When does a beam start to bend under its own weight?

[Derbyboy]

I don't think you need to make it that complicated. Attach a board with approximately the dimensions you have in mind and stand on it and jump a little. I'm sure it will feel okay. A 200 mm beam is quite thick. Reduce the center-to-center distance if it feels unstable. Bridges are often a bit unstable and that's perfectly fine. It will definitely hold.
In wintertime, it only needs to support its own weight. The deflection won't be many mm, even with a lot of snow.
I also guess that the fastening will be more crucial than the actual wooden beam.

I think I'll be able to manage the fastening pretty well. It's rock, and the idea is to drill through the board with a threaded rod m1 but before that use 2-3 joist hangers to make it easier to drill the board plus the rock in one go.

 

[Unikt namn]

Ja hängbro kan jag glömma

In another thread, a similar request was discussed, albeit with a little longer overhang. Seems to be speculated about rather thick beams.

https://www.byggahus.se/forum/threads/brygga-i-besvaerligt-laege-beraekningshjaelp.430505/

Maybe you can ask ts there what it ended with.

 

[Kane]

But I'm not quite sure if you can calculate like that as you've done. I haven't quite settled in understanding how you account for the overhang in your calculation.

If not even glulam at 66x315 mm can handle a 4-meter span fixed at both ends, it will be tough to get 75x200 mm to handle 2 meters in snow zone 2.

 

[nino]

If even glued laminated timber of 66x315 mm can't handle a 4-meter span clamped at both ends, it will be tough to get 75x200 mm to handle 2 meters in snow zone 2.

But what's the tolerance on that? A few mm maybe?
Here, it probably doesn't matter if it bends down 1-3 cm

 

[Kane]

But what is the tolerance for that? Maybe a few mm?
Here it probably doesn't matter if it bends down 1-3cm

Tolerance is the wrong word, more a question of uncertainty in the calculation. But if significantly stronger timber than what you intended to use deforms 22 mm in the calculation model above, then you probably need to rethink (or add more). But it's up to each person to decide.

 

[nino]

Tolerance is the wrong word, it's more a question of uncertainty in the calculation. But if significantly stronger timber than what you intended to use deforms 22 mm in the above calculation model, then you probably need to rethink. But it's up to each individual to determine.

Well, I should admit that I don't really have any clue...
But what is the load on that glulam beam or is it 22mm of its own weight? If so, that's not good.
A footbridge doesn't get many 100kg.

 

[Derbyboy]

I'm also thinking that there should be some standard load that my bridge doesn't quite meet.

Additionally, there will never be a large amount of snow remaining for an extended period, and the breaking point is surely not close.

So, if in the worst case, the snow bends the bridge down 5 cm for 3-4 weeks, does it matter or will it spring back up in the spring?

 

[Kane]

Well, I have to admit that I don't really have any clue...
But what is the load on that glulam beam or is it 22mm of dead weight? If so, that's not good.
A bridge doesn't get many 100kg

Snow load and dead weight of 230 kg/m2 (if I remember correctly).

 

[Hasse C]

Be a little realistic now. Three pieces of 75x200. It's going to be super rigid.
Go to the building supply store, take such a beam and place it between two supports and jump on it. It won't be the same as a fixed end with a free end, but at least you'll get an idea of the strength.

 

[Kane]

Be a bit realistic now. Three pieces of 75x200. It will be super stiff. Go to the building store, take such a beam and place it between two supports and jump on it. It won't be the same as a clamped with a free end, but you'll get at least some idea of its strength.

However, you want it to hold when docking with the Princess sixty-two......

 

[Dilato]

You want it to hold when you dock with the Princess sixty-two......

You mean the dinge