Sizing of joists for a jetty

[martinradbo]

We are going to build a pier on the west coast that will primarily be used as a swimming pier. It will therefore be moderately high, maybe 50-70 cm high at normal water level. See sketch

Simple construction, two telephone poles at the end that will be pressed/struck down with the help of a barge. Doing it by hand will be too difficult in this case. At the inner edge, the pier rests on the rock.

My question concerns the choice of the two beams or equivalent that will go from the poles to the rock. 8.5 meters is quite a distance. Is it even possible? I want to avoid having to place a pair of poles in the middle of the pier as well.

The length also means that there are no treated beams available to buy in the standard range.

Can anyone calculate what might be needed?

 

[Pjosk75]

A steel beam with appropriate dimensions should work fine. Someone else has to calculate what it is.

 

[Pjosk75]

Or if you have access to uncut telephone poles, you can use them as well.

 

[martinradbo]

Or if you have access to unused telephone poles, you can use them too.

I have a couple of telephone poles that might be usable, the question is how straight and healthy they are. Steel beams work of course from a structural perspective, but steel and saltwater make me a bit apprehensive...

 

[Jan_G]

Railroad tracks are very common in pier construction on the west coast. The rust aspect then becomes uninteresting ;-)

 

[fribygg]

If you accept the bending that occurs, utility poles/telephone poles should work, if you can't get those, a regular pine from the site might be worth considering; if the ice and winds are harsh, it might not even be worth using roslagsmahogny to treat the pine trunks.

 

[Edlunn]

Steel beam type HEA or HEB.

 

[martinradbo]

(I apologize for the late response from my side).

I have long "telephone poles" or whatever they are, lying where the dock is to be built, so they are definitely an option. I think they are just over 20 cm in diameter. They should be strong enough.

The alternatives when I read up are:
1. Pressure-treated laminated beams
2. Steel beams.

Option 1 requires that they can be purchased at a reasonable price.
Option 2 requires that I find someone who sells with the right treatment. What should one look for then?

 

[martinradbo]

The deflection on a pier can probably be accepted to a greater extent than, for example, when building indoors and planning to tile. 🤔

 

[fribygg]

Now it's about time to get started if you want to have the dock ready by summer.. pictures/ build thread?

 

[martinradbo]

Now it's about time to get started if you want the bridge finished by summer.. pictures/build thread?

"Summer" doesn't start until August... 😜

Joking aside, I'm going to sort this out now. I've probably solved the piling on the outer edge, so the question remains about longitudinal beams for an 8.5-meter bridge.
Telephone pole, H-beam, or treated glulam beam? All maybe correct, but need to narrow it down to one instead of three options...

 

[fribygg]

If you have telestolp/ power line poles available, I think you should use them

 

[fribygg]

"Summer" doesn't start until August... 😜

Meteorologists say summer has begun, I say it's high time to start working..

 

[martinradbo]

If you have telecommunication poles/ power line poles available, I think you should use them

Yes, it might end up there. But I would have liked to present a few different alternatives. Steel beams, for example, feel very sturdy and straight, and with the right surface treatment, they probably last longer than the wood alternatives 🤔

 

[fribygg]

Yes, it might end up there. But I would have liked to present a few different options. Steel beams, for example, feel very rigid and straight, with the right surface treatment they probably last longer than the wood alternatives 🤔

Possible, but steel doesn't handle ice better, is probably harder to get in place, and is difficult to attach the dock deck to.