Dynamic response analysis of towed cable during deployment/retrieval

A numerical approach was developed to analyze the transient behavior of towed cable during ac- tively controlled deployment/retrieval (DR). The cable motion is described by the lumped parameter method, its corresponding boundary conditions are presented. In view of its varying length during DR, two auxiliary arguments are introduced to describe its continuous varying length and discrete number of nodes(equations), the length is determined by the pay out(or reel-in) rate, which is then used to determine the node number by a logic relation. For the discrete mathematical model of towed cable, an algorithm was developed to deal with the discrete governing equations. The simulation results indicate that the cable experiences more com- plex motions due to its varying length, and tension fluctuates seriously in the startup and ending stage of deployment/retrieval. The effect of towing ship's motion in waves on cable during deployment/retrieval is also considered via numerical simulation.     

Numerical Investigation of the Dynamics for Low Tension Marine Cables

This paper presents a numerical investigation into the dynamics of marine cables which are extensively used in offshore industry. In this numerical study, the Euler-Bernoulli beam model is adopted to develop the governing equations of the cable. Bending stiffness is considered to cope with the low tension problem in local area of towing cable, and thus a more accurate solution with the consideration of the axial elongation can be given.The derived strongly-coupled and nonlinear governing equations are solved by a second-order accurate, implicit,and large time step stable central finite difference method. The quadratically convergent Newton-Raphson iteration method is applied to solving the discrete nonlinear algebraic equations. Then a towed array sonar system(TASS)problem is studied. The numerical solutions agree reasonably well with the experimental data and the simulated results of the references. The specified program of the present paper shows great robustness with high efficiency.     

Cable Sliding at Supports in Cable Structures

To develop an effective numerical method for the cable sliding problem in cable structures，two-node catenary cable element was built to model the cables based on analytical solution of elastic catenary．Cooperated with Newton method，continuation method Was used to solve the nonlinear equations．This approach is more efficient than using Newton method only and has a wider range to select initial values for the process to converge．The relationship between the tension on a cable segment and its unstrained length was derived and used to calculate the unbalanced cable tensions at the supports．An example is presented to show the correctness and efficiency of the proposed method．     

一种悬索桥静力分析的解析元法

将悬索桥的主缆简化为具有拉伸刚度的质点系,给出了缆索结构2维解析元法的基本方程和求解方法,单元间的作用力与坐标变化的关系可以用解析法得到,对所得到的反映结构特性的质点系方程组进行力的平衡迭代,求解方程组.采用自动的动态可变步长的迭代方法,能够提高计算效率,保证收敛.这种方法既考虑了几何非线性,又适用于材料非线性的计算,比有限元法优越之处还在于,它不用求解线性方程组,所以适用范围广,允许求解多自由度的几何可变体系,而有限元法在求解此类问题时经常不收敛.     

Dynamic Effect Research of Cable-Lead-In Rod on Towed System

This paper aims to research the cable-lead-in rod effect on a towed system through mathematical modeling and numerical simulations. The rod dynamics, as a key part of this study, is modeled using the combination of cable node governing equations and kinematic constraint conditions. As the first attempt to analyze such a problem, the rod is simply treated as an elastic cable segment so as to be incorporated into the dynamics of the cable, and a set of algorithm is then proposed based on the kinematic constraint conditions to fully describe its motions. Meanwhile, the cable and the underwater vehicle are modeled by the traditional lumped mass method and the 6 degree-of-freedom maneuverability equations for submarines respectively; the coupling boundary conditions besides the rod dynamics are also given to form the whole system's model. Several numerical cases are performed to investigate the rod effect on the system in different maneuver situations. Some meaningful conclusions are drawn through comparative analysis.     

下承式系杆拱桥吊杆索力测试计算模型研究

对基于频率法测试系杆拱桥吊杆索力的计算模型的选用进行了研究,重点分析了吊杆长细比对模型计算精度的影响规律。通过某实际系杆拱桥中吊杆索力的计算分析表明,随着吊杆长细比的不同,不同计算模型的计算精度有显著差异,需要根据吊杆长细比来合理选用计算模型,才能得到合理的计算精度。文章推荐了与吊杆长细比相对应可满足工程精度要求的索力计算模型。     

无支架缆索吊装系统单跨双吊点主缆计算

利用缆索静力平衡原理,建立了主缆按双吊点位置的分段曲线方程,推导了相应的主缆垂度和水平张力计算公式,分析了主缆双吊点距离、主缆跨径、主缆自重及吊重等参数对水平张力的影响。结果表明:影响主缆水平张力的主要因素是两吊点间距与主缆跨径之比,当两者之比在0.05以内时,用单吊点法和双吊点法计算结果差异很小,可忽略不计。     

参激屈曲梁非线性现象的数值模拟

研究了一端固定一端滑动承受轴向简谐载荷的屈曲梁的非线性振动现象,建立了系统的非线性偏微分控制方程,利用Galerkin法,得到微分动力系统,采用数值模拟研究了系统基本参数共振和主参数共振的两种情况,得到了响应的时间历程及相图,揭示了系统的倍周期分岔、暂态混沌和混沌运动等复杂动力学行为.     

Dynamic Behavior of Two Part Towing Cable System During Turning

An improved numerical method is used to simulate the dynamic behavior of a two part towing cable systems during turnings. In U turns and full turns, periodical heave motions are found both for the towed vehicle and for the depressor. Periodic motions of the subsea units and of the cable surface tension are closely related to the turning parameters, such as turning velocity and turning radius. System parameters, such as length of the second cable and the vehicle hydrodynamics, also damp turning instability.     

A study on dynamic response of cable-seabed interaction

A numerical method is developed to investigate the dynamic response of cable-seabed interaction in this paper. The motion of cable is described by the Lumped Parameter Method, while the seabed, unlike the prevailing simplified model of elastic foundation, is modeled as an irregular continuous rigid surface with rebound and friction existing, and the forces exerted by the seabed consist of normal counterforce and isotropic tangential Coulomb friction resistance. To describe the detailed dynamic response, two coefficients are introduced by analogy with the theory of rigid body collision with friction. The cable-seabed kinematic and dynamic contact conditions are formulated subsequently, and are used to incorporate the seabed effect into the cable dynamics to produce a set of ordinary differential governing equations. In this paper, we employ 4th order Runge-Kutta method to solve these equations. Several simulation cases are presented to illustrate the seabed effect. The results show that friction and impact have a prominent influence on the statics and dynamics of the cable.     

面向损伤识别的独塔斜拉桥模型的设计与分析

模型试验方法是桥梁结构损伤识别研究的一种重要手段。以某虚拟的独塔斜拉桥为原型,面向损识别设计制作了独塔斜拉桥试验模型。试验模型各主要构件（主梁、主塔、斜拉索）均独立加工制作,其中主梁选用铝合金材料,截面采用箱形,划分为不同长度的阶段,各节段均采用螺栓连接。通过改变节段板厚的方法实现主梁不同损伤程度的模拟,不同位置的损伤通过更换不同位置的板厚实现,从而方便的实现了模拟模型斜拉桥主梁的各种损伤状态。采用特殊的设计实现了斜拉桥结构索力的实时测试。对模型进行了静态试验,并与有限元模型计算的结果进行了对比分析。试验研究与数值分析为今后的损伤识别研究奠定了基础。     

轴压作用下CFRP加固圆钢管短柱的静力承载力分析

为了研究轴压作用下碳纤维增强复合材料（carbon fibre-reinforced polymer，CFRP）加固圆形空心截面（circular hollow section，CHS）钢管短柱的极限承载力，对轴压作用下CFRP加固CHS钢管短柱进行了理论和数值分析. 理论分析中，利用等效截面法推导了两种不同粘贴方式（全环向粘贴以及环向和纵向交替粘贴）的CFRP加固圆钢管短柱在轴压作用下静力承载力的理论计算公式；数值分析中，将特征值屈曲与Riks法相结合建立了轴压作用下CFRP加固圆钢管短柱的非线性有限元分析模型. 对该模型中的环向和纵向CFRP进行应力分析后发现，环向CFRP处于拉伸状态，约束钢管的径向变形；纵向CFRP会承担轴压荷载中的部分压力，限制钢管的变形. 最后，将所建立的有限元分析模型结果和所推导的理论公式结果与已有文献的试验结果进行对比，发现三者之间的最大误差不超过2%，验证了建立的有限元模型和所推导的理论公式分析结果的准确性.      

两类混凝土索塔钢锚箱结构特性比较研究

内置式钢锚箱和外露式钢锚箱均适用于混凝土斜拉桥索塔。从两类钢锚箱型式的计算比较上得到：在斜拉索索力作用下,钢锚箱侧板能承受大部分拉力,锚板及拉板受到的应力较大,混凝土塔壁承受了较小的拉索水平分力;外露式钢锚箱与钢锚箱内置式结构型式类似。只是存在因与混凝土塔壁相对位置不同而造成的受力分摊比例上的不同而已。钢锚箱具体的结构型式可根据实际情况设计。     

斜拉桥施工阶段初张索力计算方法研究

提出了用差值法确定一次张拉斜拉桥施工阶段拉索初张力的实用计算方法,该方法只需按施工步骤进行正装迭代计算。通过消除成桥阶段最优目标索力与正装迭代所得成桥索力之间的差值,可获得施工阶段拉索初张力。该方法避免了传统倒拆法无法考虑混凝土收缩、徐变和几何非线性等问题,同时给出了差值法加速收敛的近似方法,并对差值法和影响矩阵法进行了比较。通过一座实际桥梁的计算分析,证明了本方法的可行性,具有一定的应用价值。     

斜拉桥施工阶段初张索力计算方法研究

提出了用差值法确定一次张拉斜拉桥施工阶段拉索初张力的实用计算方法,该方法只需按施工步骤进行正装迭代计算。通过消除成桥阶段最优目标索力与正装迭代所得成桥索力之间的差值,可获得施工阶段拉索初张力。该方法避免了传统倒拆法无法考虑混凝土收缩、徐变和几何非线性等问题,同时给出了差值法加速收敛的近似方法,并对差值法和影响矩阵法进行了比较。通过一座实际桥梁的计算分析,证明了本方法的可行性,具有一定的应用价值。     

大岩洞特大桥拱圈脱架时背索和扣索索力优化计算

建立了大岩洞特大桥拱圈平转施工状态的三维有限元模型,交界墩和上转盘采用实体单元,扣索和背索采用索单元,拱圈劲性骨架底板采用壳单元,其余采用梁单元,支架则采用只压单元模拟;将最优化计算理论和有限元计算分析相结合,利用MIDAS有限元软件,以支架不受轴压或受压轴力很小为目标函数,对扣索力和背索力进行优化,使拱圈"脱离"支架实现转体,从而获得了扣索力和背索力的最优组合与拱圈最优内力分布.结果表明,拱圈骨架拱脚底板为控制截面,本文计算方法和结论为同类桥梁的建设具有参考价值.     

Mechanical Behaviors of Submerged Floating Tunnel under Current Effect

Introduction Submerged floating tunnel ( SFT) provides acomplete new option for crossing of waterways, andcan connect both lands and channels where appropri-ate[1-5]. Being a structure not buried deeply in theground, but suspended in a certain depth below…     

钢管混凝土拱桥拱肋吊装线形控制的分步算法

针对钢管混凝土拱桥拱肋分节段安装由扣索张拉引起的高程差问题,以裸拱自重变形后的拱轴线形为控制目标,基于最优化理论和一次扣索张拉法,提出先用零阶优化法按整体安装计算出各拱肋节段的预抬量和扣索索力,再以整体安装计算结果为目标,根据拱肋节段安装顺序,通过迭代方法计算出各个节段安装时的预抬量和扣索索力。将该算法应用到主跨240m的巫山新龙门大桥拱肋安装线形控制中,松索成拱后的线形与目标线形吻合良好。     

基于模糊神经网络的拉索耐久性评价模型

将模糊理论与神经网络技术相结合,建立了基于模糊神经网络的拉索耐久性评价模型;网络训练采用改进的梯度下降动量BP算法,经过265次学习,确定了网络各层参数值,得到了网络的收敛解;最后通过5个校验样本验证了拉索耐久性模型的正确性。研究结果表明:拉索构件的耐久性评价指标分为拉索索力、锚固系统、拉索保护层、减震装置4种;采用动态BP算法对网络进行计算时,网络的收敛速度优于常用的BP算法;训练好的模糊神经网络很好地获得并储存了评价专家的知识、经验和判断,可将网络应用于拉索构件的耐久性评价。     

码头系泊船舶缆绳线力的混沌解法

码头系泊船舶缆绳张力的理论计算对于缆绳的选取、系泊设备的设计、系泊方式、缆绳预紧力的确定,以及船级社规范的制订都有着重要的指导意义。文中对小波浪水域码头系泊船舶缆绳张力的计算建立了数学模型,引入混沌优化的方法对非线性系泊方程组进行了求解,其结果与实验结果对比有较好的一致性。