Aqueduct loading

[thebraketester]

I think I know the answer to this but I wanted to see what people thought.

When designing an aqueduct, is the total weight of the maximum number of barges possible on the structure factored in to the loading calculations?

Thanks
TBT

[RizzoTheRat]

No because it doesn't change the weight on the bridge. A floating object displaces it's own mass of water. All they need to take in to account is the maximum possible water level.

[LimmerickLad]

thebraketester said:

I think I know the answer to this but I wanted to see what people thought.

When designing an aqueduct, is the total weight of the maximum number of barges possible on the structure factored in to the loading calculations?

Thanks
TBT

How many people on each barge and what is their avge weight?

[C4ME]

RizzoTheRat said:

No because it doesn't change the weight on the bridge. A floating object displaces it's own mass of water. All they need to take in to account is the maximum possible water level.

Does it not depend if the displaced water has somewhere to flow. In a closed system will not the result of the barges be the same volume of water but a slightly higher water level ?

[Collectingbrass]

C4ME said:

RizzoTheRat said:

No because it doesn't change the weight on the bridge. A floating object displaces it's own mass of water. All they need to take in to account is the maximum possible water level.

Does it not depend if the displaced water has somewhere to flow. In a closed system will not the result of the barges be the same volume of water but a slightly higher water level ?

Depends on the total surface area of the canal boundary for the water level to rise in relative to the surface area of aqueduct. The rise in water level on the surface area of the aqueduct due to displacement is probably a negligible additional mass on the aqueduct structure. Also don't forget that the canal was designed for fully laden barges, and what is in the barges today is mainly air & ale, meaning the mass of water displaced, and consequent increase in volume, today will be even less than the original designers assumed.

[RizzoTheRat]

Yes if the aqueduct was sealed at each end. Bit in reality there's usually going to be a lock someway away in both directions so the volume of water will be spread out a fair bit, and the water level is managed with weirs.

If the canal was 10m wide and 1km long, a 10 tonne boat would raise the water level by 1mm

[Beati Dogu]

The edge of the trough is only about a foot above the water level, so if for some reason the water was allowed to rise, it would automatically drain over the side. Thus limiting the load on the structure.

It sure makes going over it a little scary.though.

[ARHarh]

The water level in the canal is maintained by various outlets to stop it flooding, so as mentioned the amount of water stays pretty stable. This canal.is fed from.the river Dee via the horsehoe falls, (a weir) at the bottom of the Horseshoe pass, meaning It can't over fill.

It might be scarey taking a narrow boat over it but try walking over it on a windy day, and don't read the sign that tells you the gaps in the railings are big enough for children to fall through.

[Murph7355]

RizzoTheRat said:

Yes if the aqueduct was sealed at each end. Bit in reality there's usually going to be a lock someway away in both directions so the volume of water will be spread out a fair bit, and the water level is managed with weirs.

If the canal was 10m wide and 1km long, a 10 tonne boat would raise the water level by 1mm

Also, the system is never "closed" as the poster suggested.

Your note about the max possible water level is on the money as a result.

[ridds]

What about the tow path and "the horses", or these days, filling the tow path with people.

Most stuff back then was either well over, or well under engineered.

[ARHarh]

The Llangollen canal will.never fill up or overflow as it is used to supply drinking water to Crewe and Nantwich. This means it is constantly flowing and therefore more like a river than a canal. As a result of is often used by people who live in boats during the winter as it does not freeze.

[Simpo Two]

When I saw the opening photo I suspected an aeroplane/conveyor belt scenario!

ARHarh said:

The Llangollen canal will.never fill up or overflow as it is used to supply drinking water to Crewe and Nantwich. This means it is constantly flowing and therefore more like a river than a canal. As a result of is often used by people who live in boats during the winter as it does not freeze.

Indeed; the current on some sections is such that the speed of your narrowboat (NOT a barge!) is halved.

I've done the Llangollen twice and frankly it's pretty poor - shallow so hard to moor, significant currents and a long one-way section with no way to know if anything's coming the other way.

[ARHarh]

Its a great place to go for a walk though, especially in winter when the tourists have gone home.

Don't look down.

https://www.google.com/maps/@52.9702155,-3.0878559...

[C n C]

..and also fun to kayak across, as we did earlier this summer.