what type of wood should i use for platform in swamp area 4

[delagina]

This platform will be in swamp area. Should I use PT wood to prevent wood decay?
I have ZERO wood design experience.
This is very simple on the structural analysis point of view and I can easily do that.

I'm looking for guidance for the size and type wood column, beam and floor and the connection that would be "practical/common" to use in this case. I can size the wood thru analysis but what size should I start.

 

[mike20793]

Since it was asked about earlier in the thread, Parallam Plus or PowerPreserve Glulams are the only engineered lumber that I know can work in saturated conditions, but I agree with boo1, no need for engineered lumber.

Sometimes the Simpson connectors are not sized for heavy timbers. I think you can get them, even if they are special order, for the sizes indicated in the original platform.

 

[Gumpmaster]

JoshPlum,

What you're talking about isn't an engineered wood product like gluelams, but more of a composite wood product, like Trex.

Composite wood products aren't typically used in serious structural applications. You can use them on your deck or other residential application, but you wouldn't want to use them for piles or real beams. The modulus of elasticity is much lower than wood and the strengths are much lower than wood. You also don't typically have a ready source of tested and probability based strengths as you do for the wood design specification. It would be much better to use preservative treated wood, or even preservative treated engineered wood products.

 

[thaidavid40]

If you want to build a platform in a swamp, build it out of swamp wood! Use cypress lumber - it grows there, and nothing lasts in that environment like it will. I have seen 75-year-old docks made of cypress that are still just as tight and strong as the day they were installed. Go for cypress wood.
Dave

Thaidavid

 

[delagina]

@littleinch, how did specify in your drawing the timber piles to be hammered until refusal? I'm curious, how would you know the length of the pile. What if it takes 50 feet or more until refusal?

 

[LittleInch]

We did a pile design based on geo tech info and end cap force or friction, I can't remember which, which gave us a length based on a load required. We had 6 piles and assumed only 4 were load bearing to give us some spare capacity.

we were going into a gravelly inner harbour so had some decent info and quite good soils.

Looking back I think it was drive it into a length or when a certain force on the hammer exceeded a certain number per 100mm of movement / refusal. We didn't want the contractor bashing the living daylights out of the pipe to get it into the ground, but an experienced timber piling contractor will know what hammer force he can use for different sized piles

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Robbiee]

This Trough-bridge in Netherlands was built with Accoya wood.

 

[KootK]

This is old as dirt and meant for residential but you may find some of the durability concepts helpful: Link

I would also have concerns about the Simpson hardware depending on the specific products used. I worry about the durability of the gauge metal hardware in exterior applications where I would be looking for "weld the hood shut" durability.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[dhengr]

Delagina:
You are kinda asking all the wrong people, all the wrong questions, at this stage of the game. I agree with a number of the earlier posts, this is not a light framing deck, this is an industrial working deck and should be designed and built accordingly. You should most certainly be talking with your client’s pipeline engineering dept. people about the lateral and vert. concentrated loads on the deck, and then also apply something like 100lbs./sq.ft. as a uniform deck loading. There will be pipe supports resting on your framing system, you can see several of them in your photos. I can easily imagine a 20' piece of pipe with several valves on it laying on the deck waiting to replace an existing like pipe section. There might be a couple small portable lifting devices (tripod legs?) standing on the deck for this change-out. They have to explain to you how they will use this deck and the loads they impose on it.

You should most likely use treated timbers to frame this deck. Ask some real industrial lumber suppliers in that area what’s available, species, grades, sizes, lengths, etc., not the local big-box store what they have in stock. Simpson or Mitec, etc. might have some usable framing hardware, but likely not. Again, it is an industrial installation, not light framing; so, while the NDS is a good guide and starting point, along with some good wood design text books, this is timber framing. You use most of the NDS methods for design, but you must use the tables for large sized members, not the 2x - 4x tables. AITC and some large timber suppliers have some good literature on timber framing. Remember that when you stack layers of framing like you photos show, you should block btwn. floor beams (fl. jsts.?) and consider proper bracing systems in all planes and directions or you are kinda building a house-of-cards, layer by layer. Even though you are using treated materials, there are some great peal-n-stick water protection products on the market now. They are applied to the tops of all members, except the deck planks, they are self healing when spikes, screws, bolts penetrate them and they shed the water off the member tops. Available lengths are much more a function of how long a piece of a large timber can be cut out of a tree these days, than are transportation length limits. Longer lengths and larger sizes bring a premium price, and the size vs. transport and lifting might much more be governed by what they can haul several miles through a swamp, and lift at the site. What type of equipment do they use for this haulage and for lifting materials out in the swamp? There should be some soils info. available from when the pipeline was being designed and then also when being built, which would be helpful. They have to inform you on these types of issues, and this in turn will inform your design. They must have some std. details for this type of work, or some plans, by others, from earlier installations. Getting large equipment out there to drive piles could be a real dog. You might take a look at some of the screw-pile/foundation systems and see if they wouldn’t work in place of long wooden piles. One of the things you have to check on their account is that the soil conditions do not cause corrosion problems with the embedded portions of the screw piles. The pile loads should not be that great, and those screw type systems are pretty easy to install with fairly small all-terrain equipment.

 

[boo1]

fasteners look at products like

http://www.portlandbolt.com/products/bolts/timber/