PY Curves for Tiebacks 1

[DallasGeotech]

I am trying to model a drilled shaft wall with tiebacks. The manual does not do a sufficient job in explaining their examples of PY curves for their tiebacks.

Any help in how to model the PY curve for tiebacks would be great. Thanks.

 

[GeoPaveTraffic]

Why would you want to model a tieback with py curves?

 

[DallasGeotech]

Oh, I really would rather not. Those who are asking for the analysis want it done in PYWALL. The only other option is to model them as lateral springs.

 

[SixDegrees]

PY curves are basically non linear springs and no appropraiet for modeling tiebacks. You can accurately model the behavior of a tieback using a lateral spring.

The spring stiffness(K) is

K=AE/L

Where
A= Area of tieback bar or strand ft^2
E=Molulus of elasticity of bar/strand kip/ft^2
L=Length of unbonded tieback (ft)

Make sure you account for the direction of the anchor.

 

[DallasGeotech]

Have modeled it both ways and get similair results. The spring method was used to check the py curve method.

The py curve for the tieback was entered as linear. The slope of the curve is the yeild capacity/yeild deformation.

 

[DRC1]

Reese & Impe in "Sigle Piles and Pile Groups Under Lateral Loading" describe setting up an anchor for a retained wall analysed with L pile. (p/y) anch = (Area rod)(Erod)/[(Length rod)*(wall length increment)]/(Anchor Spacing)

Note thaqt the quality of the answer for such an analysis is dependent on the quality of your soils information. A hand solution may be just as accurate, if not more, and might be easier.

 

[PEinc]

"Note that the quality of the answer for such an analysis is dependent on the quality of your soils information. A hand solution may be just as accurate, if not more, and might be easier. "

I agree with DRC1. The PY analysis for a tiedback wall sounds like overkill to me.