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提出1种适用于海上风力发电支撑结构的模态振型扩阶方法。该方法无需借助转换矩阵实现振型扩阶,而是依靠实测模态并通过修正有限元模型对应振型在未测试自由度的振型值而获得空间完备的模态振型,并且所发展的方法在一定程度上可以忽略有限元模型存在的建模误差,是1种直接的估算方法,计算效率相对较高。文中采用三桩导管架式海上风力发电支撑结构验证提出方法的正确性以及在低阶模态振型扩阶上的优越性。数值结果表明,该方法对传感器位置、数量依赖程度低,尤其对于海上风电结构,仅在结构的水深较浅部位布置少数传感器即可比较精确的实现低阶模态振型扩阶,具有良好的工程应用前景。 相似文献
13.
This study investigates strategies for solving the system reliability of large three-dimensional jacket structures.These structural systems normally fail as a result of a series of different components failures.The failure characteristics are investigated under various environmental conditions and direction combinations.Theβ-unzipping technique is adopted to determine critical failure components,and the entire system is simplified as a series-parallel system to approximately evaluate the structural system reliability.However,this approach needs excessive computational effort for searching failure components and failure paths.Based on a trained artificial neural network(ANN),which can be used to approximate the implicit limit-state function of a complicated structure,a new alternative procedure is proposed to improve the efficiency of the system reliability analysis method.The failure probability is calculated through Monte Carlo simulation(MCS)with Latin hypercube sampling(LHS).The features and applicability of the above procedure are discussed and compared using an example jacket platform located in Chengdao Oilfield,Bohai Sea,China.This study provides a reference for the evaluation of the system reliability of jacket structures. 相似文献
14.
—The forces of random wave plus current acting on a simplified offshore platform(jacket)mod-el have been studied numerically and experimentally.The numerical results are in good agreement withexperiments.The mean force can be approximated as a function of equivalent velocity parameter and theroot-mean-square force as a function of equivalent significant wave height parameter. 相似文献
15.
To investigate the seismic response of a pile group during liquefaction, shaking table tests on a 1/25 scale model of a 2 × 2 pile group were conducted, which were pilot tests of a test project of a scale-model offshore wind turbine with jacket foundation. A large laminar shear box was utilized as the soil container to prepare a liquefiable sandy ground specimen. The pile group model comprising four slender aluminum piles with their pile heads connected by a rigid frame was designed with similitude considerations focusing on soil–pile interaction. The input motions were 2-Hz sinusoids with various acceleration amplitudes. The excess pore water pressure generation indicated that the upper half of the ground specimen reached initial liquefaction under the 50-gal-amplitude excitation, whereas in the 75-gal-amplitude test, almost entire ground was liquefied. Accelerations in soil, on the movable frames composing the laminar boundary of the shear box, and along the pile showed limited difference at the same elevation before liquefaction. After liquefaction, the soil and the movable-frame accelerations that represented the ground response considerably reduced, whereas both the movable frames and the piles exhibited high-frequency jitters other than 2-Hz sinusoid, and meantime, remarkable phase difference between the responses of the pile group and the ground was observed, all probably due to the substantial degradation of liquefied soil. Axial strains along the pile implied its double-curvature bending behavior, and the accordingly calculated moment declined significantly after liquefaction. These observations demonstrated the interaction between soil and piles during liquefaction. 相似文献
16.
Among numerous offshore structures used in oil extraction, jacket platforms are still the most favorable ones in shallow waters. In such structures, log piles are used to pin the substructure of the platform to the seabed. The pile’s geometrical and geotechnical properties are considered as the main parameters in designing these structures. In this study, ANSYS was used as the FE modeling software to study the geometrical and geotechnical properties of the offshore piles and their effects on supporting jacket platforms. For this purpose, the FE analysis has been done to provide the preliminary data for the fuzzy-logic post-process. The resulting data were implemented to create Fuzzy Inference System (FIS) classifications. The resultant data of the sensitivity analysis suggested that the orientation degree is the main factor in the pile’s geometrical behavior because piles which had the optimal operational degree of about 5° are more sustained. Finally, the results showed that the related fuzzified data supported the FE model and provided an insight for extended offshore pile designs. 相似文献
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Constructing concrete jackets is a common technique when strengthening reinforced concrete (RC) columns, particularly in seismic regions. However, there are many uncertainties concerning the behavior of the composite specimen, particularly at the interface between the old and new concrete. In this paper, monotonic finite element (FE) analyses are performed to examine the behavior of strengthened columns under monotonic and cyclic loading. Through investigating two independent series of experimental results, it is demonstrated that monotonic FE analysis with appropriate assumptions can simulate both monotonic and cyclic loading conditions to a reasonable degree of accuracy. According to the results of this study, it is found that a simulation of the interface between the old and the new concrete is vital and cannot be ignored by simply considering a perfect bond at the interface. In the case of strengthened RC columns subjected to cyclic loading, strength degradation at the interface has to be included and can be effectively modeled by reducing the coefficients of friction and adhesion by using a proposed formula. Finally, the effect of jacket concrete shrinkage is simulated that leads to a reduced maximum load and stiffness of strengthened columns. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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20.
Optimum Design of Structure Shape for Offshore Jacket Platforms 总被引:1,自引:1,他引:0
FENG Sheng 《中国海洋工程》2000,14(4):435-445
With the introduction of the design variables of nodal coordinates,which reflect the em-bedded depth of the pile and the jacket bed height,a shape optimum design model for offshore jacket plat-forms is established.A sequential two-level optimum algorithm is developed based on the design variablegradation.On the basis of the finite element method,the sensitivity of the objective function and nodal dis-placement is analyzed.As an example,the BZ281 oil storage offshore platform,which lies in the Bohai oilfield,is designed with the shape optimum model.The results are compared with the cross-section optimumdesign.The tendency of design variables and its reasons in the two methods are analyzed.In the shapeoptimum design,the value of objective function is obviously smaller than that of the initial design and thecross-section optimum design.Therefore,the advantage of structure shape optimum design for jacket plat-forms is remarkable. 相似文献