Monopod bucket foundations under cyclic lateral loading

The monopod bucket foundation can be a cost-reducing sub-structure for offshore wind turbines. To avoid problems during the turbine operation, the long-term effect of cyclic loading must be considered in the design of the foundation. In this paper a 1g testing rig is adopted to extend the knowledge on bucket foundations under lateral cyclic loading. The test setup is described in detail and a comprehensive experimental campaign is presented. The foundation is subjected to cyclic overturning moment, cyclic horizontal loading and constant vertical loading, acting on the same plane for thousands of cycles. Three buckets with different embedment ratios are tested. The data interpretation is focused on the long-term permanent rotation of the foundation and, particularly, on understanding how the controlling variables influence the potential for rotation accumulation. New and more general parameters of an empirical model predicting the long-term plastic rotation are proposed on the base of the experimental results.