Pre-stressing FRP reinforcement method

The prestress reinforcement method refers to the application of the principle of prestress, a strengthening method of applying certain initial stress (i.e. prestress) in the additional components or original components, such as the beam body of the main beam. This method is mainly applied to:

•  the insufficient bearing capacity of the normal section or the corrosion of reinforcement in the tension section of the normal section.
• the beam deflection caused by Liang Kangwan stiffness is beyond the norm or the width of the crack in the tensile area of the beam exceeds the specification.
• it is applicable to the insufficient shear capacity of beams.

In fact, the prestressed reinforcement method has changed the original force system of the beam body. After the structure is strengthened, the mechanical behavior of the new force system under the load is different from the original structure. Due to the effect of prestress, the original load structure will have different degrees of unloading phenomenon, resulting in redistribution of internal forces of the original structure. Different from other prestressing structures or other reinforcement methods, the load of the bridge before reinforcement is composed of constant load and live load, and the tension control value of the prestressed reinforcement is read under the constant load of the superstructure, that is to reinforce the load with the load. Therefore, the effect of live load should be considered only when calculating the stress increment of prestressed tendon.

The prestressed reinforcement method is a kind of active reinforcement method, which can greatly improve or restore the bearing capacity of the bridge; the construction technology is simple, the interference of traffic is less, the equipment is simple, the manpower is short, the time limit is short, and the economic benefit is obvious. Due to the pre stress reinforcement of beam bridge, the prestressing tendons are arranged outside the beam section, which are easy to be affected by the environment, and reliable anticorrosion design is needed.

CFRP composite strengthening 

The bonding carbon fiber reinforcement method is to use a matching bond resin to protect the protective layer of epoxy mortar or cement mortar. The corroded carbon fiber sheet of the steel plate is pasted on the surface of the structure or component. The degree of the formation of the composite material is difficult to be estimated. The reliability of the reinforced component is reduced, the body CFRP is added, and the coordination with the structure or the component is added. The work will enhance the maintenance cost of the bridge at the later stage. At the same time, in order to facilitate the reinforcement of the structural members and improve the mechanical properties of the construction process, the steel plate is pressurized and the steel plate is prevented from peeling, and the steel plate is added. This method is mainly applicable to the concrete beam bridge and slab bridge when it is flexural and solid. It is necessary to adopt the necessary bolt and anchorage measures, which will inevitably be reinforced with shear. For the beam with low reinforcement or serious corrosion of steel, it can cause certain damage to the original structure, so it is generally not suitable for bending and shear reinforcement of the plate. It can achieve good effect. The reinforcement of the beam and plate with a high reinforcement ratio at the high density of the reinforcement and the complex reinforcement of the steel bar is only used to paste carbon fiber. Sheet reinforcement design. The reinforcement effect often fails to meet the requirements, and the hybrid reinforcement method can be considered. The method is also applicable to shear strength, compressive strength, seismic ductility reinforcement and repair after earthquake damage.