Project Overview 

Awu Bridge is located at K283+700 of Line G212. The upper structure is a 1-13m reinforced concrete hollow slab, the lower structure is a U-shaped abutment, and the open-cut expansion foundation is used. In the bridge inspection, it was found that there were cracks distributed in the transverse bridge direction on the bottom surface of almost every plate. Some are even transverse seams of the whole board. The crack width is about 0.2mm, and the cracks are mainly distributed in a section near the middle of the span. Considering the need for flood discharge during the flood season, the contract construction period is only 40 days. May 1st to June 10th. The construction period is quite tight, in line with the principle of simple construction technology and economical application. The bridge-span structure is reinforced by the reinforcement method of carbon fiber cloth.

Design Points 

(1) After unloading the original bridge deck pavement and hinged joint concrete. Close plate cracks. Paste three layers of two layers of 25em wide carbon fiber cloth and a layer of lamination on the bottom of each board. Improve the tensile strength of the plate body. Limit crack development.

(2) Carbon fiber composite materials

1) Carbon fiber should use small tow polypropylene hydroxyl (PAN-based fiber) not more than 12K. 1. The fiber mass per unit area of single-layer carbon fiber cloth should not be lower than 200g/m2, and ~ i" should be higher than 300g/m2.

2) The lap length of the fiber composite material along the fiber stress direction should not be less than 10cm. When using multiple layers or multiple fiber cloths, the overlapping positions should be staggered from each other. The fiber direction should be consistent with the tension direction of the component.

3) Adhesive The adhesive used in this design is A-grade adhesive, and unsaturated polyester resin, alkyd resin, etc. shall not be used as the impregnating and pasting adhesive. The safety performance index of the repair glue for crack injection or pressure infusion of the main beam must meet the requirements of the "Safety Performance Index Table of Crack Repair glue (Injection)"

Benefit Analysis 

After the bridge is reinforced, the whole board is in a state of stress. When the heavy vehicle passes, the lower deflection of the plate body is significantly reduced, and the vibration of the plate body is also significantly reduced. A total of 4 G212 lines, including Awu Bridge, were reinforced, all of which were pasted with carbon fiber cloth. After nearly two years of operational observation, the reinforced bridge has no potential safety hazards, the cracks at the bottom of the slab are effectively suppressed, and the reinforcement effect is good.