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1.
疲劳破坏是海洋结构物发生破坏的一种主要形式,深水半潜平台在海上运输、作业、停滞时会受到交变的风、浪、流载荷作用,进而引起结构关键节点处的疲劳损伤,影响平台安全性。以"海洋石油981"半潜钻井平台为研究对象,利用光纤光栅应变传感器对结构高应力区进行应力监测,获取测点处应力时历数据。将监测位置划分为四个监测板块,采用四点雨流计数法对测点应力进行处理,得到以离散形式给出的应力循环幅度与相应循环周次。参照DNV《海上钢结构疲劳设计规范》推荐的S-N曲线,基于Miner线性疲劳累计损伤原则,得到各个测点处的总体疲劳损伤度。选取具有最大疲劳损伤度的危险测点,并结合海上实测总时长,预测半潜平台的总体疲劳寿命。 相似文献
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灌浆连接段的疲劳性能对于海上风机单桩支撑结构至关重要。基于385种工况下的某实际5 MW单桩风机支撑结构在风、浪荷载作用下的动力响应分析,获取了灌浆连接段荷载边界条件时程。建立灌浆连接段精细化有限元子模型,将荷载边界条件转化为应力时程。对于剪力键采用"热点应力"方法进行疲劳性能评价。对于灌浆材料,选取剪力键附近灌浆材料单元积分点处的第三主应力进行疲劳性能评价。采用Palmgren-Miner线性损伤累计准则和雨流计数方法进行疲劳损伤的累计。在某实际灌浆连接段20年的设计寿命周期内,最大剪力键总疲劳损伤为1.35×10~(-10);最大灌浆材料总疲劳损伤为1.54×10~(-3)。由此可见,灌浆连接段的疲劳性能由灌浆材料控制,且损伤值远小于限值1/3,在现有的荷载条件下,灌浆连接段不会发生疲劳破坏。分析产生损伤较大的几种工况可知,风速对现有单桩结构灌浆连接段疲劳的损伤起控制作用。 相似文献
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- In this paper, using the theory of stochastic analysis of the response to earthquake load, a stochastic analysis method of the response of piled platforms to earthquake load has been established. In the method, the strong ground motion is considered as three dimensional stationary white noise process and the pile-soil interaction and water-structure interaction are considered. The stochastic response of a typical platform to eqrthquake load has been computed with this method and the results compared with those obtained with the response spectrum analysis method. The comparison shows that the stochastic analysis method of the response of piled platforms to earthquake load is suitable for this kind of analysis. 相似文献
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Previous steel catenary riser (SCR) models targeted for VIV prediction are truncated at touchdown point (TDP) where simple constrain and rotation stiffness are generally applied. In this study, a time domain approach accounting for the SCR–soil interaction is proposed to predict the cross-flow (CF) VIV induced fatigue damage of a SCR near TDP. The hydrodynamic force is simulated based on the forced vibration test data as a function of the non-dimensional amplitude and frequency, and an empirical damping model. When the non-dimensional frequency associated with the calculated frequency falls in the excitation region, the natural frequency closer to the frequency corresponding to the maximum excitation force is taken to be the dominant frequency, and applied to obtain the excitation force. The SCR–soil interaction model takes into account the trench shape, and the mobilization and release of the soil suction. Fatigue damage is linearly accumulated by using the rain-flow counting methodology. To validate the proposed models, simulation for a riser model test is carried out, and the envelopes of RMS displacement, curvature, and fatigue damage are compared. Further works focus on the sensitivity of VIV induced fatigue damage near TDP to the seabed parameters, such as mudline shear strength, shear strength gradient and soil suction, and some conclusions are obtained. 相似文献
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洪涛 《中国海洋大学学报(自然科学版)》1991,(4)
对20名受试者进行动态心电频谱研究。结果表明:1.递增负荷运动时,未疲劳心肌的心电积分(IECG)、平均功率频率(MPF)和均方根振幅(RMS)与运动负荷、射血加速度、射血前期线性相关。随着运动负荷的增加,心电频谱发生“右移”,并出现“频率集中”现象。指出心电频谱指标能在一定程度上反映心肌的收缩性.可作为运动时评价心脏负荷的指标。2.优秀运动员的IECG、RMS及其相对值与无训练者有显著性差异。同级负荷工作时,相对值IECG/HR、RMS/HR可同时反映心率和每搏心缩强度的比例,指出该指标可作为评价训练程度的参考指标。同时还分析了心电频谱变化的原因,提出“心肌分级收缩形式”和“心肌收缩功能态”的概念。 相似文献
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生物发光现象在海洋中广泛存在,基于微光成像技术对深海发光浮游生物的发光现象进行视觉捕获是一种先进的原位观测手段,但目前缺乏有效的方法对获取的生物发光影像资料进行自动分析。针对此问题,本文提出一种基于多特征匹配跟踪的发光浮游生物自动计数方法,基于同一目标在连续帧间的运动具有连续性的思想,首先采用帧间质心差小于一定阈值的原则进行初始粗匹配,然后针对目标过近造成的误匹配问题再进一步进行运动方向的匹配,提高帧间匹配精度,从而准确计数。采用所提出的方法对深海发光浮游生物的真实视频数据进行了自动分析,实验结果证明该计数方法具有较好的准确率,对生物发光区域的尺度变化、发光目标间距过近等情况具有较好的鲁棒性,能达到较好的计数效果。 相似文献
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Remotely sensing in detecting the water depths and bed load of shallow waters and their changes 总被引：1，自引：0，他引：1
Bed load is a type of sand drift and accumulation on the sea-bed. Sand drift is a very important index to survey the erosion or deposition of coastal zone. The change of water depths indicates the change of bed load in shallow waters. The conventional method for measuring water depth uses the shipboard echo sounder, which is accurate for point-measurement, but is a time-consuming and labor-intensive task. For periodic survey of bathymetry as synoptic scale, the remote sensing method may be a viable alternative. Wave spectrum bathymetric (WSB) method takes advantages of remote sensing to obtain the bathymetry of shallow waters safely, economically and quickly. The WSB method is feasible to detect the change of water depths over coastal zones where water depths are less than about 12 m. This remote sensing method is worthy to be well developed and efficiently applied to change detection of water depths and bed load in shallow waters. 相似文献
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Investigated is the coupled response of a tension leg platform (TLP) for random waves. Inferred are the mass matrix, coupling stiffness matrix, damping matrix in the vibration differential equation and external load of TLP in moving coordinating system. Infinitesimal method is applied to divide columns and pontoons into small parts. Time domain motion equation is solved by Runge-Kutta integration scheme. Jonswap spectrum is simulated in the random wave, current is simulated by linear interpolation, and NPD spectrum is applied as wind spectrum. The Monte Carlo method is used to simulate random waves and fluctuated wind. Coupling dynamic response, change of tendon tension and riser tension in different sea conditions are analyzed by power spectral density (PSD). The influence of approach angle on dynamic response of TLP and tendon tension is compared. 相似文献
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Sandwich panel is commonly used in ship and marine engineering equipment, such as side structure and superstructure deck of a ship, which is of good anti-explosion performance. This paper addresses a study on the dynamic response of the U-typed sandwich panel under explosion load through the numerical simulation and theoretical methods. Based on the orthotropic plate theory, the U-typed sandwich panel is simplified and transformed into a single degree of freedom (SDOF) spring system, the equivalent motion equation of the SDOF system and the expression of triangular explosion load function are established based on the SDOF theory, and the maximum response spectrum of the SDOF system is obtained. Then, the response of the equivalent SDOF system of the U-typed sandwich panel under explosion load is analyzed, and the theoretical results match well with the numerical simulation results, which verifies the accuracy of the theoretical method proposed in this paper. The theoretical method proposed in this paper could have good engineering applications for the structural anti-explosion design, and provide a reference for the evaluation of the anti-explosion performance of ship and offshore platform structures.
相似文献10.
在地质导向钻前建模过程时,通常利用水平井附近的多口邻井确定钻遇地层的深度及方位,该层的井间横向构造起伏可以利用解释层位来控制趋势;当井眼处测井解释的深度与解释的地震层位深度有差异时,建立的前导模型将有很大的误差。此文采用测井地震联合建模的方法来控制误差范围。该方法首先利用测井解释结果对大套的地震解释层位进行校正,根据每口井解释的小层厚度,利用滑动平均算法构造小层等厚体数据,然后利用校正后的地震解释层位横向约束控制地层起伏,建立每一地质小层的构造图,以此提高地质导向水平井着陆精度。实际资料验证,该方法会大大减小误差,能把模型误差控制在2m的范围内。 相似文献
11.
Bok Kyoung Choi Suk Wang Yoon 《Oceanic Engineering, IEEE Journal of》2001,26(1):125-130
Sound attenuation has been solely used to estimate bubble size distributions of bubbly water in the conventional acoustic bubble sizing methods. These conventional methods are useful for the void fraction around 10-6 or lower. However, the change of compressibility in the bubbly water also should be considered in bubble sizing for the void fraction around 10-5 or higher. Recently the sound speed as well as sound attenuation was considered for acoustic bubble size estimation in bubbly water. In this paper, the sound speed estimated from sound attenuation in bubbly water by an iterative method is used for a bubble counting. This new iterative inverse bubble sizing technique is numerically tested for bubble distributions of single-size Gaussian, and power-law functions. The numerical simulation results are in agreement with the given bubble distributions even for the high void fractions of 10-4-10-3. It suggests that the iterative inverse technique can be a very powerful tool for practical use in acoustic bubble counting in the ocean 相似文献
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MnO2共沉淀直接β计数测定小体积海水中的234Th 总被引：2，自引：0，他引：2
探讨了MnO2共沉淀直接β计数测定小体积海水中234Th方法在固体闪烁α/β计数仪上实现的可能性,对实验流程空白、流程化学回收率、仪器探测效率、MnO2共沉淀量对全程回收率的影响以及检测核素的特征性等进行了研究.结果表明,该方法具有稳定的流程空白和全程回收率、高的探测效率和化学回收率,且所检测核素与234Th的理论半衰期基本吻合.将该流程应用于亚热带北太平洋表层水中234Th的分析也得到了令人满意的结果.与传统方法相比,该方法具有流程简单、所用水样体积小、快速获得结果等特点,适合于船载分析,由此可实现高时空分辨率数据的获取,为海洋颗粒有机碳输出通量以及颗粒物迁移速率的研究提供了更好的分析手段. 相似文献
14.
A-man Zhang Ling-yu Zeng Xiao-da Cheng Shi-ping Wang Yu Chen 《Applied Ocean Research》2011,33(4):240-251
Whipping response will happen when a ship is subjected to underwater explosion bubble load. In that condition, the hull would be broken, and even the survivability will be completely lost. A calculation method on the dynamic bending moment of bubble has been put forward in this paper to evaluate the impact of underwater explosion bubble load on the longitudinal strength of surface ships. Meanwhile the prediction equation of bubble dynamic bending moment has been concluded with the results of numerical simulation. With wave effect taken into consideration, the evaluation method of the total damage of a ship has been established. The precision of this evaluation method has been proved through the comparison with calculation results. In order to verify the validity of the calculation results, experimental data of real ship explosion is applied. Prediction equation and evaluation method proposed in this paper are to be used in ship structure design, especially in the preliminary prediction of the ultimate withstanding capability of underwater explosion damage for the integrated ship in preliminary design phase. 相似文献
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—In this paper,the second-order perturbation method in frequency domain is used to calculateRAO and spectra of motion and mooring line tension of a turret-moored tanker in ballast condition.Thecalculated results are compared with corresponding experiment results.In the experiment the wave head-ing is 180°,and the wave spectra is the P-M spectrum and white noise spectrum.In the theoretical calcu-lations,the damping coefficient of slow oscillation of the tanker is determined on the basis of the dampingobtained from a test of irregular waves where the mooring system is replaced by a nonlinear spring withnonlinear stiffness similar to that of the mooring system.From the comparison between theoretical calcula-tions and experimental results,it can be found that the theoretical results obtained by the second-orderperturbation method in frequency domain are in good agreement with the experimental results,indicatingthat the damping coefficient of slow oscillation of the tanker required in frequency domain calcu 相似文献
16.
In this article, two full-scale pile loading tests were conducted to observe the field performance of the super-long bored piles, and a simplified approach for nonlinear analysis of the load-displacement behavior of a single pile was presented. The field tests on piles indicates that, under the maximum test load, more than 70% of the pile top settlement is caused by the compression of pile shaft. For practical purposes, the pile top settlement can be reduced through improving the pile shaft strength. When the load reaches the maximum test load, the proportion of the load carried by the pile tip is approximately 30%. The super-long pile is functioning as an end-bearing friction pile. The skin friction at shallow depth is fully mobilized and decreases from a peak value with increasing load. However, the skin friction of deeper soil is not fully developed due to less relative displacement. Furthermore, a BoxLucas1 model is used to capture the relationship between unit skin friction and pile-soil relative displacement, whereas a hyperbolic model is used to describe the relationship between toe stress and pile base displacement. Based on the BoxLucas1 model and the hyperbolic model, a load transfer method is used to clarify the response of a single pile, and a computational flow chart is developed. The efficiency and accuracy of the present method is verified using the field tests on piles. The proposed simple analytical approach is economical and efficient, resulting in savings in time and cost. 相似文献
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降雨条件下的导航X波段雷达海浪参数反演算法研究 总被引：1，自引：0，他引：1
X波段的电磁波受降雨影响容易产生衰减,这导致导航X波段雷达在降雨时无法用于海浪观测。本文提出了一种新的降低降雨影响的算法来反演海浪参数。首先,对X波段雷达图像做主成分分析,获得波浪变化的主成分,利用一维傅里叶变换得到波数谱,对其滤波减小降雨对雷达图像的影响;然后,选取JONSWAP(Joint North Sea Wave Project)谱作为理论谱,建立以观测谱与理论谱的最小化差异为目标函数的模型,求解该模型估算海浪的有效波高。与浮标测量的有效波高相比,该方法反演的有效波高的均方根误差是0.23 m,证明了该方法的可行性。 相似文献
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The elastic-plastic method is often used in designing the inner flat bulkhead plates of submarines, and the upper structure of ships and drilling platforms. Such bulkhead plates can bear the load only once. For the improvement of the load-carrying capacity or the reduction of the weight of plates, the yield line analytical method is employed in this paper to design the bulkhead plate to improve economy and increase the effiective load. Besides, a further sutdy of this method has been made theoretically and experimentally, and the data of the limited load-carrying capacity of the plate have been obtained. Furthermore, the safety coefficients for such a method are presented, which can be used as reference for related departments and staffs. 相似文献