×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

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

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

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

(OP)
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.






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

What's the plan for foundation? Driven wood piles?

I would likely be specifying PWF material which provides better preservation than P.T. material.

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

(OP)
I think it's a driven wood pile that will also act as a column or platform support. Can you be more specific with pwf. Pwf is only for the piles? The beams and flooring would be what? Also what connection would you recommend.

I'm googling pwf, that's a good start for me thanks. This looks very simple but I have no wood design exp. I need to know the practical sizes and type of wood to use. I have a wood design book but it's more about analysis.

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

The wood piles will have their own preservative rating. I'm not familiar enough with them to discuss the specifics.

The rest of the platform wood I would be using PWF material (Preserved Wood Foundation). Without dimensions and proposed loads I doubt anyone here would even take a stab at rough sizing. Although that existing platform appears to be framed with some pretty hefty timber.

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

(OP)
If I use 8"x8"xlength' Southern Yellow Pine, Treated, for the timber pile,

would the geotech soil report give me the capacity of the pile?

Also I plan to use SYP, treated lumber/timber for all joist, deck, pile or you recommend another type of wood?

for the flooring, I plant on using 1"x6" or you recommend 2"x6"?

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

1x6 decking works great for residential. I would not use it for commercial purposes. 2x6 at a minimum. Timber piles have different treatment requirements than your standard home depot treated 8x8. Please do some more research into timber piling.

Use whatever lumber you can get around there with the treatment you want. Where I am all the treated lumber (or most) is SPF. But so is all of the other lumber. We don't use SYP for anything because it's not readily available.

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

(OP)
I think I got this figured out. I will be using Simpson strong-tie for the connections, is this ok or I should use something else?

Also nobody answered yet, if this is driven wood piles then it's geotech scope to give me the wood pile capacity, right?

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

Treated Yellow Pine sha!

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

A geotech tells you the soil properties, not the structural capacities. You are on your own on this one.

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

delagina - The platform in the photos is designed for heavy industrial use... see the marked up photo for the clues:



Note the closely spaced, heavy stringers.
Decking that appears to be a nominal 4" thick.
Pile bracing.

Get the geotech working on this project first thing. The piles are likely friction (not end bearing) with significant embedment length in the poor soils often present in swampy areas. Based on the apparent size of the decking, stringers, and probable long length, nominal 8" piles are probably undersized.

Establish a realistic live load rating, if the client can't provide one, reverse engineer the existing platform superstructure (that won't be hard) to come up with one. IMHO, it probably in the 150 lb/ft2 (or higher) class (no live load reduction).

Simpson does not offer hardware suitable for this type construction. Plan on heavy bolted connections.

I agree with boo1 on the 2.5 pcf CCA treatment and hot dip galvanized fasteners. If creosote is used, specify 12 pcf retention.

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

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

I built a structure in a shallow marine environment a few years ago for a water pump and filter for an oil field development using "green" i.e. fresh cut Oak piles, 12" square, hammered in until refusal and then just chain sawed them off. We were going to use hardwood, but getting the "sustainability" certificate proved too difficult.

some simple googling gives a few good results though

http://www.theconstructioncivil.org/timber-piles/

http://www.forestry.gov.uk/pdf/Timber-piles-and-fo...

http://www.woodworks.org/wp-content/uploads/Rollin...

https://www.fema.gov/media-library-data/20130726-1...

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

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

I'm not really a "wood guy", so I can't offer any sage advice of my own.

I am surprised that no one specifically recommended some type of engineered wood products. I've been following this thread because I was hoping someone would. Then I could look them up and learn some more about them. Instead, I will ask the question, why not?

There are engineered wood products that combine plastics and wood to make strong, dense products. I would have thought would be less prone to moisture problems than traditional wood. Am I mistaken? Or, is there a reason why these products would not be good for an application such as this?

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

(OP)
Why can't I use Simpson strong-tie hot-dipped galvanized connection?
I think the loadings here are very minimal. This is just a simple maintenance platform.

I think the existing wood platform (picture) was overdesigned.

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

"Most" of the engineered wood products I've seen actually have disclaimers about not being used in exterior type exposures. There are some Glu-lam beams that receive treatment quite well but none of the LSL, PSL and LVL stuff I've seen allows for this level of exposure to the elements.

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

JoshPlum - Agree with jayrod12. Another reason that comes to mind is that engineered wood is optimized to make the best use material for specific loading conditions. For industrial applications loading is less predictable. The bulky size an resiliency of sawn lumber is actually an advantage. Say one the heavy flanged valves (perhaps a few hundred pounds) is "plopped" down during maintenance, putting a point, impact load on the decking. Sawn lumber will deflect, without breaking, thereby sharing the load with adjacent members. Another situation could be a workboat slamming into the platform during docking.

delagina - You know more about the client's needs than we do... but you did ask the questions, and they are good ones. The cost of the substructure for this type platform will be substantial (driven piling in a swamp). Would be a shame to put a "cheap" superstructure on top of it. Besides, this is obviously an industrial application - not in the same league with Simpson's residential and commercial construction focus.

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

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

no need for Engineered wood.
Round piles with 4x (SYP if east coast) decking/beams with heavy galv connections.
Low risk, available and cheap

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

We use a lot of plastic lumber for the Navy but primarily for blocking, curbing, and semi-structural stuff like that. It's too flexible compared with wood and the plastic with reinforcing is not cost competitive with wood.

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

(OP)
just want to confirm. timber pile capacity should be on geotech report, right? I don't think I can calculate the skin friction of the timber pile if it's not in the report.

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

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.

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

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.

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

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

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

(OP)
@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?

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

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.

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

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

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

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.

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

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.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources