Converting P-Y Curves to Soil Springs?

[visitor]

Im working on a bridge that will have large diameter CIDH piles (>10 feet) at the bridge bents. I used the LPILE program to come up with the P-Y curves. This site consists of alluvium (sand) over weak bedrock. My problem is converting the P-Y curves to Soil Springs. I need to come up with springs at different depths along the pile so that the structural engineer can use them in the program Staad. Help!

 

[ishvaaag]

Since I don't know the exact input and output data, you may make yourself a FEM model of the pile under the same setup than LPILE but with lateral soil springs till you get a good fit.

If you have reactions along the shaft and dislacemnt there, divide the integrated force for the segment by the representative lateral displacement.

 

[FM1]

Hi,

A P-Y load deflection curve represents a nonlinear spring for the soil at the stratum it is derived for. To do what you are planing I would consider an Ultimate expected working load(e.g. max expected load increased by safety factors....etc) and plot it on each curve then derive the spring value for that point on the curve, K=P/Y. You can only derive a linear spring value for loads up to your working load i.e. a straight line drawn from origin to the point you plotted on the curve which by inspection will give you a softer spring value for loads less than the working load than you really would have if you follow along the P-Y curve. You would therefore be somewhat on the conservative side for lower loads.

FM1