Concrete Dock Float

Epoxy, my first thought when you said lead anchor..

Isn’t your pof the bolt holding the turdbuckle to the mount? Serious question, I apologize.

I think this doesn’t get a standard shear rating due to the floppiness/unevenness. I wouldn’t worry about tensile loading on the turnbuckle.

@gonzo what happens to the shear rating of the bolt in a connection like this one? Is it measurable? Not as in destructive testing, but can you calculate it?

 

Excellent questions. I don't know what you mean by lead anchor. Lead plugs? These are expanding wedge anchors. A properly installed SS ⅜ wedge like these has a typical pullout failure around 2800#, and I installed 8. But thousands of shock loads might work them out.

The mechanism of failure is likely to be anchors pulling out. The bolt may wear through under endless load cycles. I am getting some UHM bushings to stop that. Each bolt could easily suspend the entire assembly.

I may lower the float side attachments to provide three link Geometry, so the peak loading goes away. There is already a geometric relationship between the lower link and the upper links, where tide entering the bay compresses the lower link, which pushes the foot of the float away from the wall. The upper links maintain a constant stand-off, so inflowing tide heals the boat toward the main float. The opposite occurs when the tide is falling. A similar evolution happens when waves lift and roll the float. Three link Geometry.

 

I think that ship has sailed John.
We spoke of this at length weeks ago.

I am curious though, why did you ask for feedback on the turnbuckles?

 

If you bush them, that will help.

The issue wth the bolts is they are not rated for misuse. They may have enough tensile strength to carry the thing, but they are not loaded that way, and you cannot use the shear ratings either due to the interface angle.

Since I have no way of knowing how much movement occurs there, I’m just seeing that they are not in a standard use, if you will. Things out in those islands vary greatly as some spots are weather beaten and others very protected, etc. So you know better what to expect.

 

You could replace the turnbuckle lengths with tension/compression double sprung struts, or shock absorbing struts to reduce shock loads on your anchor bolts, while still holding out a distance which you set. I don't know the technical names or brand names, but I've seen them in industry. The two rod ends's shafts slide inside or alongside each other, and a central plate across one strut backs a spring on either side, contained by plates attached to the other end strut, allowing some tension/compression give when stressed axially, reducing shock loads, and a bounce back when not stressed. Also, could you run wire or rod spring lines either side of the raft/shed, to reduce the angular attitude of the turnbuckle ends, so they stay 90 deg to the wharf anchor plates ? That would make it all last longer I think, at a smallish extra cost.

 

That is a clever idea @seasquirt .

Thanks @fallguy . They are indeed loaded in a non-standard way. That poses a concern. Unfortunately it is impossible to calculate what the actual loads will be. All I, or anyone else can do is see what has previously worked, or do a series of calculations based on assumptions. In this case I used dock hinges scavenged from large docks that had withstood decades of use at the site. Those would have been adequate, but they could not manage how the weight of blackwater in the tank will vary by an actual ton in service. So I used the geometry of a three link rear main automotive suspension.

 

Automotive struts are the ones I can find, but even those for heavy trucks are relatively weak. I will look further.

 

@BlueBell, I asked for feedback, because critical questions are a good way to test my thinking.

I remembered the term. The lower turnbuckle acts as a Panhard rod.

 

Latest. The rise and fall of the float with heavy wave action sheared off the bolts on the panhard rod analog. So I added shackles to make U-joints.

 

Mmmhm, but schackles don't transmit compressive forces.....?

 

Same like the other comment; there needs to be some give. In my head, I think snubber. The way the snubbers are made so the float doesn’t move is basically like tying up a boat with the snubbers competing against each other.

…worth my fee

Consider tying up a large yacht…this is not any different.

…or think mooring whip, also give

when they tie off the barges down here, they use tires as snubbers, etc

 

Good point about the compressive forces. The fork at the turnbuckle end bears on the fixed bracket, so that is the load path. I ordered some more appropriate brackets from my fabricater, so I can take out the shackles. I just need something that can rise and fall beyond the range of the first system.

 

Dock work

 

Some things in life are not fair. Your view is one of them.

 

Inside view of the house. And I get paid too.