Bridge strengthening

Engineering background

The design of the B ramp bridge for the interchange of a highway meets the requirements of the current standard. However, considering that the actual load is larger than the original design load for other reasons, it is necessary to reinforce the bearing capacity of the bending normal section.

Alternative options include external prestressing, glued steel plate reinforcement and carbon fiber reinforcement sheet.

The external prestressing reinforcement method is applied in the bridge reinforcement both at home and abroad. It has the advantages of balancing a part of the load, improving its stiffness, closing the cracks, reducing the width of the cracks, and improving the performance of the cracks. However, because this method needs special tension devices, such as anchors and steering blocks, and the external prestressing tendons need anticorrosion treatment, the construction technology is rather complicated.

At present, the adhesive steel reinforcement method is widely used in China. Because of its low price and convenient construction, it does not require special tensile and tensile equipment compared with the external prestressing reinforcement method, but it is easy to rust at the interface of adhesive and steel plate, thus weakening the bond strength, thus affecting the strengthening effect.

Carbon fiber reinforcement method began in developed countries such as 1980s, Japan and other developed countries. Compared with the stick steel method, this method does not weaken the interfacial bond strength, and does not need the complex tension equipment, equipment and technology necessary for the reinforcement of the external prestressing method. Carbon fiber reinforcement method, with its excellent mechanical properties, simple construction technology, good corrosion resistance under harsh field climate conditions and good fatigue resistance under dynamic load, has been widely used in civil engineering reinforcement and reconstruction. In recent years, our country has also made great progress in this field. The research center of the national industrial building diagnosis and reconstruction engineering technology is one of the earliest units engaged in the study of the reinforced concrete reinforcement after the reinforcement of CFRP. Many research achievements have been obtained, and many engineering applications have been carried out. After rigorous technical and economic feasibility study and the consent of the owner, the carbon fiber reinforcement method was adopted.

The characteristics of reinforcement of carbon fiber reinforced polymer(CFRP) wrap

1. The ultimate bearing capacity of reinforced beams under different initial bending moment is obviously improved.

2. Under cyclic loading, the stiffness of CFRP reinforced bridge plate is almost no degradation, and has good linear elastic characteristics. The reinforced structure of CFRP has good fatigue resistance.

3. The CFRP strengthened bridge deck has little effect on the stiffness of the steel before yielding, but the stiffness of the reinforcement after yielding is quite significant, and the deformation of the bridge plate is significantly reduced.

4. The CFRP strengthened bridge deck has a considerable inhibitory effect on the development of cracks. The width, spacing and height of the cracks are smaller, the cracks become thinner, denser and shorter, and the performance of the bending cracks is improved obviously, and the corrosion resistance of the bridge plate in the bad environment is improved.