Bridges are important transportation infrastructure in China. With the continuous erosion of heavy-duty vehicles and wind and rain, many highway bridges built in 1980s and 1990s have appeared cracks and other diseases. However, the bridge belongs to a long-span structure, and the environment is relatively bad. Which method to maintain the bridge has become a difficult problem. After the research and development of science and technology, a new kind of material for bridge reinforcement - carbon fiber composite has emerged.

Stress Analysis of Bridges Strengthened with CFRP fabric

1. Carbon fibre cloth with excellent tensile properties is bonded to the bottom of the girder or the inner wall of the box girder, so that it can bear the tension together with the steel bars arranged in the original structure, so as to improve the bearing capacity of the old bridge. Compared with other reinforcement methods, CFRP guarantees that the original structure will bear force together within the design load range, and changes the stress distribution of the original structure to a lesser extent.

2. Carbon fibre sheets are pasted along the direction of the main tensile stress (or orthogonal to the crack) of the bridge. The anchorage ends at both ends can restrain the cracks on the surface of concrete, prevent the cracks from expanding, improve the flexural rigidity of members, reduce the deflection of members and improve the stress state of beams.

3. The CFRP should be used reasonably to reinforce reinforced concrete beam bridge according to the actual situation. When CFRP is used to reinforce concrete members, it can not only improve the flexural bearing capacity, but also affect the failure mode of flexural members. When the amount of CFRP is too much, the failure mode of the component changes from the failure caused by the breakage of CFRP to the sudden crushing of concrete. Because carbon fiber is a fully elastic material, its working with steel bars will weaken the plastic properties of steel bars, and the ductility of components will be reduced if the amount of carbon fiber cloth is too much.

4. The failure mode of bridge structures strengthened with CFRP changes to sudden (brittle failure such as breaking or peeling). The ultimate bearing capacity of bridge structures should be calculated according to 2/3 of the tensile strength of CFRP, which can not be considered as ordinary reinforced concrete.

5. CFRP can improve the shear capacity of concrete beams. Its mechanism is similar to that of stirrups. It can also improve the deformation performance of members and enhance the deformation capacity of members.