Bridge Cables Research Articles

Investigation of torsion angle measurement method in spatial cables of suspension bridges

Spatial cables in suspension bridges may twist between two adjacent suspension points due to transverse tension. To determine the spatial torsion angle of the cables, a scale-reduced suspender bridge model was fabricated and tested in this study. The cable torsion angles of the bridge model under different loading cases were obtained and presented. Theoretical methods (e.g., the coordinate method and the angle method) to calculate the spatial cable torsion angle in the suspender bridge were developed by analyzing the deforming characteristics of the suspender cables. The feasibility and predictive accuracy of the proposed methods were assessed using the experimental results. Results show that the proposed coordinate and angle methods produced similar torsion angles for the main cables, showing a maximum relative error of 10.4 %. Compared to the coordinate method's complex data transformation and measurement procedures, the angle method is more convenient, efficient, and easier to calculate the torsion angle of the main cable. Despite the capability of calculating the spatial cable torsion angles, the coordinate method also exhibits advanced capability in determining the geometric curves of the main cable under different spatial angles.

A passive fire protection method for main cables and slings of suspension bridges utilizing fiber felt/aerogel composites

The paper proposes a fire protection method for the main cables and slings (cables for short) of suspension bridges based on fiber felt/aerogel composites. Glass fiber felt/aerogel composite (GFAC), basalt fiber felt/aerogel composite (BFAC), and high silica fiber felt/aerogel composite (HSFAC) were prepared using silica aerogel as filler. Heat-shielding tests and thermal stability analysis were conducted on these three thermal insulation composites. A fire test platform was established to study temperature distribution and fire protection range of suspension bridge cables. The following results were obtained: (1) Within 6000 s, the 5 mm-thick HSFAC can resist 700 °C butane fire, while 7 mm-thick HSFAC blocks 1000 °C flame. The 10 mm-thick HSFAC provides better thermal insulation. (2) Two fire protection zones are identified according to temperature ranges of 1000 °C to 700 °C and 700 °C to 300 °C, respectively, with minimum heights of 12.8 m and 20.8 m. (3) For a 90-minute fire protection, the main cables in the former zone are wrapped with 10 mm-thick HSFAC, while the slings are chosen to be 7 mm-thick HSFAC. In the latter zone, main cables and slings are covered with 5 mm-thick HSFAC. The fire protection method has been implemented on a suspension bridge in Guangzhou, China.

Damping in stay cable with damper: Practical universal damping curve and full-scale measurement

This paper includes two main parts which are the development of a universal damping curve for cables of cable-stayed bridges with dampers and a full-scale measurement of cable damping. In the first part, the universal damping curve is derived for cables with viscous dampers or High Damping Rubber (HDR) dampers. The proposed damping curve is a single curve which incorporates several cable-damper parameters like cable bending stiffness, boundary conditions at cable ends (hinged, fixed or restraint ends), damper stiffness, damper support stiffness and added negative stiffness. A numerical approach by a finite difference method (FDM) is also developed to verify the proposed universal damping curve. In addition to FDM, the accuracy of the proposed curve was confirmed with damping formulations in literature over ten different damper types. The results showed a good agreement of estimated damping between proposed damping curve and others. Additionally, a significant improvement in estimating cable damping was observed through two available full-scale tests, which compared the results between proposed curve and current curve. The second part in this study presents a full-scale measurement of cable vibration and a real application of the proposed damping curve for the identification of damping in cables of Shinminato Bridge (cable lengths from 100 to 200 m). Both HDR and viscous dampers were used for the cable vibration control of the bridge. The results of damping analysis indicated that the HDR damper effectiveness was higher than 0.7 whereas this effectiveness was smaller than 0.4 for the viscous damper.

Fatigue of suspender anchorages under axial and bending loads of suspension bridges

Fatigue-induced damage is the primary failure mode observed in cables used in cable-supported bridges, such as suspenders in suspension bridges, stay cables in cable-stayed bridges, and hangers in arch bridges. Typically, cable failures occur at their anchorages in a combination of axial and bending fatigue. A computational framework to estimate axial and bending fatigue load spectrums caused by girder buffeting and train load is presented for suspenders of suspension bridges. The threaded rods of upper suspender anchorages were then accordingly evaluated. The results show that under girder buffeting of 15 m/s mean wind speed, short suspenders at the mid-span experience a maximum axial stress range of up to 35.00 MPa and a maximum rotation angle range of approximately 0.90°. Under train loads, the suspenders exhibit a maximum axial stress range of 26.88 MPa and a maximum rotation angle range of 1.42°. Threaded rods used in all suspenders generally do not experience damage under the axial fatigue load spectrum, but short suspenders in mid-span may experience significant cumulative damages under the bending fatigue load spectrum due to girder buffeting and train load. Girder buffeting tends to cause about 3 to 5 times more damage than train load. The predicted life for a failed suspender is generally consistent with actual observations (2.6 versus 2.0 years). Therefore, it is strongly recommended that the bending fatigue of short suspender anchorages due to girder buffeting should be carefully investigated in fatigue design, in addition to the bending fatigue of train load excitation.

Corrosion Fatigue Assessment of Bridge Cables Based on Equivalent Initial Flaw Size Model

Bridge cables under traffic loads are more prone to failure during the service life due to the corrosion–fatigue coupling effect. In this study, a novel lifespan model based on the equivalent initial flaw size (EIFS) theory is established to analyze the various stages of the lifespan of steel wires. Additionally, a comprehensive corrosion-fatigue lifespan calculation method for parallel steel wire cable is established based on the series–parallel model. A case study of the Runyang Suspension Bridge is conducted to evaluate the evolution of corrosion-fatigue damage in bridge cables during the service life. The results indicate that under the action of corrosion-fatigue, steel wires are more prone to crack initiation, and their fracture toughness is further reduced. In cases where the corrosion level is relatively low, the steel wires of the bridge cables experience no corrosion-fatigue fracture. When the steel wires have initial defects and are subject to corrosion-fatigue conditions, their fracture lifespan is dependent on the severity of the corrosive medium. The reduction in the service life of the cables under the corrosion environment is much greater than that under heavy loads. This research may contribute to the understanding of corrosion-fatigue damage in bridge cables, involving assessment, maintenance, and replacement for bridge cables.

Experimental and numerical study of the fatigue properties of stress-corroded steel wires for bridge cables

In this paper, the fatigue tests of stress-corroded steel wires were carried out to investigate the effects of corrosion age, stress level, stress range on the failure mode, fatigue life and S-N curve of steel wires. Then, the fatigue fracture and crack growth rate of steel wires with different corrosion degrees were analyzed by SEM scanning, revealing the crack initiation and propagation mechanism of corroded steel wires. Finally, a numerical analyzing method for the fatigue life of steel wires considering the corrosion surface was proposed, and the relationship between the surface stress distribution and fatigue life was studied. The results shows that the fatigue life of steel wires decreased gradually with the increase of corrosion degree. When the corrosion degree was 5.0%, 10% and 20%, the fatigue life of steel wires decreased by 32.67%, 48% and 67.84%, respectively. The influence of corrosion degree on the fatigue life of steel wire was first sensitive and then insensitive. Meanwhile, compared with the unstressed corrosion state, the fatigue life of stress-corroded steel wires decreased by a maximum of 56.45%. In addition, stress corrosion affected the crack initiation location and shortened the crack propagation depth. The higher corrosion depth and the sharp surface were more likely to be the fatigue crack source. With the increase of corrosion degree, the striation spacing and crack growth rate of fatigue fracture increased, and the proportion of crack initiation and propagation zone decreased from 45% of the diameter to 28% of the diameter of the cable. Finally, the proposed numerical analysis method considering the real corroded surface can effectively reveal the fatigue failure mechanism and evaluate the residual fatigue life of corroded steel wires.

Experimental study on corrosion resistance of Zn–Al–Mg alloy coating of high-strength steel wires for bridge cables

Purpose This paper aims to figure out the conundrum that the corrosion resistance longevity of steel wires for bridge cables was arduous to meet the requirements. Design/methodology/approach The “two-step” hot-dip coating process for cable steel wires was developed, which involved first hot-dip galvanizing and then hot-dip galvanizing of aluminum magnesium alloy. The corrosion rate, polarization curve and impedance of Zn–6Al–1Mg and Zn–10Al–3Mg alloy-coated steel wires were compared through acetate spray test and electrochemical test, and the corrosion mechanism of Zn–Al–Mg alloy-coated steel wires was revealed. Findings The corrosion resistance of Zn–10Al–3Mg alloy-coated steel wires had the best corrosion resistance, which was more than seven times that of pure zinc-coated steel wires. The corrosion current of Zn–10Al–3Mg alloy-coated steel wires was lower than that of Zn–6Al–1Mg alloy-coated steel wires, whereas the capacitive arc and impedance value of the former were higher than that of the latter, making it clear that the corrosion resistance of Zn–10Al–3Mg was better than that of Zn–6Al–1Mg alloy coating. Moreover, the Zn–Al–Mg alloy-coated steel wires for bridge cables had the function of coating “self-repairing.” Originality/value Controlling the temperature and time of the hot dip galvanizing stage can reduce the thickness of transition layer and solve the problem of easy cracking of the transition layer in the Zn–Al–Mg alloy coating due to the Sandelin effect.

Non‐Destructive Testing of Bridge Cables using MIT

AbstractThis article presents the importance of non‐destructive testing (NDT) in maintaining the safety and functionality of bridge cables, and focuses on the practical use of magnetic‐inductive testing (MIT) and ultrasonic testing (UT) for NDT of bridge cables in free length and in the area of the end connectors. MIT is a non‐invasive method that can effectively detect defects such as broken wires, corrosion symptoms, and other imperfections, making it a promising technique for inspecting and maintaining bridge cables. A research project investigated various types of magnetic induction testing on different tension members made of single wires and evaluated the advantages and limitations of the MIT method. The study also explored the impact of factors such as cable diameter and measurement speed on the effectiveness of the technique. The results suggest that the MIT method can accurately detect defects in bridge cables and provide valuable information for maintenance and repair purposes. However, the article highlights the need for further research to optimize the MIT technique, particularly in automating the detection and characterization of signals, and to expand its applicability to a wider range of cable diameters and conditions.

Electromagnetic testing of multi‐strand stay cables: novel technique and instrumentation

AbstractSteel stay cables are widely applied in various civil constructions. In recent decades, the so‐called multi‐strand stay cables have become widely used, particularly in the construction of cable‐stayed bridges. Conventional method of stay‐cable diagnostics utilizes magnetic rope testing instruments. However, because of the large diameter of multi‐strand stay cables, the appropriate magnetic instrument should have an inappropriate high mass and create a significant force of attraction between the magnetic head and the stay cable, which likely would cause damage to the cable's outer protective shell. Alternatively, the eddy current method can be used for testing of stay cables. The special probe was developed that provides equal sensitivity to surface and subsurface breaks of the strands and reduces a disturbance of irregularity of magnetic properties along the cable. On the basis of this probe, a specific electromagnetic instrument was designed for nondestructive testing of multi‐strand stay cables. The instrument was tested on a multi‐strand mock‐up and applied for inspection of the stay cables of bridges. Results of this are discussed in the article.

Case study: use of SHM to support bridge assessment, maintenance and operation

AbstractThe assessment of infrastructure conditions is at present a topic of great interest and importance, as well as great challenge. This paper presents a case study of the Samuel De Champlain Bridge (Montreal, QB, Canada), an outstanding stay cable bridge equipped with a comprehensive monitoring system (SHM). Among other SHM features, particular attention was paid to implementation of a strategic corrosion monitoring system. This paper intends to describe the concept design, implementation and data interpretation. Here corrosion sensors have been embedded during construction stage to monitor long term evolution of key electro‐chemical parameters for controlling deterioration of materials. Furthermore, these sensors measure stray current interference generated from the rail system that can cause corrosion. In both cases, abnormal values would warn the owner of the associated increased risk of corrosion. This gives them the possibility to take corrective measures to protect the structure before corrosion becomes a serious threat.

A Scarless Method for Correcting Tanzer Group IIB-Constricted Ear Without Cartilage Grafting.

Tanzer group IIB-constricted ear is described as a deformity of the helix, antihelix, or scapha. Deficiency of the auricular skin and cartilage is a key point in the reconstruction of the cartilaginous framework. Traditionally, the treatment of a constricted ear mainly includes 2 aspects: correction of cartilage deformity and restoration of skin volume deficiency. By mimicking the suspension principle of a cable bridge, our technique only requires adjustment of the spatial directions and mechanical forces between the 2 flaps to achieve an aesthetic effect. The authors were able to avoid harvesting the costal cartilage. The desired ear shape was obtained immediately postoperatively. Therefore, Vaseline gauze was not applied and was modeled along the scapha and antihelix. Expansion of the ear was remarkable in both horizontal and vertical lengths. Our technique causes less damage, less scarring, shorter operation time, fewer complications, faster rehabilitation, and no delays.

Gabor wavelet transform combined with area CNN in appearance intelligent detection of stayed cables

The major structure for transmitting forces in a cable-stayed bridge is the stay cable. If the stay cable system fails, the whole bridge will collapse. At present, there is no very mature technical means for the detection of bridge cables. The most common method is for workers to perform regular manual inspection and replacement of cables. Although the defect condition of the cable can be detected to a certain extent, the real-time monitoring of its health cannot be realized. Therefore, the research used the median filter, mean standardization method and Retinex algorithm to preprocess the image data. And after extracting the stay cable picture’s macroscopic characteristics using the Gabor wavelet transform, it implemented image segmentation using the OTSU approach. The obtained feature images were applied to the Faster Regional Convolution Neural Network (RCNN) recognition model to detect microscopic defects. During the research, the training efficiency of traditional Convolution Neural Network (CNN) was not high. Therefore, Faster RCNN built a cable defect recognition model. Based on this, the research built an intelligent detection model for apparent defects of stay cables based on Gabor wavelet transform and improved RCNN. Through the experimental analysis, the model built for the study has a recognition accuracy rate of 94.14 %, which can achieve dynamic bridge health monitoring and instantly identify the condition of the stay cables, and maintain the safety of the bridge.

A Novel Methodology for Inspection and Strength Evaluation of Suspension Bridge Main Cables

A novel methodology is proposed to evaluate the ultimate strength of the main cables of suspension bridges using information obtained from site inspections and from tensile strength tests on selected wire samples extracted from the bridge’s main cables. A new model is proposed accounting for the spatial variation of individual wires’ strength along their length, an important physical attribute of corroded wires considered here for the first time. This model includes (1) mapping the corrosion stage variation along one-panel-long wires that are visible during an inspection; (2) establishing probability distribution functions for the ultimate tensile strength of 0.46 m (18 in.)–long wire segments in each corrosion stage group; (3) generating random realizations of the ultimate strength of all the wires in the cable’s cross section, accounting for their strength variation along the entire panel length; and (4) accounting for the effect of broken wires in the evaluation panel as well as in adjacent panels. A Monte Carlo simulation approach is finally proposed to generate random realizations of the ultimate overall strength of the cable, using an incremental loading procedure. The final outcome is the probability distribution of the ultimate strength of the entire cable. The methodology is demonstrated through the cable strength evaluation of the Franklin Delano Roosevelt Mid-Hudson Bridge using results of a 2009 inspection, and compared with corresponding results obtained using current guidelines. The proposed methodology provides estimates of higher accuracy and reliability for the cable’s ultimate strength, without essentially increasing the cost of inspections.

Effect of Coating on Stress Corrosion Performance of Bridge Cable Steel Wire

Hot galvanization on steel surfaces can isolate the steel from corrosive environments and alleviate the stress corrosion cracking caused by the anodic dissolution mechanism. However, the cathodic protection potential of the coating is excessively negative, which may aggravate the hydrogen embrittlement problem. The effect of a coating on the stress corrosion performance of bridge cable wire was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), a thermal desorption analysis (TDA), an electrochemical workstation, and an FIP test. The results show that hot-dip ZnAl and ZnAlMg alloy coatings can significantly prolong the stress corrosion fracture time of steel wire substrates. From a macroscopic perspective, the stress corrosion cracking fracture is a brittle fracture caused by hydrogen embrittlement. Moreover, the coating type has little effect on the fracture morphology of bridge cable wire. In NH4SCN solution (50 °C, 20 wt.%), a corrosion product layer composed of ZnS and Al2O3 was formed on the surface of the coated steel wire. The electrochemical analysis showed that the corrosion resistance of the ZnAlMg coating was better than that of the ZnAl coating, which was the main reason for the improvement of the stress corrosion performance.

Correlation between corrosion level and fatigue strength of high-strength galvanized steel wires used for suspension bridge cables

This study investigated the relationship between “rust color distribution ratio,” “corrosion surface shape,” and “fatigue strength” of high-strength galvanized steel wires used in cable supported bridges. The study utilized a digital image color analysis system to classify the rust color distribution rate and categorize corrosion levels based on the distribution ratio. The relationship between cross-sectional loss rate and corrosion depth tendency was visually and quantitatively comprehended from the categorized corrosion levels. The study found that fatigue and tensile strengths of the specimens from the corrosion levels set in this study were equivalent to or higher than those of new wires. However, the possibility of variations due to the small number of specimens or insufficient corrosion progress cannot be ruled out.

Damage diagnosis and fretting wear performance analysis of short suspenders in cable-supported bridges

Bridge suspenders with short length suffer from significant damage, usually following short service life, heavy casualties and property losses. In this paper, damage in the short suspenders was investigated macroscopically by inspection and field measurement. Inter-wire fretting wear due to different axial deformation and lateral shrinkage deformation of the wires with helical angle was confirmed as one of the damage cause. To investigate the fretting wear effect in the short suspender, refined FE models of the wire rope were generated by using parametric modeling method. Furthermore, inter-wire deformations and contact stresses were simulated and analyzed. Investigation of damage mechanism and fretting wear performance analysis of the short suspender contributes to the understanding of damage mechanism and the service safety of bridge cables.

Characteristic Parameters of Magnetostrictive Guided Wave Testing for Fatigue Damage of Steel Strands.

Steel strands are widely used in structures such as bridge cables, and their integrity is critical to keeping these structures safe. A steel strand is under the working condition of an alternating load for a long time, and fatigue damage is unavoidable. It is necessary to find characteristic parameters for evaluating fatigue damage. In this study, nonlinear coefficients and attenuation coefficients were employed to evaluate fatigue damage based on magnetostrictive guided wave testing. Unlike pipe and steel wire structures, there is a phenomenon of a notch frequency when guided waves propagate in steel strands. The influence of the notch frequency on the nonlinear coefficient and attenuation coefficient is discussed. The relationship between the nonlinear coefficient, attenuation coefficient, and cyclic loading times was obtained through experiments. The amplitudes of the nonlinear coefficient and attenuation coefficient both increased with the increase in cyclic loading times. The experiments also showed the effectiveness of using these two characteristic parameters to evaluate fatigue damage.

Modal analysis and vibration control of a vertical cable with dual tuned mass dampers

This paper proposes a vibration model for modal analysis and vibration control of a vertical cable-dual tuned mass damper (C-DTMD) coupled system. The proposed model introduces several non-dimensional parameters to describe the in-plane vibration of the coupled system. Moreover, the phenomenon of modal split is comprehensively studied to present the complex vibration modes. Parameter analysis is conducted to show the influence of length ratio, mass ratio, damping ratio, and frequency ratio on vibration reduction. In addition, the theoretical model is verified using finite element methods. A practical vertical cable in Jiangyin Bridge with designed wind loads is chosen as a numerical example. The results show that DTMD devices can effectively reduce the modal vibration and have great potential for multi-mode vibration control of vertical cables in suspension bridges. The proposed model can accurately describe the in-plane vibration modes of C-DTMD systems and provides a basis for the optimal design of damper parameters.

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.