Main Cables Research Articles

Phase-to-Phase Communication Scheme for Downhole Monitoring Tool Design in Electrical Submersible Pump Systems

Electrical submersible pumps (ESPs) are commonly used artificial lift method in deep wells in oil industry. To monitor ESP systems operation, downhole monitoring tools are used to transmit data representing the physical condition of the downhole such as temperature, pressure, and vibration to the surface. The most common communication method for downhole monitoring tools in the field is to use a direct current (dc) signal over three phases of the main power cable, and the ground serves as a return path. However, this method cannot operate in the event of a single-line-to-ground (SLG) fault, although the ESP is still in operation due to ungrounded practice in its downhole zone. This method is also prone to failure in the presence of voltage unbalance. To overcome issues in the existing downhole monitoring tool design, a new phase-to-phase communication scheme is proposed in this paper. Intentional disturbances are applied to the ESP system and used as means of binary communication. In this paper, theoretical formulas of the proposed method are derived, and its performance is evaluated using simulation through case and sensitivity studies.

Monitoring the structural health of main cables of suspension bridges

In this paper, the results of a study focused on the development of a corrosion monitoring system for main cables of suspension bridges are presented. These sensors measure corrosion rate as well as quantities like temperature and relative humidity that are directly correlated to corrosion activity. Such a sensor network was first tested in a laboratory setting using a full-scale cable mock-up and, later, tested on the main cable of one of the major suspension bridges in the New York metropolitan area. Having the possibility of measuring temperature and relative humidity inside th1e cross-section of a main cable also allowed us to test the effectiveness of the cable dehumidification strategy.

Influence of Central Buckles on the Modal Characteristics of Long-Span Suspension Bridge

Finite element analysis (FEA) and a dynamic test are employed to investigate the influence of central buckles on the modal characteristics of the Aizhai bridge. The FEA result shows that (1) the longitudinal floating frequency of the bridge can be significantly raised with central buckles; (2) the influence of central buckles on anti-symmetrical lateral bending frequencies is larger than that on symmetrical mode; and (3) rigid central buckles can raise the symmetric vibration modal frequencies of main cables, whereas the flexible central buckles nearly have no effect. Further testing on the dynamic behavior of the aero-elastic model of the Aizhai bridge is conducted. The result indicates that (1) the anti-symmetric lateral bending modal frequencies increase with the increasing stiffness of the central buckles; (2) central buckles have slight influence on the vertical modal frequencies; and (3) central buckles can enhance the entire stiffness and natural frequencies of suspension bridges, especially for anti-symmetric torsional and longitudinal vibration frequencies.

Approximate Calculation for Deformation of Multi-Tower Suspension Bridges

This paper presents a method for solving tower deformation and girder deflection in multi-tower suspension bridges. An equivalent model is proposed to simulate a multi-tower suspension bridge in which the towers and main cables are treated as a series of springs. This model can be used for cases of live load acting on one or more spans , and the simple explicit formulas can be used to resolve deformation of the towers and girders as well as for the increment of horizontal cable force in the loaded span. The superposition principle can be used for live loads acting on more than one main span. This paper also presents a finite element model (FEM) of a multi-span suspension bridge with five towers and six spans to verify the analytical formula. Results calculated with the FEM show good agreement with those of the proposed method. This indicates that the proposed method is effective for the preliminary analysis and design of multi-tower suspension bridges.

Km3Net Italy – Seafloor network

The KM3NeT European project aims to construct a large volume underwater neutrino telescope in the depths of the Mediterranean Sea. INFN and KM3NeT collaboration, thanks to a dedicated funding of 21.000.000 € (PON 2007–2013), are committed to build and deploy the Phase 1 of the telescope, composed of a network of detection units: 8 towers, equipped with single photomultiplier optical modules, and 24 strings, equipped with multi-photomultipliers optical modules. All the towers and strings are connected to the main electro optical cable by means of a network of junction boxes and electro optical interlink cables. Each junction box is an active node able to provide all the necessary power to the detection units and to guarantee the data transmission between the detector and the on-shore control station. The KM3NeT Italia project foresees the realization and the installation of the first part of the deep sea network, composed of three junction boxes, one for the towers and two for the strings. In July 2015, two junction boxes have been deployed and connected to the new cable termination frame installed during the same sea campaign. The third and last one will be installed in November 2015. The status of the deep sea network is presented together with technical details of the project.

The MEUST deep sea infrastructure in the Toulon site

The MEUST (Mediterranean Eurocentre for Underwater Sciences and Technologies) is a permanent deep sea cabled infrastructure currently being deployed off shore of Toulon, France. MEUST is shared between the neutrino physics and astro-physics communities in the context of the European KM3NeT project, and the Environmental Science communities as the West- Ligurian site of the EMSO European network of submarine observatories. The MEUST submarine network has a modular and extendable topology which will allow hosting up to 120 neutrino detection units and to instrument a seafloor area with sea science sensors. The MEUST terrestrial base is located in La Seyne sur Mer near Toulon, where a new building is planned to host the technical activities, including a control room of the infrastructure. The MEUST submarine site has been selected after intensive characterization campaigns conducted in the past years leading to the choice of the site located ˜40km offshore of Toulon at a depth of 2500m and 15km west of the Antares site. The full MEUST submarine network has up to 6 nodes connected to the shore by two Main Electro Optical Cables (MEOC). The MEOCs are standard telecommunication cables with optical fibres for data transfer and one electrical conductor for power transfer. The nodes are equipped each with 8 wet mate-able connectors allowing to connect at least 20 neutrino detection units (daisy chained by 4) and a set of environmental instruments, with some redundancy. The power transfer is performed in HV AC with sea return, as for Antares, and provides a usable power of ˜10kW on each node (˜1kW/connector). A dedicated control/command system controls the power and optical systems. The data transfer uses Dense Wavelength Division Multiplexing (DWDM). The proposed talk will focus on the design and the status of the infrastructure with the first lessons learnt from the ongoing deployments.

Research on the Exchangeable Main Cable of Suspension bridge

Research on the Exchangeable Main Cable of Suspension bridge

Estimation of main cable tension force of suspension bridges based on ambient vibration frequency measurements

In this paper, a new approach based on the continuum model is proposed to estimate the main cable tension force of suspension bridges from measured natural frequencies. This approach considered the vertical vibration of a main cable hinged at both towers and supported by an elastic girder and hangers along its entire length. The equation reflected the relationship between vibration frequency and horizontal tension force of a main cable was derived. To avoid to generate the additional cable tension force by sag-extensibility, the analytical solution of characteristic equation for anti-symmetrical vibration mode of the main cable was calculated. Then, the estimation of main cable tension force was carried out by anti-symmetric characteristic frequency vector. The errors of estimation due to characteristic frequency deviations were investigated through numerical analysis of the main cable of Taizhou Bridge. A field experiment was conducted to verify the proposed approach. Through measuring and analyzing the responses of a main cable of Taizhou Bridge under ambient excitation, the horizontal tension force of the main cable was identified from the first three odd frequencies. It is shown that the estimated results agree well with the designed values. The proposed approach can be used to conduct the long-term health monitoring of suspension bridges.

Mechanism of Hanger Oscillation at Suspension Bridges: Buffeting-Induced Resonance

This article presents the results of an investigation of the wind-induced resonance of hangers on a long-span suspension bridge. The data from field observations, numerical simulations, and wind tunnel experiments presented in this article show that the hangers experience buffeting-induced resonance oscillations and that the source of the excitation is the buffeting of the main cables to which the hangers are attached. Because of the dense natural frequencies of the main cables and the broad-spectrum structural buffeting that takes place, it appears that these oscillations occur as energy is transferred from the main cables to the hangers. Hence, it is the main cables rather than the hangers that trap energy from the oncoming turbulent wind field. The numerical results presented indicate that the resonance of the hangers could be sensitive to positions along the bridge deck, wind speeds, and damping ratios. This article also includes the results of simplified wind tunnel experiments that verified this kind of resonance, disregarding whether the wind loads developed directly on the hanger.

Torsional asymmetry in suspension bridge systems

In this paper a dynamic linear model of suspension bridge center spans is formulated and three different ways of fixing the main cables are studied. The model describes vertical and torsional oscillations of the deck under the action of lateral wind. The mutual interactions of main cables, center span, and hangers are analyzed. Three variational evolutions are analyzed. The variational equations correspond to the way how the main cables are fixed. The existence, uniqueness, and continuous dependence on data are proved.

THE INFLUENCE OF CABLE SAG ON THE DYNAMIC BEHAVIOUR OF CABLE-STAYED SUSPENSION BRIDGE WITH VARIABLE SUSPENSION TO MAIN SPAN RATIO

The demand of long span bridge is increasing with infrastructure magnification. To achieve maximum central span in bridges is a motivating rational challenge. The bridge with more central span can be achieved using high strength materials and innovative forms of the bridges. The cable-stayed bridge has better structural stiffness and suspension bridge has ability to offer longer span thus combination of above two structural systems could achieve very long span cable-stayed suspension hybrid bridge. To distinguish behaviour and check the feasibility of this innovative form of hybrid bridge, 1400m central span and 312m side span cable-stayed suspension hybrid bridge is considered for analysis. The suspension portion length in central span is also playing important role in behaviour of the entire bridge. Bridge behaviour is presented for variable length of suspension portion in form of suspension portion to main span ratio. The main cable sag in central span is playing important role on behavior of the entire bridge. It directly influences the inclination angles of the main cables, the height of pylon and thus forces in pylon. The axial force in main cable is directly depending on the sag of main cable. The effects of main cable sag is studied by considering dimensionless parameter as sag to main span ratio as 1/9, 1/10 and 1/11. Paper also discusses results of nonlinear static analysis and modal analysis carried out using SAP2000 v14.0.0. The time period of bridge is used to present the behavior of bridge.

Evaluation of load and resistance factors for the reliability-based design of the main cables of earth-anchored suspension bridges

This paper presents load and resistance factors for the reliability-based design of the main cables of earth-anchored suspension bridges for the Strength I Limit State defined in the AASHTO LRFD Bridge Design Specifications. Reliability analyses are performed for three suspension bridges in Korea with main span lengths ranging from 650 m to 1545 m, and the reliability indices and the Most Probable Failure Points (MPFP) of random variables are evaluated. The strength, load and stiffness parameters are taken into account as random variables. The advanced first-order second-moment method is employed to evaluate the reliability indices and the MPFP of the random variables. The elastic catenary cable element is utilized to discretize the main cables. Load factors are proposed based on the normalized MPFP of each load component considered in the Strength I Limit State. The resistance factor that yields the reference target reliability index for the main cable is found as 0.53. Two alternative resistance factors, which give lower and higher reliability indices than the reference value, are also proposed. The proposed load and resistance factors lead to a uniform reliability level for a main cable regardless of the length of the main span of a suspension bridge.

Impact of cross-tie design on the in-plane stiffness and local mode formation of cable networks on cable-stayed bridges

Suppressing unfavorable stay cable vibrations using cross-ties is becoming more popular on cable-stayed bridges though the mechanics of the formed cable network is yet fully understood. In practice, the main task in designing cross-ties or cable networks is to choose the cross-tie installation location, stiffness and number based on the main cable properties in the network. To have a more comprehensive picture of how to choose these design parameters to achieve higher in-plane network stiffness while minimizing the number of excited local modes, it is imperative to examine dynamic behavior of cable networks with general configurations. In the current study, an analytical model of a general cable network consisting of multiple main cables interconnected by multiple lines of transverse flexible cross-ties will be developed. A new term, defined as the local mode cluster, will be introduced to assess the severity of local mode excitation. Criteria for identifying the presence of local mode cluster will be proposed. A parametric study will be conducted to evaluate the impact of cross-tie installation location, stiffness and number on the network modal response. Results obtained from the present study will provide deeper insight into the selection of these system parameters to achieve the combined benefits of increasing network in-plane stiffness and minimizing the excitation of local modes.

Probabilistic optimization of the main cable and bridge deck of long-span suspension bridges under flutter constraint

The reliability based design optimization of a long-span suspension bridge is performed considering probabilistic flutter constraint accounting for the stochastic nature of parameters such as the extreme wind velocity and experimentally obtained flutter derivatives. The objective of this study is to seek the minimum volumes of the main cables and bridge girder by varying the main cable area and girder plate thicknesses while satisfying the required safety level under flutter. Three methods of Reliability Index Approach, Performance Measure Approach and Sequential Optimization and Reliability Assessment are utilized to solve this problem. The main code to perform the entire RBDO process is written in Matlab®, which is linked to Abaqus finite element models to obtain structural responses and FLAS code developed by our research group to compute aeroelastic responses of the bridge. The three RBDO methods were applied to the Messina Bridge project to examine their numerical performance and computational efficiency.

지중송전계통에서 OF 및 XLPE 케이블 혼용 연계 운용의 효용성 평가

OF cable with excellent reliability and economic efficiency, has been used as the main cable of underground transmission in Korea. However, as XLPE cable is excellent in view points such as reduction of loss, convenience on the construction/operation, and manufacturing technology, it has been replaced as instead of OF cable. Also, when the aging occurs in some sections of OF cable, the section is replaced as XLPE cable without changing of whole cable line. However, there are some differences like electrical constants between both types of cables. Therefore if underground transmission system will be operated as combined connection composited of both cables, it should be proved that overvoltage is stable in steady and transient state. This paper describes the effectiveness of connection operation in combined OF and XLPE cable. For the evaluation of effectiveness, some important analysis such as sheath component voltage, lightning and switching overvoltage, single line-to-ground fault are carried out in steady and transient state. EMTP/ATPDraw is used for modeling and analysis of system.

Seismic Responses of the Supporting Structure of FAST under Multiple-Support Excitations

Seismic ground motions are spatial incoherent partly due to uncertainty in fault mechanism and wave propagation. The spatial coherency and its effect can be important and need to be investigated for multiple-support structures. In this study, an investigation of seismic responses of a five-hundred-meter aperture spherical telescope (FAST) is investigated. The structure is a cable net structure with multiple supports. For the structural analysis, parameters of an existing coherency model for excitations along the same orientation but considering the multi-component excitations and spatially separated locations are developed using the records from Taiwan. This coherency model together with adopted target power spectral density function and phase difference spectrum model are used to simulate multi-component seismic ground motions at 338 grid points covering the FAST. The simulated records are used as the basis to interpolate the time history of the ground motions at 2395 supports for the considered structure. The time-history responses of the structure under incoherent multiple-support excitations are evaluated and compared to that under uniform excitations. The results show that the influence of coherency on the supporting structure of the FAST in three excitation directions differs. The analysis results show that as compared to uniform excitations, the consideration of the seismic coherency in seismic excitations leads to, on average, 87% of increase in stress for 94% of the main cables, and 22% of increase in stress for 44% of the tie-down cables. It was also noted that the maximum tensile stress of the cable by considering the coherency is 835 MPa while that under uniform excitations is 671 MPa. In both cases, they are smaller than the characteristic tensile strength of the cables used for design and construction of the FAST.

Operational modal analysis of a long-span suspension bridge under different earthquake events

Structural health monitoring (SHM) has gained in popularity in recent years since it can assess the performance and condition of instrumented structures in real time and provide valuable information to the asset\'s manager and owner. Operational modal analysis plays an important role in SHM and it involves the determination of natural frequencies, damping ratios and mode shapes of a constructed structure based on measured dynamic data. This paper presents the operational modal analysis and seismic response characterization of the Tsing Ma Suspension Bridge of 2,160 m long subjected to different earthquake events. Three kinds of events, i.e., short-distance, middle-distance and long-distance earthquakes are taken into account. A fast Bayesian modal identification method is used to carry out the operational modal analysis. The modal properties of the bridge are identified and compared by use of the field monitoring data acquired before and after the earthquake for each type of the events. Research emphasis is given on identifying the predominant modes of the seismic responses in the deck during short-distance, middledistance and long- istance earthquakes, respectively, and characterizing the response pattern of various structural portions (deck, towers, main cables, etc.) under different types of earthquakes. Since the bridge is over 2,000 m long, the seismic wave would arrive at the tower/anchorage basements of the two side spans at different time instants. The behaviors of structural dynamic responses on the Tsing Yi side span and on the Ma Wan side span under each type of the earthquake events are compared. The results obtained from this study would be beneficial to the seismic design of future long-span bridges to be built around Hong Kong (e.g., the Hong Kong-Zhuhai-Macau Bridge).

Structural health monitoring of suspension bridges with features affected by changing wind speed

Tools based on multivariate statistical analysis are becoming very popular for automatically revealing the existence of damage in structures using vibration data under changing environmental and operational conditions (typically temperature, humidity and traffic intensity). In this paper, methods of multivariate statistical analysis are newly applied for monitoring the structural health state of the main cables of suspension bridges, with the main contribution of removing non-linear aeroelastic correlations between dynamic features and wind speed.Considering natural frequencies as damage-sensitive features, an analytical parametric model of suspension bridge with damage in one main cable and subjected to wind loading is formulated, at first, as an extension of previous work. Model predictions demonstrate that apparent frequency variations caused by changes in incoming wind speed can likely be more significant than those produced by a small damage. A technique based on principal component analysis and novelty detection is adopted to cope with this issue and its application to long-term pseudo-experimental buffeting response data, generated by means of the analytical model, is presented. The results demonstrate the feasibility of permanent monitoring systems to reveal the existence of damages in wind-excited long-span bridges producing relative variations in the most sensitive natural frequency smaller than 0.1%.

Analytical Calculation Method for the Preliminary Analysis of Self-Anchored Suspension Bridges

The stiffening girder of self-anchored suspension bridge (SSB) is subjected to huge axial force because the main cable is directly anchored on the end of the stiffening girder. To obtain a simple model and accurately understand the mechanical behavior of the whole structure in preliminary design, this paper proposed an analytical calculation method considering the combined effects of the main cable-suspender-stiffening girder. On the basis of the deflection theory of the stiffening girder, the relation between the girder shape and the suspender force was explored. The relation between the main cable end force (MCEF) and the suspender force was derived through segmental catenary theory, and iteration method was further improved to avoid the divergence condition. Finally the solution was obtained through satisfying the compatibility condition. The proposed method does not need to iterate manually and can save calculation time. Examples are introduced to verify the applicability of this method, with the result that this method considers the combined effects of the main cable-suspender-stiffening girder, and the finished bridge state satisfies the minimum strain energy of the stiffening girder. Results also indicate that this method has fast convergence speed and high precision.

EMI Analysis and Suppression of the Ship Digital Grounding System

Based on the digital serial communication, E1 and Ethernet port circuits connecting the electronic equipment on ships, characterizations of the digital signals transmitted through the circuits are analyzed. The situations when the EMI generated by the digital systems causing pollution to the grounding system and the grounding voltages coupled to the signal-transmitting circuits are simulated. Furthermore, the influence of the equivalent impedance of the main and branch grounding cables on the grounding performance are analyzed quantitatively. Therefore, the grounding demand is obtained. Finally, some anti-interference measures so as to improve the grounding performance are proposed.