Pile Load Testing - to what load?

[nseguin]

thread507-321109

Hello,

Are any of you aware of any existing requirements for pile load testing with regards to what the applied load should be? For instance, with an LRFD design, a structural resistance factor of 0.5 is applied to the ultimate load for the nominal structural compressive resistance for H-piles in severe driving conditions (AASHTO LRFD Bridge Design Spec.'s - 5th ed., 2010). This may or may not govern the pile's actual resistance, depending on the geotechnical resistance achieved through side/skin friction and end bearing (to which a resistance factor of 0.45 may be applied for a static analysis method, such as the Nordlund method).

If a static load test is to be performed, is the pile to be loaded to the magnitude of its nominal resistance, its factored resistance, or some other multiple thereof? Is this up to the designer? It would seem as though you would want to avoid loading a pile to its nominal (or loosely put, its "ultimate") resistance.

Any feedback would be greatly appreciated!

Thanks in advance,
Nate

 

[GeoPaveTraffic]

I'm not a LRFD expert, or really all that familure with it. In the "old" days you would load the pile to twice it's allowable design load or to till failure; whichever was achieved first. As long as the test pile is not a production pile, load it till failure. Then you know the ultimate(nominal)capacity and can apply the load factors to that value.

Mike Lambert

 

[GeoPaveTraffic]

Should have included that it also depends on what you are trying to accomplish with the load test. If the goal is just to verify the design, then stopping at some multiple of the nominal capacity, i.e. somewhere around twice the design load; would be appropriate. If the goal is to use the load test to modify the design, then you need to take the pile to failure.

Mike Lambert

 

[PEinc]

Why not ask the pile designer what the service design load is and then test to twice the service dewsign load? Or, just ask to what load the pile is to be tested. The nominal pile capacity could be much more than the factored DL. A contractor should not be responsible for determining the nominal capacity of a pile so that the pile can be tested to some higher percentage. A factored load could be approximately 1.6 x the service load. Therefore, for a 100 ton (factored design load) pile, the service load could be about 100 tons / 1.6 = 62.5 tons. A normal test load would then be about 2 x 62.5 tons = 125 tons which is only 1.25 x the 100 ton factored design load.

http://www.PeirceEngineering.com