Deformation behavior of piles subjected to cyclic lateral loading from a varying direction

Describing the behavior of laterally loaded piles is a complex topic, since the
overall behavior of the pile-soil-system needs to be analyzed. If cyclic loading is regarded, the analysis is even more complicated. Research on the deformation behavior of laterally loaded piles under cyclic loading has resulted in a number of methods to estimate the de-formations that are to be expected, e.g. during the lifespan of a wind turbine foundation. These methods were derived from physical modeling and considered the load to come from one direction only.Wind turbine loads mainly arise from wind and waves. These can hardly
be assumed to be one-directional. Research at Hamburg University of Technology shows that a changing loading direction increases the deformations considerably. The effects of a changing loading direction were studied in tests at different scale and acceleration level. In this paper, the results of small scale 1g-testing, centrifuge testing and testing at reduced prototype scale are presented to demonstrate the necessity to consider the change of loading direction during the design process of wind turbine foundations.