Embedment Effects on Vertical Bearing Capacity of Offshore Bucket Foundations on Cohesionless Soil

Barari, Amin; Ibsen, Lars Bo; Ghalesari, Abbasali Taghavi; Larsen, Kim André

doi:10.1061/(asce)gm.1943-5622.0000782

Cited by 48 publications

(17 citation statements)

References 33 publications

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“…In the numerical simulations, the pipe section of the monopile was replaced by a solid section with equivalent bending stiffness. The suitability of this simplification was previously confirmed by [1,4]. The bottom boundary of the model was taken to be 15 m below the base of the monopile.…”

Section: System Analyzed and Fe Modelmentioning

confidence: 88%

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Deformation mechanisms for offshore monopile foundations accounting for cyclic mobility effects

Barari

Bagheri

Rouainia

et al. 2017

Soil Dynamics and Earthquake Engineering

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There has been a huge surge in the construction of marine facilities (e.g., wind turbines) in Europe, despite the many unknowns regarding their long-term performance. This paper presents a new framework for design strategy based on performance measures for cyclic horizontally loaded monopile foundations located in saturated and dry dense sand, by considering pile deformations and pore pressure accumulation effects. A three-dimensional finite element model was developed to investigate the behavior of large-diameter piles. The model accounts for nonlinear dynamic interactions in offshore platforms under harsh combined moment and horizontal environmental loads, with emphasis on the cyclic mobility of the surrounding cohesionless subsoil and associated shear.The maximum moment applied in the cyclic analyses is varied from 18% to 47% of the ultimate resistance. The considered data reflect behavior at the expected load amplitudes and cycle numbers during the service life of operation.For low numbers of load cycles (<1000 cycles), there were no differences between the power law and logarithmic approaches in terms of describing the accumulated deformations; however, for high numbers of cycles (<10,000 cycles), the logarithmic law was less suited to describe the accumulation response. Magnitude of cyclic loads was found to cause a linear increase in the accumulated rotation. The results from short-term and long-term dynamic response of monopiles indicate that few load cycles with higher load levels are the main concerns in accumulation of pile rotation rather than thousands of load cycles with low amplitudes.

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Section: System Analyzed and Fe Modelmentioning

confidence: 88%

“…Recently, such structures have been developed extensively in Europe (e.g., see [27,2,[4][5][6][7]29,22,23,24,9,15,28]). Foundation concepts that are frequently used for offshore wind turbines include monopiles, jackets, and tension-leg floating substructures.…”

Section: Introductionmentioning

confidence: 99%

Deformation mechanisms for offshore monopile foundations accounting for cyclic mobility effects

Barari

Bagheri

Rouainia

et al. 2017

Soil Dynamics and Earthquake Engineering

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“…These tests were conducted on buckets with varying sizes, aspect ratios, and load paths. Barari and Ibsen [27][28][29] presented experimental and numerical results of vertical and moment loading on small-scale circular surface and suction bucket models on Baltic clay at Aalborg University. Ding et al [30] conducted several eld tests on the bearing capacity of WideShallow Composite Bucket Foundations (WSCBF) for o shore wind turbines in saturated clay.…”

Section: Literature Reviewmentioning

confidence: 99%

Evaluation of behavior of bucket foundations under pure loading

Ghaseminejad

Rowshanzamir

2017

Scientia Iranica

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Abstract. O shore wind turbine as a green renewable resource can have important roles in changing energy structure. In this study, the results of three-dimensional nite-element analyses of the pure horizontal, vertical, and moment loading of bucket foundations in medium-dense sand are presented. Sensitivity analyses have been performed on di erent bucket diameters and length-to-diameter aspect ratios (L=D); the responses for pure horizontal, vertical, and moment loading have been compared with each other. To determine the pure horizontal, vertical, and moment-bearing capacities of the bucket foundation, di erent methods have been compared. Charts and functions derived from nite-element results and responses are presented as failure envelopes in M H plane. The results show that pure ultimate capacity of the bucket signi cantly depends on bucket geometry and aspect ratio.

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“…1. The undrained vertical bearing capacity of such foundations has been investigated by several researchers using analytical, numerical and experimental methods [2], [3], [4]. It is well established that the embedment provided by the skirts increases the bearing capacity significantly.…”

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confidence: 99%

Undrained bearing capacity of tripod skirted foundations under eccentric loading

2015

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The undrained bearing capacity of a group of three rigidly connected skirted foundations (tripod) under vertical, moment or combined vertical-moment IntroductionSkirted foundations designed to sustain strong environmental forces such as winds, waves and currents have been extensively used for offshore structures (e.g. oil and gas platforms) in past decades. Although other types of foundation are also very common, skirted foundations have been shown to be cost-efficient and easy to install. Recently, their application has been investigated for the foundations to offshore wind turbines. In such structures the foundation, commonly a monopile, accounts for up to 35 % of the total cost [1] and therefore the use of suction caissons is an attractive alternative solution. Skirted foundations are shallow foundations with a peripheral vertical skirt that penetrates to depth B below the seabed, as shown in Fig. 1. The undrained vertical bearing capacity of such foundations has been investigated by several researchers using analytical, numerical and experimental methods [2], [3], [4]. It is well established that the embedment provided by the skirts increases the bearing capacity significantly. For vertical loading only and uniform soil, skirted foundations are equivalent to shallow foundations with a foundation depth equal to the skirt length [5]. The peripheral skirt also resists lateral movement, and consequently increases the lateral bearing capacity. It also increases the uplift capacity due to the development of suction within the skirt, and therefore also increases overturning moment capacity in the case of groups of skirted foundations (as considered in this study). Since such foundations are employed in offshore applications, most studies available consider combined loading, either through equivalent two-dimensional or full three-dimensional modelling [5]− [9]. Based primarily on numerical analysis, several normalized failure load surfaces have been proposed in order to take account of the effect of inclined and/or eccentric loading on the undrained bearing capacity of skirted foundations [10]− [18].Offshore wind turbines are subjected to very large overturning moments because of the horizontal wind pressures acting high above foundation level [19]− [22]. Very large foundation dimensions are generally required to carry these highly eccentric loads. As a consequence, the use of skirted foundations for offshore wind turbines is more challenging than in the case of oil and gas platforms, where vertical loading is dominant. An alternative to single skirted foundations (monopods) is the use of rigidly connected groups of three or four skirted foundations (tripods and tetrapods), which provides increased bearing capacity and drastically reduces the required minimum diameter of each footing, especially under eccentric loading. In this case, however, possible interactions between the footings need to be taken into account in the design.Unlike the case of single foundations, very few published studies consider the undrain...

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Embedment Effects on Vertical Bearing Capacity of Offshore Bucket Foundations on Cohesionless Soil

Cited by 48 publications

References 33 publications

Deformation mechanisms for offshore monopile foundations accounting for cyclic mobility effects

Deformation mechanisms for offshore monopile foundations accounting for cyclic mobility effects

Evaluation of behavior of bucket foundations under pure loading

Undrained bearing capacity of tripod skirted foundations under eccentric loading

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