Modeling Piles

[Yavoran]

Hi All.

Have a question.
On my project i ama sked to dsing A portal frame (3m span)
The foundations are 1.2m Piles 23 to 34m long. The soils are lose sands.

The question is.
After I have calculated the nonlin soil springs for the latteral pile supports. What shall I do to take into account that the stiffnes is different for the dead @live loads.
By now I have applied the dead loads, obtained the Deformed shape of te structure, transfered it to a new moddel.
The question is:
As some of the soil defprmatons allreadu have ocured do I have to Apply the live load springs but only this part where the deffs are greater than those aleady occuring under dead loads???

Thanks in advance
Y


(to get it right assume you are wrong)

 

[DRW75]

Yavoran,
I'm a bit confused (but I usually am anyways...).
You're doing a portal frame with a 3 metre span but your using 1.2 metre piles? and they are embedded 20-30 meters deep?

Thats besides the point i suppose.

What software are you using to do the analysis? Some packages should allow for a non-linear spring (approximated by a series of linear springs of varying stiffness).

If your stuck doing a full stepped analysis, then what you'll want to do is run the analysis for the DL portion with the specific ground support spring conditions. Then run another analysis with only the LL combinations with the new ground support spring conditions. This is where this can get tricky depending on your software.

Some packages can merge the two analyses to get the net stresses and deflections of the entire system which is the nice and easy way.

If your package can't do this then you may have to impose displacements into you LL model - however I wouldn't be confident that this is 100% accurate since the boundary conditions will be different. It would likely be best to resolve the stresses from each individual analysis and combine stresses (and deflections) as appropriate (a-la superposition). There should obviously be some consideration for any deflections from the DL condition which will cause substantial P-Delta effects for the LL condition.

DRW