piled bases tension loads

[oneintheeye]

There has been a few discussions on modelling bases for piles using FEA and making the piles springs to model loads. How does this translate to tension in the piles? Axially the pile would reach design load (theoretically) and deflect thus sharing the load to the slab and into adjacent piles, hence the spring concept. Is this a true model though for tension loads present on the piles?
If a use a spring model i have no tension. If a use a rigidly supported model I have tension above my capacity.

 

[patswfc]

You should still get tension in a spring support unless the software you use doesnt incude this.

 

[swearingen]

patswfc has it exactly - don't use tension only springs. Put in a support with a given axial stiffness. Most programs allow you to give axial and torsional stiffnesses to supports.





If you "heard" it on the internet, it's guilty until proven innocent. - DCS

 

[oneintheeye]

yes that is what ive done. What i'm saying is the results do not show tension. (they do if the model calculates tension). My query is which is the correct way of modelling for this. A pinned (i.e. riged) support gives tension loads. A spring support gives diferent results. I'm happy with the theoretical basis for the positive axial loading of piles but not so on the tension uplift as this would require deflection (all be it small) of the pile head upwards.