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Journal articles on the topic 'Offshore pile performance'
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1
Li, Zheming, Malcolm D. Bolton, and Stuart K. Haigh. "Cyclic axial behaviour of piles and pile groups in sand." Canadian Geotechnical Journal 49, no. 9 (September 2012): 1074–87. http://dx.doi.org/10.1139/t2012-070.
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Piled foundations are often subjected to cyclic axial loads. This is particularly true for the piles of offshore structures, which are subjected to rocking motions caused by wind or wave actions, and for those of transport structures, which are subjected to traffic loads. As a result of these cyclic loads, excessive differential or absolute settlements may be induced during the piles’ service life. In the research presented here, centrifuge modelling of single piles and pile groups was conducted to investigate the influence of cyclic axial loads on the performance of piled foundations. The influence of installation method was investigated and it was found that the cyclic response of a pile whose jacked installation was modelled correctly is much stiffer than that of a bored pile. During displacement-controlled axial load cycling, the pile head stiffness reduces with an increasing number of cycles, but at a decreasing rate; during force-controlled axial load cycling, more permanent settlement is accumulated for a bored pile than for a jacked pile. The performance of individual piles in a pile group subjected to cyclic axial loads is similar to that of a single pile, without any evident group effect. Finally, a numerical analysis of axially loaded piles was validated by centrifuge test results. Cyclic stiffness of soil at the base of pre-jacked piles increases dramatically, while at base of jacked piles it remains almost constant.
2
Zhang, Zhaohui, Peng Guan, Jinlong Xu, Benzhang Wang, Hui Li, and Yongkang Dong. "Horizontal Loading Performance of Offshore Wind Turbine Pile Foundation Based on DPP-BOTDA." Applied Sciences 10, no. 2 (January 9, 2020): 492. http://dx.doi.org/10.3390/app10020492.
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Offshore wind power is becoming attractive in the wind-power field. With the rapid development of wind-power technology, high-power wind turbines have been implemented in practice. However, the increase in the length of the wind turbine blade causes the pile foundation to withstand a prone overturning moment. For overcoming the problems of traditional sensing technology and meeting the monitoring requirements of pile foundations, a 20 cm spatial resolution differential pulse pair Brillouin optical time-domain analysis (DPP-BOTDA) technique is used to measure a 69 m long offshore wind turbine pile under horizontal loading. From the distributed strain data collected in the test, the maximum stress location of the long pile under the horizontal load can be obtained. By analyzing the load and maximum strain (F-εmax) curve, the horizontal bearing capacity of the pile foundation can exceed 900 kN, which is the maximum horizontal load of the design. The distributed displacement calculation method based on distributed strain data is proposed, according to the force characteristics of steel pipe piles. By comparing the calculated displacement data with the measured data by the dial indicators, the mean absolute percentage error (MAPE) value is only 0.03548. Results show that the 20 cm spatial resolution DPP-BOTDA technology is very suitable for the bearing capacity test of offshore wind turbine steel pipe pile foundations.
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Yang, Jing Ping. "Numerical Analysis on Performance of Frame-Shear Structure with High Pile under Complex Load." Advanced Materials Research 1044-1045 (October 2014): 650–53. http://dx.doi.org/10.4028/www.scientific.net/amr.1044-1045.650.
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In order to acquire mechanical performance of High cap supporting frame-shear structure, in view of the sea high cap supporting frame-shear theory analysis and numerical simulation of structure is less, this paper performs numerical simulation analysis for pile caps-soil-the upper structure using the finite element software ANSYS. Expression equation of wave force is given, and three-dimensional finite element model is established. By Analysis the deformation and stress of pile foundation and pile caps under different load combinations are obtained, and the deformation, bending moment of pile top, axial force are checked, finally the feasibility of the system is verified, and these can provide a reliable basis and reference for reasonable design of offshore structures. High cap supporting frame-shear structure for its strong adaptability is widely used in offshore construction system.
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Basack, Sudip. "Analysis and Design of Offshore Pile Foundation." Advanced Materials Research 891-892 (March 2014): 17–23. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.17.
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The ocean environment necessitates the pile foundation supporting the offshore structures to be designed against cyclic load, moments and torques initiated by a combined action of waves, wind, tides, currents, etc. Such a complex loading condition induces progressive degradation in the pile-soil interactive performance introducing significant reduction in bearing capacity with increased settlement and displacements. The Author has carried out extensive experimental (laboratory model tests) and theoretical investigations (boundary element analysis) to study the salient features of this degradation and developed a design methodology for offshore pile foundation. The works conducted and the major conclusions drawn are highlighted in this paper.
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Xu, Xiangtao, James A. Schneider, and Barry M. Lehane. "Cone penetration test (CPT) methods for end-bearing assessment of open- and closed-ended driven piles in siliceous sand." Canadian Geotechnical Journal 45, no. 8 (August 2008): 1130–41. http://dx.doi.org/10.1139/t08-035.
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The cone penetration test (CPT) has been used as a means of assessing the end bearing of driven piles in sand for many decades. This paper examines the predictive performance of four new such CPT-based methods recently included in the commentary of the 22nd edition of the American Petroleum Institute’s recommended practice for fixed offshore structures. It is demonstrated that the formulations given by one of these methods, referred to as UWA-05, provides better predictions than the three other CPT methods when tested against (i) an existing database of base-capacity measurements, (ii) results from a new series of load tests on small-diameter piles, and (iii) base capacities measured in two recently conducted load tests on 1.5 m diameter pipe piles. It is shown that the UWA-05 has better predictive performance (and hence reliability) as it accounts explicitly for the effects of partial plugging during pipe–pile installation and for variations in CPT resistance in the vicinity of the pile tip.
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Barbosa, V. D., and N. S. Galgoul. "Designing Piled Foundations with a Full 3D Model." Open Construction and Building Technology Journal 12, no. 1 (March 30, 2018): 65–78. http://dx.doi.org/10.2174/1874836801812010065.
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Background:The analysis of piled foundations, where horizontal environmental loads play a very important role, has taken foundation design a step further in the 1970s and 80s. Nonlinear analyses considering P-y, T-z and Q-z curves became the state-of-the-art which also included group effect calculations thanks to an approximation proposed by [1] on the [2] equations. For some reason, however, foundation design continued to be refined using finite element calculations, but the corresponding developments never made their way into the main offshore platform design codes such as [3,4].Objective:Considering the enormous advantage that this brings for topics such as group effect and negative friction, it is obvious that opening the offshore market to this enhancement is totally desirable. This is exactly what this paper is trying to achieve.Method:In order to increase the accuracy of the prediction of piled foundations lateral displacements when group effect is considerable, a complete 3D model will be proposed using the finite element method and compared to the codes’ model and also experimental data.Results:The model in DIANA showed good performance in comparison to the codes’ model and experimental data for the single pile. When the pile group model, when the codes’ have known deficiencies, was tested, both efforts on each pile and mean displacement of the pile group fit the experimental data. However, the behavior of each pile of the group, if separately analyzed, didn’t fit many experimental data, which was attributed to the soil model utilized.Conclusion:This improved modeling procedure has been proven to improve the lateral displacement prediction of a piled foundation when group effect is considerable, when compared to codes [3,4] proposed models. However, the study of more accurate soil models could help on achieving more realistic results.
7
Wang, Zhuo, Zhuang Li, Tao Wang, and Bo Zhang. "Study on Clamping Mechanism of Internal and External Variable Diameter Lifting Tool for Offshore Foundation Pile." Machines 9, no. 1 (January 17, 2021): 19. http://dx.doi.org/10.3390/machines9010019.
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Large marine foundation piles are an important part of offshore structural pile foundations, and their lifting operations have always been a major problem in the construction and construction of marine structures. Based on IHC’s bilateral marine foundation pile spreader, this paper proposes a structural scheme of “internal and external clamping type variable diameter marine foundation pile spreader”. It solves the problem of poor adaptability of spreaders to foundation piles of the same specification and different pipe diameters. At the same time, this article has conducted in-depth research on the two clamping methods of friction clamping and wedge tooth embedded clamping. Through experiments, it is found that under the same lateral load, the load capacity of the wedge teeth tightening is three times that of the friction clamping. Aiming at the embedding and clamping method of the wedge teeth of the spreader, first of all, the influence of the tooth profile angle of the wedge teeth on their embedding performance was studied by the plastic mechanics slip line field theory and Abaqus simulation analysis. Subsequently, the elastic mechanics theory and Abaqus simulation analysis were used to study the stress characteristics of the wedge teeth during the lifting process, and the internal stress distribution was obtained. The article aims to provide a reference for the design of spreaders in actual projects.
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Basack, Sudip, and Abhik Kumar Banerjee. "Offshore Pile Foundation Subjected to Lateral Cyclic Load in Layered Soil." Advanced Materials Research 891-892 (March 2014): 24–29. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.24.
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The pile foundations supporting offshore structures are required to be designed against cyclic load, moments and torques initiated by a combined action of waves, wind, tides, currents, etc. Such a complex loading condition produces progressive degradation in the pile-soil interactive performance which is likely to introduce significant reduction in bearing capacity with increased settlement and displacements. This paper is based on a numerical model developed by the Authors to study the response of pile foundation under lateral cyclic load in layered soil. The model is validated with a field test data and thereafter, parametric studies have been carried out. A brief description of the works conducted and the major conclusions drawn are highlighted in this paper.
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Tirandazian, Mehran, and Gholamreza Nouri. "Numerical modeling of the seismic performance of monopile supported wind turbines in sandy soils susceptible to liquefaction." International Journal of Engineering & Technology 7, no. 2.13 (April 15, 2018): 263. http://dx.doi.org/10.14419/ijet.v7i2.13.12676.
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Since 1980, as wind farms have moved from coastal to offshore areas, the wind energy industry has been completely transformed which in turn has led to the increase in the construction of wind turbines. On the other hand, harsher offshore environmental conditions have led to larger lateral loads and anchorages applied to the wind turbines and specifically to their piles than other coastal and offshore structures. Thus, more solid piles are required to ensure proper rigidity and bearing capacity. Liquefaction is one of the most important seismic hazards through which various damages caused to different parts of wind turbines. In order to develop coastal and offshore structures in Iran, a study of liquefaction is of great importance due in part to the high risk of seismicity. In this study, the effect of liquefaction on seismic response of offshore wind turbines is examined taking advantage of a finite element model. To this end, all analyzes have been carried out in both occurrence and non-occurrence of the liquefaction, so that by comparing these two modes, the mechanisms affecting the seismic behavior of wind turbines are understood. As depth increases, the possibility of liquefaction is reduced due to higher pressure. Liquefaction is considered to a depth of 20 m and structural behavior is evaluated based on the level of seismic hazard, the thickness of the susceptible layers, soil compaction, the non-fluidizing top layer, the gradient of the earth, the thickness of the monopole, the dimensions of the wind turbine and different soil layering conditions. According to the mentioned factors, a comprehensive and parametric study of the behavior of wind turbines in seismic zones, and in different loading conditions, pile diameters and soil layering is carried out in soils prone to liquefaction. Since analyzes are performed in both occurrence and non-occurrence of the liquefaction, the number of analyzes and computational cost in this research becomes enormous. Therefore, there is a need for a highly effective software and a practical modeling method that will allow for this comprehensive study. Open Sees software and beam on nonlinear Winkler foundation approach are used to model the soil-pile-structure interaction. The minor differences observed in the laboratory values compared to the numerically calculated ones may refer to the fact that the chamber is not modeled. In the bottom layer, as the depth decreases, the elastic response spectra record larger values which are due to the resonance in the structure.
10
Jalbi, Saleh, Joseph Hilton, and Luke Jacques. "Assessment of Practical Methods to Predict Accumulated Rotations of Monopile-Supported Offshore Wind Turbines in Cohesionless Ground Profiles." Energies 13, no. 15 (July 31, 2020): 3915. http://dx.doi.org/10.3390/en13153915.
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Monopiles supporting offshore wind turbines can experience permanent non-recoverable rotations (or displacements) during their lifetime due to the cyclic nature of hydrodynamic and aerodynamic loading exerted on them. Recent studies in the literature have demonstrated that conventional cyclic p–y curves recommended in different codes of practice (API-RP-2GEO and DNVGL-RP-C212) may not capture the effects of long-term cyclic loads as they are independent of the loading profile and the number of applied cycles. Several published methodologies based on laboratory scaled model tests (on sands) exist to determine the effect of cyclic lateral loads on the long-term behaviour of piles. The tests vary in terms of the pile behaviour (rigid or flexible pile), number of applied loading cycles, and the load profile (one-way or two-way loading). The best-fit curves provided by these tests offer practical and cost-efficient methods to quantify the accumulated rotations when compared to Finite Element Method. It is therefore desirable that such methods are further developed to take into account different soil types and the complex nature of the loading. The objective of this paper is to compare the performance of the available formulations under the actions of a typical 35-h (hour) storm as per the Bundesamt für Seeschifffahrt und Hydrographie (BSH) recommendations. Using classical rain flow counting, the loading time-history is discretized into load packets where each packet has a loading profile and number of cycles, which then enables the computation of an equivalent number of cycles of the largest load packet. The results show that the loading profile plays a detrimental role in the result of the accumulated rotation. Furthermore, flexibility of the pile also has an important effect on the response of the pile where predictions obtained from formulations based on flexible piles resulted in a much lower accumulated rotation than tests based on rigid piles. Finally, the findings of this paper are expected to contribute in the design and interpretation of future experimental frameworks for Offshore Wind Turbine (OWT) monopiles in sands, which will include a more realistic loading profile, number of cycles, and relative soil to pile stiffness.
11
Chen, Libo, Xiaoyan Yang, Lichen Li, Wenbing Wu, M. Hesham El Naggar, Kuihua Wang, and Jinyong Chen. "Numerical Analysis of the Deformation Performance of Monopile under Wave and Current Load." Energies 13, no. 23 (December 4, 2020): 6431. http://dx.doi.org/10.3390/en13236431.
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The research on the deformation mechanism of monopile foundation supporting offshore wind turbines is significant to optimize the design of a monopile foundation under wave and current load. In this paper, a three-dimensional wave-pile-soil coupling finite element model is proposed to investigate the deformation mechanism of monopile undercurrent and fifth-order Stokes wave. Different from the conventional assumption that there is no slip at the pile-soil interface, Frictional contact is set to simulate the relative movement between monopile and soil. Numerical results indicate that under extreme environmental conditions, the monopile foundation sways within a certain range and the maximum displacement in the loading direction is 1.3 times the displacement in the reverse direction. A further investigation has been made for a large-diameter pipe pile with various design parameters. The finite element analyses reveal that the most efficient way to reduce the deflection of the pile head is by increasing the embedment depth of the monopile. When the embedment depth is limited, increasing the pile diameter is a more effective way to strengthen the foundation than increasing the wall thickness.
12
Xiong, Min, and Yu Huang. "Static and Dynamic Reliability Analysis of Laterally Loaded Pile Using Probability Density Function Method." Journal of Marine Science and Engineering 8, no. 12 (December 5, 2020): 994. http://dx.doi.org/10.3390/jmse8120994.
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Pile foundation is one of the common foundation forms in marine geotechnical engineering, especially in wind power engineering. Its operation safety is seriously affected by many uncertainties, such as the randomness of ground motion in intensity and frequency. The stochastic reliability analysis method can better characterize these uncertainties in the evaluation of the safety performance of pile foundation. The probability density functions (PDFs) of stochastic systems are important prerequisites for reliability analysis. However, for geotechnical problems, the coupling between parametric and excitation randomness and the nonlinear mechanical properties of rock and soil make it very difficult to obtain the associated PDFs. Instead, the probability density evolution method (PDEM) is introduced and is used to investigate the static and dynamic reliability of laterally loaded piles as an example of a geotechnical problem. Compared with Monte Carlo stochastic simulations, PDEM-based computing is shown to be highly efficient when applied to the seismic design of pile in geotechnical engineering, and its calculation efficiency is 20 times of the former for the seismic dynamic reliability of pile foundation. This study provides a new reference for the efficient design and safety evaluation of offshore pile foundation engineering based on static and dynamic reliability of multiple random factors.
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Wang, Zhuo, Bo Zhang, and Tao Wang. "Analysis and Experiments of Embedded Gripping Mechanism Used in Large-scale Tools Holding Up Pile Foundation in Ocean." Polish Maritime Research 26, no. 3 (September 1, 2019): 15–21. http://dx.doi.org/10.2478/pomr-2019-0041.
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Abstract With the rapid development of the marine economy and continuous improvement of the industry, the scale of the offshore engineering is increasing. This raises interest in studying, theoretically and experimentally, gripping and bearing mechanisms for large-scale holding and lifting tools used in foundation pile installations. In this paper, the embedded gripping mechanism is studied based on the theory of elastic-plastic mechanics. The embedded and bearing performance of the tooth is simulated and the influence factors are studied. In addition, the device used in the simplified embedded experiment on the tooth of the embedded block is designed. The relationship between embedded depth, load, and tooth profile angle is identified and validated. Meanwhile, the embedded performance of linear and ring type teeth is compared experimentally in order to select the suitable type of tooth for various situations. This comparison makes the basis for designing an upending gripper for the marine pile foundation, which can realize the operation of holding the pile to prevent its falling.
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Kim, Hyun-Gi, Bum-Joon Kim, and Kwang-Ho Lee. "Analysis of Piled Concrete Foundation for a 3-MW Class Offshore Wind Turbine along the Southwest Coast in Korea." Journal of Marine Science and Engineering 8, no. 3 (March 20, 2020): 215. http://dx.doi.org/10.3390/jmse8030215.
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Concrete foundations have received attention as offshore wind turbine support structures because of their various advantages. However, because of the lack of information on structural analysis and the design method of complex marine environmental loads, concrete foundations cannot be applied on actual sites. Therefore, the structure behavior mechanism and concrete reinforcement design need to be evaluated based on soil-structure interactions. Herein, an efficient method for analysis of piled concrete foundations (PCFs) is presented, and the stability of PCF structures is evaluated under environmental conditions of the coast in Korea for a 3-MW wind turbine. Three analytical parameters for PCF models were defined to consider soil-structure interaction. The results of each model were compared with the displacement, stresses, and natural frequencies. Using the analysis results, a prestressing reinforcement design for concrete foundations was proposed. Quasi-static analysis showed that maximum displacement was sufficiently small and the maximum stresses did not exceed the allowable stresses. PCF showed excellent dynamic performance and structural stability. In addition, stiffness of the soil spring model influenced the natural frequency rather than the stiffness of the pile type. Detailed analysis of the connections between piles and concrete need to be studied in the future.
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Kunitaki, Denise Margareth Kazue Nishimura, Beatriz Souza Leite Pires de Lima, Alexandre Gonçalves Evsukoff, and Breno Pinheiro Jacob. "Probabilistic and Fuzzy Arithmetic Approaches for the Treatment of Uncertainties in the Installation of Torpedo Piles." Mathematical Problems in Engineering 2008 (2008): 1–26. http://dx.doi.org/10.1155/2008/512343.
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The “torpedo” pile is a foundation system that has been recently considered to anchor mooring lines and risers of floating production systems for offshore oil exploitation. The pile is installed in a free fall operation from a vessel. However, the soil parameters involved in the penetration model of the torpedo pile contain uncertainties that can affect the precision of analysis methods to evaluate its final penetration depth. Therefore, this paper deals with methodologies for the assessment of the sensitivity of the response to the variation of the uncertain parameters and mainly to incorporate into the analysis method techniques for the formal treatment of the uncertainties. Probabilistic and “possibilistic” approaches are considered, involving, respectively, the Monte Carlo method (MC) and concepts of fuzzy arithmetic (FA). The results and performance of both approaches are compared, stressing the ability of the latter approach to efficiently deal with the uncertainties of the model, with outstanding computational efficiency, and therefore, to comprise an effective design tool.
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Gantes, Charis J., Maria Villi Billi, Mahmut Güldogan, and Semih Gül. "A Novel Tripod Concept for Onshore Wind Turbine Towers." Energies 14, no. 18 (September 13, 2021): 5772. http://dx.doi.org/10.3390/en14185772.
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A wind turbine tower assembly is presented, consisting of a lower “tripod section” and an upper tubular steel section, aiming at enabling very tall hub heights for optimum exploitation of the wind potential. The foundation consists of sets of piles connected at their top by a common pile cap below each tripod leg. The concept can be applied for the realization of new or the upgrade of existing wind turbine towers. It is adjustable to both onshore and offshore towers, but emphasis is directed towards overcoming the stricter onshore transportability constraints. For that purpose, pre-welded individual tripod parts are transported and are then bolted together during erection, contrary to fully pre-welded tripods that have been used in offshore towers. Alternative constructional details of the tripod joints are therefore proposed that address the fabrication, transportability, on-site erection and maintenance requirements and can meet structural performance criteria. The main structural features are demonstrated by means of a typical case study comprising a 180-m-tall tower, consisting of a 120-m-tall tubular superstructure on top of a 60-m-tall tripod substructure. Realistic cross-sections are calculated, leading to weight and cost estimations, thus demonstrating the feasibility and competitiveness of the concept.
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Hasani, H., A. A. Golafshani, and H. E. Estekanchi. "Seismic performance evaluation of jacket-type offshore platforms using endurance time method considering soil-pile-superstructure interaction." Scientia Iranica 24, no. 4 (August 1, 2017): 1843–54. http://dx.doi.org/10.24200/sci.2017.4275.
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Xie, Mian, and Susana Lopez-Querol. "Numerical Simulations of the Monotonic and Cyclic Behaviour of Offshore Wind Turbine Monopile Foundations in Clayey Soils." Journal of Marine Science and Engineering 9, no. 9 (September 20, 2021): 1036. http://dx.doi.org/10.3390/jmse9091036.
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Most of the reported centrifuge tests available in the existing literature on offshore wind turbine foundations are focused on the behaviour of monopiles in sands, but very few studies on clayey soils can be found, due to the very long saturation and consolidation periods required to properly conduct experiments in such materials. Moreover, most of the reported numerical simulations using finite element analyses have been validated with monotonic centrifuge tests only. In this research, both monotonic and cyclic performance of offshore wind turbines in clay are validated and justified. The relationship between the monopile rotation in clays and the geometry and strength of the soil has been found and quantified. A prediction of the rotation for a high number of cycles of loading, based on the one experienced by the pile during the first cycle, can be obtained using the correlation derived in the paper. For those cases in which the rotation does not reach a steady value after a high number of cycles, the cumulative rate has been found significantly larger than the prediction conducted with standard analytical methods. A new design methodology for the design of offshore monopile foundations in clay is presented.
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Cobby, G. L., and R. J. Craddock. "WESTERN AUSTRALIAN GOVERNMENT DECISION-MAKING CRITERIA INVOLVED IN THE REGULATION OF DRILLING FLUIDS OFFSHORE." APPEA Journal 39, no. 1 (1999): 600. http://dx.doi.org/10.1071/aj98039.
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Traditional regulatory regimes have focussed upon the regulation of classes of drilling fluids based on their chemical category. The Western Australian Department of Minerals and Energy (WADME) has developed an alternative approach to the regulation of drilling fluids offshore.This alternate approach is based on an objective case- by-case assessment of each drilling proposal. The WADME assesses the likelihood and consequence (environmental risk) of potential environmental events associated with the total drilling proposal in determining the acceptability of that proposal.This approach uses a framework of assessment criteria to assist in decision making. These criteria include the environmental sensitivity of the well location; the oceanographic conditions and the potential for cuttings accumulation; the type and quantity of the proposed drilling fluid and cuttings; the method of cuttings disposal; the environmental performance of the drilling fluid under standard test protocols and the technical justification for the proposed use of the drilling fluids.This framework offers a more holistic assessment of the potential environmental impacts of a drilling proposal. This paper considers each criterion in this assessment and introduces cuttings pile removal as a topic for discussion.
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Hemmati, Arash, and Erkan Oterkus. "Semi-Active Structural Control of Offshore Wind Turbines Considering Damage Development." Journal of Marine Science and Engineering 6, no. 3 (September 5, 2018): 102. http://dx.doi.org/10.3390/jmse6030102.
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High flexibility of new offshore wind turbines (OWT) makes them vulnerable since they are subjected to large environmental loadings, wind turbine excitations and seismic loadings. A control system capable of mitigating undesired vibrations with the potential of modifying its structural properties depending on time-variant loadings and damage development can effectively enhance serviceability and fatigue lifetime of turbine systems. In the present paper, a model for offshore wind turbine systems equipped with a semi-active time-variant tuned mass damper is developed considering nonlinear soil–pile interaction phenomenon and time-variant damage conditions. The adaptive concept of this tuned mass damper assumes slow change in its structural properties. Stochastic wind and wave loadings in conjunction with ground motions are applied to the system. Damages to soil and tower caused by earthquake strokes are considered and the semi-active control device is retuned to the instantaneous frequency of the system using short-time Fourier transformation (STFT). The performance of semi-active time-variant vibration control is compared with its passive counterpart in operational and parked conditions. The dynamic responses for a single seismic record and a set of seismic records are presented. The results show that a semi-active mass damper with a mass ratio of 1% performs significantly better than a passive tuned mass damper with a mass ratio of 4%.
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Robinson, Mouafo Teifouet Armand, and Zhenyu Wang. "The effect of the TMD on the vibration of an offshore wind turbine considering three soil-pile-interaction models." Advances in Structural Engineering 24, no. 12 (April 16, 2021): 2652–68. http://dx.doi.org/10.1177/13694332211008316.
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In this paper we propose the use of the power series method and the Newmark-Beta algorithm to study the mitigation by the tuned mass damper (TMD) of an offshore wind turbine(OWT). The monopile of the OWT is taken as slender beam buried in a homogeneous soil while the tower is considered as tapered slender beam. Mathematically, both monopile and tower are modeled as elastic Euler-Bernoulli beams, with a point mass at the tower top representing the rotor nacelle assembly (RNA). First of all, the power series method is utilized to calculate the first natural frequencies of AF and CS models. The obtained results are compared with the first natural frequency of DS model obtained from FEM-Abaqus with good satisfaction. Next, the obtained mode shapes are used to establish the system of ordinary differential equations (ODE) governing the dynamic of OWT subjected to a TMD. Afterwards, the Newmark-Beta algorithm is employed to solve the ODE. Accuracy of the introduced approach is verified by setting a comparison between our results with those obtained using FEM-Abaqus. Finally, the influence of several parameters on the performance of TMD is shown in some plots.
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Bea, R. G. "Evaluation of Uncertainties in Loadings on Offshore Structures due to Extreme Environmental Conditions." Journal of Offshore Mechanics and Arctic Engineering 115, no. 4 (November 1, 1993): 237–45. http://dx.doi.org/10.1115/1.2920118.
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This paper summarizes results from a Canadian Standards Association (CSA) sponsored study of the uncertainties associated with extreme (1000 to 10,000-yr return periods) environmental loadings acting on offshore structures (Bea, 1991). The evaluations of the loadings addressed loading effects that resulted from dynamic and nonlinear interactions of the structures. Loading uncertainties were organized and characterized in two categories: 1) inherent randomness (aleatory uncertainty), and 2) analytical variability (epistemic uncertainty). The study addressed the global ultimate limit state performance of three structures designed according to the provisions of the draft CSA guidelines (1989a, 1989b) for offshore structures: 1) a concrete Gravity Base Structure (GBS) located off the East coast of Canada (Hibernia), 2) a steel pile template located on the Scotian Shelf off Sable Island, and 3) a caisson retained island located in the Mackenzie Delta area of the Beaufort Sea (Amuligak). The results of this study indicate that, based on presently available information and data, it is often not possible to develop unambiguous characterizations of uncertainties. The different technical communities that background environmental conditions and forces (storms, earthquakes, ice) recognize and integrate these uncertainties into loading characterizations in different ways. In many cases, major sources of uncertainty are not included in probabilistic characterizations. Because of the needs for design code information sensitivity and consistency in demonstrating compliance with target reliability goals, there is a need for well-organized and definitive evaluations of uncertainties in extreme environmental loadings and load effects (Bitner-Gregersen et al., 1993).
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Sahdi, Fauzan, David J. White, Christophe Gaudin, Mark F. Randolph, and Noel Boylan. "Laboratory development of a vertically oriented penetrometer for shallow seabed characterization." Canadian Geotechnical Journal 53, no. 1 (January 2016): 93–102. http://dx.doi.org/10.1139/cgj-2015-0165.
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Current site investigation practice for offshore pipeline design relies on soil parameters gathered from boreholes or in situ test soundings to depths of 1–2 m below the mudline. At these depths, the fine-grained seabed is very soft and possesses low undrained strength, which can be difficult to measure. This paper describes a centrifuge test programme undertaken to evaluate the feasibility and performance of a novel penetrometer designed to assess the shallow strength of soft seabed over continuous horizontal profiles. This device is termed the vertically oriented penetrometer (VOP). Tests were performed on a normally consolidated kaolin sample, with the VOP translated horizontally at velocities ranging from 1 to 30 mm/s, after embedding the VOP at 30 and 45 mm depths. All tests involved many cycles of VOP forward and backward movement to assess its potential to derive the ratio of intact to fully remoulded strength. Strength determination is achieved by dragging the VOP at a specified embedment depth along the soil surface, and deriving the soil strength from the measured resistance as if the VOP were a laterally loaded pile. The VOP is shown to yield comparable strength measurements to that of a T-bar penetrometer. The VOP is a potentially valuable addition to the range of tools used to characterize soil strength, both in small-scale centrifuge models and, following practical development, potentially also in the field.
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Akpila, S., and I. Omunguye. "Theoretical modeling of horizontal-vertical loading of circular foundation in the offshore Niger Delta of Nigeria." World Journal of Engineering 11, no. 1 (March 1, 2014): 49–54. http://dx.doi.org/10.1260/1708-5284.11.1.49.
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Theoretical modeling on the performance of offshore circular foundation installed on clay and subjected to combined horizontal-vertical load in the Niger Delta has been attempted. Analytical methods of Skempton, Brinch Hanson, and Vesic were used to evaluate concentric vertical loads on offshore piles. Horizontal forces, H were evaluated for varying wave heights on circular piles of 1.0 to 2.0 m diameters using available meteorological and oceanographic offshore records. The results revealed that sliding failure commenced when the ratio of vertical load to footing area and undrained shear strength, V/Asu assumed negative values (i.e. at H > 0.082 Asu). The maximum mean vertical load is 6.107 Asu, and to guide against the occurrence of bearing capacity failure by sliding, V > 0.75H for cases where the ratio of footing depth to breadth ratio is lesser than one, (D/B < 1.0) and V > 0.70H when footing depth to breadth ratio is greater than one (D/B > 1.0).
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Kouichirou, Anno, and Takeshi Nishihata. "DEVELOPMENT ON OFFSHORE STRUCTURE." Coastal Engineering Proceedings 1, no. 32 (January 31, 2011): 50. http://dx.doi.org/10.9753/icce.v32.structures.50.
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Authors have developed the offshore structure for control of sea environment named S-VHS construction
method, which is composed of the sloping top slit-type caisson and steel pipe piles. The sloping top form enables to
realize the remarkable reduction of wave force exerted on the dike body compared with the conventional one.
In this paper, hydraulic feature with wave dissipation ability and wave force reduction effect are verified
through some hydraulic experiments. After the preliminary study for the valid structure form, reflection and
transmission ability for the selected structure models were tested with the hydraulic experiment relevant to the ratio of
caisson width and wave length. Finally, wave force experiment was executed and it revealed the performance of wave
force reduction. Based on the results, we proposed specific design wave force formula for S-VHS construction method.
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Konstandakopoulou, Foteini, Maria Konstantinidou, Nikos Pnevmatikos, and George D. Hatzigeorgiou. "Safety and Performance of Offshore Platforms Subjected to Repeated Earthquakes." Infrastructures 5, no. 4 (April 22, 2020): 38. http://dx.doi.org/10.3390/infrastructures5040038.
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In this work, a systematic study is conducted on the behavior of three-dimensional offshore oil/natural gas platforms under the action of seismic sequences. Such repeated earthquakes result in a noteworthy accumulation of damage in a platform since, in many cases, any rehabilitation process between any two or more successive ground motions cannot be essentially materialized because of lack of time. Conversely, in the past, the seismic response of offshore platforms has been exclusively investigated for the case of single earthquakes. In this study, two three-dimensional platforms are examined, where the first one is assumed to be completely constrained at its base (fixed boundary conditions), while the second one is founded in deformable soil with the aid of long piles. These structures are subjected to real seismic sequences which have been recorded by the same station in a short period of time. Additionally, the platforms under consideration are also subjected to artificial seismic sequences. In this study, we found that sequential earthquakes have a significant effect on the response of these special structures, and this finding should be taken into account in their design.
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Tavasoli, Omid, and Mahmoud Ghazavi. "Effect of tapered and semi-tapered geometry on the offshore piles driving performance." Ocean Engineering 201 (April 2020): 107147. http://dx.doi.org/10.1016/j.oceaneng.2020.107147.
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Bhattacharya, Subhamoy, Domenico Lombardi, Sadra Amani, Muhammad Aleem, Ganga Prakhya, Sondipon Adhikari, Abdullahi Aliyu, et al. "Physical Modelling of Offshore Wind Turbine Foundations for TRL (Technology Readiness Level) Studies." Journal of Marine Science and Engineering 9, no. 6 (May 29, 2021): 589. http://dx.doi.org/10.3390/jmse9060589.
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Offshore wind turbines are a complex, dynamically sensitive structure due to their irregular mass and stiffness distribution, and complexity of the loading conditions they need to withstand. There are other challenges in particular locations such as typhoons, hurricanes, earthquakes, sea-bed currents, and tsunami. Because offshore wind turbines have stringent Serviceability Limit State (SLS) requirements and need to be installed in variable and often complex ground conditions, their foundation design is challenging. Foundation design must be robust due to the enormous cost of retrofitting in a challenging environment should any problem occur during the design lifetime. Traditionally, engineers use conventional types of foundation systems, such as shallow gravity-based foundations (GBF), suction caissons, or slender piles or monopiles, based on prior experience with designing such foundations for the oil and gas industry. For offshore wind turbines, however, new types of foundations are being considered for which neither prior experience nor guidelines exist. One of the major challenges is to develop a method to de-risk the life cycle of offshore wind turbines in diverse metocean and geological conditions. The paper, therefore, has the following aims: (a) provide an overview of the complexities and the common SLS performance requirements for offshore wind turbine; (b) discuss the use of physical modelling for verification and validation of innovative design concepts, taking into account all possible angles to de-risk the project; and (c) provide examples of applications in scaled model tests.
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Zitti, Gianluca, Nico Novelli, and Maurizio Brocchini. "Preliminary Results on the Dynamics of a Pile-Moored Fish Cage with Elastic Net in Currents and Waves." Journal of Marine Science and Engineering 9, no. 1 (December 24, 2020): 14. http://dx.doi.org/10.3390/jmse9010014.
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Over the last decades, the aquaculture sector increased significantly and constantly, moving fish-farm plants further from the coast, and exposing them to increasingly high forces due to currents and waves. The performances of cages in currents and waves have been widely studied in literature, by means of laboratory experiments and numerical models, but virtually all the research is focused on the global performances of the system, i.e., on the maximum displacement, the volume reduction or the mooring tension. In this work we propose a numerical model, derived from the net-truss model of Kristiansen and Faltinsen (2012), to study the dynamics of fish farm cages in current and waves. In this model the net is modeled with straight trusses connecting nodes, where the mass of the net is concentrated at the nodes. The deformation of the net is evaluated solving the equation of motion of the nodes, subjected to gravity, buoyancy, lift, and drag forces. With respect to the original model, the elasticity of the net is included. In this work the real size of the net is used for the computation mesh grid, this allowing the numerical model to reproduce the exact dynamics of the cage. The numerical model is used to simulate a cage with fixed rings, based on the concept of mooring the cage to the foundation of no longer functioning offshore structures. The deformations of the system subjected to currents and waves are studied.
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Xianhui, You, Wu Zhaoqi, and Chen Zehao. "Comparison of Prediction Methods for Axial Strength of Grouted Connections with Shear Keys." Applied Sciences 10, no. 6 (March 12, 2020): 1942. http://dx.doi.org/10.3390/app10061942.
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Grouted connections are commonly used in marine engineering, especially on oil platforms, cross-sea bridges, and offshore wind power turbines. The prediction methods for axial carrying capacity of grouted connections with shear keys and their application ranges in current codes were analyzed in this paper. The calculated results by using different codes were compared based on a practical grouted connection between steel piles and the jacket foundation of a wind turbine. The research team conducted axial compression tests on seven specimens, collected a wide range of experimental results to establish a database, and finally compared the standard calculation results with the experimental results. The study indicates that the axial strength of grouted connections predicted by different methods is distinct. The calculation formula of the British Health and Safety Executive (HSE, 2002) has obvious limitations; specifically, with increased shear keys, strength is overestimated, resulting in insecure design outcome of structures. The results calculated by the Norwegian Det Norske Veritas (DNV, 2013) are generally consistent with the experimental results, in which the reduction effect of multiple shear keys was considered. The prediction method of the American Petroleum Institute (API, 2007), which undervalues the bearing performance of connections, is excessively conservative. The method of the combined Norwegian and German Det Norske Veritas–Germanischer Lloyd (DNV-GL, 2016) has wider applicability and is safe, reliable, and economical.
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Karamjavan, Abbas Firouzi. "STUDY ABOUT THE EFFECTS OF PILE SPACING ON THE PERFORMANCE OF PILE GROUP UNDER COMPOSITE LOADS, ADJACENT STRUCTURE LOADS, AND BENDING MOMENT IN SAND." Archives for Technical Sciences 1, no. 16 (July 27, 2017). http://dx.doi.org/10.7251/afts.2017.0916.055a.
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Pile group is a particular type of deep foundations which is designed and installed as the ultimatesolution to foundation construction, load transition to the resistant subsurface layers, providing lateralresistance, and overcoming the poor performance of surface soils. Pile design should be done withrespect to structural consideration, the load-carrying capacity of the surface and surrounding soil,settlement, and constructional, technical and environmental problems. Piles are mostly and widelyutilized in coastal and offshore structures, and sustain vertical and lateral loads. Considering theimposed loads on structure, the effect of these loads on the pile behavior should be analyzed with anappropriate method. In this study, a 4x4 pile group with piles of 100-cm diameter and center-to-centerspacing of 2, 3, 4 times the diameter is modeled using the Plaxis 3D foundation program, which usesthe finite element method, and the Mohr-Coulomb model, and the behavior of piles subjected toloading, driven in sand, are investigated. Taking the achieved results, the mechanism of the pile groupbehavior under composite loads, adjacent structure loads, and bending moment are calculated, anddisplacement in the x-direction, y-direction and along the length, the bending moment and the axialforce for each pile within a distance of 2, 3, 4 times the diameter are attained.
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Martinez, Alejandro. "Skin Friction Directionality in Monotonically- and Cyclically-Loaded Bio-inspired Piles in Sand." DFI Journal The Journal of the Deep Foundations Institute 15, no. 1 (April 30, 2021). http://dx.doi.org/10.37308/dfijnl.20200831.222.
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Piles can be subjected to axial loading in opposite directions during their installation and service life. For instance, piles for offshore jacket structures and load testing reaction systems are subjected to compressive loading during installation and tensile or cyclic loading during service life. This creates a design dilemma: while a large skin friction can lead to refusal at shallower depths than required during driving, it also promotes a large pile axial capacity. This paper describes the load-transfer behavior of piles with surfaces inspired by the belly scales of snakes that mobilize a direction-dependent skin friction. The investigation presented herein consists of a series of twelve centrifuge pile load tests on bio-inspired and smooth reference piles in dense and loose deposits of Ottawa F65 sand. Test results indicate that greater skin friction forces are mobilized when the bio-inspired piles are displaced in the cranial direction (i.e. soil moving against asperities) relative to the caudal direction (i.e. soil moving along asperities). This is observed during pushing and driving installation, where greater skin friction forces were mobilized during installation by pushing in the cranial direction and driving in the cranial direction required more blows per meter. Similarly, the skin friction mobilized during pullout tests was between 82% and 198% greater in the cranial direction than in the caudal direction, and the skin friction mobilized during pullout by the bio-inspired pile in the cranial direction was between 560% to 845% greater than that mobilized by the reference untextured pile. During cyclic loading, degradation of the skin friction magnitude and pile secant stiffness was observed in both cranial and caudal directions; however, the mobilized magnitudes were generally greater in the cranial direction. Discussion is provided on the potential benefits that the bio-inspired surface texture could realize on the overall performance of axially-loaded piles.
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Cerfontaine, Benjamin, Michael John Brown, Jonathan Adam Knappett, Craig Davidson, Yaseen Umar Sharif, Marco Huisman, Marius Ottolini, and Jonathan David Ball. "Control of screw pile installation to optimise performance for offshore energy applications." Géotechnique, September 20, 2021, 1–52. http://dx.doi.org/10.1680/jgeot.21.00118.
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Honarvar, M. R., M. R. Bahaari, and B. Asgarian. "Effect of Grouting in Jacket Type Offshore Platforms Pile-Leg Interaction in Nonlinear Range of Deformation." Journal of Offshore Mechanics and Arctic Engineering 130, no. 4 (September 26, 2008). http://dx.doi.org/10.1115/1.2904586.
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The annulus between the pile and leg in jacket type offshore platforms may be filled with cement grout mainly to reduce horizontal deflections, inhibit corrosion, and increase the energy absorption capacity. This paper discusses an approach, which can be used to demonstrate an enhanced structural performance due to the both presence and lack of grouted piles. The compressive stress-strain response of the grout has been derived from the performed experiments. Having this response, the fiber beam column post-buckling element in the commercial code, DRAIN-3DX, was being used to investigate the behavior of grouted and ungrouted jackets and also the relative pile-leg interaction. It is therefore concluded that in the cases where the existing structure is ungrouted or incompletely grouted, adequate grouting can be considered as a relatively inexpensive method to improve the strength and performance of the structure. In fact, the cement filling of a tubular member increases its overall strength and also provides additional stability. The lateral force-deformation curves are equivalents for the cases where the axial force is less than 30% of the yielding force, Pyielding. However, as the axial force increases, the grouted portal element gradually gives a much better performance compared to the ungrouted element. By increasing the axial force, the lateral hysteretic behavior deteriorates in both grouted and ungrouted cases; however, this deterioration is more severe in the case of an ungrouted portal element.
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Doherty, James P., and Barry M. Lehane. "An Automated Approach for Optimizing Monopile Foundations for Offshore Wind Turbines for Serviceability and Ultimate Limit States Design." Journal of Offshore Mechanics and Arctic Engineering 140, no. 5 (April 24, 2018). http://dx.doi.org/10.1115/1.4039523.
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Pile foundation design is conventionally conducted using a process of trial and error, where the dimensions of a pile are estimated and the performance is computed and compared with design criteria. The dimensions are varied and the process is repeated in order to converge to a safe and economical design. In this paper, this time-consuming and labor intensive process is replaced with an automated approach using the example case of an offshore monopile supporting a wind turbine. The optimum length and diameter of the monopile are determined with the aim of minimizing the pile weight while satisfying both serviceability and ultimate limit state criteria. The approach handles general soil and loading conditions and includes an ability to incorporate cyclic loading.
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Guo, Zhen, Luqing Yu, Lizhong Wang, S. Bhattacharya, G. Nikitas, and Yuelong Xing. "Model Tests on the Long-Term Dynamic Performance of Offshore Wind Turbines Founded on Monopiles in Sand." Journal of Offshore Mechanics and Arctic Engineering 137, no. 4 (August 1, 2015). http://dx.doi.org/10.1115/1.4030682.
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The dynamic response of the supporting structure is critical for the in-service stability and safety of offshore wind turbines (OWTs). The aim of this paper is to first illustrate the complexity of environmental loads acting on an OWT and reveal the significance of its structural dynamic response for the OWT safety. Second, it is aimed to investigate the long-term performance of the OWT founded on a monopile in dense sand. Therefore, a series of well-scaled model tests have been carried out, in which an innovative balance gear system was proposed and used to apply different types of dynamic loadings on a model OWT. Test results indicated that the natural frequency of the OWT in sand would increase as the number of applied cyclic loading went up, but the increasing rate of the frequency gradually decreases with the strain accumulation of soil around the monopile. This kind of the frequency change of OWT is thought to be dependent on the way how the OWT is cyclically loaded and the shear strain level of soil in the area adjacent to the pile foundation. In this paper, all test results were plotted in a nondimensional manner in order to be scaled up to predict the consequences for prototype OWT in sandy seabed.
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Deng, Zhengzhi, Pinjie Wang, and Pengda Cheng. "Hydrodynamic Performance of an Asymmetry OWC Device Mounted on a Box-Type Breakwater." Frontiers in Marine Science 8 (June 22, 2021). http://dx.doi.org/10.3389/fmars.2021.677030.
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To share the construction and maintenance cost, an asymmetric oscillating water column (OWC) device integrated with a pile-fixed box-typed offshore breakwater is considered experimentally and numerically. A fully nonlinear numerical wave tank is established and validated with the open source solver OpenFOAM. The effects of the width and draft of rear box, and the incident wave height on the wave energy conversion efficiency, reflection and transmission coefficients, and energy dissipation coefficient are examined. In addition, the superiority of the present coupling system, compared to the traditional box-type breakwater, is discussed. With well comparisons, the results show that the existence of the rear breakwater is beneficial for the formation of partial standing waves and further wave energy conversion. In the range of wave heights tested, the higher the incident wave height, the larger the energy absorption efficiency except for the short-wave regimes. Moreover, the OWC-breakwater coupling system can obtain a similar wave blocking ability to the traditional one, and simultaneously extract wave energy and decrease wave reflection.
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Thöns, S., M. H. Faber, and W. Rücker. "Fatigue and Serviceability Limit State Model Basis for Assessment of Offshore Wind Energy Converters." Journal of Offshore Mechanics and Arctic Engineering 134, no. 3 (February 22, 2012). http://dx.doi.org/10.1115/1.4004514.
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This paper develops the models for the structural performance of the loading and probabilistic characterization for the fatigue and the serviceability limit states for the support structure of offshore wind energy converters. These models and a sensitivity study are part of a risk based assessment and monitoring framework and will be applied for establishing the “as designed and constructed” reliability as prior information for the assessment and the design of monitoring systems. The constitutive physical equations are introduced in combination with the fatigue and serviceability limit state requirements as the starting point for the development of the structural performance and loading models. With these models introduced in detail, several modeling aspects for both limit states are analyzed. This includes analyses of the influence on the hot spot stresses by applying a contact formulation for the pile guide brace connection and the application of a finite element formulation using solid elements. Further, the comparison of the natural frequencies of a discrete rotor model with a continuous rotor model is documented. To account for uncertainties associated with the structural and loading models, a probabilistic model is derived on the basis of literature review and measurement data from a prototype Multibrid M5000 support structure. The sensitivity study is based on the calculation of a nonlinear coefficient of correlation in conjunction with predetermined designs of experiments. This is conducted by a systematic analysis of the influence of the random variables on limit state responses and hence on the structural reliability. Integrating the analyses and sensitivity studies of the fatigue and serviceability limit state models developed in this paper as well as the ultimate limit state models in Thöns et al. (“Ultimate Limit State Model Basis for Assessment of Offshore Wind Energy Converters,” ASME J. Offshore Mech. Arct. Eng.), the model basis for the assessment is completed. The process of establishing and analyzing such a model basis contributes to a detailed understanding of the deterministic and probabilistic characteristics of the structure and provides valuable insights in regard to the significance of available data.
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"Prediction and performance of piles on cemented offshore sediments: two case studies." International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 27, no. 5 (October 1990): 297. http://dx.doi.org/10.1016/0148-9062(90)93066-u.
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