Bridge Cables Research Articles

Identification of the dynamic parameters of bridge elements using unmanned aerial vehicle

The condition of the bridge may deteriorate due to the traffic that passes over it, as well as weather and environmental conditions. To ensure the safety and structural stability of the bridges, regular inspections of the bridge elements should be carried out. Recent advances in unmanned aerial vehicles (UAVs) can provide tools for accurate and even autonomous inspection of bridge structures without interrupting normal bridge operations. In this paper, we focus on the determination of the dynamic structural parameters of a suspension bridge. The proposed method is based on the estimation of the natural vibration frequency of the bridge cables using the videos captured by the UAV. We provide a detailed theoretical description of the algorithm and an analysis of the simulation results and the data collected during the experiments in the laboratory and in the real case study. In addition to the vision based method for estimating vibration frequency, we tested the ability of the UAV’s on-board sensors to record structural oscillations when the UAV landed on the surface of the bridge.

Investigation of the Temperature Actions of Bridge Cables Based on Long-Term Measurement and the Gradient Boosted Regression Trees Method

Cable-stayed bridges have been commonly used on high-speed railways. The design, construction, and maintenance of cable-stayed bridges necessitate an accurate assessment of the cable temperature field. However, the temperature fields of cables have not been well established. Therefore, this research aims to investigate the distribution of the temperature field, the time variability of temperatures, and the representative value of temperature actions in stayed cables. A cable segment experiment, spanning over one year, is conducted near the bridge site. Based on the monitoring temperatures and meteorological data, the distribution of the temperature field is studied, and the time variability of cable temperatures is investigated. The findings show that the temperature distribution is generally uniform along the cross-section without a significant temperature gradient, while the amplitudes of the annual cycle variation and daily cycle variation in temperatures are significant. To accurately determine the temperature deformation of a cable, it is necessary to consider both the daily temperature fluctuations and the annual cycle of uniform temperatures. Then, using the gradient boosted regression trees method, the relationship between the cable temperature and multiple environmental variables is explored, and representative cable uniform temperatures for design are obtained by the extreme value analysis. The presented data and results provide a good basis for the operation and maintenance of in-service long-span cable-stayed bridges.

A general data quality evaluation framework for dynamic response monitoring of long-span bridges

The structural health monitoring system (SHM) of long-span bridges inevitably produces low-quality data. It is important to evaluate the data quality and screen out normal data. Most existing studies on data anomaly detection have focused on abnormal data with abnormal waveforms in time domain. Usually there are pseudo-normal data in the SHM system, which seems normal in time domain. However, the pseudo-normal data of bridge dynamic responses may cause wrong dynamic characteristics identification. In this study, the existing data anomaly detection was further expanded to data quality evaluation, and both obvious abnormal and pseudo-normal data are evaluated. A general data quality evaluation framework for dynamic response monitoring of long-span bridge structures was proposed. The time–frequency characteristics of monitoring data were obtained by continuous wavelet transform, and the data quality was classified and evaluated by constructing and training a convolutional neural network (CNN). The proposed framework was verified by using acceleration monitoring data of a cable-stayed bridge. The results reveal that this framework solves the problem that CNN cannot detect pseudo-normal data through time-domain characteristics, and improves the accuracy of data quality evaluation by using time–frequency information of the monitoring data. The acceleration monitoring data of a suspension bridge and a single pylon cable-stayed bridge were used to demonstrate the feasibility of the cross-object application of the proposed framework. The evaluation accuracy for the acceleration data quality of the suspension bridge exceeded 96%. After the reinforced training of a small number of pseudo-normal data samples, the evaluation accuracy for the acceleration data quality of the cables of the cable-stayed bridge reached 96.8%. The framework shows a good generalization capacity and robustness in cross-object applications.

Bridge Cable Anomaly Detection Based on Local Variability in Feature Vector of Monitoring Group Cable Forces

The cable is the key supporting component of the cable-stayed bridges, and damaged cables will directly affect the safety and stability of the bridge in operation. Therefore, this paper proposes a bridge cable anomaly detection and localization method based on the variation in the group cable force feature vector. First, mechanical analysis was carried out on the correlation of cable forces between two cables on the same side induced by the single-vehicle case and a cable force feature vector was established to reflect the mechanical characteristics of the group cable forces. Second, a bridge cable anomaly detection method was proposed based on the variation in the group cable force feature vector. Third, the isolation of abnormal components of the cable force feature vector, which can accurately localize abnormal cables, was presented. The long-term monitoring data of an in-service cable-stayed bridge were utilized to validate the effectiveness of the proposed method. The results demonstrated that the proposed method could effectively detect abnormal cable conditions and accurately localize abnormal cables. In addition, the proposed bridge cable feature index and anomaly detection method were robust to the situation of partially missing data due to sensor fault.

REQUIREMENTS FOR THE MONITORING SYSTEM OF WIRE ROPE CABLE BREAKS

One of the modern trends in the improvement of structures in construction is the use of steel-reinforced concrete systems. In such systems, cable-stayed ropes are used to absorb tensile forces. The cited works did not consider the issue of the interaction of the rope and the node connecting its ends to the structure. Ropes are used in various fields of technology: suspended cableways, mine and elevator equipment, lifting cranes, etc.
 The construction of such ropes is close to traditional round ones. At the same time, the conditions of operation, assembly of structures using them are different from traditional round ropes. Thus, cable-stayed cables of bridges perceive significant wind loads. Transportation of ropes for the perception of significant loads is complicated due to their significant bending stiffness.
 An elliptical shape or a shape similar to this section of the rope will reduce the impact of wind loads. Technically, this can be implemented by creating a cable rope as a composite structure in the form of a system of parallel cables connected by an elastic material, such as polyurethane or rubber.
 A multi-layer rope can be obtained by vulcanizing the connection of single-layer or double-layer rubber ropes directly at the installation site. The practice of use has proven their advantages - the service life of rubber balancing ropes exceeds the service life of ordinary ropes by 6 times.
 The design requirements of the study will contribute to those given in the bridge design standards and will correct the current lack of knowledge regarding the analysis of sudden or gradual cable pull. This will also provide a more realistic estimate of the dynamic amplification factor expected in the case of failure. The requirements for the gust detection system are intended to provide a potential improvement in the structural strength of cable-stayed bridges and provide economic benefits to society.

Development and sensing performance study of a smart CFRP cable assembled by multi-group anchorage units

ABSTRACT Carbon fiber reinforced polymer (CFRP) can be applied for bridge cables due to its excellent properties. As the important load-bearing structural component, real-time force monitoring of the CFRP cable is required. This paper presents a new smart CFRP cable that combines the self-sensing rods with embedded sensors and the anchorage system using extrusion technology. By embedding optical fiber (OF) and coaxial cable Fabry-Perot interferometer (CCFPI) into CFRP rods respectively, two types of self-sensing rods (CFRP-OF rod and CFRP-CCFPI rod) were fabricated. A new anchorage unit using an extrusion process was proposed as a basic component of smart CFRP cables. Anchorage units holding a CFRP-OF rod and a CFRP-CCFPI rod were tested to obtain their sensing and mechanical properties. Three anchorage units were assembled to form a smart CFRP cable with self-sensing functionality. A verification test was carried out to confirm the capability of monitoring the cable force. The test results demonstrate that the smart CFRP cable composed of multiple anchorage units has good potential in bridge engineering.

Effect of pitting corrosion on the mechanical properties and fracture model of steel wires for bridge cable

PurposeThis paper aims to investigate the effect of characteristic parameters of pits on the mechanical properties and fracture model of cable steel wires.Design/methodology/approachThe tensile test and finite element analysis of steel wires with corrosion damage were carried out. The stress development of corroded steel wire under corrosion morphology was studied by the 3D reverse reconstruction technology. The internal relationship between the stress triaxiality, equivalent plastic strain and pit depth, depth-width ratio of corroded steel wire was discussed.FindingsWith the increase of corrosion degree, the neck shrinkage phenomenon of steel wire was not significant, and the crack originated near the pit bottom and expanded to the section inside of specimen. The fiber area of corroded steel wire decreased while the radiation area increased, and the ductile fracture gradually changed to brittle fracture. The pit size significantly changed the triaxial degree and distribution of stress and accelerated the initiation and propagation of internal cracks at the neck shrinkage stage.Originality/valueThe proposed fracture model based on the void growth model could accurately simulate the fracture behavior of steel wires with corrosion damage.

PRACTICAL APPLICATION OF A HIGH VOLTAGE POWER SUPPLY CABLE FASTENING

High flame retardant drag chain power sheathed cables are used for equipment power supply, and in the outdoor environment, the power transmission power cable needs to be fixed to the wall, usually along the industrial route. The cable bridge moves, extends more frequently, the power supply cable needs to be fixed with a cable sling device, because there is no such special sling device on the market, so the use of the existing card fixing method leads to the cable often squeezed and damaged insulation layer cable failure power outage. This article addresses this problem and proposes for feasible countermeasures.

Evaluation of Cable Tension Using Static and Dynamic Test on R.H. Fisabilillah Cable-Stayed Bridge, Batam-Indonesia

R.H. Bridge Fisabilillah (Bridge I) is a cable-stayed bridge, included in the series of Barelang Bridges (Batam-Rempang-Galang) which were built from 1992 to 1998. With the service life of the bridge reaching 25 years, it is necessary to check the health condition of the bridge structure. Bridge cables are one of the most important elements of a cable-stayed bridge. These cable elements dominantly experience tensile forces when transmitting loads from the decks to the bridge pylons. Cable force inspection methods can be carried out through the direct measurement method (e.g. static test using a lift-off method) and indirect measurement (e.g. dynamic test using accelerometer sensors, electromagnetic/EM sensors, and so on). This study aims to compare the cable tensile force based on the static test (lift-off method) in 2017 against the dynamic test (accelerometer sensors) in 2022. Evaluation of the cable tensile force based on the dynamic test was carried out using the taut string theory and beam string theory approaches. From the study, the two empirical approaches yielded insignificantly different results where a difference in the mean difference of -1,71% was found with a maximum difference of 28,15%. The study also shows an increase in cable force capacity to a maximum of 47,20% UTS (ultimate tensile strength) based on the taut string theory and a maximum of 53.37% UTS based on the beam string theory. This value is greater when compared to the results of the cable force based on the static test (lift-off) in 2017, which was a maximum of 41.64% UTS. It is recommended to carry out further and more comprehensive studies to determine the effect of changes in cable force distribution on the behavior of the structure on the R.H. Fisabilillah Bridge.

An optimization neural network model for bridge cable force identification

Accurate determination of cable force values is the most important technical means to avoid damage to the cable bridge. In order to avoid the influence of the difficulty in distinguishing the boundary conditions and the lack of low-order natural frequency on the cable force determination results, an intelligent method for determining the bridge cable force based on the vibration method is proposed. With the cable length, linear density, flexural stiffness and input frequency as input units and the cable force as output unit, a neural network is established to identify the cable force by combining the finite element simulation data, and the model is optimized using the intelligent swarm optimization algorithm. The results show that compared with the cable force prediction models using generalized regression neural network (GRNN) and GRNN optimized using particle swarm optimization (PSO-GRNN) and canonical identification methods, the GRNN optimized using sparrow search algorithm (SSA-GRNN) proposed in this paper has a better identification effect. The prediction error of short cables is essentially within 10%, and that of long cables is within 5%. It can not only realize the accurate identification of bridge cable force by ignoring the boundary conditions and vibration frequency order of cables, but also has a wide range of applications.

Arch and Cable Suspended Bridges

An arch bridge is a mainly horizontal deck with an arch as its load-carrying structure. The arch works by transferring the weight and other external vertical loads into a horizontal thrust on the abutments placed at both sides. When the main load on the arch is the homogeneously distributed deck weight, and the arch is properly shaped, the arch rib is subjected to pure compression along its whole extension. Both tensile forces along the arch rib and shear forces transversal to it are absent. Bending moments vanish as well. This has made possible the use of masonry for arch bridges, which uses materials such as stone, brick, and concrete that are strong in compression but very weak to tension and shearing. In the following sections, we determine mathematically this optimal arch shape, which turns out to be a parabola. The novelty is that these well-known results are obtained using just basic algebra and trigonometry, without any mention of infinitesimal calculus, including in the demonstration of the absence of shearing forces. Subsequently, the method is extended to cable suspended bridges.

Defect Characterization Method for Bridge Cables Based on Topology of Dynamical Reconstruction of Magnetostrictive Guided Wave Testing Signals

Defect Characterization Method for Bridge Cables Based on Topology of Dynamical Reconstruction of Magnetostrictive Guided Wave Testing Signals

An Experimental Study on Ice Accretion under Bridge Cable in Different Conditions

The ice accumulation on the surface of the stay cable of the bridge is a frequently identified problem that threatens the safety of bridge traffic. Therefore, it is important to investigate the ice accumulation on the stay cable under different conditions. To understand the distribution characteristics and variation rules of ice, this study analyzed the effects of ambient temperature, cable inclination angle, and diameter on the ice accumulation of the high-density polyethylene (HDPE) stay cable. The results show that the ambient temperature significantly affects ice formation in the lower part of the stay cable. Low temperature facilitates the formation and growth of icicles, while larger size and inclination angle of the stay cable inhibit the icicle growth. When the inclination angle of the cable is less than 60°, icicles easily form at the bottom of the cable. Smaller-diameter cables are more likely to accumulate icicles at the bottom.

Cross-leg free flaps and cross-leg vascular cable bridge flaps for lower limb salvage: experience before and after COVID-19.

Previous reports have evidenced the disruptive effect of the COVID-19 in microsurgical and reconstructive departments. We report our experience with cross-leg free flaps and (CLFF) and cross-leg vascular cable bridge flaps (CLVCBF) for lower limb salvage, technical consideration to decrease morbidity, and some structural modifications to our protocols for standard of care adapted to the COVID-19. We retrospectively included consecutive patients undergoing reconstruction with CLFFs and CLVCBFs for lower limb salvage from January 2003 to May 2022. We extracted data on baseline demographic characteristics, mechanism of trauma, and surgical outcomes. Twenty-four patients were included, 11 (45.8%) underwent reconstruction with CLFF while 13 had CLVCBFs (54.2%). Fifteen patients (62.5%) underwent lower limb reconstruction under general anesthesia while 9 (37.5%) had combined spinal-epidural anesthesia. During COVID-19 pandemic, six CLFF cases were performed under S-E (25%). The average time for pedicle transection of muscle CLFFs and muscle CLVCBFs was comparable between groups (60 days versus 62 days, p = 0.864). A significantly shorter average time was evidenced for pedicle division of fasciocutaneous flaps in the CLFF group when compared to CLVCBFs (45 days versus 59 days, p = 0.002). In selected patients, CLFFs and CLVCBFs offer an optimal alternative for lower limb salvage using recipient vessels out of the zone of injury from the contralateral limb. Modification in the surgical protocols can decrease improve resource allocation in the setting of severely ill patients during COVID-19.Level of evidence: Level III, Therapeutic.

Effect of rare earth content on microstructure and corrosion resistance of hot-dip Zn–5Al alloy coated steel wire for bridge cables

Effect of rare earth content on microstructure and corrosion resistance of hot-dip Zn–5Al alloy coated steel wire for bridge cables

Data-driven evaluation of abnormal vibration of cables during typhoon In-Fa

The input–output characteristics of cables of a long-span cable-stayed bridge in time and frequency domains were studied during the whole process of typhoon In-Fa landfall based on monitoring data. According to the signal characteristics of the time series of wind speed and direction, a new adaptive extraction method of quasi-steady wind speed and direction was developed, fusing wavelet transform and the certain-length time series averaging method. The central tendency and fluctuation about the wind speed and direction were assessed and the influences of wind and rainfall on cable abnormal vibration were analysed. Using the short-time Fourier transform, the characteristics of the evolution of vibrational energy in the time–frequency domain for abnormal cable vibration during the typhoon were reproduced. Slice analysis of the power spectrum in the frequency domain was performed at typical moments. The results of this work revealed the following. The extremely high-amplitude non-Gaussian section of abnormal cable vibrations in this typhoon event was caused by the simultaneous action of wind and rain. A high wind speed or a wind direction with low fluctuation will more likely excite high-amplitude abnormal cable vibration. Sufficient damping may help cables suppress rain-wind-induced high-amplitude vibration.

Application Research on Nb Microalloying of High-Carbon Pearlite Bridge Cable Wire Rods

The application of Nb microalloying to high-carbon pearlite bridge cable wire rod steel has always been controversial, especially in the actual production process, which will be affected by the cooling rate, holding temperature and final bonding temperature. In this paper, the experimental characterization, finite element simulation and phase diagram calculation of the test steel were carried out, then the microstructure and properties of different parts of Nb microalloying of bridge cable wire rods were compared and analyzed. The phase transition interval of pearlite during the water-cooling process of bridge cable wire rods is increased due to the refinement of austenite grains, and the significant increase in the end temperature of the phase transition makes the average interlamellar spacing of pearlite increase. The cooling rate of different parts of bridge cable wire rods simulated by Abaqus has little difference. At the same time, Nb microalloying effectively increases the proportion of low-angle grain boundaries, so that the overall average misorientation representing the surface defects is reduced. This helps to reduce the surface energy and increase the stability of the microstructure. Combined with the mechanical properties of microtensile rods, it is found that the grain refinement effect of Nb is greater than that of coarsening interlamellar spacing during hot rolling deformation in actual production, which makes the tensile strength at the 1/4 section increase significantly. The overall tensile strength and area shrinkage of the steel wire have also been effectively improved.

Effects of damping and helical fillets on galloping vibration of stay cable installed with a rectangular lamp

Lamps attached on the stay cable can change the stable circular cross-section of the stay cable, which is easy to cause galloping vibration. Stay cables of the Kuipu bridge in the Fuzhou City of China were equipped with damper and helical fillets. After the installation of rectangular lamps on this bridge, no obvious vibration of the stay cables was observed. This is totally different from another bridge, the Kuimen bridge in the Chongqing City of China, which has been recently reported by the authors. The purpose of this study is to clarify the effects of the helical fillets and the structural damping on galloping vibration. The features of galloping vibration of the stay cable attached to a rectangular lamp were carefully studied, and the effectiveness of damping and helical fillets in reducing the galloping vibration was evaluated. First, the force measurement wind tunnel tests on the segmental test model were carried out, and the lift and drag coefficients of the stay cable attached to the rectangular lamp were measured. The dangerous wind attack angle of galloping vibration was predicted by the galloping force coefficient. Second, 3-dimensional vibration measurement wind tunnel tests were carried out to measure the wind-induced response of the cable-lamp test models. The variation of wind-induced response of stay cable with yaw angle and wind velocity was measured for test models with and without helical fillets. In the test, the features of wind-induced vibration were studied at the damping level of 0.1%, 0.6%, 0.7%, 0.8%, and 1.0%. According to Den Hartog’s theory, the minimum coefficient of galloping force is about −9.8. The experimental results of 3-dimensional vibration measurement wind tunnel tests show that the helical fillets wrapped on the cable surface can enhance the critical wind velocity to a certain extent, but the critical wind velocity is still far lower than the design wind velocity. When the damping ratio of the stay cable is up to 1.0% ( SC = 35.1), the galloping vibration of the stay cable attached to a rectangular lamp on the Kuipu Bridge can be effectively mitigated.

Static Experimental Study on New Arc Multi-Tendon CFRP Cable Anchorage System

CFRP has the potential to replace steel cables in large-span cable-stayed bridges due to its high strength and lightweight material properties. However, the weak lateral force performance of CFRP material creates the challenge of anchoring. This study introduces a new inner cone + arc + straight cylinder bond-type anchorage system to optimize CFRP tendons’ force state. Experimental and finite element analyses verified the new anchoring system’s performance. In static load tensile tests, six groups of seven CFRP tendon anchorage systems with different sleeve grooves were used to study the failure mode and load–strain variation law. The difference in mechanical properties between the new and traditional anchorage is evaluated in the finite element analysis. The results indicate that the new anchorage system can lower the stress concentration in the anchorage zone and enhance anchorage performance. The groove design of the sleeve can effectively increase the anchoring efficiency, where the groove depth is proportional to the anchoring efficiency and the groove spacing is inversely proportional to the anchoring efficiency. The magnitude of the stress inhomogeneity in the multi-tendon anchoring system during tensioning is proportional to the beginning conditions and the load size. When the inner wall of the sleeve becomes more abrasive, the force heterogeneity of the anchorage system reduces. The tests and finite element analysis show that the new anchoring may improve stress distribution and anchorage efficiency. In engineering practice, it can be utilized as a dependable anchorage system.

Real-time cable force identification based on block recursive Capon spectral estimation method

Cables are critical force-bearing components of cable-supported structures that greatly influence structure security. The changes in cable forces can reflect the cable service state and provide an important basis for structural health assessment. This paper proposes a method for real-time cable force identification (CFI) to tracking its varying rules. First, a recursive Capon method based on block updating is derived to estimate the amplitude spectrum at each observation moment. Second, determine the natural frequency (and corresponding mode order) in the transformed frequency domain and calculate the cable tension according to related formulas. Proper algorithm optimization and parameter selection are studied to ensure that the calculation cost meets the real-time requirement of CFI. The proposed method is applied to an experimental cable and the cables of a half-through arch bridge for validation.