Effects of vertical loading on lateral screw pile performance

Abstract

The offshore wind energy sector faces new challenges as it moves into deeper water deployment. To meet these challenges, new and efficient foundation solutions are required. One potential solution is to upscale onshore screw piles but they require verification of performance for new geometries and demanding loading regimes. This paper presents a three-dimensional finite-element analysis investigation of screw pile behaviour when subjected to combined vertical and lateral loading in sand. In the investigation, the screw pile length and helical plate diameter were varied on piles with a fixed core diameter while subjecting the piles to combined axial and lateral loading. The results were compared with results from straight shafted piles with the same core diameter. The results of the analysis revealed that vertical compression loads increased the lateral capacity of the screw piles whereas vertical uplift loads marginally reduced the lateral capacity. The downside of this enhanced lateral capacity is that the screw piles experience higher bending moments. This suggests that, when using screw piles for offshore foundation applications, structures should be designed to maintain axial compressive loads on the piles and induced bending moments need to be adequately assessed when deciding on appropriate structural sections.

A finite element approach for determining the full load–displacement relationship of axially loaded shallow screw anchors, incorporating installation effects

“…The failure mechanism of mul -helix anchors depends on the inter-helix spacing. If two adjacent helices of iden cal diameter are sufficiently close, a cylindrical failure surface, whose diameter is equal to the helix diameter, is assumed to form between them in tension or compression (Tsuha et al 2007;Knappe et al 2014;Al-Baghdadi et al 2017a). At greater spacing, the helices may act independently.…”

“…). Table cap on list Table 1 Geometry, crowd force (Fy,min) and upli capacity (Fy) of the different screw pile models at prototype scale for UoD (Davidson et al 2019) and UWA (Hao et al 2018) tests Table 2 Proper es of the plate elements (iden cal for pile core and helices), assumed iden cal for all tests Table 3 Number of elements and nodes of the meshes for each simula on (stage 1) Table 4 HSsmall parameters for the HST95 Congleton sand, (a er Al-Defae et al 2013, Lauder et al 2013, Al-Baghdadi et al 2017a, reference s ffness is for a reference pressure p ref = 100kPa. Table 4 Comparison of the upli capacity and CPU run me as a func on of the mesh refinement for the U1VD-B.…”

Nonlinear Lateral Response of RC Pile in Sand: Centrifuge and Numerical Modeling

“…2). The distance between the front face of the pile to the boundary of the soil container was more than 13 , so no boundary effect on the pile lateral performance should be expected (Al-Baghdadi et al 2017). To saturate the soil model for Test S, the bottom of the model package was connected to a water reservoir, and the water elevation was increased in steps.…”

“…Due to the conventional use of elastic materials in physical modelling of piles, it was commonly assumed that the pile behaves in a linear elastic manner when conducting numerical back-analysis of model tests (e.g., Al-Baghdadi et al 2017). Although this might be a reasonable assumption for relatively small lateral pile displacements, when subjected to large lateral displacements RC piles would exceed their elastic range and form plastic hinges as tension cracks developed (Broms 1964).…”

Performance Assessment of Screw Piles Embedded in Soft Clay

“…Screw piles have become the focus of experimental studies in Geotechnical laboratories are studying the resistance to compressive or pull-out forces and the behavior of these piles under axial loads from the structure itself. Screw piles also have good tensile and compressive capacity (2 to 3 times the capacity of a conventional pile [15] and can be used for a variety of soil layers above and below water.…”