非粘结柔性立管静态分析

海洋柔性立管因材料和结构上的复杂性在设计分析中存在许多技术难题。本文在变形能原理和能量守恒的基础上,推导出了柔性立管各层的刚度矩阵。将各层刚度矩阵进行叠加,得到柔性立管总体刚度矩阵,并用总体刚度矩阵求解静载荷作用下立管变形响应。同时基于ABAQUS软件建立八层非粘结柔性立管有限元模型,并将有限元计算结果和刚度矩阵计算结果进行比较。结果分析表明：运用推导得到的刚度矩阵求解静态载荷下立管的变形是一种简便且准确的方法。     

串列非粘结柔性立管碰撞影响规律分析

考虑基于骨架层和压缩铠装层各向异性中轴向材料属性,本文研究了串联非粘结柔性立管的碰撞规律影响特性。利用ABAQUS海工软件划分和加密典型八层非粘结柔性立管的最外层外护套层外表面参与碰撞的区域,讨论立管在不同的碰撞速度、管间摩擦系数和管内壁压单因素变量下,碰撞区域沿碰撞方向的应变、应力和碰撞力的时程曲线特性,总结对非粘结柔性立管碰撞影响规律。同时,对比单层立管与非粘结柔性立管的碰撞过程发现,两者都发生了多种碰撞行为,其中第一次碰撞过程最为剧烈。三个单因素变量对非粘结柔性立管的碰撞规律特性有不同影响。就立管的碰撞速度而言,在第一次碰撞过程中,碰撞力随碰撞速度的增加而增加,应变和应力呈现先增大然后减小的趋势;随着管间摩擦系数的增大,碰撞过程中应变和应力呈先减少后增加的趋势;碰撞中应变和应力随管内壁压的增加而增加。     

基于OrcaFlex的海洋柔性管水动力分析

柔性管水动力分析的准确性与保守性直接影响着其疲劳性能计算。文章针对一种非黏结性柔性管,通过OrcaFlex对其进行整体水动力分析,得到载荷曲线;并通过波浪筛选提取典型波浪工况,将其施加到OrcaFlex分析模型中,得到了柔性管各位置处的载荷响应;最后提取了柔性管的最大弯矩和拉伸力数据,为下一步疲劳性能计算提供了数据支持。     

压力载荷下非粘结柔性立管应变影响因素分析

基于Abaqus/Explicit准静态和质量放大方法研究了一类典型非粘结柔性立管在压力载荷作用下应变响应特性,对影响立管整体轴向延伸率和绕轴向扭转角度的因素进行了分析。数值模型计入金属层实际截面形状、铺设角度以及几何、接触、材料非线性。计算结果表明：数值解与理论值吻合较好;立管端部边界条件对轴向延伸率影响不大但对绕轴向扭转角度影响较大;抗压铠装层为径向压力主要受力构件,其铺设角度虽然对压溃性能不大,但在应变分析中不可忽略;拉伸铠装层铺设角度对应变影响同样较大。文中数值方法可弥补理论方法限定在小位移、小变形范围,无法计入层间摩擦、材料非线性及初始制造椭圆率等缺陷。     

缓波型柔性立管构型优化及敏感性分析

针对缓波型柔性立管存在的波型较陡和浮子段张力较大的问题,对其进行优化,将单波构型优化为双波构型,运用集中质量法对改进前后的2种结构形式进行分析,确认双波构型在静力和动力响应下的张力及弯曲特性更优。在此基础上,对双波型柔性立管进行敏感性分析。在静力状态下,悬挂点和第2段浮子段末端对浮子段间隔和浮子段长度敏感;在动力响应下,悬挂段到第1段浮子段的张力变化和最小弯曲半径对浮子段间隔和大悬挂角非常敏感。研究得到的敏感性参数结论可作为缓波型柔性立管总体布置设计的参考。为提升缓波型柔性立管的性能,可合理增加浮子段与浮子段的间隔和悬挂角,但同时要满足规范的要求,避免关键部位动力响应过大。     

层间粘结性能对沥青路面抗剪强度的影响

比较了不同改性剂掺量的SBS改性沥青的技术指标,并采用直剪试验和45°斜剪试验比较了其作为层间粘结材料的抗剪强度,提出了抗剪强度高且适于施工的改性剂掺量;同时比较了粘层沥青洒布量为0、1．2、1．5、1．8、2．1kg／m^2时的抗剪强度,提出了1．8kg／m^2是层间最佳的洒布量。用GTM试验法比较了沥青路面结构在热接、冷接状态时的层间抗剪强度。     

玻璃纤维增强柔性管组合荷载下极限状态分析

以玻璃纤维增强柔性管为研究对象,通过理论及有限元方法对其在内压拉伸组合荷载下的力学性能进行研究,最终得到其在组合和荷载的极限方程,该极限方程的计算结果与有限元算例结果高度吻合,证明了极限方程的可靠性,同时,该极限方程也为管道设计人员提供了可靠、简便、准确的内压拉伸组合荷载下极限状态校核。     

非粘接柔性管力学性能验证实验方法研究

非粘接柔性管是一种特殊的复合材料,由多种材料非粘接复合而成,相比粘接性柔性管,其可设计性、弯曲性、施工安装及回收利用有很好的优势。在海洋工程中,非粘接柔性管被大量的应用于海洋油气管道中。在风、浪、流等复杂的海况条件下,海洋油气管道的力学性能引起更多的关注。为了研究海洋油气管道的拉伸、弯曲以及压溃等力学性能,减少在海洋工程作业中的意外事故,需要对原型管子进行相应的验证试验。     

Axisymmetric structural behaviours of composite tensile armoured flexible pipes

To address the weight and corrosion challenge in deep-water, replacing the steel tensile armour in flexible pipes with composite materials is an alternative conceptual approach. An axisymmetric structural responses model is built for this novel composite armoured flexible pipe, with interlayer gaps that may occur in the unbonded structure considered through an iterative algorithm. The tensile strength of steel and composite armoured pipes are predicted based on different constitutive relations of steel and composite. Essential quantities are obtained, such as tensile stiffness, deformations of each layer and interlayer gaps or contact pressures. Considering the helix form of carcass and pressure armour, a finite element model is established for the verification of the theoretical model. Case study shows that the tensile stiffness of flexible pipe is overestimated with the interlayer gap ignored. Compared with steel armoured flexible pipe, the composite armoured pipe, whose tensile stiffness decreases less as external pressure increases, meanwhile has higher values of tensile ultimate strength and torsion stiffness. Some suggestions about fiber types and volume fraction for composite tensile strips are given to ensure good performance of axial tensile strength and stiffness.     

Structural response of a flexible pipe with damaged tensile armor wires under pure tension

This article studies the structural response of a 6.0” flexible pipe under pure tension considering intact and damaged conditions. In the damaged condition, several wires of the tensile armor layers are assumed to be broken. A three-dimensional nonlinear finite element (FE) model devoted to analyze the local mechanical response of flexible pipes is employed in this study. This model is capable of representing each tensile armor wire and, therefore, localized defects, including total rupture, may be adequately represented. Results from experimental tests validate the FE predictions and indicate a reduction in the axial stiffness of the pipe, a non-uniform redistribution of forces among the remaining intact wires of the damaged tensile armor layers and high stress concentrations in the wires near the broken ones. Moreover, the FE model indicates that significant normal bending stresses may arise in the pressure armor and inner carcass due to an uneven pressure distribution on these layers. Finally, the results obtained are employed to estimate the pull out capacity of the studied flexible pipe.     

JYXR系列舰用挠性接管研究

  目的  为了研究凯夫拉纤维增强型挠性接管（FW-FP）管体发生局部异常变形而引发管体破裂失效的问题,  方法  提出一种基于电阻检测原理的管体变形检测方法,通过传感器缠绕模型的设计,分析管体3种变形状态。运用建立的基准阈值模型,对典型的DN100挠性管体进行数值计算分析。  结果  结果表明,管体局部异常变形引起电路电流的变化量可达0.25 A,而管体正常变形引起电路电流的变化量可忽略不计。  结论  所提方法可有效识别管体上的局部异常变形,并可排除正常变形带来的信号干扰。该检测方法得到的结果可为后续评估此类挠性接管管体使用寿命提供依据。     

Burst pressure of steel reinforced flexible pipe

The burst pressure of steel reinforced flexible pipe (SRFP) considering plasticity is investigated through experimental, theoretical and numerical methods. The results obtained from the aforementioned methods are in good agreement with each other, which illustrates the accuracy and reliability of the proposed theoretical and numerical models. The mechanical responses of PE layers and the steel strips are studied in detail, and the rationality of the strain uniformity assumption for the steel strip's cross section in the theoretical model is confirmed from its von Mises stress variation along the width at different points in FEM. Some influential parameters of SRFP on the burst pressure are also investigated in order to guide its cross-section design. The theoretical model and the FEM proposed in this paper can not only give an estimation to the safety and reliability of the pipe when it is subjected to internal pressure, but can also provide some reference for improving and optimizing its cross-section design.     

Mode transitions in vortex-induced vibrations of a flexible pipe near plane boundary

A pipe model with a mass ratio（mass/displaced mass） of 4.30 was tested to investigate the vortex-induced vibrations of submarine pipeline spans near the seabed.The pipe model was designed as a bending stiffness-dominated beam.The gap ratios（gap to diameter ratio） at the pipe ends were 4.0,6.0,and 8.0.The flow velocity was systematically varied in the 0-16.71 nondimensional velocity range based on the first natural frequency.The mode transition between the first and the second mode as the flow velocity increases was investigated.At various transition flow velocities,the research indicates that the peak frequencies with respect to displacement are not identical along the pipe,nor the frequencies associated with the peak of the amplitude spectra for the first four modes as well.The mode transition is associated with a continuous change in the amplitude,but there＇s a jump in frequency,and a gradual process along the pipe length.     

挠性接管安装工艺对系统振动传递影响试验研究

为了解挠性接管安装工艺状态对机械隔振系统振动传递特性的影响,选取某型船舶上典型的管路系统及挠性接管为研究对象,采用二分法进行了挠性接管不同安装工艺偏差对系统振动传递特性影响的试验研究。结果表明,在一定安装工艺偏差范围内,船体结构振级、马脚下部振级、挠性接管远设备端振级变化不大,在安装过程中应控制挠性接管工艺参数在规定偏差范围内。     

The hydraulic performance and structural integrity of A-Jack armour layer

A-Jacks are concrete armor units that are used in both open channel and coastal applications.In open channel applications,they are used for bank and toe protection,flow and grade control,bridge pier scour protection,energy dissipation,and habitat.These small units may be fabricated in standard block machines.In coastal applications,A-Jacks are used in breakwaters,jetties,revetments,and habitat development.Coastal units are generally much larger and more robust than the small open channel units.This paper focuses on coastal applications and in particular,combines results on three topics:(1)recent hydraulic model studies,(2)alternative fabrication methods,and(3)bundle placement construction methods.Hydraulic models studies were conducted that examined the standard random and uniform placement methods,and also the bundle placement method.In bundle placement,3~20 A-Jacks are banded together,lifted with a spreader bar,and placed as a single crane pick.This significantly decreases installation time during construction.It also provides a more hydraulically stable placement technique.The hydraulic model tests examined the bundle stability in random waves for cases where the binding remains in tack and is removed.The geometry of A-Jacks enables a variety of fabrication techniques.One option is to fabricate the A-Jacks as two pieces using flat forms and then grout the two pieces together.Flat forms may be used in conventional block machines for A-Jacks sizes up to 1.3 m.Larger sizes may be wet cast in flat forms or gang forms.The A-Jacks geometry has been recently modified to increase grouting efficient and strength.Large A- Jacks may also be cast in a single piece using "clam shell" type forms.     

近海环境中PHC管桩防腐蚀对策

PHC管桩在沿海地区应用广泛,然而氯离子的渗透会影响PHC管桩的耐久性.PHC管桩受损后难以发现和修复,影响结构物抗震能力,因此应考虑对PHC桩采取防腐蚀措施.针对PHC管桩构造和施工特点,介绍多种工况下,适合于PHC管桩各个部位的防腐蚀措施,为有防腐要求的PHC管桩施工项目提供参考.     

用于预测含层间间隙缺陷柔性立管的静水压溃强度的弹性支撑拱结构模型

  目的  随着油气勘探涉入超深水领域,一旦柔性立管的外层结构发生破损,其内部的骨架层将承载巨大的外部水压。如果骨架层与铠甲层之间存在层间间隙,则将削弱骨架层的压溃强度,进而引发所谓的湿压溃。  方法  针对该问题,提出一种弹性支撑拱结构模型,并将骨架层的湿压溃过程分为接触前与接触后2个阶段。在接触之前,采用单环结构的稳定性理论分析内骨架层的失稳行为;当层间间隙闭合之后,骨架层开始受到铠甲层的支撑,该结构进入接触后阶段,此时外部铠甲层可以简化为径向支撑弹簧,用于支撑内部骨架层的分离拱状部分。基于此,建立有限元压溃模型,用以验证该解析模型的可靠性。  结果  2类模型的预测结果吻合良好,压溃压强对铠甲层刚度和间隙宽度均非常敏感;当初始层间间隙宽度由0增加至0.5 mm时,柔性立管的压溃压强将降低18%左右;如果紧密拟合的骨架由更硬的铠甲层支撑,则将大幅提高其抗压溃强度。  结论  对于具有较硬铠甲层和较小层间间隙的柔性立管而言,该解析模型可以有效预测其静水压溃强度。     

锚拉板式索梁锚固结构构造参数分析

鉴于锚拉板式索梁锚固结构受力复杂、应力集中等问题,以厦漳跨海大桥南汊主桥Z12锚拉板式索梁锚固结构为例,采用ANSYS有限元软件对锚拉板式索梁锚固结构进行构造参数分析。结果表明,增大板厚、加长剪切剪焊长度以及增大塑性区半径均能改善应力集中状态,但以增大塑性区半径最为明显。