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Multi-wire cables are widely used in suspension bridges and cable-stayed bridges as primary load bearing structural elements. Broken Wires in cables can lead to catastrophic accidents such as bridge collapse. Magnetostrictive guided wave testing technology has been employed to detect the broken wire defects in multi-wire cables, and the defect size is estimated by analyzing the defect echo signals. However, there are many studies on the guided wave testing for the seven-wire steel strands but fewer for the bridge cables which have a large number of wires. Moreover, the relationship between the guided wave testing signal features and the defect size of multi-wire structures is imprecise, which means the defect size estimated by the features may deviate significantly from the real defect size. In this paper, large-scale topological features are extracted by using persistent homology from the dynamical reconstruction topology of the guided wave testing signals to characterize broken wire defects in the bridge cable. The broken wire experiments were performed on a 61-wire cable. The experimental results show a good linear relationship (the goodness of fit 0.9946) between the large-scale topological features and the number of broken wires in the cable. It indicates that it is feasible to extract topological features from the topological domain of the testing signals to characterize the broken wire defects of bridge cables. [ABSTRACT FROM AUTHOR]

Long span cable-stayed bridges face risks of fire and explosion accidents caused by vehicles transporting fuel or chemicals. Such accidents may lead to damage to the stay cables, which in turn reduces the load capability of the bridge. This report introduces a newly developed fire and blast protection system for the multi-strand stay cables of Rod El Farag Axis Bridge in Egypt. The protection system consists of a thermal insulation blanket wrapped on cables and a steel tube covered with an anti-blast layer. Fire and blast tests were carried out to verify the effectiveness of the developed protection system. [ABSTRACT FROM AUTHOR]

This paper focus on parameter identification of the main cables of cable suspension structures. Based on the dynamic stiffness theory, an inverse analysis characteristic function (IAC function) for identifying the main cable parameters (such as cable tension, moment of inertia, cable length, and mass per unit length) is established. This function allows for the consideration of cable flexural rigidity, sag, inclination, and additional lumped masses sustained by the suspender. The effects of the cable tension and moment of inertia on the IAC function are investigated via a numerical method. On this basis, a method for identifying the two parameters based on the peak-ridges of the IAC function is proposed. The method comprehensively utilizes measured multimode frequencies. It is unnecessary to determine the fundamental frequency and frequency order. A 20-m real cable test with suspended lumped masses is conducted to verify the correctness of the proposed methods. With the increase in the weight of suspended lumped masses, the advantages of the proposed method are more obvious. For operational cable tension less than 50% of the cable breaking tension, the cable moment of inertia is less affected by suspended lumped masses. [ABSTRACT FROM AUTHOR]

Negative stiffness mechanism has been found able to improve damping performance of dampers on a stay cable which otherwise is limited by the damper installation distance from a cable end. This study provides a practical negative stiffness device (NSD) with adjustable negative stiffness and experiments are performed to validate the negative stiffness effect. The NSD is then combined with a viscoelastic damper in parallel or series for cable damping improvement. Explicit design formulas are derived for optimal design with a target enhancement effect in damping considering the damper described respectively using the Kelvin model and the linear hysteretic damping model. The formulas are verified by analytical and numerical solutions. Parametric analyses show damping enhancement effects of the NSD and it is found more efficient when combined with a damper in series because both deformation amplitudes of the damper and the NSD are further increased in this configuration. Subsequently, case studies are carried out based on two cables of the Sutong Bridge respectively with a shear-type viscous damper and a high damping rubber damper. The results show that the designed NSD can fulfill practical requirements. Particularly, a 100% increase in damping can be achieved by the presented NSD when combined with the damper installed on a cable of 546.9 m long. [Display omitted] • Practical NSDs are presented and experimentally tested for cable damping improvement. • Damping effects of a cable with the NSD and dampers in parallel and series are investigated. • The NSD is shown to be more efficient when placed with the dampers in series configuration. • Achieved negative stiffness is found sufficient for stay cables even longer than 500 m. [ABSTRACT FROM AUTHOR]

Rain-wind-induced vibration (RWIV) is a typical large-amplitude vibration for stay cables. Due to the complex influencing factors and unclear mechanism, a Scruton number criterion S c is usually adopted for RWIV-resistant design. However, this criterion has proved to be too conservative. The original S c number characterized independently by mass and damping can not accurately reflect RWIVs' characteristics, and it is still difficult to compare test results with field measurement using the traditional S c number. In this work, cable vibrations were studied through wind tunnel experiments and field measurements, and it is concluded that aerodynamic damping varies with mass also influences cables' responses. The variation law of aerodynamic damping is analyzed by wind tunnel experiments, while the total damping of an actual cable of the Jintang Bridge has been identified by an empirical mode decomposition (EMD) method and the random decrement technique (RDT). A revised S c * number with clear physical meaning considering aerodynamic damping is proposed. The aerodynamic damping for lighter models can be up 10 times that of prototypes, which makes the S c * numbers the same order of magnitude. The results of different wind tunnel experiments and field measurements show that most large-amplitude vibrations occur at S c * = 1–2.5. And, it is necessary to consider aerodynamic damping for more comparable work and more accurate prediction. • The Scruton (Sc) number effects on the rain-wind-induced vibrations (RWIVs) were studied in wind tunnel experiments. • Aerodynamic damping is approved to be an additional resistance during RWIV initial stage, which strongly dependents on vibration amplitude and mass. • A revised Sc criterion considering aerodynamic damping is proposed for stayed cable wind resistance design. [ABSTRACT FROM AUTHOR]

Rain–wind–induced vibrations (RWIVs) can cause the large-amplitude vibration of flexible cables in cable-stayed bridges; such vibration is one of the engineering safety problems that must be resolved. Currently, aerodynamic measures, such as dimples and spirals, are typically used as measures for suppressing vibration in stay cables. By calculating and comparing the equivalent static wind loads (ESWLs) of six typical cable-stayed bridges, the proportion of ESWL acting on the cable to that acting on the entire bridge increases approximately linearly with the bridge span. Hydrophobic coating can effectively suppress RWIVs and evidently relieve the ESWL. Hence, compared with the commonly used aerodynamic measures with surface roughness, this coating has a considerable potential as an alternative for suppressing vibration. Based on the foregoing, the wind resistance design optimization of two actual cable-stayed bridges with main spans of 420 and 1160 m is implemented to investigate the construction costs of cable wind load reduction. After optimization, the structural responses of the main towers are reduced by 4%–12%, and the optimized tower and foundation sizes are reduced by 5%–8%. The optimization for the two bridges exceed 5% and 7%, respectively. The construction investment savings are approximately 2.3 million and 7.2 million USD, respectively. These values further improve with increasing bridge span and design wind speed. •The static wind load of stay cables is estimated for cable-stayed bridges of different spans. •A new aerodynamic measure, hydrophobic coating, has a considerable potential as an alternative for suppressing vibration. •Aerodynamic measure optimization effect on construction cost is illustrated through two actual engineering design cases. [ABSTRACT FROM AUTHOR]

This paper presents a full-scale experimental study on dynamics of hybrid cable networks composed of three real cables, a rigid cross-tie and three viscous-shear dampers. For comparison, an improved numerical model of cable networks considering cross-ties, dampers, and cross-tie pretension is also provided. The measured frequencies and mode shapes of the cable networks with different configurations and cross-tie locations are found in good agreement with corresponding theoretical predictions. The characteristics of damping variation with respect to cross-tie location and the layout observed from the experiments are generally consistent with the theoretical analysis, although there is a discrepancy between identified and computed values of damping. The experiments show that the cross-tie when located close to the dampers can lead to a reduction in modal damping of low-frequency modes. The dampers in the cable networks provide relatively large damping to global modes and modes dominated by vibrations of cable segments to which the damper is connected. Furthermore, when the cross-tie is installed far away from the external dampers, the cross-tie extended to the ground can effectively improve the system modal damping, as the length of the cable is reduced equivalently and the relative distance of the damper away from the closest anchor as compared to the cable length is increased. [ABSTRACT FROM AUTHOR]

A cable network of cables interconnected with cross-ties and attached with dampers represents the generalized solution for vibration mitigation of stay cables. It is of significant interest as completely suppressing vibrations of long cables vulnerable to various excitation mechanisms is still challenging. Although many theoretical studies on cable networks exist, large-scale and full-scale experimental validations and investigations are lacking. Therefore, this study first presents a full-scale experiment setup for experimental studies on cable networks, which consists of at most three cables with adjustable length and the maximum length is 41.35 m. The experimental setup is subsequently used for studying effects of a pretensioned cross-tie on cable network dynamics, with the focus placed on the pretension, location and anchoring form of the cross-tie. The experimental results are then discussed in detail with reference to a theoretical model of a three-cable network with cable sag and cross-tie pretension accounted. It is found that the experimental results on system frequencies and mode shapes are consistent with those predicted using the analytical model. Particularly, both the pretensioned cross-tie induced increase and decrease in cable network frequencies have been validated by the experiments. Furthermore, the grounded cross-tie is found to significantly improve the system fundamental frequency, but the increase in frequencies of other local vibration modes is limited. Besides, the test results have validated that a rigid cross-tie has very limited damping effect on the cable network. • A full-scale experiment setup for experimental studies on cable networks. • The effects of the pretensioned cross-tie on cable network dynamics studied experimentally. • A theoretical model established for a three-cable network with a pretensioned cross-tie. • Experimental validation of the theoretical model and analytical findings. [ABSTRACT FROM AUTHOR]

Efficient force identification of bridge cables is important to the performance evaluation of cable-supported bridges. For this purpose, sensors are conventionally installed on the cables to record vibration responses, which is nevertheless time-consuming and labor-intensive. This study develops a fully automated and noncontact cable force identification method using microwave radar sensing, enabling forces of a group of cables to be identified simultaneously and thus largely improving the efficiency. The fast sieve method with a linear time complexity is proposed to find the local maxima of the Fourier spectrum of the displacement measurements. Subsequently, the weighted hash voting is presented to identify the mode orders of the picked frequencies. An appropriate cable vibration model can then be used to compute the tension force. The proposed method has been validated in cable force identification of a newly constructed railway cable-stayed bridge during loading tests. Cable force variations in the loading tests are discussed. • A fully automated method for force identification of cables using microwave radar. • The fast sieve method proposed for frequency picking. • The weighted hash voting proposed to determine mode orders. • The methods validated by field tests on a long-span cable-stayed bridges. [ABSTRACT FROM AUTHOR]