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应用Morison方程和有限元法,将悬浮隧道管体假定为与岸坡固定的Euler-Bernoulli梁结构,通过将锚索与悬浮隧道管体、海底平面铰接,实现了锚索、悬浮隧道管体以及岸坡三者之间的动力学耦合,将线性波浪理论应用于Morison方程计算波浪荷载,在时域内采用Newmark-β隐式时间积分法迭代求解悬浮隧道的运动控制方程,进而构建了水下悬浮隧道的三维动力学耦合数值模型。研究结果表明:在长周期波主导的海域,适当增大水平方向的系泊刚度,将有利于控制悬浮隧道整体的位移幅值;隧道近岸处的锚索由于边界条件的影响,在波浪条件下将承受更大的张力,工程中应适当增加或加粗近岸端部锚索,排除安全隐患;悬浮隧道的锚索布置间距宜固定在250~300 m的范围内。 相似文献
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为研究不同锚泊方式悬浮隧道在随机波作用下的动力响应,设计对应的节段模型试验,分析考虑随机波作用的3种锚泊方式悬浮隧道的动力特性。根据相似准则,考虑波流水槽的尺寸,设计几何比尺为1∶150的物理模型试验。将数值模拟结果与试验结果相对比,验证试验结果的准确性和可靠性。开展不同工况下的模型试验,分析随机波作用下3种典型锚泊方式悬浮隧道管体结构的横荡、垂荡和横摇运动响应,以及锚索的受力情况。研究结果表明:锚泊方式1的抑振能力最差,锚索缆力最大,安全性最差;锚泊方式2在垂荡方向上具有较好的抑振能力,锚索缆力比锚泊方式1小;锚泊方式3在横荡、纵荡、横摇运动响应和锚索缆力方面的表现均较佳,安全性更好。该研究可供悬浮隧道工程及其他类似工程的锚泊设计提供参考。 相似文献
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为研究波流作用下悬浮隧道局部锚索的破断动力响应,运用ANSYS/AQWA软件建立悬浮隧道及其锚泊系统的有限元模型.通过单元生死功能和时控法模拟锚索破断行为,对比分析不同波流条件对悬浮隧道局部锚索破断动力响应的影响.研究结果表明:锚索破断之后,会对剩余锚索产生冲击效应,缆力瞬态增量随着与破断位置距离的增加而逐步递减;规则波、均匀流和锚索破断作用引起的悬浮隧道动力响应具有不同的特征,规则波主要引起结构产生周期运动,均匀流主要引起结构产生大幅偏移和低频运动,锚索破断主要引起结构产生冲击效应和高频振动;锚索破断之后,剩余结构的阻尼增大、刚度降低,导致锚索破断前后的结构运动行为出现明显的不同. 相似文献
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根据锚索式悬浮隧道的运动特性,将锚索假设为两端铰接的非线性梁模型,在海流作用下,锚索会产生顺流向与横流向的涡激振动。当海流方向和管体轴向存在夹角时,管体运动可简化为作用在锚索上部端点的质点运动,并将质点运动沿锚索坐标系方向逐一分解。根据Hamilton原理建立锚索三向振动方程,并通过Galerkin方法和Runge-Kutta方法对该方程进行求解,选取典型悬浮隧道的结构进行数值分析。结果表明:当锚索上部端点的输入频率与锚索固有频率的比值为整数时,锚索会发生共振现象;如上部端点除锚索轴向方向外的某一方向质点运动与锚索振动方向一致,则锚索在该方向上的振动会出现显著变化,而对另一方向振动的影响较小;在多数情况下,锚索振动平衡位置的偏离与上部端点所输入的运动频率有紧密联系,但与幅值联系不大。 相似文献
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利用GDS多功能三轴仪对宁波地区原状粘土进行了不同应力路径作用下K0固结三轴压缩试验,探讨了增P、等P和减P3种应力路径条件下宁波粘土的应力-应变、孔隙水压力和强度特性,并结合试验结果分析了粘土的总应力路径和有效应力路径特性。结果表明,总应力路径和有效应力路径的变化趋势基本一致,不同应力路径下q-ε1非线性关系明显,土体呈现弱软化型;不同应力路径下土的峰值强度和土中孔隙水压力差异明显;应力路径对粘聚力影响较大,对内摩擦角影响不大,有效强度指标则呈相反趋势。 相似文献
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研究预应力锚索锚固洞室在爆炸波作用下的动力反应特征对认识预应力锚索加固机理和完善洞室加固设计有着重要的意义。通过室内模型试验和数值模拟,研究了在集中装药爆炸波作用下直墙圆拱式洞室围岩介质内应力波宏观变化特征和峰值应力衰减规律,从而得出抗爆锚固洞室周边围岩的受力变形状态和动力反应特征,分析了预应力全长粘结式锚索的索端张力变化特征和锚固段轴应变变化波形,结果表明抗爆洞室围岩抵抗变形能力得到一定地提高。采用显式动力分析程序得出的计算结果与试验数据的吻合性较好,进一步证实了模型参数和建模的有效性和正确性。 相似文献
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To achieve rational design in waves for a submerged floating tunnel which has emerged as a new offshore transportation infrastructure, it's necessary to understand its hydrodynamic behavior. For simple but accurate estimation of hydrodynamic forces, a theoretical method is proposed and the tests with physical models in a wave flume were carried out for verification. Morison's equation was used to estimate wave loads composed of inertia force and drag force. Forces calculated by applying the linear wave theory to Morison's equation coincided well with those measured by the tests. The test results showed that mooring systems played a significant role in the movement of the submerged floating tunnel in waves. A pendulum model could be used to describe the motion of the submerged floating tunnel with a single vertical mooring. Based on the verified relations, a simple slack condition which causes the submerged floating tunnel to be unstable was also proposed. The simplified approach proposed by this study proved to be useful in designing the submerged floating tunnel in the initial stage. 相似文献
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This work investigated the influence of two types of mooring systems on the hydrodynamic performance of a two-body floating wave energy converter(WEC). It also investigated the effects of the physical parameters of the mooring system on the amount of extractable power from incident waves in the frequency domain. The modeled converter comprised a floating body(a buoy), a submerged body with two mooring systems, and a coupling system for two bodies. The coupling system was a simplified power take-off system that was modeled by a linear spring-damper model. The tension leg mooring system could drastically affect the heave motion of the submerged body of the model and increase relative displacement between the two bodies. The effects of the stiffness parameter of the mooring system on power absorption exceeded those of the pretension tendon force. 相似文献
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This paper presents parametric studies of nonlinear wave forces on large-scale submerged tunnel element. A transportation project of submerged tunnel element under irregular wave conditions is taken as the research background. Three-dimensional diffraction potential and radiation potential associating with the motion of the floating body are utilized, and an efficient three dimensional Green function is implemented to solve the radiation-diffraction problem. A computational method for calculating the nonlinear wave forces of the submerged tunnel element is developed. The present method is validated by the existed methods and experimental data, and good agreements are observed for all test models. The effects of wave parameters and structural parameters on the second-order nonlinear wave forces are studied. Results from the present study can provide valuable recommendations for the weather window and downtime frequencies, the configuration of tugboats, the arrangement of sea-route, and the size and type of the design and construction of the submerged tunnel element. 相似文献
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Stress evaluation of a submerged floating tunnel (SFT) is an issue important for determining the section dimensions required to resist environmental loads. However, the complex interaction between an SFT and surrounding fluid has confined most research on SFTs to longitudinal global time-history analyses based on Morison's equation [1]. Even though these analyses give sufficient information in the longitudinal direction, too little information about the circumferential direction compels an SFT section to be designed conservatively. This means that SFT design requires additional information on the structural behavior of the tunnel in the circumferential direction for efficient design. Accordingly, a supplementary approach by which to obtain structural responses in the circumferential direction is introduced in this paper. Upon consideration of the static responses equivalent to the dynamic behavior, three-dimensional (3-D) finite-element analyses of an SFT were performed by application of static loads corresponding to dynamic loads equivalent to those of wave, current and earthquake. The validation of each equivalent static load was supported by the results from comparison of the tension forces in mooring lines obtained using OrcaFlex [2] and ABAQUS [3]. These were used mainly for longitudinal dynamic analysis and 3-D stress evaluation, respectively, of an SFT. Based on the stresses obtained in the longitudinal and circumferential directions, the selection of suitable section dimensions for an SFT is considered. 相似文献
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This study investigates the hydroelastic analysis of a moored SFT (submerged floating tunnel) and the corresponding hydrodynamic pressure distribution under wave excitations. Time-domain discrete-module-beam (DMB) method, in which an elastic structure is modeled by multiple sub-bodies with beam elements, is employed to express the deformable tunnel with multiple mooring lines. Moreover, the top-down scheme is also adopted for detailed structure analyses with less computational cost, which applies the calculated hydrodynamic pressure distribution over SFT's surface to the three-dimensional finite element model. The hydrodynamic pressure includes both wave-induced diffraction pressure and motion-induced radiation pressure. For the validation of the developed numerical approach, comparisons are made with computationally intensive hydroelastic-structural direct-coupled method, two-dimensional wave flume experiment, and independently developed inhouse moored-SFT-simulation program. Furthermore, the influences of flexural motions with buoyancy-weight ratio (BWR) (or bending stiffness) and regular/irregular wave conditions on the dynamic pressure distribution and the resulting local stresses are investigated. 相似文献
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On the slack phenomena and snap force in tethers of submerged floating tunnels under wave conditions
Under severe sea wave conditions, the mooring tethers of submerged floating tunnel (SFT) might go slack. It may cause the structure failure during the service lifetime of SFT. The paper investigated SFT dynamics when going through tether slacking and the related snap force under wave conditions. Besides the nonlinearity of fluid drag and of structural geometry for a relative large structure displacement, the problem is characterized by the nonlinearity due to the discontinuity in axial stiffness of the tethers. To include these nonlinearities, the method of Lagrange energy is used to build the governing equations of SFT motion, and a bilinear oscillator is introduced to simulate the mooring tether operating in an alternating slack-taut state. The sensitivities of the occurrence of tether slacking to wave height and wave period are investigated. Results show that at a large wave height SFT tether will go slack and snap force occurs. SFT responses are categorized into three types of state according to the dynamic response characteristics of tether tension. Effects of two fundamental structure parameters, buoyancy-weight ratio (BWR) and inclined mooring angle (IMA), on the dynamic responses of SFT are analyzed. A slack-taut map of SFT tethers is built. It intuitively describes the occurrences of slack and snap force with different combinations of the two parameters. An analytical approach for slack prediction by deriving the slack criterion is provided to reveal the mechanism of the presented slack-taut map. By present research, the authors tried to make their effort to provide an alternative philosophy for SFT structural design on concerning preventing the occurrence of tether slacking and snap force. 相似文献