Dynamic Analysis of Towed and Variable Length Cable Systems

Towed cable systems are frequently used in marine measurements where the length of the towed cable varies during launch and recovery. In this paper a novel method for modeling variable length cable systems is introduced based on the finite segment formulation. The variable length of the towed cable is described by changing the length of the segment near the towing point and by increasing or decreasing the number of the discrete segments of the cable. In this way, the elastic effects of the cable can be easily handled since geometry and material properties of each segment are kept constant. Experimental results show that the dynamic behavior of the towed cable is consistent between the model and the physical cable. Results show that the model provides numerical efficiency and simulation accuracy for the variable length towed system.

Parametric study on the axial performance of a fully grouted cable bolt with a new pull-out test

Modified cable bolts are commonly used in underground mines due to their superior performance in preventing bed separation when compared with plain strands. To better test the axial performance of a wide range of cable bolts,a new laboratory short encapsulation pull test(LSEPT) facility was developed. The facility simulates the interaction between cable bolts and surrounding rock mass,using artificial rock cylinders with a diameter of 300 mm in which the cable bolt is grouted. Furthermore,the joint where the load is applied is left unconstrained to allow shear slippage at the cable/grout or grout/rock interface.Based on this apparatus,a series of pull tests were undertaken using the MW9 modified bulb cable bolt.Various parameters including embedment length,test material strength and borehole size were evaluated. It was found that within a limited range of 360 mm,there is a linear relationship between the maximum bearing capacity of the cable bolt and embedment length. Beyond 360 mm,the peak capacity continues to rise but with a much lower slope. When the MW9 cable bolt was grouted in a weak test material,failure always took place along the grout/rock interface. Interestingly,increasing the borehole diameter from 42 to 52 m in weak test material altered the failure mode from grout/rock interface to cable/grout interface and improved the performance in terms of both peak and residual capacity.

Efficient modeling of cable-pulley system with friction based on arbitrary-Lagrangian-Eulerian approach

In conventional modeling of a cable-pulley system, the cable must be finely meshed with Lagrangian elements for valid contact detections with pulleys, leading to extremely low efficiency. The sliding joint method based on the arbitrary-Lagrangian- Eulerian （ALE） formulation still lacks an efficient cable element, and in particular, modeling of friction between a sliding joint and the cable has not been studied. This paper presents efficient multi-body modeling of a cable-pulley system with friction. A variable- length cable element with a node movable along the cable, which is described with ALE, is developed to mesh the cable. A transitional cable element is then proposed to model the contact part of the cable by fixing its two nodes to the two corresponding locations of the pulley. Friction of the cable-pulley is derived as a simple law of tension decay and embedded in the multi-body system modeling. It is simplified as a generalized friction force acting only on the arc-length coordinate. This approach can use a rough mesh on the cable, and is free of contact detections, thus significantly saving computation time. Several examples are presented to validate the proposed method, and show its effectiveness in real engineering applications.

Analysis of the Superconducting Cable Transposition in Low Resistance CICC Joint

In an integrated structure low resistance CICC joint, current is conducted by outer cable strands coming into touch with the conductive Cu sole. So it is an important condition for satisfying joint performance that each strand of the cable inside the joint is able to come to the outermost by transposition. This paper presents analysis, calculation and figures for the strand transposition. According to the twist procedures of the superconducting cable, the author computed the actual pitch of each stage cable, consecutively computed the projection of each stage cable on the axis of the cable (z axis) and the corresponding twist angle as the z coordinate changes, which is then drawn by AutoCAD. From the results shown in the figures, the minimal cable length, which enables each strand to transpose almost equally to the outermost of the cable in such a length, call be determined as the optimal joint length.

Optical Cable Telecommunication Networks

1. Southern Coastal Optical Cable Engineering Project. The cable was completed and put into operation in 1992, and has a total length of 2,800km, starting from Nanjing in the north, via Shanghai, Hangzhou, Fuzhou, Xiamen, Huizhou, leading to Guangzhou in the south, covering Jiangsu, Shanghai, Zhejiang, Fujian and Guangdong. The whole line has

Numerical Simulation of Slurry Diffusion in Fractured Rocks Considering a Time-Varying Viscosity

To analyze the effects of a time-varying viscosity on the penetration length of grouting,in this study cement slur-ries with varying water-cement ratios have been investigated using the Bingham’sfluidflow equation and a dis-crete element method.Afluid-solid coupling numerical model has been introduced accordingly,and its accuracy has been validated through comparison of theoretical and numerical solutions.For different fracture forms(a single fracture,a branch fracture,and a fracture network),the influence of the time-varying viscosity on the slurry length range has been investigated,considering the change in the fracture aperture.The results show that under different fracture forms and the same grouting process conditions,the influence of the time-varying viscosity on the seepage length is 0.350 m.

矿用锚索捻距与拉伸力学性能及锚固效果关系研究

矿用锚索主要由多根钢绞线缠绕而成,具有可弯曲、抗破断能力强及成本低廉等优点,在煤矿巷道围岩,特别是巷道顶板稳定性控制中广泛采用。捻距是制作锚索的重要参数之一,当选取煤矿锚索时,因了解尚浅而往往忽略这一参数。为探究捻距参数对锚索拉伸力学性能与锚固效果是否存在影响,论文采用理论分析与室内试验相结合的方法,初步厘清了捻距参数对锚索拉伸时的几何变形特征的影响,明晰了其对锚索锚固力的影响机制。基于试验获得的锚索拉伸及锚固拉拔数据构建数值模拟模型,与井下试验结果进行对比,得到了捻距与其极限拉伸载荷、最大锚固力的关系式,获取了能够充分发挥锚索拉伸力学性能与锚固效果的最佳捻距。研究结果表明:当锚索受到拉伸时,在一定范围内捻距与延伸率的关系为负相关,与拉伸极限载荷的关系为正相关;锚索-锚固剂界面存在一定的几何匹配关系,当捻距减小至其13倍公称直径时,最大锚固力随着捻距的减小而增大;综合分析锚索极限拉伸载荷与最大锚固力等因素发现,能够充分发挥锚索拉伸力学性能与锚固效果的最佳捻距为13~14倍公称直径。研究成果增加了锚索捻距对拉伸力学性能影响的认识,明晰了对其锚固机制的理解,为锚索制作及选取煤矿锚索提供了参考及理论支撑。

大跨度斜拉桥半平行钢丝拉索对称断丝损伤分析模型

为了准确地评估半平行钢丝斜拉索在断丝后的恢复长度,本文提出了考虑断丝后索力重分布的斜拉索损伤评估模型。建立了半平行钢丝的变形相容方程、断丝平衡方程、摩擦力和接触力方程以及护套紧箍效应方程。确定未知量和建立控制方程,采用最小二乘法求解断裂钢丝的恢复长度。根据恢复长度计算斜拉索沿轴向的损伤系数,并代入有限元模型中对斜拉索面积进行修正,反复迭代直至斜拉索轴向应变的计算结果满足收敛条件。以常泰长江大桥为工程背景,揭示了断丝恢复长度和损伤系数沿斜拉索长度方向的分布规律。

常泰长江大桥斜拉索施工期扭转影响分析及防控装置设计研究

常泰长江大桥是世界上最大跨径斜拉桥,主跨跨径为1208 m。斜拉索规格和索力大,施工过程中斜拉索扭转问题突出。本文开展斜拉索扭转对主梁安装控制影响的研究,计算分析表明,斜拉索扭转对斜拉索钢丝应力、斜拉索索力均有一定影响,对主梁线形影响显著,斜拉索扭转0.5°,主跨位移变化0.46 m;提出了一种斜拉索张拉防扭转装置及其设计方法,现场应用中斜拉索张拉过程中无扭转现象,施工过程中最大线形误差小于5 cm。

斜拉桥由成桥状态求解施工初始索力方法研究

该文针对斜拉桥由成桥状态求解施工初始索力的问题,提出一种结合无应力索长与正装迭代的方法。该方法首先由成桥状态计算斜拉索无应力长度,然后基于无应力索长进行施工正装计算,求得拉索原始初始索力,再通过差值迭代调整施工初始索力,最后根据主塔变形微调施工初始索力,来获取满足偏差要求的成桥状态。以一座斜拉桥为研究背景,该桥已知成桥目标状态,采用该方法确定施工过程的张拉索力。通过算例说明该方法不需要进行复杂计算,能取得满足工程精度的结果。

基于有限元方法的斜拉索线形参数计算

随着斜拉桥的跨径越来越大,斜拉索的非线性特征所引发的问题变得更加突出,精确计算斜拉索的线形成为重要研究课题。以往计算斜拉索的线形参数均是采用解析方法,现将以有限元方法为计算工具,构建可调节无应力索长的斜拉索有限元模型,通过二分法迭代,精确计算出斜拉索的线形,再提取其设计参数,并与解析计算结果作对比。结果表明用该方法计算斜拉索线形参数得到的精度较高,可以应用于斜拉桥设计。

基于调研数据的部分斜拉桥设计关键参数研究

针对部分斜拉桥设计关键参数缺少足够规范指导的问题,通过对国内外的部分斜拉桥进行设计主要参数调研统计,并与现有相关规范、科研成果进行对比研究,讨论了部分斜拉桥各型结构体系适用性、拉索布置形式,总结给出拉索倾角和间距、边主跨比、塔跨比、索梁刚度比和无索区长度等重要设计参数取值范围。结果表明,拉索倾角一般为11°~35°,主梁上拉索间距一般采用3.5 m~8 m,塔上的拉索间距一般采用0.5 m~1.2 m;3跨布置时,边主跨比一般集中在0.41~0.70,塔跨比宜采用1/3~1/13,索梁刚度比宜小于30;主跨跨中无索区长度与跨径之比宜取0.06~0.21。

平行钢丝斜拉索更换施工新索无应力长度确定方法研究

为准确确定平行钢丝斜拉索更换施工新索无应力长度,基于悬链线法和无应力状态法,并结合斜拉索索力、锚点间距、斜拉索原始加工长度和实际锚固位置等数据,综合提出5种针对不同数据场景下的平行钢丝斜拉索新索无应力长度快速计算方法。以攀枝花炳草岗大桥为背景,采用5种方法计算该桥新索无应力长度,分析其合理性,并进一步提出6项新索无应力长度复核计算准则。结果表明:在充分研判炳草岗大桥基础资料并对照6项复核计算准则的合理性后,基于无应力状态法,并结合旧索加工总长和实测锚具伸出量,准确给出了新索无应力长度。该桥新索张拉锚固完成后,塔、梁端实际锚固位置合理、可控,成功解决了其基础资料混乱、斜拉索锚固位置不当的问题。

基于数字化三维技术二次电缆长度自动统计方法

针对在二次电缆长度测量和统计过程中,接触式的方法过度依赖选择的测量仪器,统计人工性较强,导致总统计成本较高。提出基于数字化三维技术的二次电缆长度自动统计方法。采用数字化三维技术处理多条基本线缆,利用线束分支结构和线束主结构,组成二次电缆三维信息模型,分析挡块与二次电缆的几何关系,测量三维位移场,获得独立的二次电缆的动态长度,从二次电缆模型中选择三个参考点,经过拼接转换计算,统计出二次电缆整体长度。实验结果表明:设计的方法测量成本和检测误差成本均低于计划成本,与常规的人工统计方法相比,经济性更高。

采用支点位移法施工的斜拉桥钢-UHPC组合梁受力分析

为了解采用支点位移法施工对大跨度斜拉桥钢-UHPC组合梁负弯矩区力学性能的改善情况,以主跨442 m的沾临高速公路黄河特大桥主桥为背景,采用MIDAS Civil软件建立主桥三维有限元模型进行受力分析。计算无应力索长及成桥状态钢-UHPC组合梁线形,并在二者保持不变的基础上,分别对采用、未采用支点位移法施工的钢-UHPC组合梁成桥及运营状态下的弯矩、梁底应力、UHPC桥面板顶(底)缘应力进行对比分析。结果表明:相比于未采用支点位移法,采用支点位移法施工的钢-UHPC组合梁斜拉桥可减小或者消除辅助墩处组合梁的负弯矩,显著增加辅助墩处负弯矩区UHPC桥面板的压应力储备,达到施加预应力的效果,显著改善了负弯矩区钢-UHPC组合梁的力学性能,应用效果良好。

倒梯形巷道顶板全长锚索联合支护技术研究

针对长城五矿1902S回风巷倒梯形煤巷的高地应力产生的围岩稳定性差,支护体失效的问题,在实地调研施工现场后,结合FLAC3D数值模拟分析原方案的支护失效体制,并提出“全长锚固锚索+组合支撑钢墩柱+W型钢带+钢筋锚网+钢带”的联合支护技术,从顶板围岩的变形量和帮部相对移近量两方面来分析矿压显现规律。结论如下:原方案锚杆锚索的组合支护体应力偏分布,不能解决倾斜顶板帮角处出现的应力集中现象,全长锚索支护对应顶板离层和应力集中位置,并采用支撑钢墩柱对顶帮角处进行补强支护,矿压监测数据显示,该技术明显改善了顶板的围岩稳定性,有效地减轻了帮部的压力和变形,锚索的承拉效果明显强于锚杆,为解决不规则巷道的顶板支护提供了重要的实践经验。

新城金矿破碎岩体巷道涨壳端锚中空注浆锚索支护试验

针对现有水泥注浆锚索施工工艺复杂、养护前期承载力差,无法在支护初期提供预紧力问题,选用涨壳端锚中空注浆锚索对新城金矿深部破碎围岩巷道进行加固支护。为验证该支护方法的支护能力和效果,分别在新城金矿9-3中段下盘运输巷和9-8中段斜坡道上坡段进行井下工业试验。试验结果表明,涨壳端锚中空注浆锚索锚固力在310 kN左右,并可在安装张拉后立即承载预定预紧力,支护效果优于传统注浆锚索。

基于GD32的同轴电缆长度检测系统设计

为快速精确地检测同轴电缆长度,以同轴电缆电容为检测对象,选用555定时器搭建多谐振荡电路,以GD32控制器为测量模块,通过GD32边沿捕获测出频率,利用频率与电缆电容、电缆长度的对应关系构建数学模型,实现电缆长度的测量。结果表明:电缆长度测量相对误差绝对值不超过2%,达到了较好的性能指标;系统按键控制与显示由串口屏实现,可实现测量控制与结果实时显示,人机交互界面友好。

线缆长度驱动的两阶段热管约束组件布局优化方法

针对航天器总体布局设计过程中需要考虑线缆长度的问题,提出一种以线缆长度最小化为目标的两阶段热管约束组件布局优化方法。面向几何、质心、热管散热以及线缆长度等多种复杂约束相互耦合的布局难题,基于分而治之的思想提出将原问题解耦为两个序贯优化子问题,通过构建并求解子问题的混合整数规划模型,实现了综合考虑多条线缆最短化目标下预埋热管舱板组件布局的高效优化设计。数值布局算例结果表明,在包含15个组件、3条有线信息链路的多种优化场景下,本方法均可以找到两级求解框架下的最优布局设计结果,充分验证了方法的可行性和有效性。

可缩性U型钢拱架卡缆节点力学特性试验研究

针对深部巷道可缩性U型钢拱架易在卡缆节点处产生破坏的问题,以U29型钢拱架卡缆节点为研究对象,建立承载力二次预紧提升率评价指标,通过室内试验和数值试验对影响卡缆节点承载力的初始扭矩、搭接长度和二次预紧等因素进行研究。试验结果表明:初始扭矩和搭接长度是影响拱架节点承载能力的主要因素;同时对节点施加二次预紧,能够有效提高拱架节点的承载能力,当初始预紧扭矩为150 N·m、搭接长度为500 mm时,二次预紧后承载力可提高35.30%;当初始扭矩大于160 N·m时,二次预紧的提升效果将不再明显;搭接长度小于400 mm时,试件在受力后期会因变形过大无法起到有效约束作用。