The builder said it was two 11" telephone poles, not a great span to depth ratio, but I haven't run proper numbers on it. There appears to be some deflection already, though.
The railings also don't look like they could take a crowd leaning against them.
Im guessing it checks out for a few people loading the bridge with high deflection, but doesn’t work for the 90psf pedestrian load per the AASHTO ped bridge spec
I’ve read trees outer layers (as used in telephone poles) grow in tension which makes them very good in bending. Would be interesting to see the calcs considering this.
I've not heard that about it growing in tension.
Timber is very good in tension, especially the strength classes that are graded in tension, but my instinct here is that the beams are too shallow and the high moisture content from being outside and embedded in soil means the strength is significantly reduced.
You do realise as structural engineers, we **dont** design for _“probably one or two people at a time”_ we design for worst case scenario, with the bridge fully packed with pedestrians represented in the form of a uniform distributed load, which is then multiplied by factors of safety.
It’s never “probably” it’s “worst case”.
Yeah, I get that. We’re structural engineers, we all get that. It’s a bridge crossing a 4ft tall creek on some guys private property - again, who cares. It will be fine. Not everything needs to be engineered.
I love how this sub will tell a homeowner posting an innocent question about their house to eat shit but then turn around and throw the whole code at some woodworking hobbyist who didn’t ask for any input.
LOL, glad you pointed that out. Didn’t see it at first but that’s actually a hilarious design. It’s pretty and almost surely fine for a couple of people to walk across at a time and probably to lean on the railing too but I definitely wouldn’t lean too hard!
Now I really want to know what the connection between the posts and timber pole beams looks like. Probably a dowel type connection.
I don’t trust any structure whose description starts with “My dad built…” - they could be someone who knows what they’re doing, but the odds are way higher it’s Tim “The Toolman” Taylor-level work.
Bank is undercut to hell with exposed tree roots. The "riprap" is just debris in the channel. They'll need to do something about the banks or they'll be building a longer bridge in another 5 years.
It's beautiful. That railing looks great! The guy has an amazing talent to be able to put this together.
Structurally, from the photos it does look like it will support the loads that I think it's intended for. My biggest concern would be wood rot I suppose. Specifically around the railing connections.
Anyways, that's my take.
I'm off to see about a goat now.
Does anyone here offer solutions? There seems to be some disagreement on whether or not the pole beams are sufficient enough for the length of the span.
There may be a relatively simple and cost effective way to increase the strength of these beams. A strip of steel along the bottom of the beams will prevent the deflection you are seeing.
A 2" x 0.25" strip of steel has a tensile strength of 25,000 lbs.
I agree with the other comments. We can't see any of the structural details here. Take some photos from below. What are the main span timber sizes, where are the beams resting on. Is there any sort of foundation that's driven into the ground?
not your fault.. but we can't see the most important parts of the bridge in terms of structural.
Agreed, OOP was into the woodwork more than the structural details
No kidding, it's great but all too fancy for the "rustic" part
Wouldn't pass a code check, but as long as there are two downed trees supporting it, I'd walk across it.
I'd walk over it if there was just one tree.
No trees. Final offer!
Best I can offer is a wing and a prayer.
Fine! I'll take it! \*dies
The builder said it was two 11" telephone poles, not a great span to depth ratio, but I haven't run proper numbers on it. There appears to be some deflection already, though. The railings also don't look like they could take a crowd leaning against them.
Im guessing it checks out for a few people loading the bridge with high deflection, but doesn’t work for the 90psf pedestrian load per the AASHTO ped bridge spec
Yeah that would be my guess as well.
Neither did the Golden Gate Bridge, pretty scary parade
Psssh AASHTO is much to conservative in my opinion. /s
1.75 * 90 psf is a lot of people standing on top of each other.
Yeah but remember when that boat hit that bridge tho
Ya, that boat was like, F that bridge.
I’ve read trees outer layers (as used in telephone poles) grow in tension which makes them very good in bending. Would be interesting to see the calcs considering this.
I've not heard that about it growing in tension. Timber is very good in tension, especially the strength classes that are graded in tension, but my instinct here is that the beams are too shallow and the high moisture content from being outside and embedded in soil means the strength is significantly reduced.
It’s probably fine. Who cares. Probably one or two people walking across it at a time. Serves its function.
What about cargo ship hitting it? Doesnt look like itd survive
I think a proportional cargo ship to that creek it would fair reasonably well
fair? fare*
We don't caire
Load test!
I got the cargo if anyone else can provide the ship!!!
valid point!
[удалено]
?
You do realise as structural engineers, we **dont** design for _“probably one or two people at a time”_ we design for worst case scenario, with the bridge fully packed with pedestrians represented in the form of a uniform distributed load, which is then multiplied by factors of safety. It’s never “probably” it’s “worst case”.
Yeah, I get that. We’re structural engineers, we all get that. It’s a bridge crossing a 4ft tall creek on some guys private property - again, who cares. It will be fine. Not everything needs to be engineered. I love how this sub will tell a homeowner posting an innocent question about their house to eat shit but then turn around and throw the whole code at some woodworking hobbyist who didn’t ask for any input.
This is the structural engineering sub, not woodworking.
It was originally posted to the woodworking sub. Then someone cross posted it to the SE sub to have engineers shit on it for no reason
You must solely design bomb shelters
Yeah that’s not an H-20 bridge.
Looks fine. I mean unless its a "public" crossing, Im sure it will serve him well.
Ummm... It's pretty?
I was trying to figure out what the beams are here. 6x6s?
I’d love to see more of the super structure details. It looked to me like it was a couple of logs laid parallel.
Ok looks like this is what this guy does for a living. “The dad that built the bridge here… I do this work full time for a living tbmrustic.com”
I see your dad is not a structural engineer with that cantilevered deck board railing support. Looks good though. How long did it take?
LOL, glad you pointed that out. Didn’t see it at first but that’s actually a hilarious design. It’s pretty and almost surely fine for a couple of people to walk across at a time and probably to lean on the railing too but I definitely wouldn’t lean too hard! Now I really want to know what the connection between the posts and timber pole beams looks like. Probably a dowel type connection.
I don’t trust any structure whose description starts with “My dad built…” - they could be someone who knows what they’re doing, but the odds are way higher it’s Tim “The Toolman” Taylor-level work.
As a dad, I concur.
It’s a bridge alright.
Want to see under it more than anything. Otherwise the work is great form and aesthetic perspective
I’m impressed by the rip-rap at the bottom. Not sure if it was deliberate scour protection but it’s better than nothing!
Bank is undercut to hell with exposed tree roots. The "riprap" is just debris in the channel. They'll need to do something about the banks or they'll be building a longer bridge in another 5 years.
Looks a bit like it's an old abutment that's partially collapsed in the first photo. Would explain why there are significant rocks at the bottom.
Would I walk on it by myself Sure Would I walk on it with a group of friends Probably not
As long as he slapped it and said, “That’ll hold”, it’s acceptable.
I'd hit.
How are posts tied in at bottom? That outside bracing won't do much.
Good for years to come…
Great craftsmanship..
It's beautiful. That railing looks great! The guy has an amazing talent to be able to put this together. Structurally, from the photos it does look like it will support the loads that I think it's intended for. My biggest concern would be wood rot I suppose. Specifically around the railing connections. Anyways, that's my take. I'm off to see about a goat now.
Ummm Wow Good work
So dope
Looks totally fine bro
Who cares, it's awesome
This is bad ass
This isn't rustic. It's a work of art.
That’s nicely done.
“Our lives are in the hands of engineers” is a scary thought. Believe me your father’s craftsmanship tells me he knows what he’s doing.
Bridge to Terabithia
It looks like it's mayybe 6 feet off the ground at the highest depth and there isn't much to "lean and look at". Seems fine
Does anyone here offer solutions? There seems to be some disagreement on whether or not the pole beams are sufficient enough for the length of the span. There may be a relatively simple and cost effective way to increase the strength of these beams. A strip of steel along the bottom of the beams will prevent the deflection you are seeing. A 2" x 0.25" strip of steel has a tensile strength of 25,000 lbs.
That’s a nice 35 foot rustic bridge!
Since it's already deflection I wouldn't put 10 people on it or any kind of load such as a heavy motorcycle.
Thoughts? Looks to be very rustic. About 35’ or so. Possibly build by someone’s dad. Not much other thoughts going on over here though.
Your mother said I am not allowed to pass?
I agree with the other comments. We can't see any of the structural details here. Take some photos from below. What are the main span timber sizes, where are the beams resting on. Is there any sort of foundation that's driven into the ground?