Foundation engineering

[Varma A.]

I have calculated horizontal, vertical, and rotational stiffness for the Pile foundation at each layer. How to convert these soil spring constant to single equivalent spring constant (single rotational, vertical, and horizontal spring) for sway rocking type model. Thank you.

 

[LRJ]

Are these individual springs input to a finite element or finite difference type of program? If so, and supposing I've understood you correctly, you would get a single 'spring' if you run your analysis for various load or displacement levels, then collate the resulting load vs. displacement behaviour at the pile head: this will produce a single pile head load-displacement curve, which can serve as a generalised 'spring' for analysis of the overlying superstructure.

 

[LRJ]

As an aside, if you are looking at a type of foundation where the vertical, horizontal, moment and torsion responses are 'coupled' (e.g. a shallow foundation), then creating a stiffness matrix would be required. Generally for deep foundations such as piles the responses are sufficiently decoupled so that you can just have a single pile head load-displacement curve for each component.