Cable Strands Research Articles

Strand Tension Control in Anchor Span for Suspension Bridge Using Dynamic Balance Theory

Strand tension control is essential in suspension bridge safety. However, few quantitative studies have examined the bending rigidity and boundary condition behavior of strands in the anchor span of suspension bridges because of their special structure and complex configuration. In this paper, a new calculation method for strand tension is explored by using dynamic balance theory to determine the effect of bending rigidity and boundary conditions. The accuracy and effectiveness of the proposed method are tested and confirmed with verification examples and application on Nanxi Yangtze Suspension Bridge in China. The results indicated that only low-order frequency calculation could be used to calculate the strand tension without considering the effect of bending rigidity to ensure control accuracy. The influence of bending rigidity on the control precision is related to the tension and the length of the strands, which is significantly determined by the specific value between the stress rigidity and the bending rigidity. The uncertain boundary conditions of the anchor span cable, which are fixed between consolidated and hinged, also have a major effect on the control accuracy. To improve the accuracy of strand tension control, the least squares method is proposed during the tension construction control of the anchor span. This approach can significantly improve the accuracy of the tension control of the main cable strand. Some recommendations for future bridge analysis are provided based on the results of this study.

Force monitoring of steel cables using vision-based sensing technology: methodology and experimental verification

Steel cables serve as the key structural components in long-span bridges, and the force state of the steel cable is deemed to be one of the most important determinant factors representing the safety condition of bridge structures. The disadvantages of traditional cable force measurement methods have been envisaged and development of an effective alternative is still desired. In the last decade, the vision-based sensing technology has been rapidly developed and broadly applied in the field of structural health monitoring (SHM). With the aid of vision-based multi-point structural displacement measurement method, monitoring of the tensile force of the steel cable can be realized. In this paper, a novel cable force monitoring system integrated with a multi-point pattern matching algorithm is developed. The feasibility and accuracy of the developed vision-based force monitoring system has been validated by conducting the uniaxial tensile tests of steel bars, steel wire ropes, and parallel strand cables on a universal testing machine (UTM) as well as a series of moving loading experiments on a scale arch bridge model. The comparative study of the experimental outcomes indicates that the results obtained by the vision-based system are consistent with those measured by the traditional method for cable force measurement.

Vertical load capacities of roof truss cross members

Trusses used for roof support in coal mines are constructed of two grouted bolts installed at opposing forty-five degree angles into the roof and a cross member that ties the angled bolts together. The load on the cross member is vertical, which is transverse to the longitudinal axis, and therefore the cross member is loaded in the weakest direction. Laboratory tests were conducted to determine the vertical load capacity and deflection of three different types of cross members. Single-point load tests, with the load applied in the center of the specimen and double-point load tests, with a span of 2.4m, were conducted. For the single-point load configuration, the yield of the 25mm solid bar cross member was nominally 98kN of vertical load, achieved at 42cm of deflection. For cable cross members, yield was not achieved even after 45cm of deflection. Peak vertical loads were about 89kN for 17mm cables and 67kN for the 15mm cables. For the double-point load configurations, the 25mm solid bar cross members yielded at 150kN of vertical load and 25cm of deflection. At 25cm of deflection individual cable strands started breaking at 133 and 111kN of vertical load for the 17 and 15mm cable cross members respectively.

Compression limit state of HVAC submarine cables

An industry accepted standard does not currently exist for determination of compression limits in a subsea cable. This has resulted in most manufacturers specifying that subsea cables are not permitted to be axially loaded in compression.Additionally industry guidance does not exist regarding the consequences of inducing compression forces within subsea cables and the resulting effect on cable integrity. Industry recommended practice and guidance also does not have any information regarding experimental test arrangements to determine allowable compression levels within a subsea cable. This lack of modelling/testing guidance along with manufacturer recommendations of zero compressive loads within subsea cables results in overly conservative and restrictive design parameters for subsea cable installation and use.Due to the complex interaction within a subsea cable structure, such as contact interaction and friction between cable strands, theoretical modelling has been unable to provide reliable stress predictions and therefore an experimental testing regime is required if compression limits within the cable are to be appropriately determined. This paper describes combined axial and bending test arrangements that can be used as a guideline for determination of allowable compression limits for subsea cables.

Study on the treatment scheme of fracture of fixed binding tape for main cable strand of suspension bridge

Study on the treatment scheme of fracture of fixed binding tape for main cable strand of suspension bridge

Shear strength properties of plain and spirally profiled cable bolts

An experimental investigation into the performance of two 22 mm diameter, 60 t tensile strength capacity Hilti cable bolts in shear was conducted using the double-shear testing apparatus at the laboratory of the School of Civil, Mining and Environmental Engineering, Faculty of Engineering and Information Sciences, University of Wollongong. The tested cable bolts were (i) Hilti 19 wire HTT-UXG plain strand and (ii) Hilti 19 wire HTT-IXG spirally profiled (smaller cross-sectional area than the plain one) cable bolt, with indentation only on the surface of the outer strands. These cable bolts are of sealed wire construction type, consisting of an outer 5.5 mm diameter wire layer overlying the middle 3 mm diameter wire strands. Both layers are wrapped around a single solid 7 mm diameter strand wire core. The double-shearing test was carried out in 40 MPa concrete blocks, contained in concrete moulds. Cable bolts were encapsulated in concrete using Orica FB400 pumpable grout. Prior to encapsulation, each cable bolt was pre-tensioned initially to 50 kN axial force. A 500 t capacity servocontrolled compression testing machine was used for both tests, and during each test the vertical shear displacement was limited to 70 mm of travel. The rate of vertical shear displacement was maintained constant at 1 mm/min. The maximum shear load achieved for the plain strand cable was 1024 kN, while the spiral cable peak load was 904 kN, before the cable bolt wires began to individually snap, leading to the cable bolt break-up into two sections. It is apparent that spiral profiles of the outer wires weaken both the tensile and shearing strength. Finally, another set of tests was undertaken using the British Standard single-shear approach, producing lower shear strength values.

Analysis of Beam-Induced Quenches of the LHC Cables With a Multi-Strand Model

In this paper we discuss results of a one-dimensional numerical model to simulate electrical and thermal transients in the superconducting cables for the LHC machine, with specific reference to the analysis of quench due to the heat released by beam losses. Two models have been developed, one based on the analysis of the behavior of a single strand, whereas the other accounts for all the strands in the multi-strand cable. As a first step the stability margin is computed considering the single strand subjected to a variable magnetic field and heat deposit along its length. The impact of the field non-uniformity is assessed by comparison with computations performed assuming a uniform field in the cable cross section. The results of this model are compared to those obtained with the multi-strand model. The numerical results are discussed in terms of current and heat redistribution between strands, and stability margin of the cable.

Evaluations of Measurement Methods for Parallel Strand Cables

Cable tension is one of the important indexes of cable integrity as well as bridge stability and can be measured by various tension measurement methods. Parallel strand cables are special in structure, so the cable force measurement is more complex and difficult than other types of cables. In order to evaluate the common measurement methods for parallel strand cables, based on the Tongling Yangtze river road-rail bridge, the monitoring data during constructions were collected for statistical analysis. This paper summarized the common measurement methods for parallel strand cables, compared the test data form different measurement methods and in different construction stages. The results show the lift-off method assisted by the vibration wire load cell method can ensure force uniformity, the difference of forces measured by the vibration frequency method, the load cell method and the lift-off method is less than 5%, which can basically meet the constructions control requirement of cable force. This paper offer good reference value to other similar parallel strand cable stayed bridges.

Study and Prototype Design of a Suspension Bridge with Ultra-Long Span and CFRP Main Cables

Using nonlinear numerical methods, the structural systems of cables system, stiffening beams, pylons, and bearing systems are comparatively analyzed. This study demonstrates the technical feasibility of suspension bridges with a 3,500 m main span and Carbon Fiber Reinforced Plastic (CFRP) main cables. Using fine finite element structural simulation, the parameter sensibility of a suspension bridge structural system with a 3,500 m main span and CFRP main cables is analyzed, and the influence of structural parameters on the static and dynamic performance of super-long span suspension bridges is discussed. In combination with numerical analysis of a structural system model, the optimum structural system of a suspension bridge with a 3,500 m main span and CFRP main cables is determined. The physical model is set up to allow theoretical measurements of the anchorage, sliding, and bending moment of the CFRP main cable strands as well as static load and fatigue testing. A bond-type anchorage that can be applied to real bridges is developed, which has an anchorage efficiency coefficient of 100%. The sliding resistance and bending performances are verified: the frictional coefficient between CFRP main cable strand and saddle is about 0.5, the frictional coefficient between the CFRP main cable strand and clamp is up to 0.331, the bending strength of the CFRP wire at the saddle point is over 90% of its tensile strength, and there is almost no bending problem at the clamp. A bridge prototype design is produced based on the test results.

Fast Algorithm and Its Application in Construction Monitoring of Parallel Strand Cables

AbstractA fast algorithm for determining the installation force of parallel strand cables is proposed in this paper. Because cable-stayed bridges are flexible structures, the algorithm must consider the sag effect of cable stays as well as the prestressing loss caused by displacements of the deck and the pylon when erecting stay cables with a strand-by-strand method. Based on the principle of the isotension method for parallel strand cables, two basic problems involved in the stretching process and the corresponding numerical computing method are fully demonstrated in this paper. To consider the nonlinearity of cables, catenary theory is used for determining the cable shape and cable forces during the entire loading process. According to said method, a corresponding calculation program was compiled, followed by an additional error analysis. Case studies are provided to compare the results calculated by the program with data measured from an ongoing road-rail cable-stayed bridge and from other calculation ...

Performance of Carbon-Fiber-Reinforced Polymer Stirrups in Prestressed-Decked Bulb T-Beams

AbstractEleven decked bulb T beams were constructed, instrumented, and tested under shear loading to failure. Nine beams were reinforced and prestressed with carbon-fiber composite cable (CFCC) strands, whereas one beam was prestressed with conventional low-relaxation steel strands and one beam was reinforced with non-prestressed CFCC strands. Half the span of each beam was reinforced with CFCC stirrups, whereas the other half was reinforced with conventional steel stirrups. Both ends of each beam were tested to evaluate the performance of CFCC stirrups versus that of steel stirrups. The investigation addressed the shear performance with respect to several shear parameters, including shear-span-to-depth ratio, stirrup spacing, prestressing force, and type of longitudinal and transverse reinforcement. All test beams failed by crushing of concrete in either the web or the top flange. No rupture of CFCC stirrups was experienced in any of the test beams. The performance of CFCC stirrups was analogous to that ...

Failure analysis of hoisting steel wire rope

During a very short operation of a steel rope in a hoist system of a drilling rig it was significantly damaged. The wires of the upper layer of cable strands were damaged. This damage was not caused by fatigue of material; therefore it was necessary to determine the reason of the rope damage. The visual inspection of the damaged spots showed that during the operation there was a progressive release of the wires from the outer layer of the outer rope strands; subsequently released wires were rolled when passing the hoist system and they started to break. In order to find out the reason of the damage the samples of the damaged rope were collected as well as the samples of the new rope from the reserve. According to the nature of the damage we decided to perform mechanical tests of the new (yet not used) rope and thereafter metallographic tests of wire ropes from the outer layer of the strand. The analysis of the mechanical tests results of the new rope revealed the fact that the rope had been manufactured in other rope grade – different from the class declared by the manufacturer. It was also found that the wires of the top layer reporting damage were made of wires of different rope grades. Mixing wires having low and high strength in the upper layer of the rope strand caused different straining of wires in the specific (given) layer thus wires having lower strength begun to release from the strands and deform which led to the development of fractures at the weaken places.

Nonlinear numerical model with contact for Stockbridge vibration damper and experimental validation

The Stockbridge vibration damper is widely used in overhead transmission lines to reduce Aeolian vibration. Although a linear analytical model has been developed to interpret characteristics of the vibration damper, a much more detailed model is needed to investigate how the nonlinear factors of the structure affect its vibration characteristics. The paper presents a full-scale finite element model of the Stockbridge vibration damper, in which contact conditions are taken into account using the linear perturbation method. Relations between the contact conditions and mode frequencies were studied. It was proved that contact conditions between each two parts of the damper have significant influence on the stiffness of the whole structure. Results obtained from the numerical model compare well with those from the experiment. Finally, this numerical model was applied to investigate how the bonding material between the counterweight and steel strand cable affects the mode frequencies of the vibration damper.

Method of Calculating the Preforming Parameters of Wires in Cable-winding with the Use of the Deform-3D Software

A new method is proposed for calculating the parameters of the preforming of wire in the winding of cable strands. The method uses the software DEFORM-3D for this purpose and it makes it possible to account for the shape and mechanical properties of the wire. Data is obtained on the effect of changes in the preforming parameters on the strain state of wires in a cable.

Technology and Tooling to Manufacture Low-Ohm <formula formulatype="inline"><tex Notation="TeX">$(< 2\ \hbox{n}\Omega)$ </tex></formula> Electrical Joints of the ITER PF1 Coil

According to the technical specification for the PF1 coil, niobium-titanium “cable-in-conduit” conductors are to be connected into a single electric circuit using low-ohm electrical joints. The joint design is proposed by the International Thermonuclear Experimental Reactor Organization. It is required to develop special equipment and technology for the removal of a stainless steel (SS) jacket from a superconducting cable and for the connection of the cable with a resistance of less than 2 nΩ in the range of operating temperatures and magnetic fields. The main features of the technology are the following. 1) Explosion welding is used to make bimetal plates of SS and copper with a thickness up to 15 mm. 2) Computer numerical control machines are used for termination box manufacturing. 3) A portable milling machine is used to remove the SS jacket without damages of the PF1 conductor cable. 4) A specially made machine compacts cable strands around an SS tube. 5) Using moveable sandblasting equipment, it is possible to carry out abrasive treatment of the cable to remove nickel coating from the strands without damages. 6) A special technique is used for electrolytic tinning of cable and termination box surfaces without an electroplating bath. These techniques and equipment are used for manufacturing of several mockups, including a full-scale mockup. The results of the first tests are mentioned in this paper.

Acceptable coupling losses in striated coated conductors or twisted cables ensuring current sharing between superconducting filaments

To reduce the coupling losses in superconducting structures, the twisting procedure for superconducting filaments and strands is usually applied. In superconducting tapes, the same effect can be achieved in some superconducting AC designs by taking advantage of the changing magnetic field direction with respect to the tape surface (internal twist). We calculate the coupling losses of twisted structures (filaments in strands, strands in cables) or striated YBa2Cu3O7 coated conductors with additional normal plates on the tape connecting the superconductors. By enabling current sharing between the superconductors, such additional normal connections can considerably enhance the stability of the full conductor. Although the coupling losses increase slightly in these structures, it is shown that they can be held at an acceptably low level. This may be very important for superconducting structures with coupling losses that are not very high and therefore require better stability. The most favorable structure for coupling losses is emphasized.

Performance of AASHTO-Type Bridge Model Prestressed with Carbon Fiber-Reinforced Polymer Reinforcement

Carbon fiber-reinforced polymer (CFRP) composite material has been widely studied and applied in bridge engineering as an alternative solution to the corrosion-related problems posed by steel reinforcement. Nevertheless, adoption of CFRP reinforcement to replace conventional steel reinforcement in highway bridges has not been fully realized yet in the field. Therefore, large-scale experimental investigations on bridges with CFRP reinforcement are essential to encourage its widespread application in highway bridges. This paper presents an experimental investigation conducted on a one-third-scale AASHTO-type bridge model prestressed with carbon fiber composite cable strands. The bridge model was designed, constructed, instrumented, and tested to thoroughly investigate its flexural behavior, strain response, and ultimate load failure. A separate one-third-scale single AASHTO-type I-beam was also constructed and tested to study its flexural and shear behavior as a control beam. In general, both the control beam and the bridge model experienced compression-controlled failure as anticipated. Significant cracking and deflection were experienced prior to failure. The ultimate strength of the control beam and the bridge model were in close agreement with the values estimated using the Unified Design Approach.

Integrated Optical Fiber Sensing System by Combing Large-Scale Distributed BOTDA/R and Localized FBGs

Structural health monitoring (SHM) has been regarded as a significant tool for the safety of civil infrastructures. Local fiber Bragg grating (FBG) sensor and distributed Brillouin optical fiber sensor have been successfully applied in civil engineering fields. Unfortunately, neither single FBG nor single Brillouin sensing technique can satisfy the requirements of simultaneously positioning full-scale structural damages and accurate local damage details. So it still matters to establish balance between localized high-precision measurement and large-scale distributed measurement with lower accuracy. This paper introduces an integration system by combining distributed Brillouin and local FBG sensors on one single-mode optical fiber. The temperature self-compensation and the data processing method of the integration system have been investigated. The integrated FBG/Brillouin sensor has been further packaged by glass fiber-reinforced polymer to be used as a robust and smart structural component. Finally the proposed integrated sensing system has been applied in three case studies, including investigation of reinforced concrete beam, smart cable, and smart steel strand to verify the feasibility. The test results illustrate that the integrated system can simultaneously provide accurate strain measurement at critical points by FBGs and the rough distributed strain measurement by Brillouin sensor, which can be further applied to various applications.

Flexural Behavior of a Carbon Fiber–Reinforced Polymer Prestressed Decked Bulb T-Beam Bridge System

AbstractExperimental and numerical investigations were conducted to evaluate the performance of a newly developed bridge system. Through the investigation, a decked bulb T-beam bridge model was constructed, instrumented, and tested under service and ultimate loads. The bridge model had a width of 2.59 m (8.5 ft), an effective span of 9.45 m (31 ft), a depth of 356 mm (14 in.), and was composed of five adjacent decked bulb T-beams. The T-beams were interconnected at their top flanges using 76-mm (3-in.)-wide ultra-high-performance concrete (UHPC) shear key joints and five full-depth equally spaced transverse diaphragms along the span. Each diaphragm was posttensioned with two nonbonded transverse carbon fiber composite cable (CFCC) strands. The investigation revealed that the developed decked bulb T-beam bridge system maintained its structural integrity under service loads with signs of distress in neither the shear key joints nor top flanges. UHPC shear keys with the transverse diaphragms were adequate to...

Critical Current in High-J$ _{\rm c}$ Nb$_{3}$Sn Rutherford Cables Affected Substantially by the Direction of the Applied Magnetic Field

Recently several Rutherford-type Nb Sn cables for possible use in new magnets for upgrades of the LHC have been measured at CERN. A summary is provided including a comparison of the critical current (Ic) of various cable types and strand materials versus their respective extracted strand measurements. The conductors were cabled at CERN and Lawrence Berkeley National Laboratory. The summary shows an unsurprising linear relation between the strand and the cable performance. However, assuming that the local peak magnetic field in the conductor is the relevant factor for determining the Ic(B) relation, a discrepancy is found when results from different directions of applied magnetic field on the cable are compared. In this paper it is shown that the critical current as a function of the peak magnetic field in the conductor can change in the range of 7-12% depending on the direction of the applied magnetic field. This effect originates from the superposition of the self field of the conductor and the applied magnetic field. When the direction of the applied magnetic field is changed, the position of the peak magnetic field in the conductor shifts. Mechanical degradation during the cabling process can create a local reduction in the critical current. When the position of the peak magnetic field shifts from a more degraded to a less degraded area, the measured Ic(B) curve of the conductor will change accordingly. The measured effect is in principle present in all cables exhibiting non-uniform cabling degradation but is substantially present in Nb3Sn conductors for the reasons mentioned.