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由于海洋平台结构长期处于恶劣的海洋环境中,并受到各种载荷的交互作用,结构容易产生各种形式的损伤。因此,对海洋平台进行实时监测有着十分重要的现实意义。本文以单筒简易导管架平台为例,主要在结构损伤的判定和定位两方面对海洋平台的实时结构健康监测进行研究,结果表明通过对结构响应信号进行小波分析,小波变换系数和小波包能量分布可以很好地定义损伤识别指标。 相似文献
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Indonesian offshore and coastal areas are vulnerable to swells from Roaring Forties and cyclone disasters. However, the understanding of the characteristics and... 相似文献
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In designing the support structures of floating wind turbines (FWTs), a key challenge is to determine the load effects (at the cross-sectional load and stress level). This is because FWTs are subjected to complex global, local, static, and dynamic loads in stochastic environmental conditions. Up to now, most of the studies of FWTs have focused on the dynamic motion characteristics of FWTs, while minimal research has touched upon the internal load effects of the support structure. However, a good understanding of the structural load effects is essential since it is the basis for achieving a good design. Motivated by the situation, this study deals with the global load effect analysis for FWT support structures. A semi-submersible hull of a 10-MW FWT is used in the case study. A novel analysis method is employed to obtain the time-domain internal load effects of the floater, which account for the static and dynamic global loads under the still water, wind, and wave loads and associated motions. The investigation of the internal stresses resulting from various global loads under operational and parked conditions and the dynamic behavior of the structural load effects in various environmental conditions are made. The dominating load components for structural responses of the semi-submersible floater and the significant dynamic characteristics under different wind and wave conditions are identified. The dynamic load effects of the floating support structure are investigated by considering the influence of the second-order wave loads, viscous drag loads induced global motions, and wind and wave misalignments. The main results are discussed, and the main findings are summarized. The insights gained provide a basis for improving the design and analysis of FWT support structures. 相似文献
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Environmental contours are often applied in probabilistic structural reliability analysis to identify extreme environmental conditions that may give rise to extreme loads and responses. They facilitate approximate long term analysis of critical structural responses in situations where computationally heavy and time-consuming response calculations makes full long-term analysis infeasible. The environmental contour method identifies extreme environmental conditions that are expected to give rise to extreme structural response of marine structures. The extreme responses can then be estimated by performing response calculations for environmental conditions along the contours.Response-based analysis is an alternative, where extreme value analysis is performed on the actual response rather than on the environmental conditions. For complex structures, this is often not practical due to computationally heavy response calculations. However, by establishing statistical emulators of the response, using machine learning techniques, one may obtain long time-series of the structural response and use this to estimate extreme responses.In this paper, various contour methods will be compared to response-based estimation of extreme vertical bending moment for a tanker. A response emulator based on Gaussian processes regression with adaptive sampling has been established based on response calculations from a hydrodynamic model. Long time-series of sea-state parameters such as significant wave height and wave period are used to construct N-year environmental contours and the extreme N-year response is estimated from numerical calculations for identified sea states. At the same time, the response emulator is applied on the time series to provide long time-series of structural response, in this case vertical bending moment of a tanker. Extreme value analysis is then performed directly on the responses to estimate the N-year extreme response. The results from either method will then be compared, and it is possible to evaluate the accuracy of the environmental contour method in estimating the response. Moreover, different contour methods will be compared. 相似文献
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Monopile-supported offshore wind turbines (OWTs) are dynamically sensitive structures whose fundamental frequencies may be close to those of environmental and turbine-related excitations. The changes in fundamental frequencies caused by pile-soil interaction (PSI) may result in unwanted resonance and serious O&M (Operation and Maintenance) issues, which have been identified as major challenges in the research field. Therefore, a novel model updating framework with an implicit objective function is proposed to monitor both the stiffness and damping variation of the OWT system based on the measured vibration characteristics, which is further verified by laboratory tests. In particular, layered soil was considered in the tests to simulate the practical soil conditions of Chinese seas. Different pile lengths were introduced to consider the long-term PSI effects for rigid piles and slender piles. The results showed that the variation in the fundamental frequency is significantly reduced in layered soil compared with the pure sand scenario. For the OWT systems in layered soil, the variation in foundation stiffness is negatively related to the burial depth under cyclic loading. The proposed model updating framework is proven reliable for support condition monitoring of OWT systems in complicated soil conditions. 相似文献
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施建荣 《交通部上海船舶运输科学研究所学报》2011,34(1)
对船舶机舱主机监控系统的电磁兼容问题进行了详细分析,对由传感器引入的干扰途径及抑制方法进行了深入探讨。同时给出了主机监控系统电源部分的抗干扰措施和相关实验结果,以及抗干扰电缆的选用方法。降低了故障发生频率,确保了船舶机舱监控系统稳定可靠地工作。 相似文献
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For offshore structures such as offshore wind turbines (OWT), typhoon is usually considered one of the most critical threats to structural safety performances and service life due to its heavy wind, wave, and even coexisted storm surge. Meanwhile, it is challenging to obtain the systematic data from the environmental conditions, structural dynamic vibrations and the SCADA record, when typhoon passes by the offshore wind farm. Taking into account these situations, a real-time multi-source monitoring system enabling the investigation of the typhoon impact on the performances of OWT, has been firstly established and implemented to a 4.0 MW mono-pile OWT in Rudong, Jiangsu, China. One of the major contributions in this work is to develop the monitoring system using a unique environment of real-world data that has been synchronously obtained from waves, winds, vibrational accelerations, inclinations of towers and SCADA data during the typhoon “In-fa” passing by the wind farm, and provide the scientific community with the underlying standards and technical recommendations. To investigate the influence caused by “In-fa”, comparison results of the measured data in the range of June to August have been analysed. It is worth noting that two conclusions have been obtained: (1) the region near the nacelle is not always the most critical vibrational area. Actually, the change of the maximum structural response in the position under different external loads should be applied to effectively evaluate the structural safety; (2) the measured accelerations exhibit an obvious decay process in the presence of the turbine rotor-stop, but not the yaw rigid-body motion. This observation promotes the accurate identification of modal parameters for the long-term monitoring. Consequently, these valuable findings to facilitate the assessment of structural operational conditions have been developed into two guide-lines. All the data and analyses presented in this paper provide a valuable insight into the design, energy efficiency, safety monitoring and damage diagnosis of OWT structures. 相似文献
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Various types of floating solar photovoltaic (FPV) devices have been previously proposed, designed and constructed with applications primarily limited to onshore water bodies or near-shore regions with benign environmental conditions. This paper proposes a novel FPV concept which can survive harsh environmental conditions with extreme wave heights above 10 m. This concept uses standardised lightweight semi-submersible floats made of circular materials as individual modules. The floating modules are soft connected with ropes to form an FPV array. We first present the conceptual design of the floats and the connection systems, including hydrostatic, hydrodynamic, and structural assessments of the floats. To verify the motion response performance, we carried out 1:60 scaled model tests for a 2 by 3 array under regular and irregular wave conditions. From the time series and response spectra, the motion characteristics of the array and the mooring responses are analysed in detail. The proposed concept exhibits excellent performances in terms of modular motions with limited wave overtopping and no contact is observed between adjacent modules under the extreme wave conditions. The findings of this study can serve as a valuable reference to developing reliable and cost-effective FPV technologies for offshore conditions. 相似文献
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This review presents a systematic summary of the state-of-the-art development of technological solutions, modeling, and control strategies of thruster-assisted position mooring (TAPM) systems. The survey serves as a starting point for exploring automatic control and real-time monitoring solutions proposed for TAPM systems. A brief historical background of the mooring systems is given. The kinematics and a simplified kinetic control-design model of a TAPM system are derived in accordance with established control methods, including a quasistatic linearized model for the restoring and damping forces based on low-frequency horizontal motions of the vessel. In addition, another two mooring line models, i.e., the catenary equation and the finite element method model, are presented for the purpose of higher-fidelity simulations. The basic TAPM control strategies are reviewed, including heading control, surge-sway damping, roll–pitch damping (for semisubmersibles), and line break detection and compensation. Details on the concepts of setpoint chasing for optimal positioning of a vessel at the equilibrium position are discussed based on balancing the mooring forces with the environmental loads and avoiding mooring line failure modes. One method for setpoint chasing is the use of a structural reliability index, accounting for both mean mooring line tensions and dynamic effects. Another method is the use of a lowpass filter on the position of the vessel itself, to provide a reference position. The most advanced method seems to be the use of a fault-tolerant control framework that, in addition to direct fault detection and isolation in the mooring system, incorporates minimization of either the low-frequency tensions in the mooring lines or minimization of the reliability indices for the mooring lines to select the optimal directions for the setpoint to move. A hybrid (or supervisory switching) control method is also presented, where a best-fit control law and observer law are automatically selected among a bank of control and observer algorithms based on the supervision of the sea-state and automatic switching logic. 相似文献
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地铁隧道建设过程中主要通过地表沉降监测反映盾构施工的安全状态,Peck公式一直被认为是最简单实用的隧道施工期地表沉降计算方法,因此针对其适用性和参数取值问题是人们研究的重点。文中结合盾构施工的特点,探讨盾构施工中引起地层扰动的主要因素,通过在建地铁隧道的实测地表沉降数据分析Peck公式的适用性和参数取值问题,并探讨了几种特殊情况下的地表沉降规律,以指导施工方案的调整,减小施工的环境影响,同时保证隧道自身的施工质量。 相似文献
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损伤舰船结构安全性评估 总被引:1,自引:0,他引:1
损伤舰船的承载能力和环境载荷涉及许多不确定因素。为评估某舰损伤情况下的结构安全性,提出了基于极限强度和极值载荷的损伤舰船结构可靠性模型,分析了损伤舰船极限强度和极值载荷的统计特征,采用拉丁超立方抽样与条件期望和对偶变数相结合的方法进行可靠性分析。可靠性分析结果表明损伤舰船目标裕度可取0.75。 相似文献
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船舶结构疲劳评估设计波法 总被引:2,自引:2,他引:0
以散货船船舯内底与底边舱斜板折角处节点为例,对船舶结构疲劳评估的设计波法进行研究.论述了设计波法的基本原理,给出了确定设计波的流程。通过分析该节点的受力情况,确定5个控制载荷参数及设计波参数。以谱分析法得到的参考应力范围为目标值,对5个控制载荷参数对应的设计波作用下的节点应力范围结果进行回归分析,从而得到了用于疲劳评估的设计波组合,并利用该方法对1艘散货船的船舯内底与底边舱斜板折角处的节点进行了计算。结果显示,设计波法与谱分析法的结果吻合较好,计算量大幅减少。 相似文献
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