共查询到20条相似文献，搜索用时 93 毫秒
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利用动柔度法来进行桩基导管架平台损伤部位诊断,需要有一个能真实地反映原始平台动力特性的模型作为比较的基准。一般可用设计过程中的有限元模型作基准,但由于材料、工艺等因素,其有限元刚度阵特别是接头刚度很难准确地确定,故需通过模态实验来修正计算模型。通常,实测模志均少于测量自由度数,更远小于有限元自由度数。为了使测点与有限元分析自由度相对应,本文提出一种计算方法,将结构分为主、次自由度,主自由度对应测试点,用凝聚得到简化模型,并对简化模型的特征解进行灵敏度分析,利用实验测得的模态来修正有限元值,从而得到一个能够正确地反映结构特性的较为精确的有限元计算模型,然后,利用广义动柔度法检测损伤位置,提出一种确定损伤位置的计算方法。在文中给出了二层框架的计算和实验结果以及修正参数和二层框架损伤位置的确定。结果表明,利用实验模态修正计算数学模型,该方法是一种可行的途径。 相似文献
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提出将基于动态特性的检测方法与局部物理检测手段相结合的探伤思路。利用动力学方法进行实时监测及损伤区域的粗略定位,再由物理探测方法实现损伤程度和位置的精确判断,从而降低对动态检测方法的精度要求。此外,文中尝试直接由结构的动力响应信号构建能量指标识别结构损伤的方法,不需要进行模态参数识别,算法简单,有望应用于海洋平台、高层建筑等可简化为串联多自由度体系的结构的实时监测和损伤初步定位。 相似文献
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浅水不规则波浪中油轮运动研究 总被引：8，自引：2，他引：6
本文对一般油轮在浅水不规则波浪中六自由度运动进行了试验分析,并对其碰底情况做了研究。试验时对有流情况下不同波高、不同装载的条件进行了分析比较。模型的六自由度运动是用非接触式六自由度运动测量与分析方法求得。该方法应用位置测量仪（ＰＳＤ）对安置在模型上的红外线发光源（ＬＥＤ）进行测量,然后所编制的软件计算出模型的六个自由度运动情况。 相似文献
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非接触式六自由度运动测量与分析方法 总被引：8，自引：2，他引：6
本文提供了一种非接触式六自由度运动测量与分析方法。首先应用位置测量仪（ＰＳＤ）对安置在模型上的红外线发光源（ＬＥＤ）进行测量,然后用所编制的软件计算出模型的六个自由度运动情况。该方法避免了接触式测量仪对模型作用一定的力而产生的误差,同时具有较高的位置解析度与频率响应能力,测量结果精度较高。该方法可同时测量空间三个点的运动坐标从而可用计算机求得模型在空间的六个自由度运动情况。测量与分析结果令人满意。 相似文献
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高桩码头在长期使用过程中结构损伤是普遍存在的问题,有效检测结构损伤特别是隐蔽性部位对保证码头安全运营具有重要作用。利用NExT-ERA模态参数识别算法和模态应变能损伤定位原理,编制模态参数识别和损伤诊断程序。通过数值算例分析,验证环境激励下高桩码头排架基于模态参数识别及模态应变能进行损伤诊断的可行性和准确性。研究结果表明:NExT-ERA模态识别方法能较精确识别出高桩码头排架的动力参数;模态应变能变化率作为损伤诊断指标对损伤单元有较强的敏感性,能够识别出高桩码头不同工况下的损伤。 相似文献
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针对大洋调查中海山地磁测量时难以设立静日变化观测站的问题,提出了一种基于多项式拟合最小二乘算法的日变校正方法,即假设静日变化磁场可以用一个关于时间的高阶多项式来拟合,利用主测线和联络测线交点误差的最小二乘估计求得多项式的系数,从而得到静日变化曲线。从调查测得的磁场中减掉静日变化磁场即可得消除静日变化影响后的海山地磁异常。理论模型和实际资料处理都表明,这种方法不仅可以较好地消除静日变化的影响,而且用计算机实现也简单。为了提高静日变化校正结果,讨论了为提高静日变化校正效果,在大洋调查中测量海山地磁时应注意的几个问题。 相似文献
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利用计算机仿真粒子图像精确控制仿真粒子亚像素位移,讨论不同窗口下二次多项式曲面拟合法与基于梯度亚像素位移算法的匹配精度。针对粒子均匀移动的理想情况,发现二次多项式曲面拟合法的匹配精度随匹配窗口的增大而提高,而基于梯度亚像素位移算法的匹配精度几乎不随匹配窗口的增大而改变,两种算法匹配精度均在0.1个像素内。分析存在理想涡旋的粒子图像发现:二次多项式曲面拟合法的匹配精度约为0.2个像素,基于梯度亚像素位移算法的匹配精度约为0.05个像素。以二次多项式曲面拟合法为例,探讨了粒子大小和浓度对测量结果的影响,发现匹配窗口越大,最合适的粒子浓度范围就越大,这与不同匹配窗口包含的粒子图像灰度值信息量不同有关。在粒子大小方面,不同匹配窗口下,粒子直径为3个像素时误差均较小,表明PIV实际使用时,选择大小为3个像素的粒子为宜。将2种亚像素匹配算法应用到水槽实验获取的PIV影像分析中,均能得到较好的效果。 相似文献
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The International Maritime Organization has developed the second-generation intact stability criteria. Thus, damage stability criteria can be established in the future. In order to identity the capsizing probability of damaged ship under dead ship condition, this paper investigates two methods that can be used to research the capsizing probability in time domain, which mainly focus on the nonlinear righting lever GZ curve solution. One method subjects the influence of damaged tanks on the hull shape down to the wind and wave, and the other method is consistent with the real-time calculation of the GZ curve. On the basis of one degree of freedom rolling equation, the solution is Monte Carlo method, and a damaged fishery bureau vessel is taken as a sample ship. In addition, the results of the time-domain capsizing probability under different loading conditions are compared and analyzed. The relation of GM and heeling angle with the capsizing probability is investigated, and its possible reason is analyzed. On the basis of combining the time-domain flooding process with the capsizing probability calculation, this research aims to lay the foundation for the study of capsizing probability in time domain under dead ship condition, as well as provide technical support for capsizing mechanism of dead ship stability and damage stability criteria establishment in waves. 相似文献
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《Ocean Engineering》2004,31(3-4):483-512
Six degrees of freedom motion response tests of a Ro-Ro model have been carried out in regular waves for intact and damaged conditions. The stationary model was tested in different wave heights and wave frequencies for the head, beam and stern quartering seas in order to explore the effect of damage and varying wave heights on the motion responses of the model. Analysis of the results indicates that damage has an adverse effect on the motion responses of the model depending upon the directionality of the waves and frequency range applied. 相似文献
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为了研究循环载荷作用下扶强材初始损伤对其极限强度的影响,进行了14组扶强材的循环加载试验和分析。构造了考虑材料累积损伤完整、断筋和大变形的扶强材单元极限承载力计算公式,提出了相应循环载荷作用下损伤扶强材单元的端缩曲线表达式和船体梁极限强度计算的简化逐步破坏法。编制了循环载荷作用下船体梁损伤极限强度计算程序,进行了船体梁极限强度计算,并与有限元结果进行对比。研究结果表明：改进的损伤扶强材模型可较为准确地描述扶强材材料损伤的完整、断筋和大变形的极限承载力退化情况,扶强材腹板断裂的损伤相较初始大变形及材料累积损伤形式承载力下降程度更明显;所提出的循环载荷作用下损伤船体梁极限强度计算的简化逐步迭代方法,能定量地计算扶强材在不同类型损伤下的极限承载力退化程度,具有较高精度,方便易行,可应用于工程设计。 相似文献
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2018年5月7日厦门岛遭遇了超百年一遇的强降水,对岸滩造成了严重影响。文章采用现场测量、无人机航拍等方法,通过对冲毁岸滩进行现场调查与测量,发现厦门岛东南部10.78km的滨海沙滩岸段,共有10个岸段的沙滩发生明显冲刷,受损岸线总长度为6.1km(占比57%),形成了28条冲刷沟,沙滩遭受的侵蚀面积为20286m2,冲刷量超过4万m3。分析其原因,主要是海岸带开发利用时,不透水面增多且具有一定的坡度,加之后方陆域地下排洪管涵排水,当短期强降水发生时,局部地形集中汇水后急速冲向海岸,导致海岸侵蚀垮塌和后退,沙滩冲刷成沟而流失大量海砂。针对不同沙滩的冲刷程度与影响机制,提出了相应的整治修复方案,可为今后沙滩维护保养提供参考。 相似文献
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In jacket-type offshore structures, corrosion damage affects the structural performance under compressive loading, which is created by the working and design loads of the main system. In this study, the effects of corrosion damage on the compressive structural behavior and strength of steel tubular members were investigated. Artificial corrosion damage was applied to the tubular specimens via mechanical processing and hand drilling to replicate the inclined nature of jacket-type offshore structures. The damage was applied to either half or all of the circumference of the specimens. The compressive failure modes of the artificially corroded tubular members were affected by the corrosion conditions. The compressive strengths were also affected by the level of corrosion. From the results of this study, the residual compressive strengths of corroded tubular steel members can be estimated based on the condition of the damaged sectional areas. 相似文献
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利用SBAS-InSAR技术和覆盖贝鲁特港口Sentinel-1B影像,对2020年8月4日发生的贝鲁特港口大爆炸进行形变追溯分析,并结合光学影像与SBAS-InSAR测量结果对大爆炸周围建筑受损程度进行评价。结果表明:贝鲁特港口大爆炸之前地表存在微弱的形变,大爆炸致使爆炸中心和周围产生了严重的形变。300m缓冲区内的大型仓库被夷为平地,爆炸中心产生了直径为140m的大坑;300~500m范围内仓库损坏严重,岸堤形变量小;500~1000m范围内的建筑在爆炸中受损程度较小。该研究探索了SBAS-InSAR技术在特大爆炸灾害监测领域的适用性,为类似大爆炸灾害的评估与追溯提供了思路。 相似文献
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Muhittin Sylemez 《Ocean Engineering》1998,25(4-5)
The purpose of the study was to develop a prediction technique to simulate the motion response of a damaged platform under wave, wind and current forces. The equations of motion were obtained using Newton's second law and the numerical solution technique of non-linear equations of motion is explained for intact and damaged cases. The analysis technique employs large displacement non-linear equations of motion. Solutions were obtained in the time-domain to predict the motion characteristics. In this study, analysis procedures were developed to calculate: (a) wave loading on asymmetrical structural configurations; (b) hydrodynamic reaction forces (inertia or moment of inertia, damping and restoring forces) on asymmetrical shapes. During the damage simulation, change in the mass of the structure as well as wave and hydrodynamic reaction forces, were taken into account. The computer program developed for the time-domain simulation is introduced. In order to avoid slowly decaying transient motions of the structure due to wave excitation forces, an exponential ramp function is used. The application of a ramp function enables a quick convergence in the time-domain solution of equations of motion. Results of a numerical motion simulation program and the experimental studies are also presented in order to make comparisons. Comparison of the test results with the numerical simulations shows good agreement for heave, roll and pitch motions. The formulations and the computational procedures given in this paper provide useful tools for the investigation of the non-linear dynamic stability characteristics of floating structures in waves for intact, damaged and post-flooding conditions in six-degrees of freedom. 相似文献
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沿海地区社会经济快速发展的同时,各种人类活动导致的海洋污染与海洋生态损害日益加剧,海洋生态损害补偿是解决海洋生态损害问题的有效途径之一。本文以温州市旧城改造工程临时性海洋倾倒区为研究对象,利用水质、沉积物、生物等监测数据,基于倾倒活动对海洋生态系统的实际损害程度,构建生态服务价值损害评估体系和生态修复海洋损害评估框架,采用市场价值法、替代成本法、影子工程法、成果参照法等模型计算倾倒活动对海洋生态造成的损害,并确定生态补偿标准。结果表明:(1)基于生态服务价值损害为1 332.61万元,一级损害类型中支持服务价值损害最大;(2)鱼卵和仔鱼、生物多样性及基因资源、气候调节和维持空气质量为倾倒区主要生态系统服务损害类型,损害价值分别为251万元、379.26万元、342.18万元,三者之和比重达73%;(3)基于生态修复海洋损害价值为1 522.37万元,其中海洋生态修复费用最高,为1 167.65万元;(4)将两种评估体系的海洋生态损害价值的平均值作为温州市旧城改造工程临时性海洋倾倒区的补偿标准,为1 427.49万元,单位面积补偿标准为0.79万元/hm~2·a。 相似文献
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This paper describes the development of a computational model to predict the response of synthetic-fiber ropes under both monotonic and cyclic loads. The model addresses the issue of damage to a rope cross-section and its effect on rope response. Isotropic damage is assumed and is therefore characterized by a scalar quantity known as the damage index. The damage index is used to quantify the amount of deterioration that takes place in a damaged rope throughout its loading history. For the current study, data obtained from static tension tests are used to determine the evolution relationship for the damage index. This relationship is based on the stiffness ratio between experimental data and simulation of rope response without any source of damage and is assumed to be described by an exponential equation. Numerical simulations of damaged rope behavior compare well with experimental results. 相似文献
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《Journal of Sea Research》2004,51(1):69-76
Predator and scavenger aggregation to simulated discards from a scallop dredge fishery was investigated in the north Irish Sea using an in situ underwater video to determine differences in the response to varying levels of discard damage. The rate and magnitude of scavenger and predator aggregation was assessed using three different types of bait, undamaged, lightly damaged and highly damaged individuals of the great scallop Pecten maximus. In each treatment scallops were agitated for 40 minutes in seawater to simulate the dredging process, then subjected to the appropriate damage level before being tethered loosely in front of the video camera. The density of predators and scavengers at undamaged scallops was low and equivalent to recorded periods with no bait. Aggregation of a range of predators and scavengers occurred at damaged bait. During the 24 hour period following baiting there was a trend of increasing magnitude of predator abundance with increasing damage level. However, badly damaged scallops were eaten quickly and lightly damaged scallops attracted a higher overall magnitude of predator abundance over a longer 4 day period. Large scale temporal variability in predator aggregation to simulated discarded biota was examined by comparison of results with those of a previous study, at the same site, 4 years previously. The community of predators and scavengers present at the bait was substantially different during the 2 studies. These changes in scavenger community were only partially related to changes in the mean background density of scavenging species. 相似文献