Publication Abstract

International Symposium on Frontiers in Offshore Geotechnics, (DFI)

Investigation of Rate Effects for Monopile Foundations: Laboratory-Scale Model Tests
Kuen-Wei Wu, Byron W. Byrne and Guy T. Houlsby

Monopiles are the most frequently used foundation for supporting Offshore Wind Turbines (OWTs) in Europe. They are routinely subjected to transient loading with highly varying loading rates. Element tests in clays and sands show rate-dependent behaviour: principally an increase in strength or stiffness with strain rate. Results from a small number of available axially and laterally loaded pile tests show a similar phenomenon, suggesting that the pile capacity increases with loading rate. Current design practice for monopile foundations, however, does not take account of rate effects, either for monotonic loading or for assessment of the cyclic response. If rate effects are properly considered as part of the design approach, then a more economical monopile design may be adopted. This paper describes a laboratoryscale investigation programme into rate effects for monopile foundations. A bespoke loading rig, allowing high loading rates to be applied to a model monopile, has been developed. The applied load eccentricity can also vary during the test. Examples of model pile testing in dry sand are described; the initial results demonstrate the capabilities of the test set-up, and some rate-sensitive responses are observed. Further examination in stiff clay is planned.

 article #3615; publication #1069 (IC-ISFOG21)