Method of Cable Tension Controlling in the Long span Cable stayed Bridge Construction

In allusion to the cable tension controlling problem in the parallel strand stayed cable construction, on the basis of construction techniques of applying tension loads one by one, the mechanical model of the cable girder tower in the process of construction was established. With the equal cable tension as a goal, the formula was deduced with the method of forward analysis, which could be used to calculate the initial tension of each strand in construction. The effect of temperature variations on the initial tension could be eliminated by using the formula with the method of equivalent tension. Moreover, a method was proposed to measure the cable tension in the processes of construction and performing the function. Finally, the practice in one cable stayed bridge in the north indicated that 1) the uniform cable tension could be obtained by the proposed method; 2) the tension error range of whether a single strand or the whole stayed cable was within 5%, and the result could meet the needs in construction control; 3) the method could provide reference for the similar stayed cable construction.     

Non-linear finite element analysis based on the spatial catenary cables

According to the elastic catenary theory,this paper derives the spatial catenary cable element from the exact analytical expression,which is used for finite element analysis of the structure.It deduces the precise expression of two-node cable element tangent stiffness matrix and the tension of cable end.The equivalent node load of cable element is expressed by the total load algorithm,and the non-linear equation is solved by double Newdon-rapson method.The proposed non-linear semi-analytical finite element method based on spatial catenary cable element can take full account of the impact of non-linear geometry.The initial configuration and the internal forces on any directional spatial loads can be solved.The example shows that the calculation method is accurate and effective.     

Comparision of Theoritical Solutions and Ultimate Span-Length between FRP Cables and Steel Cables

As the self weight of cable affects mechanical behavior obviously with the inerease of span length.FRP (fiber reinforced polymer) cable that has the lighter weight than the conventional cables has advantage for long span structures.The analysis of single cable is the fundamental theory for the design of cable structures.Based on different considerations of gravity loads.the solutions of the single cable on gravity loads have three sets of solutions: parabola solution.catenary solution and elastic catenary solution.And the equations for the three sets of solutions are derived by taking the end tension force of cable as the control parameter.The comparison between FRP cables and steel cables is conducted by elastic catenary solution.and the results show that the lager span structure can be realized by FRP cables.The precision for the parabola solution and catenary solution is compared for stay cables and horizontal cables.and the proper ranges of both approximate methods are proposed.Based on the above methods.the ultimate span length of FRP cable and steel cable are analyzed.It is concluded that the ultimate span of FRP cable is 4.4 times larger than that of steel cable.     

A New Method to Measure Cable Force and Its Application in Cable Structures

In cable structures cables are very important components. The magnitude of cable pretensioning is a vital parameter in the design of cable structures and a crucial component in controlling the construction of such structures. Developing a new sensor type is an innovative theme in the monitoring and control of cable structures construction. Based on the elastic magnetic characteristics of ferromagnetic material, we introduce a theory of an elastic magnetic method to measure cable force and developed a new flux sensor. Applying this method in the model test of an hyperbolic cable net demonstrates that it can acquire the accurate cable force value conveniently. This study can provide scientific references for structural engineering.     

Fault check & safeguard system of optical cable for communication based on GIS

Once fault occurs on the optical cable, it will seriously impair communication. In order to solve the terrible result caused by faults, the system implements the management of the spatial database of the optical cable and the information along it and location fault spots with celerity and legitimacy, according to the spatial and environmental characteristics on geographic distribution of the optical cable network and based on GIS, as it displays the multimedia information around the fault spot, such as landform and physiognomy. Combining the buffer with path analysis function of GIS, the system searches for the optimum path to the fault spot on the optical cable, and also gives emergency schemes to dispose the fault. This application has gained a satisfactory result for effectively managing communication optical cable resources, shortening the repair time, and diminishing the loss caused by faults.     

折线型屋架平房仓不同部位温度变化研究

通过对仓房仓顶内外、仓房南面和西面仓墙内外及仓内西南、东北角及正中间和粮堆表上层等部位安装数字式测温电缆,经过10个多月的跟踪检测,初步摸清了环境温度对折线型屋架平房仓及储粮表上层的影响情况。     

Floyd Dijkstra Algorithm Applied to the Design of Cable Laying

On the application of F D(Floyd Dijkstra) algorithm to the design of cable laying,we provide a method to achieve optimal design of cable laying in this paper,and it is verified by practical examples.     

A static equilibrium method for tension identification of in-service cable

To identify the tension of in-service cable expediently and accurately, a cable tension identification method based on static testing measures is proposed by taking cable stress stiffening effect and principle of static equilibrium into account. According to the analysis on the process of cable tension identification and the key technique, a new compound clamp type with the soft metal lining is proposed. The rule of the contact distortion evolvement between the clamp and the cable is analyzed by dynamic nonlinear explicit analysis method, and the law of the friction change following the clamping force is studied. Thus, the reasonability and feasibility of this method is theoretically illuminated. The identified tension only depends on the displacement of load application point and the load force. The proposed method avoids the drawback of normal cable measuring methods where the measuring accuracy is greatly affected by cable boundary conditions and values of material parameters. The tension measured in the method is only related to the displacement of force point and the value of force. Therefore, it provides a new idea for cable tension identification of flexible cable.     

Numerical simulation on galloping of iced donductors

To investigate galloping of iced conductors, with the release of the bending degree of freedom of Euler beam element and setting the material to be ‘No Compression’ in ABAQUS software, a cable element with torsion degree of freedom is obtained. And then the aerodynamic loads including drag, lift and torque on the iced conductor are simulated by means of the user defined element. The galloping of iced single conductor and iced twin bundle conductor are numerically analyzed to demonstrate the efficiency of the proposed method. The effects of initial attack angle,span length and initial tension in conductor on the behavior of galloping are investigated by numerical simulation.     

Prediction of crosstalk characterisation in cables bundles

Based on the heterogeneity of cable bundles and the randomness of wire spacing in cable bundles, this paper adopts the statistical theory to explore a method to predict the uneven cable bundle crosstalks. Under the assumption of electrically small and weak coupling, the mean value and standard deviation of the near end crosstalk voltage ratio are derived. 273RDSI numerical simulations are used to predict worst case crosstalk and to test the model effectiveness . The difference of the wire number and the bundles height from the ground are analyzed. The results indicate that for a given number of wires by increasing the bundle height the mean value increases, whereas the standard deviation is substantially independent of height. Moreover, the standard deviation decreases with the number of sections. By increasing the number of wires, both the mean value and the standard deviation decrease, whereas the sensitivity of the mean value to the bundle height increases.     

A Calculation Method of Hawser Forces in Loading and Unloading States

In this paper,several calculation methods for hawser cables as the crane stability system in loading and unloading forces is put out by coordinating principle of deformed body.It is convenient for adjustment of crane in unloading state to benifit accurance of the equipment installation and safrty of device during hoisting.It is also a more accurate and practical method for choice of the cable.     

Detecting Technology of Cabel Surface Defect Based on DSP and Image Recognition

The damage of bridge cable directly hazards the normal use of bridge and the safety of people. The paper discussed the signal acquisition and detection system which takes embedded DSP processor as core technology, combined with CCD, video decode chip, SDRAM, FLASH ROM, and established the fast measuring algorithm of the surface corrosion and damage, which includes deteminating the processing region, improving medium filter, sobel edge detection and dynamic threshold segment, close operation of morphology, computing defect area and saving. The experimental resuits show that this method implemented the real-time, non-contact and intelligence detecting of cable surface defect and gives the specifications of the system.     

Intelligent Diagnosis Method of Optical Cable Based on GIS and OTDR

Aiming at the difficulty optical cable-maintaining, this paper issues an intelligent diagnosis system based on GIS and expert system. To improve the optical cable-maintaining efficiency, the rules of the expert system are established according to the characteristic of the optical cable faults in the OTDR output. And the GIS is also established contained the information of the optical cable and the region the cable locates in.     

索承式桥梁吊索钢丝腐蚀疲劳寿命评估

根据吊索镀锌钢丝腐蚀疲劳破坏特点,把镀锌钢丝腐蚀疲劳纹形成和扩展过程分解成镀锌层腐蚀失效、蚀坑萌生、蚀坑形成、短裂纹扩展、长裂纹扩展和断裂破坏等阶段,建立各阶段时间表达式,得到镀锌钢丝疲劳寿命表达式,提出基于断裂力学的吊索钢丝腐蚀疲劳寿命评估研究结果方法。通过算例分析复杂运营条件下腐蚀环境和应力幅等因素对吊索钢丝腐蚀疲劳寿命的影响,研究结果表明：吊索钢丝腐蚀疲劳寿命主要由钢丝镀锌层腐蚀、蚀坑发展和短裂纹扩展等3个阶段组成,为了准确地评估吊索腐蚀疲劳寿命,需要掌握大桥的运营环境和交通荷载。     

Nonlinear Predictive Control of Small Sag cable with Axial Displacement

An approach for the control of a small sag cable is presented.The approach is based on a nonlinear predictive control scheme that determines the required axial displacement input so that the predicted response match the desired Results.It is accomplished by minimizing the norm squared local errors between the predicted and desired values.Finally simulation results that use the new control strategy to demonstrate the effective are show.     

联合板索基础抗拔机理及容许上拔力

针对目前使用的既抗压又抗拔基础存在的缺陷和不足,构建了联合板索基础并获得了发明专利授权。在研究联合板索基础与扩底桩基础的抗拔机理基础上,研究了联合板索基础与扩底桩基础所能承受的极限上拔力,通过联合板索基础与扩底桩基础的对比研究,揭示了联合板索基础的抗拔机理,并借助扩底桩基础的上拔力容许设计值和稳定验算公式,解决了联合板索基础设计和稳定验算问题。     

Parametric Analysis of the Cable''s Vortex-Induced Vibration of Submerged Floating Tunnel

The cable's motion was modeled by a spring-mass-damper system. The flow field was calculated by RSM combined with the enhanced wall function model and the vibration equation of the cable was solved by the Four Step Runge-Kutta Algorithm, which was written into FLUENT software to be analyzed. It was adopted to analyse the factors influencing vortex-induced vibration of submerged floating tunnel cable, such as mass ratio, damping ratio of the cable and whether to consider streamline movement. The main conclusion included: mass ratio has little influence on the transverse vortex induced vibration amplitude of the cable, but has a big influence on the region of the reduced velocity; damping ratio almost has little influence on the region of the reduced velocity of cable's viv, but has an influence on the cable's vibration amplitude significantly; In the case of low-mass ratio, considered the impact of the cable streamline movement, the transverse vortex-induced vibration amplitude is bigger than not considered the case.     

Stress Analysis of Anchorage Zone on Tower of Long span Cable stayed Bridge

Anchorage zone on tower of cable stayed bridge has complex structures and stress distributions, and keeping it on a safety state under a large tonnage tension and prestress is more concerned in design and construction. The stress distribution of the anchorage zone was analyzed by 3D finite element method. Furthermore, the mechanical properties and the rules of stress distributions were investigated and compared in three different load cases. The results show that the disposition form of level prestressing tendon is reasonable. The stress of the entire tendon is very close to 1 116 MPa under the tension control stress of 1 260 MPa. It is shown that the intensity of the tendon has given full play to prestress and it is not appropriate to increase the tension control stress.     

Calculation of the ampacity of XLPE power cable based on FEM and analysis of the influential factors

Based on the principle of heat transfer theory and finite element method (FEM), a model for power cable thermal field and ampacity computation has been developed by adopting the soil region division method. The soil region around the cable is divided according to the difference of the soil thermal resistance. Based on the structural parameters of XLPE cable and the physical parameter of the laying area, different layers temperature distribution of XLPE cable is analyzed through the model, and the dichotomy is employed to calculate the cable ampacity. Comparing the calculated result by this method with the calculation by the standard, shows that compared to IEC60287 standard, the model has high-accuracy and is more convenient to the external environment. Through simulation example, the corresponding relationship between the influencing factors and the cable ampacity is obtained, which provides important theoretical basis for the optimization of the cable laying.     

Suppression of Periodic Narrowband Interferences in Cable Partial Discharge Detections

There are background noises and interferences in the signal acquired,due to partial discharge(PD) detection system covers a broad frequency band.To suppress periodic narrowband signal which is a quite serious interference in PD measurement,the existing suppression method is introduced,the new method of wavelet packet transform is mainly studied to de-noise the periodic narrowband in XLPE cable PD detection system,which is based on the db4 basic wavelet using soft threshold.The results of the experiment show that wavelet packet transform is effective in restraining the periodic narrowband interferences to extract the PD pulses in XLPE cable PD monitoring system.