LPile Loads

[RyUIUC]

I am analyzing a single pile using LPile V.5 using analysis Type 1- Computation of Pile Response Using Elastic Pile Stiffness (Basic Modeling). In trying to determine the maximum factored bending/shear forces along the pile length, are you supposed to enter in factored loads to determine these values directly from the output report/graphics or are you supposed to input unfactored loads and factor the results?

If factored loads are used, does a seperate run have to be performed for unfactored loads to determine an accurate deflection?

 

[IDS]

Unless it is specified in the applicable design codes, it's up to you. In my opinion carrying out the analysis with unfactored loads then applying a single factor to the resulting actions in the pile is the simplest approach and is covered by at least one national design code (the Australian Bridge Design Code, Part 3).

If you did the analysis with factored loads for the Ultimate Limit State, then yes, you should do another analysis with reduced factors (often all equal to 1) for the Serviceability Limit State, including deflections.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[amec2004]

Here in Alberta Canada the LPile analysis is normally carried on by Geotechnical engineer and the LPile analysis results are presented as charts in the soil report issued by Geotechnical engineer.

Structural engineer may also play with LPile and Group if there is P-Y curves provided in the soil report, but, legally it shall be coming from Geotechnical engineer.

Given the fact that the soil report is produced at the early time of the project and Geotechnical engineer has no control on the load combination factors used by Structural engineers, the LPile analysis charts coming from Geotechnical engineer is *ALWAYS* analyzed and presented using unfactored lateral load as the serviceability related check is always unfactored.

We normally take the chart, use it for serviceability check, and simply multiply a generic load factor such as 1.5 to get factored pile shaft moment and shear for pile section check. That should be accurate enough.
If you are analyzing the concrete pile, do remember to analyze twice, one for uncracked section and one for 0.25EI cracked section, which actually is quite conservative.

LPile claims that it can handle the non-linear concrete section by segments instead of a generic 75% stiffness reduction. I haven’t tried that yet and all the time I got from Geotechnical engineers is 2 sets of chart, one uncracked and one 0.25EI charts.


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