Carbon Fiber Reinforcement

1 Zhang Zhizhong’s residence

The Mansion of General Zhang Zhizhong is located on Zhongshan North Road, Gulou District, Nanjing. It was built in 1959 and has a total area of about 1,000  m2. The entire house is in the shape of an airplane and is divided into a nose, two wings and a fuselage. The nose is a two-story tall building; the wings and fuselage are a one-story building with a floor height of 5  m. The renovation and reinforcement of the building is conducive to ensuring its original historical appearance; the preservation and restoration of its mansion is conducive to the continuation of the historical context, the protection of my country’s excellent cultural heritage, and the material carrier for modern people to see things and think about people. Carrying the spiritual sustenance of modern people. Therefore, it is of far-reaching significance to repair the residence of General Zhang Zhizhong.

2 Features of roof truss

This article will strengthen the fuselage part of the mansion. The structure of General Zhang Zhizhong’s mansion is a light brick-wood structure, the roof truss part is an all-wood frame structure, and the surrounding walls are brick walls. The total construction area is 350  m2. The seismic fortification classification of the building is Class C, the seismic and crack resistance strength is seven degrees, and it is a Class III site category. The structural safety level of the building is Class II, and the design service life is 50 years. The roof truss is in the form of a wooden roof truss. There are six triangular herringbone wooden roof trusses, which are composed of upper string, lower string, belly rod, purlin and rafter. After inspection, the author found that the fourth wooden roof truss had undergone major reinforcement and transformation (see Figure 1).

The study found that the new wood after reinforcement has no obvious damage and deformation, the old wood is slightly corroded, and there are some moth-eaten phenomena, and the upper chord, diagonal brace and bottom chord of the old wood have small cracks, but it does not affect the main structural performance . The most serious situation is the third truss. The side of the upper string of the wooden truss has a shrinkage crack with a width of 9  mm, with a diagonal pattern and a slope of 1/17. The surface is slightly rotted and has a slight moth-eaten phenomenon. There are many shrinkage cracks in the purlin part. The diagonal brace has 7  mm×750  mm×10  mm shrinkage cracks, and the surface layer is decayed, but there is no obvious sign of heart decay. There are 5  mm×2 300  mm×11  mm shrinkage cracks on the side of the lower string, slightly twisted, the surface layer is slightly decayed, there are slight moth-eaten phenomena, and there are many small cracks at the nodes. Wood roof truss and masonry structure supports have high moisture content and slight corrosion.

3 Application of new reinforcing materials in the repair of wooden roof frames of ancient buildings

The main problems in the wooden roof truss to be reinforced are more shrinkage cracks and corrosion of the roof truss. The length and depth of the cracks are different. Some cracks are shrinkage cracks formed after long-term air-drying of wood. There are many such cracks. There are also some cracks that are surface corrosion that occurs after the wood is damp, and the handling of such cracks must be careful and patient. When dealing with cracks, first use a brush or other tools to thoroughly clean the deposits and floating ash at the cracks. After the reinforced surface is completely exposed and the cleaning is completed, spring the line on the wooden beam and determine the outline, especially the rotten place. Thoroughly remove the rotten wood with a blade and control the surrounding moisture. Then determine the size of the carbon fiber cloth according to the elastic thread, and fill and level the cracks with the special tung oil and lime mixture for wood. Finally, the cut carbon fiber cloth is tightly wound around the reinforced wooden frame. When pasting carbon fiber cloth, pay attention to the reliable lap of the carbon fiber cloth, and leave enough lap length, and ensure that the carbon fiber structural glue is in full contact with the wood and carbon fiber cloth, and the carbon fiber structural glue should be fully infiltrated into the carbon fiber filaments as much as possible (The needle can be used to inject glue in the details). After pasting, use a special rolling tool to continue rolling to remove internal bubbles and ensure adequate bonding. After bonding, apply dipping glue to maintain the carbon fiber cloth.

4 Construction effect of carbon fiber reinforcement technology

After the wooden roof truss of General Zhang Zhizhong’s residence was reinforced with carbon fiber this time, its comprehensive mechanical properties have been greatly improved. The compressive and deformation resistance of the wooden roof truss has been further enhanced, and the further spread of cracks has also been reduced. In addition to the reinforcement of the wooden roof truss, the author also used the reinforcement method to thoroughly reinforce the surrounding walls of the auditorium. The reinforced wooden roof truss not only meets the existing safety load requirements, but also provides strength support for the later reconstruction of the large conference room.

It can be seen that the use of carbon fiber reinforcement technology can greatly reduce the input of manpower and material resources, and has significant economic benefits. At the same time, the conference room has repeatedly broadcast live videos of the hospital's operating room, providing a place for medical staff to study and study, which has good social benefits. The project took only one month from testing the performance of the wooden roof truss to the final reinforcement, while the construction of the carbon fiber cloth only took 4  d. Compared with the reinforcement of iron fasteners, carbon fiber reinforcement technology does not require on-site painting of anti-rust paint and other coatings, and it has less environmental pollution. Compared with the reinforcement of concrete, there is no large amount of materials and equipment stacked on site, and the construction area is small.

Generally speaking, carbon fiber reinforcement has the advantages of short construction period and low construction difficulty. Compared with traditional reinforcement methods, carbon fiber reinforcement technology is safe, reliable, and environmentally friendly. For projects that pursue time efficiency, carbon fiber reinforcement is a time-saving tool.

5 Conclusion

Culture is the soul of a city. City history and culture are the precipitation of the wisdom of predecessors and an important symbol of the city's connotative quality and characteristics. The old building is the carrier of historical context, which records the humanities of different regions, records the trajectory of changes in the times, contains rich historical and cultural connotations, and is the material basis of multiculturalism. If modern people can make full use of science and technology to carry out reasonable repairs to these old buildings, so that these old buildings can not only meet the use function of modern society and realize objective economic value, but also can effectively protect various cultural relics in different regions and realize cultural relics. So the protection and repair of old buildings is richer in inheritance value, which is also the essence of inheritance and development