If you plot the raw strain gage readings (in strain units) on the x-axis versus the pile head load on the y-axis, the slope of the curve will give the axial stiffness AE directly.
The graphs should initially be concave, becoming parallel when the shear transferred to the soil above each level...
Piles and pile groups exhibit nonlinear load-deflection behavior, under both axial and lateral loading. Unless you can closely control either the loads or the movements, there will be no "stiffness matrix" or constant stiffness.
In any event, the stiffness will be a function of the load or...
Try the city and county codes. Sometimes they conflict, and you need to be sure of the jurisdiction. If all else fails, ask one of the older engineers in your firm. They are usually quite eager to train a younger engineer to share their load.
A simple solution would be to consider the piles in the direction of lateral load on the structure as providing a resisting couple, with tensile (downward reactions) from the trailing piles and compressive (upward reactions) from the leading piles. The resisting moment due to axial loading of...
