STATIC LOAD TEST ON AN EXISTING TIMBER PILE

[jpyach]

Does anyone have any experience with performing a static load test on an existing timber pile which is part of a deep foundation system of a building currently still in service?

Background:

I have a project where the structural engineer wants to add 6 stories to an existing building. The building columns are seated on pile caps which are supported by 20 ton design load piles. (Building built 1914)To eliminate the need to add new piles, it was suggested that a load test be performed on the existing piles to determine if we can get 3-6 tons more out of each exisitng pile.

Problems:

Building slab will need to be cut.Pile cap area will need to be excavated around. Piles will need to be cut for the placement of the hydraulic jack.

Has anyone seen or been on a project where a testing setup has been placed under a pile cap, within a pile group in a very tight space?

Thanks for any help, insight, websites, specs or information pertaining to load testing of existing piles! I really appreciate it!

 

[SlideRuleEra]

Most static pile load tests are conducted in accordance with ASTM 1143. The pile is loaded, in steps, to 300% of design load (say 78 tons for your example). Here are a couple of references for general background:

http://www.dot.state.ny.us/tech_serv/geo/gcp-18.pdf

http://www.preservedwood.com/pil/timber_manual/timber09.pdf

Possibly the area to consider first is "What (inside the building?) will resist the 78 tons that is being applied by the hydraulic jack to the pile?" If you reach a solution, the other problems can probably be overcome too.

The next question is how many piles to test? The structural engineer will probably want to test several.

If the piles you test is typical of all the other piles (a big if) AND they pass the test, the structrual engineer MAY accept the results.

In summary, there are probably more cost effective ways to solve the problem, such as micro piles. See thread256-78173

 

[Focht3]

That sounds very risky to me. Adding six stories to a 100 year old building is bad enough; but trying to load test a single 100 year old timber pile - and using that single test as the sole basis for adding (an apparently) significant load onto the foundation as a whole - borders on recklessness.

But perhaps you can provide more information - and I will have some reason to 'back off' from my initially unfavorable impression. Where is the building? How tall is it now? What are the existing piles made of? Length? Butt diameter/tip diameter? Condition? Soil and groundwater conditions?

And what are the consequences to the building if some of the pile groups can't carry the additional load?



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"

 

[PEinc]

I agree with Focht3. The idea of using very old piles with the 6 story addition sounds outlandish.

Also, I'd be surprised if the existing building is capable of supporting the 6 story addition.

 

[CSEllc]

I hope you now some good lawyers....if not your insurance company will certainly introduce you to several during your court case.