Abstract
Pile foundations supporting large structures (such as high-rise buildings, oil drilling platforms, bridges etc.) are often subjected to eccentric lateral load (in addition to the vertical loads) due to the action of wind, waves, high speed traffic and ship impacts etc. The eccentric lateral load, which is usually cyclic (repetitive) in nature, induces torsion in the pile foundation. This paper presents a numerical model based on boundary element approach to study the performance of a single pile subjected to the torsional cyclic load. The model is initially validated by comparing it with the experimental data available from the literature. Thereafter, the model has been utilised to conduct a parametric study to understand the influence of the torsional cyclic loading parameters on the axial pile capacity. The results indicated that the model is able to capture the degradation in the axial pile capacity due to the torsional cyclic loading with a reasonable accuracy. Moreover, the parametric study showed that the frequency, amplitude and number of cycles play a significant role in the torsional cyclic response of the pile. The present study is essential for the development of design guidelines for pile foundations subjected to torsional cyclic load.
Highlights
The construction of large structures such as high-rise buildings, oil drilling platforms, electrical transmission towers, wind turbines, bridges, and railway embankments over a soft compressible clay poses a serious challenge to the design engineers
Twist angle with the loading parameters can be evaluated using the present model and a permissible limit could be established. Another practical aspect of the present study is the proper assessment of the in-situ load carrying capacity of the pile foundation subjected to cyclic torsional loading. This assessment might help in the design of a suitable ground improvement measure such as electro-osmosis and high-voltage electro-kinetics, which could significantly improve the load carrying capacity of the pile foundations subjected to cyclic torsional loading
The present study attempts to investigate the effect of the cyclic loading parameters namely, frequency, number of cycles and the amplitude, on the axial load carrying capacity of the pile foundation subjected to axial and torsional cyclic load
Summary
The construction of large structures such as high-rise buildings, oil drilling platforms, electrical transmission towers, wind turbines, bridges, and railway embankments over a soft compressible clay poses a serious challenge to the design engineers. A cost-effective foundation system with an acceptable degree of safety is required and these structures are usually supported by pile foundations. These piles are often subjected to cyclic (repetitive) lateral loads in addition to the vertical loads, during their service life due to wind, sea waves, high speed train traffic and ship impacts etc. The inadequate design of these piles against the cyclic torsional loading may affect the safety and serviceability of the foundation, leading to disastrous consequences (Vickery, 1979; Barker and Puckett, 1997). In case of foundations supporting offshore platforms, the amplitude (magnitude) of the cyclic torsional load is high and is usually accompanied with low frequency vibrations, while the reverse is true for onshore structures including railways (Nimbalkar and Indraratna, 2016)
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