Quote

Today's world is not peaceful, a variety of accidental or deliberate explosions occur around the world, large-scale air strikes in the war on the ground targets while accurately attacking, but also caused great damage to buildings, causing great losses to human life and property. Usually, the capacity of civil buildings to resist explosive load is very small. The collapse of buildings and the high-speed splash of structural debris caused by the insufficient anti-explosive bearing capacity of structures seriously threaten the safety of indoor personnel. How to improve the anti-explosion capability of existing buildings and ensure the safety of people's lives and property has aroused widespread concern in civil engineering circles around the world.

Now most of the buildings are reinforced concrete structures, which urgently needs an economical, efficient and convenient method of anti-explosion reinforcement. With the development of new material technology, a variety of high-tech reinforced fiber materials have been developed, such as glass fiber (GF), carbon fiber (CF), aramid fiber (AF) and so on. Of all the reinforcing fibers, CF is currently the most sophisticated and used in the field of civil engineering.

Carbon fiber reinforced polymer (CFRP) has excellent mechanical properties. Because of its high strength, light weight, extremely thin veneer, wide adaptability and convenient construction, it shows excellent technical and economic benefits, and has a broad development prospect. And CFRP has the characteristics of fatigue resistance, corrosion resistance, creep resistance, material size stability, construction convenience and other materials can not be compared, not only in the aerospace, aviation and military fields is irreplaceable high-tech materials. With the maturity of technology, popularization and substantial increase in sex/price ratio, it has been widely used in industrial, construction and other civil fields.

1 Characteristics of bonding carbon fiber cloth reinforcement technology

Carbon fiber reinforced polymer (CFRP) reinforcement is widely used in civil engineering in recent years. In this method, carbon fiber fabrics arranged in the same direction are impregnated with epoxy resin and bonded to the surface of the structure at room temperature. As a new whole, the two fabrics are loaded together. It is a very simple and effective reinforcement method. The reinforcement method has the following characteristics:

1.1 High strength and high efficiency. The tensile strength of CFRP is about 10 times that of steel, and the modulus of elasticity is equal to that of steel (about 0.01); the specific strength (i.e. the ratio of strength to density of material) can reach more than 2 000 MPa /(g.cm-3), while the specific strength of A3 steel is only about 59 MPa /(g.cm-3), and its specific modulus is also higher than that of steel.

1.2 Light weight and thin thickness. The most mature technology is also the largest amount of consumption. Degree is about 0.1-0.2 mm, area density is about 1/100 of the steel plate; after strengthening with CFRP, the quality and size of the original structure will not be increased and the use space will not be reduced.

1.3 Good durability and corrosion resistance. Carbon fiber cloth can be used at 2 000 C, and it is not melted or soft in 3 000 C non-oxidized environment. Carbon fiber cloth materials have good corrosion resistance in various environmental conditions, and can resist the corrosion of acid, alkali, salt and atmospheric environment often encountered in buildings. It has better fatigue resistance. Therefore, all kinds of projects can be reinforced by CFRP.

1.4 Construction is convenient. Carbon fiber cloth is soft, easy to process, manual operation, no large-scale machinery, no wet operation, high construction efficiency. If suitable binder is selected, rapid reinforcement can be achieved.

1.5 The scope of application is wide. It is not limited by the shape of the structure, CFRP can be pasted in the tension zone, which can improve the bearing capacity of the flexural members and supplement the deficiency of the reinforcement. Sticking to both sides of the beam can improve the shear capacity of the beam. Winding around the outside of the concrete column restrains the lateral deformation of the concrete, which can improve the bearing capacity and axial compression ratio of the column. The nodes wrapped around the truss can strengthen the joints.

It is suitable for beams, slabs, columns, bridges, tunnels, chimneys and other structures of various industrial and civil buildings. It does not change the shape of the structure and does not affect the appearance of the structure.

1.6 The quality of construction is easy to guarantee. Perfect workmanship and well-trained workers can achieve an effective pasting area of more than 99%, low maintenance costs.

2 Overseas research on the blast resistance of reinforced concrete structures strengthened with carbon fiber sheets

Khalid M.Mosalam is the CFRP and the CFRP and the Computer and the Computer and the CFRP and the CFRP and the Computer and the Computer and the CFRP, and the example of the the example, and the the CFRP is is be the example to the the example.

(1) The reinforced concrete slab strengthened by CFRP has increased its bearing capacity by 2 times.

(2) Under explosive loading, the overall stiffness and strength of reinforced concrete two-way slabs strengthened by CFRP are greatly improved. Due to the destruction of concrete, the base frequency of the unreinforced plate is reduced by 85%, and less than 50% after reinforcement. In addition, the maximum displacement of the CFRP strengthened plate decreases 40% to 70% before the reinforcement.

(3) Under explosive loading, CFRP reinforcement of reinforced concrete slabs limits the time and space expansion of the yielding tendons, and significantly improves its ability to resist local failure.

(4) Double side reinforcement is the best.

3. Summary

The advantages of CFRP reinforcement technology are obvious. Many scientific research institutions at home and abroad have carried out a lot of research work, and most of them have been applied to practical projects, which is recorded in many documents. However, the research on CFRP reinforcement technology is mostly confined to static load, and there is no report on the research of reinforced concrete members strengthened by CFRP under explosive load in China.

A series of experimental studies abroad have shown that CFRP can effectively improve the anti-explosion capacity of the structure, and its overall bearing capacity and the ability to resist local damage have been significantly improved. However, the shear strength of CFRP is very low, the elongation is small, less than 1/10 of the general steel, the stress-strain relationship curve is almost linear, no plastic platform, in this sense, CFRP is a brittle material, in the design and construction should pay attention to. The dynamic performance of CF material itself, the factors influencing the effect of CFRP reinforcement on existing buildings under explosive load, the design method, construction technology and other issues need to be further studied.