On April 28, 2022, Shandong Bridge was officially opened to traffic, becoming the first carbon fiber stayed cable vehicular bridge in China.
The highlight of the bridge is the use of carbon fiber composites in the stay cables.
Carbon fiber is a kind of engineering material with light weight, high strength and excellent performance. It is an indispensable key material in national defense, aerospace, major infrastructure construction and other fields, and has important strategic significance for its research, development and application.
LZOW scientific research team overcame the difficulties in processing, anchoring and engineering application of large tonnage domestic carbon fiber cable, and formed the application technology and products of kiloton carbon fiber cable;
It has created many firsts in the application field of carbon fiber civil engineering;
The world's largest span and the first domestic vehicular bridge using carbon fiber stayed cables,
China's first 1000 ton carbon fiber cable engineering application.
The successful implementation of this project has achieved a major breakthrough in the application technology of Chinese carbon fiber.
Reasons for the Application of Carbon Fiber Composite Cable in Bridges
The performance of bridge cables has become a decisive factor in bridge design, construction, service life and safety performance.
Corrosion is also the main reason for the damage of bridge cables and slings, which requires high resistance to fatigue and corrosion of materials.
Carbon fiber materials have excellent corrosion resistance, fatigue resistance, strength, elastic modulus, etc., so some scholars try to use carbon fiber reinforcement as the material for making stay cables and slings.
For example, the stay cables of Winterther Storchenbrooke Bridge, built in 1996, are partially made of carbon fiber composites. The bridge uses two stay cables made of carbon fiber composites, and each cable is composed of 241 5 mm carbon fiber composite tendons.
At present, the Carbon Fiber Composite Cable[CFCC] and reinforcing bars are still in the development stage and are being continuously applied to bridge engineering, especially the carbon fiber cable, which has shown great potential in solving the span, life, wind and rain resistance vibration of cable-stayed bridges/suspension bridges.
With the continuous progress of science and technology, the continuous improvement of the performance of carbon fiber composite and the decline of its cost, the proportion of its application in cables and slings will continue to increase.
The cable used in bridge engineering is also generally made of high-strength steel, and the new CFRP is gradually applied to bridge engineering.
For traditional steel cables, the advantages of CFCC are:
1、 Small creep and low relaxation rate
CFCC has the properties of small creep and low relaxation rate. The test shows that when the stress level of CFRP reinforcement is maintained at about 60% of its strength, the creep after 1000h is almost zero, and the stress relaxation is less than 1%;
The test results of CFRP reinforcement used by DSI in Germany for DYW1CARB system show that the relaxation rate is 0.8% after 1000h and the creep rate is 0.01% after 3000h.
2、 Good fatigue resistance and corrosion resistance
The cable of bridge is usually subject to wind load and dynamic load on the bridge deck, and the long-term stability of the bridge is determined by the fatigue resistance.
The anti fatigue ability of fiber composite depends on its failure mode, that is, from the weak link to the joint surface gradually. At this time, the joint interface between the fiber and the matrix will prevent crack growth, and the carbon fiber is particularly outstanding in this respect.
It has been proved that the CFCC of 19 monofilaments is × The fatigue strength is about 4 times of that of the steel cable under the same conditions.
Steel is generally not acid resistant, especially acid containing chloride ions. Even aluminum containing stainless steel will be corroded quickly in this medium.
However, CRFP can be used for a long time in acidic media containing chloride ions. The composite material made of alkali resistant carbon fiber can also be used in strong alkali medium.
The nonmagnetic performance and good anti-corrosion performance of CRFP make it unnecessary to take anti-corrosion measures for the structure, thus making the maintenance work easier.
As the "lifeline" of suspension bridges, the service life of suspension bridges is seriously affected by the poor corrosion resistance of steel cables.
The carbon fiber composite cable has strong corrosion resistance, which can be well adapted to the highly corrosive marine atmosphere environment and greatly improve the service life of the bridge.
3、 The coefficient of thermal expansion is small
Cantilever construction is widely used in modern cable-stayed bridges. The internal force and deformation of the structure caused by temperature difference (mainly sunshine temperature difference) in the construction project have a great impact on the continuity of the construction;
At the same time, in the operation stage, the internal force caused by temperature difference is the same as the deformation. Replacing traditional steel cables with CFCC can basically eliminate the internal force and deformation caused by cable deformation, because the thermal expansion coefficient of CFCC is very low, which is only about l/12 or lower than that of steel cables.
4、 Improve the effective bearing capacity and wind rain vibration resistance of the bridge
Thanks to the high specific strength and specific modulus of CFRP, when CFRP is used as the main cable of suspension bridge, the use of CFRP material as the main cable of super long span suspension bridge will greatly reduce the percentage of main cable self weight stress in the main cable stress, and increase the percentage of live load stress, thus improving the utilization of materials, and the vertical bending fundamental frequency, transverse bending fundamental frequency and torsional fundamental frequency of the structure will also be greatly increased.
As cable of cable-stayed bridge, CFCC can reduce the possibility of early damage caused by resonance during operation.
In addition, the interface between carbon fiber and matrix has the characteristics of strong vibration absorption ability and large vibration damping. For example, the light metal alloy beam will stop vibrating after 9 seconds when the same size beam is used for the same test, and the surface carbon fiber resin composite beam will stop vibrating after only 2.5 seconds. Therefore, CFCC has better weather vibration resistance.
5、 Achieve greater span. More than 85% of major engineering structures are self weight, and huge weight means high load, high seismic response and high cost of structures
At present, bridge cables are made of steel wires. Due to the material characteristics of steel, the ratio of steel cables is large, which will limit the limit span and bearing efficiency of steel cable system bridges.
The unit weight of carbon fiber composite is only 1/5 of steel. Compared with steel cable, the use of carbon fiber composite cable can improve the limit span of suspension structure,The research shows that the limit span of steel cable is 7.7km, and that of carbon fiber composite cable is 37.5km. Therefore, the bridge can achieve a larger span.