Load test on existing piles

[longisland]

I'm asked to design a restaurant on an existing jetty which is a rc slab sitting on top of
timber piles. Other than taking the design load capacity of the foundation from the original plans as a guide, I need to assess the integrity & soundness of the existing jetty supports as well; considering the structure is 20-year-old, how do I go about this?
I'm thinking of using Pile dynamic analyser to determine the pile capacity & integrity. what about lateral load test & impact test?

Thanx in advance

Longisland

 

[KAM_imported]

You have two issues here--one involves determining the structural integrity of the existing piles, and the other their ultimate compression capacity. The integrity of the piles can be evaluated by visual inspection, probing the piles with an ice pick, and by small diameter cores. We have used a diver before to inspect and sample timber piles. You may want to counsult the website

http://www.woodadvisory.com,

as well.

The PDA can be used to determine the compressive capacity of the piles, but you will need to expose the top of the pile, and you will need a pile hammer to strike the pile. High strain dynamic testing using a drop weight could also be used. This procedure is similar to PDA testing, but a pile hammer is not required. Contact GRL for more information. Depending on new load requirements, if driving records and boring logs are available for the existing structure, a competent geotechnical engineer should be able to estimate the existing pile capacity using static and dynamic (Wave Equation) methods to give you a reasonable idea of available pile capacity. A factor of safety of 2.5 would be appropriate in this case. A lateral load test can be performed, but will be expensive, unless there is something available to jack against.

 

[Riz]

Normally timber piles are liable to decay at the fluctuating water table zone/high and low tide levels. Sometimes the immersed portions are liable to attack by marine organisms too. Kam has advised correctly.

New construction over existing, what sort of load is it.
Is it light weight construction, than should be okay.

If the piles appear to be in acceptable condition, I do not advocate lateral load test as the jetty while in use has been receiving enough horizontal ( dynamic ) forces.
For vertical loading, from sub-soil profile and parameters carry out the pile design check. See if it can take additional loading.
I am sure that information on pile testing during construction is hanging somewhere. This can give u an indication of settlement as pile tests are normally taken beyond the allowable loads.