Bridge reinforcement

Preface

It has been more than ten years since carbon fiber fabric was used to reinforce RC structures, and it has been widely used abroad. In China, CFRP fabric has become a new field of geotechnical engineering. In recent years, carbon fiber reinforced polymer (CFRP) fabric has been widely used in the reinforcement of highway bridges. It is the first time that CFRP fabric is used to reinforce bridges in our city. The reinforcement project described in this paper is an example of strengthening the old bridge with CFRP fabric reinforcement technology.

Project

Jinhua Bridge is located on Nanshan River in Yunfu City. It is 56.4 meters in length and 9.5 meters in width. The upper part of the bridge is constructed with 2 *25m reinforced concrete rigid frame arch. The first span is supported by three pieces of rigid frame arch. The lower part is gravity pier and abutment. The foundation is shallowly excavated and enlarged. The bridge has been operating for more than 20 years, and various diseases have appeared.

In April 2005, Guangdong Highway Engineering Quality Monitoring Station carried out a comprehensive inspection of Jinhua Bridge, the inspection situation is as follows. There are two or three small cracks in both sides of arch rib and arch foot. The crack width is 0.15mm. The longest crack length is about 30cm. There are fewer cracks in the arch foot of middle arch rib. Cracks appeared at the root of some diagonal braces, the width of cracks was about 0.6 mm, and the concrete at the support of piers under chord rods was damaged and bars were exposed. This shows that the bridge has serious safety problems and needs urgent reinforcement and maintenance.

Selection of reinforcement schemes

Since the bridge is located in the busy traffic section of the city, it is required that the time for traffic closure should be as short as possible. At the same time, since the bridge was built in the 1980s, the technical standards adopted at that time were relatively low, so it is required to reinforce the old bridge as far as possible without increasing the load. For this reason, this project adopts the CFRP fabric reinforcement scheme.

Characteristics of CFRP fabric reinforcement scheme

No increase in dead load and section size.

Simple construction

Carbon fiber reinforced polymer is used to reinforce the original structure without causing any new damage.

It can effectively seal cracks in concrete.

Carbon fiber fabric has excellent chemical resistance.

Does not affect the appearance of the structure.

Conclusion

(1) The results show that the old Jinhua Bridge strengthened by CFRP fabric can basically restore the original bearing capacity.

(2) The CFRP fabric reinforced section bridge is a new technology. The CFRP sheet is light, the site pasting does not need heavy equipment, the facilities are simple and convenient, and it is easy to be used in highway bridges.

(3) At present, the methods of bonding carbon fiber sheets are often supplemented by crack grouting and crack sealing.