New data analysis methods for instrumented medium-scale monopile field tests

Harvey J Burd,William J A P Beuckelaers,Guy T Houlsby,David M Potts,David J P Igoe,Byron W Byrne,Christopher M Martin,Kenneth G Gavin,Lidija Zdravković,Richard J Jardine,Ross A Mcadam,David M G Taborda,Alastair Muir Wood,Jesper Skov Gretlund

doi:10.1680/jgeot.18.pisa.002

Harvey J Burd, William J A P Beuckelaers + Show 12 more

Open Access

https://doi.org/10.1680/jgeot.18.pisa.002

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Abstract

The PISA Joint Industry Research Project was concerned with the development of improved design methods for monopile foundations in offshore wind applications. PISA involved large-scale pile tests in overconsolidated glacial till at Cowden, north-east England, and in dense, normally consolidated marine sand at Dunkirk, northern France. This paper describes the experimental set-up for pile testing, with unique features of load-application mechanisms and built-in fibre optic strain gauges. New procedures are described for the interpretation of pile loading data, and specifically for providing precise interpretation of pile displacements.

Highlights

A field testing campaign has been completed, as part of the PISA (Pile–Soil Analysis) project, to investigate the response of monopile foundations subjected to monotonic and cyclic lateral loads (Byrne et al, 2015, 2017; Zdravkovicet al., 2019a)
The test piles were instrumented with inclinometers, strain gauges, displacement transducers and a load cell
Likely ground movements developed during the tests (Zdravkovicet al., 2015). These results indicated that predicted lateral ground movements reduce significantly with radial distance from the pile, and that they become negligibly small beyond a distance of about five pile diameters

Summary

INTRODUCTION

A field testing campaign has been completed, as part of the PISA (Pile–Soil Analysis) project, to investigate the response of monopile foundations subjected to monotonic and cyclic lateral loads (Byrne et al, 2015, 2017; Zdravkovicet al., 2019a). A process was developed to infer vG and θG from the field measurements, in a consistent manner for all tests, exploiting redundancy in the data when available This process is described below, and illustrated using monotonic loading data from one of the Cowden medium-diameter test piles (CM3, L/D = 10, t = 25 mm) as an example (Byrne et al, 2019). To acknowledge the complex behaviour of the flanged connection, values of flexural stiffness and crosssectional area for the flanged connection (EIF and AF respectively) were determined from the measured data using a best-fit process, such that common values of EIF and AF were used for the flanged connections employed for all of the medium- and large-diameter pile tests. The bending moment, M, and shear force, S, induced in the above-ground structure are

H EI hz þ z2 2 þ

Extensometers

CONCLUSIONS