The technology of cement concrete bridge reinforcement is very important. Only by understanding the original intention of reinforcement can we better solve practical problems. The handling of every detail is very critical. Zhongda Consulting will explain to you the technology of cement concrete bridge reinforcement.
1. Overview
Bridge projects require huge investments and play an important role in the development of the national economy. Therefore, people always take various measures and leave no stone unturned in the construction of bridges. Ensure project quality. However, as time goes by, newly built bridges will eventually become old bridges, and damage and destruction will gradually occur. According to the laws of nature, this is an irreversible process. One of the common problems is the reinforcement of the bridge superstructure. At present, the domestic reinforcement methods of bridge beams mainly include: external additional prestressing method; increasing cross-section method; changing structural system method; external beam pasting steel plate method; pasting carbon fiber cloth method and Chemical grouting method, etc.
II. A detailed introduction to the reinforcement methods of bridge beams
(1) External additional prestressing method
The external additional prestressing method refers to the use of prestressed The principle of stress is a reinforcement method that applies a certain initial stress (prestress) to additional components or original components to offset part of the self-weight stress and play an unloading role, thus greatly improving the load-bearing capacity of the beam. The advantages of the external prestressed reinforcement method are:
1. When the self-weight increase is very small, the stress condition of the original structure can be greatly improved and adjusted, and the stiffness and crack resistance of the load-bearing structure can be improved;
2. Since the increase in the weight of the load-bearing structure is small, it has little impact on the stress conditions of the pier and foundation, which can save the reinforcement of the pier and foundation;
3. On the bridge The operational impact is small, and reinforcement construction can be carried out without restricting traffic;
4. The prestressed reinforcement method can be used as a temporary reinforcement method for bridges passing heavy vehicles, and can also be used to permanently increase the load of the bridge Level measures.
(2) Increasing cross-section reinforcement method
The enlarging cross-section reinforcement method refers to pouring a new layer of concrete above or below the original bending member and adding corresponding Steel bars are used to improve the load-bearing capacity of original components. It is a reinforcement method commonly used in engineering. To reinforce the cap beam, a new cap beam is pasted under the old cap beam. The main structure of the new cap beam is three I-beams welded by steel plates.
(3) Changing the structural system method
This method of reinforcement and transformation is to improve the load-bearing capacity of the bridge by changing the bridge structural system. There are many ways to change the structural system, but they often require operations under the bridge or the installation of permanent facilities, thereby reducing the clearance under the bridge, or affecting traffic during construction, so the impact on traffic volume must be considered.
(4) Beam external pasting steel plate method
Beam external pasting steel plate method is to use epoxy resin series adhesive to paste the steel plate on the tensile edge or weak point of the reinforced concrete structure. It is a reinforcement method that forms an integral part with the structure and is used to replace the additional reinforcing steel bars that need to be added to improve the load-bearing capacity of the beam and achieve the reinforcing effect. Bonding steel plates to strengthen bridges has many advantages. It has been widely used at home and abroad in the past and has become a traditional reinforcement method. The advantages of this reinforcement method are:
1. There is no need to destroy the geometric dimensions of the original reinforced structure;
2. The construction process is simple and the construction quality is relatively easy to control;
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3. The construction period is short.
(5) Pasting carbon fiber cloth (plate) method
The test results show that after being reinforced with carbon fiber sheets, the ultimate load of flexural members is greatly increased. The bending stiffness and crack resistance of the structure have been improved to varying degrees. This reinforcement method has been widely used in seismic reinforcement of bridges in Europe, the United States and Japan, and corresponding technical specifications have been compiled.
Its principle is similar to that of pasting steel plates, but it has some unique advantages, as follows:
1. Using carbon fiber cloth reinforcement technology can improve the bending resistance, shear bearing capacity and stiffness of box beams; Increase the strength and safety reserve of the bridge structure. At the same time, the high strength and high elastic modulus of carbon fiber materials can effectively restrain the deformation of concrete and limit the development of cracks.
2. Carbon fiber has good durability and can It resists various corrosion caused by the atmospheric environment. Using this reinforcement method to treat the structure not only eliminates the need for regular maintenance and saves a large amount of maintenance costs, but also can protect the internal concrete structure. Achieve the purpose of double reinforcement;
3. The construction is convenient, the work efficiency is high and the construction quality is easy to ensure, and the impact on the road opening can be reduced to a minimum. Compared with traditional reinforcement methods such as pasted steel plate reinforcement, carbon fiber reinforcement has many outstanding features and advantages.
(6) Chemical grouting method
Cracks are a common phenomenon in the main stress-bearing structures of ordinary reinforced concrete bridges. The use of chemical grouting to repair cracks in concrete structures can restore the integrity and performance of the structure. It is a technology widely used in bridge maintenance and reinforcement at home and abroad. However, for cracks caused by insufficient structural bearing capacity, in addition to chemical grouting repair methods, other corresponding reinforcement measures should be taken to improve the bearing capacity of the bridge to ensure the safety and reliability of the bridge structure. According to the different degrees and locations of the development of each crack, the corresponding reinforcement measure adopted in this bridge is to paste carbon fiber. The reinforcement construction process is as follows:
1. Use epoxy chemical pressure grouting to reinforce existing cracks. Chemical grouting should be performed according to the following steps:
a Positioning of the grouting nozzle;
b Sealing the joints;
c Implementing grouting, according to the cracks and cracks in different parts Determine the corresponding model of grouting glue for different widths;
d Confirm that the grouting is completed, and remove the machine after the resin has initially set.
2. Remove the weathered or deteriorated concrete on the bottom plate of the box beam and repair it with high-strength polymer mortar.
3. For areas where the calculated stress cannot meet the stress requirements, the bottom and sides of the box beams are reinforced by pasting carbon fiber cloth. The construction steps for pasting carbon fiber cloth are as follows:
a. Polish the base;
b. Apply the underlying resin CFP (its function is to penetrate into the concrete to improve the bond between the concrete and the carbon fiber) Bonding.
c Use the leveling material CFE to repair and fill the uneven and defective parts of the beam base surface;
d Apply and paste the resin CFR, and then start to paste the carbon fiber cloth. Repeat step (4) when pasting multiple layers;
e Apply a layer of CFR resin after pasting the last layer of carbon fiber cloth.
The process technology during the construction process should be strict. Follow the relevant requirements in the "Technical Regulations for Reinforcement and Repair of Concrete Structures with Carbon Fiber Sheets" of the China Engineering Construction Standardization Association.
4. Reinforce the corbel joints with multiple layers of carbon fiber cloth.
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