Field experiments on instrumented winged monopiles

Abstract

This paper presents the results of field tests performed to investigate the field behaviour of winged-monopile foundations. The principle of the winged monopile is that steel plates are attached to a standard monopile (in the area near the ground or seabed surface) to increase the foundation stiffness and lateral resistance. The experimental tests described in this paper consisted of load tested driven instrumented prototype scale standard (reference) monopiles and piles with varying wing geometries at two sand sites. The overall load–displacement performance and mobilised bending moment profiles were examined to assess the potential benefits of adding wings to monopiles. Experimental p–y curves were developed for the piles to analyse how the presence of wings influenced the soil–structure interaction of the foundation system. The use of simplified p–y methods for predicting the winged-pile response was assessed. The experiments proved that the addition of wings greatly improved the lateral resistance and stiffness of the piles; however, the results suggest that conventional p–y curve methods are limited as they cannot account for the effect that the enhanced stresses mobilised by the wings have on the strength and stiffness response of the pile below the wing location.

3D FEM approach for laterally loaded monopile design

“…Test pile P1 was instrumented using strain gauges attached to the tension and compression faces of the pile. The strain gauge data was used to derive bending moment profiles for each load increment applied in a static load test as described in detail by Xue et al and Murphy et al [32,33]. The test piles were loaded (using maintained load increments) until pile head displacement continued without the addition of a further load increment.…”

“…The modelling approach was further validated by comparing the calculated pile shaft bending moments in P1 to those measured using strain gauges as shown in Fig. 7 [33]. A comparison of sample p-y curves extracted from the pile P1 "Jacked" and "Wished-in-Place" models are provided in Fig.…”

Editorial

“…They performed model tests on different arrangements of the piles and loading regimes and obtained interesting results. This paper follows a number of others on monopiles published in this journal in the previous issue (Murphy et al, 2016) and last year (Chen et al, 2015;Li et al, 2015). We will no doubt see more papers published in this journal on this hot topic, perhaps in next year's themed issue on geotechnics in energy provision, for which we have received a remarkably high number of submissions and for which the peer-review process is well under way.…”

Monopiles subjected to uni- and multi-lateral cyclic loading

“…These environmental loads induce high numbers of cycles (about 10 7 to 10 9 ) of lateral loading on the foundations over the life span of the structure. A number of studies have investigated monopile behaviour under large numbers of cycles and unidirectional loading (Arshad and O'Kelly, 2016;Chen et al, 2015;Leblanc et al, 2010;Li et al, 2010Li et al, , 2015Murphy et al, 2016;Peng et al, 2011). These studies were conducted at small L/D ratios and various mechanisms such as winged monopiles (Murphy et al, 2016) and piled cruciform (Arshad and O'Kelly, 2016) were examined to reduce the horizontal moment.…”