Drilled Shaft - LPile Lateral Deflection - Serviceability and Ultimate Capacity

[engjg]

In using LPile for the design of Drilled Shifts for free head pole structures subjected to wind loading. I think one should select shaft lengths to limit the pile head deflection/rotation for serviceability considerations using service level design loads. My question comes in with verifying adequate factor of safety for ultimate capacity/permanent deflection. When I look at sand p-y curves I see a generally elastic initial region transitioning into a plastic region. I think one would want to keep the maximum lateral deflections (occurring at the pile head) to within the elastic region. I would think displacement past the elastic region will not fully rebound and therefore I associate this with ultimate capacity failure. Is this a valid approach? If so what level of loads would be appropriate to use in the analysis? Or should one developed an ultimate permissible mobilized soil reaction? What code criteria if any are available for maximum permissible deflection/rotations? i.e. AASHTO, IBC, ASCE (Elec. Trans/Dist), EIA-TIA (Tele.)