In this study, the scope of CFRP cables in cable-stayed bridges is studied by establishing a numerical model of a 1400-m span of the same. The mechanical properties and characteristics of CFRP stay cables and of a cable-stayed bridge with CFRP cables are here subjected to comprehensive analysis. The anomalies in the damping properties of free vibration, nonlinear parametric vibration and wind fluctuating vibration between steel cables and CFRP cables are determined. The structural stiffness, wind resistance and traffic vibration of the cable-stayed bridge with CFRP cables are also analyzed. It was found that the static performances of a cable-stayed bridge with CFRP cables and steel cables are basically the same. The natural frequencies of CFRP cables do not coincide with the major natural frequencies of the cable-stayed bridge, so the likelihood of CFRP cable-bridge coupling vibration is minuscule. For CFRP cables, the response amplitudes of both parametric vibration and wind fluctuating vibration are smaller than those of steel cables. It can be concluded from the research that the use of CFRP cables does not change the dynamic characteristics of the vehicle-bridge coupling vibration. Therefore, they can be used in long-span cable-stayed bridges with an excellent mechanical performance.

To evaluate the residual service performance of corroded high-tensile steel wires, a batch of in situ wires that had served for 13 years in the hangers of an arch bridge was investigated. Four types of corroded wires were derived from the in situ wires by placing them in the indoor environment for 1.5 years (Type A) or treating them in an alternate dry–wet environment for 0.25–1.5 years (Types B, C, and D). The mechanical properties of the corroded wires were investigated with tensile and fatigue tests, and the fracture characteristics were observed. Fatigue tests on Type A wires with different stress ranges were conducted, and the stress intensity factor range ΔK_p at the bottom of crack-initiation pits was analyzed. According to the S-N curve for Type A wires, the crack-propagation characteristics of steel wires were investigated. The linear elastic fracture mechanics (LEFM) approach was used to predict the residual life of corroded wires in two systems of arch bridges. The tests show that the ultimate strain of corroded wires decreased with an increase in degree of corrosion. The fatigue properties of wires were found to degrade significantly at the early corrosion stage, and the degradation rate slowed down with further development of corrosion. The correlation between the fatigue life and the stress intensity factor range ΔK_p at the bottom of corrosion pits shows that larger pitting size tended to have shorter life under the same stress range, and fatigue cracks were difficult to initiate at the corrosion pits below the fatigue threshold. The crack-growth parameters of the Paris law identified from the S-N curve of Type A wires were m = 2.87, C = 8 × 10 ⁻¹² under the stress ratio R = 0.5. The residual life predicted by LEFM shows that in a dry environment, corroded wires with an initial pitting depth of 0.6 mm can serve for more than 30 years in arch–beam combination-system bridges, whereas they can only serve for 5 years in floating-system arch bridges.

Carbon fiber reinforced plastic (CFRP) cables are superior to steel cables in cable-stayed bridges due to their light weight and excellent durability. It is a kind of flexible structural component with strongly weak shear stiffness. Hence, understanding the dynamic properties of CFRP cables poses a significant issue in bridge engineering. In this paper, the parametric vibrations of CFRP cables is performed and compared with steel cables by using a non-linear finite element method. The CFRP and steel cables of a cable-stayed bridge with a span of 1400 m, designed by the same criteria, are studied as typical cases. The material damping, aerodynamic damping and viscous dampers are simulated in the analysis, and the variations of the material damping and aerodynamic damping due to amplitude variations are taken into consideration. The dynamic responses of cables due to stochastic and harmonic support excitations are investigated. Numerical results show that the vibration amplitudes of steel cables are greater than that of CFRP cables. The parametric vibration of CFRP cable is more sensitive to damping than that of steel cable. The effects of material damping and viscous dampers on parametric vibration of both steel and CFRP cables are very significant, while that of aerodynamic damping is inferior to the former two dampers.

Low-frequency noise radiated from bridge vibrations has been reported as an environmental noise problem in many countries. In order to investigate the mechanism of low-frequency noise radiated from bridge vibration, a steel bridge with a double-box is adopted for study. Modal parameters of the bridge, including natural frequency, damping ratio and mode shape, are identified from field tests by a combination of Eigensystem Realization Algorithm and Fast Fourier Transformation. Then the grillage model of the bridge is established and physics parameters of the model are updated by genetic algorithm according to identified natural frequencies. The dynamic response of the bridge by the action of a moving vehicle is calculated and assumed as the sound source of low-frequency noise. Then low-frequency noise due to bridge vibration is estimated according to sound wave propagation theories. The validity of the numerical method is verified through comparison with experimental results. Furthermore, noise reduction methods are proposed and corresponding effects are discussed. Results show that numerical simulation is feasible in assessing low-frequency noise due to traffic induced vibration of a bridge, which offers a possible way for environmental assessment as well as being a good reference for noise reduction design of bridges. The deck plate of the bridge is the primary source of low-frequency noise. Hence, increasing the stiffness of a deck plate is effective for noise control. Improving the road roughness can also reduce low-frequency noise.