When non-linear foundations are present in the model, the correct reaction force is only calculated when the deflections are exactly along the global x or y directions.
Bladed versions affected: 4.0 to 4.13. Fixed in 4.12.0.9 and 4.13.0.8 onwards.
Article last updated: 10th March 2023
The problem arises from the way Bladed calculates foundation loads from their components in the x and y directions, combined with the nonlinearity of the soil response. An illustrative example may help. The figure below shows a top view of a pile which undergoes a horizontal displacement of d metres in a direction 45° from the axes.
The foundations screen in Bladed allows non-linear soil stiffness characteristics to be defined as lookup tables.
The calculated restoring force is derived from displacement, via the force/displacement (F/d) curve for a given axis (x, y or z). For simplicity we will assume x-y symmetry, so that the curves for the x and y axes are the same. In the illustration below, a displacement of d metres corresponds to a restoring force of F2 Newtons.
