The current reinforcement method is divided into two categories in principle: passive reinforcement and active reinforcement.
Passive reinforcement
Directly increase the tensile reinforcement material in the tension zone of the component . Such as sticky steel reinforcement, external bonded carbon fiber reinforced polymer( CFRP) materials, etc.,
The characteristics: only live load stress and the stress of the constant load .
The defect of passive reinforcement:the carbon fiber cloth as an example.Reinforced weak components of the bridge, the design will generally consider segmented force. Compared with the original reinforced concrete force, passive reinforcement only bear the increased load, and its stress and strain is relatively lag. Generally in the limit state, the stress can not reach the tensile strength designed.
According to the study, it is shown that the tensile strength of the high-strength materials is difficult to be obtained due to the step-by-step CFRP reinforcement .When we strengthen the bridge,the high strength FRP materials can’t play a main role, generally 30% to 70% of the material no effect. In order to further improve the utilization of materials, there has been active reinforcement.
Active reinforcement
First apply prestressing to tension zone，then form a prestressed reinforcement system such as a prestressed carbon fiber sheet reinforcement system and an external cable reinforcement technique.
This reinforcement method is characterized by the post-reinforcement material active force.Relying on pre-stressed effect, to improve the original reinforced concrete bridge .Indirectly, achieve the purpose of reinforcement reinforcement. At the same time, the prestressing of the reinforcement material can solve the problem of stress and strain lag , improve the utilization rate of the material and create a good reinforcement effect.
