Study On The Application Of CFRP Cables In Long-span Cable-supported Bridges

At present, the cables of long-span cable-supported bridges are commonly made of the conventional high strength steel wires. As compared to the conventional cable material of high strength steel ,CFRP has properties of higher tensile strength, lighter mass density, and excellent corrosion-resistant and fatigue- resistant ability, and therefore most suitable for application as structural member where maximum stiffness, light weight, and good durability are required such as the cables in cable-stayed bridges and suspension bridges. Through replacing steel cables with CFRP cables, the dead load of bridge superstructure can be reduced, and therefore the size of substructure and further the construction difficulty can be also decreased, and the span capability and economy are finally increased. In this paper, mechanics performance of the CFRP cables and the static behavior under service load, dynamic behavior, wind stability and seismic behavior of cable-supported bridges using CFRP cables are investigated numerically, and the application of CFRP cables in cable-supported bridges are also discussed. The research work has a good theoretical significance and reference value for the design of super long-span cable-supported bridges.Firstly, through the theoretical analysis, the static behavior (including the cable shape, the sag effect, the equivalent elastic modulus, the self-weight stress, the limit length and load-carrying efficiency etc) and dynamic behavior of CFRP cables are studied. Secondly, based on the RunYang Bridge and a cable-stayed bridge with main span of 1400m, suspension bridges with CFRP cables and cable-stayed bridges with CFRP stay cables are designed, in which the cable's cross-sectional area is determined by the principles of equivalent cable strength and stiffness, by using the finite element analysis software MIDAS/Civil, 3D nonlinear aerostatic analysis procedure BSNAA and aerodynamic analysis procedure BSLFA, the static behavior, dynamic behavior, wind stability and seismic behavior of the cable-supported bridges using either steel or CFRP cables are numerically investigated.The results shows that:(1)compared with steel cables, the CFRP cables have the characteristics of smaller sag effect, higher equivalent elastic modulus, smaller self-weight stress, longer limit length and higher load-carrying efficiency and also better dynamic behavior; (2) compared with the case of using steel cables, the bridge using CFRP cables, especially under the case that the cable's cross-sectional area is determined by the principle of equivalent cable stiffness, has smaller internal forces and deformation, greater natural frequencies, and better wind stability and seismic behavior. Therefore, the use of CFRP cables in super long-span cable-supported bridges is feasible; (3) the cross-sectional area of CFRP cables should be determined by the principle of equivalent axial stiffness.