A P Smithling

Bio: A P Smithling is an academic researcher from National Grid plc. The author has contributed to research in topics: Dynamic load testing & Earth anchor. The author has an hindex of 1, co-authored 1 publications receiving 16 citations.

Dynamic uplift capacity of helical anchors in sand

Abstract: Earth anchors are becoming a very useful technique for securing temporary and permanent foundation systems subjected to uplift loads. In recent years, helical anchors have become more widely used because of their ease of installation and low cost. Past research has concentrated on static loading. Recent investigations into the cyclic capacity of anchors have increased rapidly due to increased construction in the ocean and the importance of anchors in advancing offshore technology. Laboratory tests were performed with one-quarter scale single-helix model anchors in dry sand at a constant relative density and embedment depth. The two parameters investigated were the displacement amplitude and prestress load. Appropriate equipment and instrumentation were used to monitor anchor deflection, dynamic load, and horizontal soil stresses during the cycle tests. Static tests were performed to determine the ultimate pullout capacity of dead anchors and the postcyclic failure capapcity of anchors. It was concluded that screw-in anchor installation technique and the application of a prestress load both produced an increase in horizontal soil stresses and soil densification in the vicinity of the single-helix anchor. Cyclic loading caused a reduction in horizontal stress and an upward cyclic creep of the anchor. Reduction of horizontal stress occurred until the active failure stress was approached. At this point, the sand had loosened and the anchor began to pullout rapidly. The post-cyclic static capacity was found to be lower than the ultimate static capacity of a dead anchor. In the prestress range investigated, a critical ratio of dynamic load to effective static capacity exists. Above this critical ratio, a failure of a prestressed anchor will occur earlier than a dead anchor failed by cyclic loading. Prestressed anchors below this critical ratio will experience an increase in anchor life.

A review on the behavior of helical piles as a potential offshore foundation system

Abstract: Helical piles are used mainly to resist tension forces generated by uplift and overturning moments of various structures, therefore they have been suggested as a potential alternative to driven pil...

Effects of Long-Term Dynamic Loading and Fluctuating Water Table on Helical Anchor Performance for Small Wind Tower Foundations

Abstract: The application of this study is to use helical anchors as a foundation system for small wind tower (1–10 kW) guyed cables. Helical anchors are currently used to anchor guyed cables of cell or transmission towers. However, the increased dynamic vibrations a wind turbine adds to the tower and foundation system under working loads, as well as extreme environmental conditions (e.g., straight line winds, ice load, or sudden furling shocks), require additional knowledge about the behavior of helical anchors. These field conditions were simulated in this study from tower-instrumented field data on wind speed and tower response. These tower responses were then transmitted to the helical anchors through an extensive, large-scale testing program that included monitoring the performance of the helical anchor foundation under dynamic loads, subject to natural variations in both wind regimes, precipitation (water level) and variations in helical anchor geometry. This paper compares the uplift prediction methods used in helical anchor design as well as discusses the effects of long-term dynamic loading and fluctuating water table on helical anchor performance.

Axial monotonic and cyclic performance of fibre-reinforced polymer (FRP) – steel fibre–reinforced helical pulldown micropiles (FRP-RHPM)

Abstract: This paper presents the results of full-scale axial testing on fibre-reinforced polymer (FRP) – steel fibre–reinforced helical pulldown micropiles (FRP-RHPM). The piles were subjected to axial one-...

Design of Dynamically Wind-Loaded Helical Piers for Small Wind Turbines

Abstract: The expansion of alternative energy has created a demand for sustainable alternatives for wind turbine foundation design. This study investigates the proposed application of helical piers as foundations for guyed cables of small (1–10-kW) wind towers. Before the foundation system can be implemented, pier response to typical working loads and extreme environmental conditions must be determined. Field conditions were determined by equipping an existing wind tower with accelerometers and load cells while monitoring wind speed to determine tower response. A full-scale testing program was conducted, which simulated dynamic loading conditions based on the tower response. The testing program varied between typical working conditions and extreme load events to determine the critical loading case and creep potential from long-term loading. This paper discusses the effects of dynamic loading on helical pier performance and compares the results to that of uplift prediction methods typically used in helical pier design.

A critical review: State of knowledge in seismic behaviour of helical piles

Abstract: Helical piles are being used in seismic regions of the U.S. and other countries, yet there remains much confusion regarding the state of practice and building codes for this pile type. Nonetheless, it is anticipated that piles with comparatively small cross-section and high anchoring capacity, such as helical piles, could be beneficial for seismic resistance due to their slenderness, higher damping ratios, ductility, and resistance to tip uplift. In addition, helical piles can be easily implemented as a retrofitting solution for foundations that are found to be deficient according to updated seismic codes. This paper is part of three phase investigation on the use of helical piles for earthquake mitigation. The results of an extensive literature and industry search for previous seismic tests performed on helical piles are highlighted as well as the current design standards used in seismic regions. Existing seismic testing results and current design standards are analysed to make recommendations about how ...