共查询到19条相似文献，搜索用时 109 毫秒
1.
轮印载荷的分布对于直升机甲板加筋板结构的设计至关重要。通过在橡胶块上加压的方式模拟轮印载荷,直接测量橡胶块与加筋板结构之间的接触压力,揭示轮印载荷分布特性,得到轮印载荷在加强筋和铺板之间的分布具有较强的不均匀性。利用ABAQUS软件进行轮印载荷分布的数值计算,结果表明,数值计算结果与试验结果吻合较好,试验工况下分布在加强筋上均布轮印载荷为接触面上均布轮印载荷的1.279倍。研究了加筋板面板初始缺陷、加强筋高度以及加筋板面板厚度对轮印载荷分布的影响。数值结果表明:考虑面板初始缺陷、降低面板厚度和增加加强筋的高度使轮印载荷分配到加强筋上的比例增大,但在相对刚度变化相同的情况下,降低面板厚度和增加加强筋高度对轮印载荷分布的影响不同。 相似文献
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针对强台风引起的平台倒塌问题,综合隐式有限元与显式动力有限元算法,建立导管架平台结构倒塌全过程仿真流程;提出基于重现期的Pushover分析方法,充分考虑平台侧向环境载荷分布的变化以及可能的甲板上浪载荷因素,使得确定的倒塌环境载荷更加真实;采用APDL编制平台隐式与显式有限元模型转化程序,有效解决波浪载荷计算与精确施加的难题;在此基础上,应用LS-DYNA实现导管架平台在强台风载荷下的倒塌全过程仿真,动态再现平台结构倒塌过程中的构件破坏失效及内力分布,深入揭示平台结构的倒塌机理。研究成果可为导管架平台结构抗台风设计及理论研究提供参考。 相似文献
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研究短期海况中海洋结构物在宽带波浪载荷作用下交变应力过程中的应力范围的概率分布及结构疲劳损伤问题.首先从应力的功率谱密度出发,利用小波变换作为工具,对应力过程进行模拟.然后用雨流计数法识别出应力过程中对结构造成疲劳损伤的应力范围,并用Weibull分布对应力范围的分布进行了拟合;最后给出了应力范围服从Weibull分布时结构疲劳损伤的计算方法. 相似文献
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本文应用传递矩阵法研究了浮动钻井隔水管随机振动的谱分析。在分析中,隔水管被简化为在轴向和横向随机载荷作用下的梁。文中以三次 Hermite 插值多项式表示分布惯性力,推导出梁随机响应的计算公式。将传递矩阵法和振型迭加法比较,前者便于考虑浮船运动对动力响应的影响和水动力阻尼。按照本文的公式编制了 Fortran 程序,可求出挠度、转角、弯矩和应力的随机解。又用此程序对 T.C.Tucker 一文中的例题进行了计算,其结果十分接近原文中的计算结果。计算结果表明:(1)有可能出现顶部张力的较佳值,使得动力响应值较小;(2)浮船运动对动力响应有较大的影响,在动力分析中应该给予考虑;(3)海浪谱对动力响应的影响很大。要对结构进行准确的动力分析,应采用长期积累的可靠的海浪信息. 相似文献
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传统的卡箍设计方法是通过建立海洋平台有限元模型并在强度分析基础上提取受损单元处完好时的最大载荷,将此载荷作为卡箍设计的初始条件。而卡箍实际承担的是平台安装上卡箍之后载荷重新分担下相应受损处承受的载荷,一般会比初始设计载荷大。着重研究载荷重新分担对膨胀式自应力灌浆卡箍防滑设计和防撬设计的影响,针对渤海湾中主要承受冰载荷作用的一个典型平台结构,提出了在线单元平台有限元模型上近似模拟卡箍的方法,提取载荷重新分担下的卡箍设计载荷进行了分析。结果表明载荷重新分担对卡箍防滑设计影响较小,但对防撬设计有着显著影响,并对此提出了在螺栓设计时增加螺栓预紧力安全系数的应对措施。 相似文献
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深水半潜式钻井平台简化疲劳分析 总被引：1，自引：0，他引：1
研究适用于中国南海的深水半潜式钻井平台结构简化疲劳分析方法。依据中国南海环境条件,计算平台结构应力响应,得到平台结构应力范围长期Weibull分布形状参数。通过结构波浪应力的长期预报,计算得到平台寿命期一遇波浪载荷,依据寿命期一遇波浪载荷计算平台结构寿命期一遇最大热点应力范围。采用简化疲劳分析方法计算平台结构疲劳寿命,用谱疲劳分析方法验证简化疲劳分析结果的准确性,证实了简化疲劳分析方法相对保守,可应用于平台的设计。 相似文献
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甲板上浪发生时产生的巨大冲击载荷可以对海洋结构物造成严重破坏,其发生时的海况比较恶劣,带有较强的非线性特点。采用CFD软件Fluent中的动网格功能造波结合软件中的VOF模块捕捉自由液面再现了单个极大波浪的生成过程,继而对固定甲板情形下的上浪问题进行了考察,波浪遭遇甲板后产生了流动的分离,甲板上下的水体表现出了完全不同的流动特点。通过可视化计算结果和深入细致的速度剖面分析,更好地加深了对这一复杂流动过程的理解。最后还将模拟结果与实验结果在定性和定量上进行了对比,表现出了良好的一致性。 相似文献
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利用Karman关于板的大挠度理论,考虑涡电流在板中引起的Lorentz力,导出了在横向磁场和横向载荷共同作用下薄板的非线性运动方程.借助Bubnov-Galerkin法将非线性偏微分方程转化为含三次非线性项的常微分方程.在定性分析的基础上,利用次谐轨道的Melnikov函数给出了发生Smale马蹄型混沌运动的阈值条件,进而数值计算了系统的分岔图、相应的相图、Poincaré映射和时程曲线,给出了混沌运动的数字特征.分析结果表明:磁感应强度和外载荷都会影响系统的振动特性. 相似文献
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研究浅水半潜式大功率浮式风力机波浪载荷和气动力引起的基础结构疲劳损伤,揭示基础结构的疲劳损伤机理。采用谱疲劳损伤计算分析方法,以10 MW风力机为例,计算波浪载荷引起的热点应力及多种海况引起的疲劳损伤。采用叶素动量理论并基于所在海域的风速分布,计算叶轮转动引起的气动力及其引起的疲劳损伤。计算结果表明,对于半潜式三立柱浮式风力机,波浪载荷引起的基础结构应力远大于气动力引起的基础结构应力,基础结构损伤主要是由波浪载荷引起,气动力引起的浮式基础结构的损伤为10-3量级,而波浪载荷引起的损伤为10-1量级。 相似文献
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Estimation of loads derived from shipping water events in naval and offshore structures is of importance to improve their structural design or to predict changes in their dynamics. For the case of vertical loads on deck of a fixed structure, it is possible to estimate analytically their evolution in time by considering the distribution of shipping water elevations. However, the classical approach to estimate this distribution (i.e., dam-break method) tends to overestimate the amount of water on deck and does not follow the generated decay trends observed experimentally. In the present work, the time evolution of the vertical loads due to shipping water events was studied analytically and experimentally. The validation of the use of a convolution model to estimate the time evolution of vertical loads is presented, aiming to improve the results obtained with classical approaches. A systematic experimental study has been conducted using the wet dam-break method to generate isolated shipping water events, measuring the slow-varying vertical loads on a rectangular fixed structure. A force balance and a high-speed camera have been used at the same sampling rate to monitor the vertical loads and the shipping water evolution on the deck. Results demonstrated that the use of the convolution model improved the representation of the time series of loads compared with the traditional dam-break approach. With this new method, it was possible to capture the peaks and the decay tendencies observed in the experimental data in an approximated way. 相似文献
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Experimental Investigation of Irregular Wave Uplift Force on Deck of Exposed High-Pile Jetties 总被引：1，自引：0，他引：1
A laboratory setup was developed to investigate irregular wave uplift loads on exposed high-pile jetties.It is shown that the dimensionless uplift load increases to the maximum with an increasing relative clearance and then decreases.The relative clearance corresponding to the peak force is linked to a range from 0.4 to 0.8.When the relative clearance exceeds a certain value,the wave can not reach the underside of the deck and the force becomes zero.Distinct trends of dimensionless force with a relative width of deck show that the force tends to decrease as the relative deck width increases,and then the decrease slows down after the relative deck width increases or decreases to a certain value.The pressure distribution length associated with the maximum uplift force is equivalent to the wave contact width x.When x is larger than the width of deck B,it is taken as B.The statistical distribution of loads obeys the Weibull distribution.The results from the analyses of the real data suggest a new dimensionless prediction model on wave-in-deck uplift loads and the conversion ratio between wave loads at different exceedance probabilities.A comparison is made between the new prediction model and the existing widely used three prediction models.These results are used as useful references for structural design of the jetty. 相似文献
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Semi-submersibles for offshore oil exploration and exploitation often suffer from severe wave impacts in extreme ocean environments.Owing to the complex wave interactions among structural components of semi-submersibles,in-depth analyses on the characteristics of wave impact events are of significance for both industry and academia.An experimental study was carried out to investigate the local wave impact loads on a semi-submersible,with focus on understanding the wave impacts by identifying typical impact modes.Quantitative criteria are proposed to classify major wave impacts on the semi-submersible into six modes and two types.The results show that the classification is reasonable and provides valuable information for studying wave impacts on semi-submersibles.The incident wave characteristics at the fore column of the semi-submersible have important influence on the wave impact mode.The fore-column dominating wave impacts exert the most intense loads on the fore column and feature well-developed breaking waves or slightly breaking waves at the fore column.However,the aft-column dominating wave impacts exert the most intense loads on the aft column or the deck bottom and feature non-breaking waves at the fore column.Energy loss during the fore-column impact weakens the impact severity on the aft column in the fore-column dominating wave impacts.The shoaling effect of the submerged pontoon and different motion configurations of the platform result in higher occurrence rate of the aft-column dominating wave impacts.Different impact modes are also distinguished by different spatial distributions of wave impact loads. 相似文献
14.
汽车荷载作用下挡土墙土压力计算方法的改进 总被引：2，自引：0，他引：2
王来福 《中国海洋大学学报(自然科学版)》2005,35(5):827-829
阐述汽车荷载作用下挡土墙土压力的计算：现行计算方法把挡土墙路基上布置的汽车荷载,在有效范围内换算成等代均布土层厚度,计算挡土墙土压力.由于简化的假定条件,使计算结果产生较大的误差;改进的计算方法是通过解析分布长度和分布宽度的方法,计算出对挡土墙最不利的土压力,并用算例说明它的实用性. 相似文献
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This paper presents an incremental elastoplastic finite element method (FEM) to simulate the undrained deformation process of suction caisson foundations subjected to cyclic loads in soft clays. The method is developed by encoding the total-stress-based bounding surface model proposed by the authors in the ABAQUS software package. According to the model characteristics, elastoplastic stress states associated with the incremental strains of each iteration are determined using the sub-incremental explicit Euler algorithm, and the state parameters describing the cyclic accumulative rates of strains are updated by setting state variables during the calculations. The radial fallback method is also proposed to modify the stress states outside the bounding surface to the surface during determination of the elastoplastic stress states. The stress reversals of soil elements are judged by the angle between the incremental deviatoric stress and the exterior normal vector at the image stress point on the bounding surface to update the mapping centre and state variables during cyclic loading. To assess the general validity of the method, the reduced scale model tests and centrifuge tests of suction caissons subjected to cyclic loads are simulated using the method. Predictions are in relative good agreement with test results. Compared with the limit equilibrium and quasi-static methods, the method can not only determine the cyclic bearing capacity, but can also analyse the deformation process and the failure mechanisms of suction caisson under cyclic loads in soft clays. 相似文献
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Steep or breaking waves may produce critical run-ups on a surface-piercing column, as represented by an unexpectedly high uprush, which has the potential of generating damaging localised wave-in-deck loads. Hence, to improve the air gap performance of offshore column-stabilised platforms, this paper proposes the mounting of an innovative multi-layer barrier on the column surface at a certain distance below the lower deck. Experiments were performed using a truncated square column to examine the performances of different versions of the barrier, namely, solid-plate, porous-plate, and intermittent-plate types, under four different focused waves. All the barrier types were found to obstruct and deflect uprush flow under storm conditions. However, the solid-plate type tended to experience considerable wave forces, with its impermeability also rendering the higher layers ineffective. The intermittent-plate type dissipated the uprush flow and decreased the wave impact, although it exhibited relatively strong flow disengaging, which decreased the efficiency under large wave run-ups. Conversely, the porous-plate type exhibited adequate performance, with a larger plate porosity and moderately high mounting elevation tending to improve the uprush obstruction performance and further decrease the wave slamming loads. A barrier with an appropriately designed plate porosity, number of layers, and mount elevation is expected to perform efficiently under severe sea states, providing protection for the lower deck against extreme wave run-ups. 相似文献
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基于3D FEMDEM方法建立三维原型尺度数值模型,模拟波浪荷载作用下斜坡上护面块体内部的应力分布。波浪作用下结构物的水动力荷载采用微幅波理论模拟,护面块体之间的运动、碰撞接触以及块体内部的应力变化采用3D FEMDEM方法模拟。块体之间的接触力采用基于势函数的罚函数法计算,有限元的变形采用中心差分的显式方法求解。应用该数值模型与ANSYS软件程序对自重作用下混凝土扭王字块的内部应力分布特性进行了比较分析,验证了数值模型应力计算的可行性和计算精度。通过数值模拟计算给出了波浪作用下斜坡上护面块体之间的相对运动和块体内部的应力分布及应力历时曲线,探讨了块体内部应力变化特性。 相似文献
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Green water loads on moored or sailing ships occur when an incoming wave significantly exceeds the freeboard and water runs onto the deck. In this paper, a Navier–Stokes solver with a free surface capturing scheme (i.e. the VOF model; [Hirt and Nichols, 1981]) is used to numerically model green water loads on a moored FPSO exposed to head sea waves. Two cases are investigated: first, green water on a fixed vessel has been analysed, where resulting waterheight on deck, and impact pressure on a deck mounted structure have been computed. These results have been compared to experimental data obtained by [Greco, 2001] and show very favourable agreement. Second, a full green water incident, including vessel motions has been modelled. In these computations, the vertical motion has been modelled by the use of transfer functions for heave and pitch, but the rotational contribution from the pitch motion has been neglected. The computed water height on deck has been compared to the experimental data obtained by [Buchner, 1995a] and it also shows very good agreement. The modelling in the second case was performed in both 2-D and 3-D with very similar results, which indicates that 3-D effects are not dominant. 相似文献
19.
Response analysis and optimum configuration of a modular floating structure with flexible connectors
In the present paper, a numerical analysis framework evaluating the connectors’ internal loads of a modular Pontoon type Floating Structure (PFS) as well as for identifying the PFS's optimum configuration under the action of regular waves is developed and presented. The PFS consists of flexible floating modules (pontoons) connected with flexible connectors in longitudinal and/or transverse directions. The numerical analysis framework includes: (a) a frequency domain ‘wet’ hydroelastic analysis for computing the PFS's ‘wet’ hydroelastic response and the connectors’ internal loads and (b) a genetic algorithms based optimization process for identifying the optimum configuration of the PFS considering predefined performance criteria. Different configurations of the PFS under the action of normal and oblique waves are taken into account, considering different number and layout of modules (grid type) and different values of the connectors’ rotational stiffness. The effect of the connector's rotational stiffness and the grid type of the PFS on the hydroelastic response and on the connectors’ internal loads is analyzed. For specific wave field characteristics, the optimum design configuration of the PFS is identified through the aforementioned optimization process in terms of performance criteria related to: (a) the vertical hydroelastic response at any predefined point of the deck of the PFS and (b) the internal loads of the PFS's connectors. The results obtained demonstrate the complex relationship between the internal loads of the connectors and the hydroelastic response of the examined PFS configurations with the connectors’ rotational stiffness and the PFS's grid type as well as with the excitation. They also demonstrate the applicability of the developed numerical analysis framework in order to properly direct the PFS's design towards a most preferable optimum configuration. 相似文献