and even a narrower contact patch with the bridge than you dual rear wheel dump truck. I just wonder how the 3 x 8 planks 30" on center would hold up if you drove right in the middle of 2 of the beams. The duals on the rear of your dumptruck probabally give a much wider contact patch.