Why is it structural strengthening and reinforcement?

According to national regulations, the service life of particularly important and monumental buildings is 100 years, the service life of ordinary buildings is 50 years, and the buildings that are replaced quickly are 25 years. The buildings in use should be maintained and inspected regularly.

Therefore, in order to ensure the durability of the building, maintenance and reinforcement are very necessary projects. Construction can only be achieved through construction. When determining the quality of construction, it is necessary to conduct inspections on the overall structure, a certain part or construction, and the structure that is judged as a hidden danger must be reinforced. When designing a building, there will be some serious errors or poor design. For example, due to the low quality of individual designers, incomplete understanding of hydrogeology and other conditions, too high estimates of foundation bearing capacity, undercounting or undercounting affect the bearing of the structure. In addition, there will also be reconstructions of the original buildings without passing calculations, resulting in insufficient load-bearing capacity of the original structure and directly changing the load and purpose of the building in use. For these problematic buildings, we don't have the energy and time to tear down and rebuild them. We only have to strengthen them to extend their service life.

Principles and points of structural strengthening and reinforcement

Pay attention to several basic principles of strengthening buildings:

①Satisfy the three characteristics of structure, applicability, durability and safety. Before reinforcement, the original structure must be identified and tested. When it is identified that reinforcement is necessary, the scope of reinforcement can be a specific area or a specific construction, or a whole building.

②Due to mechanical damage caused by high temperature, corrosion, freezing and thawing, etc., resistance should be taken to reduce unfavorable factors. The adoption of this countermeasure can ensure that the structure is safe and reliable after reinforcement.

③When strengthening the structure, it is necessary to take into account the economic effect, try to reinforce without stopping production, reduce the dismantling of components and not damage the original components.

④ When strengthening, pay attention to safety precautions. Once a structure with serious defects is found, stop immediately and eliminate hidden dangers before continuing construction.

⑤ When carrying out reinforcement design, consider feasible construction methods to ensure that the original structure and the current structure work together.

The reinforcement plan should proceed from the perspectives of practicability, economy and safety, and combine the characteristics and requirements of the structure to strengthen the surrounding environment. The plan is to reinforce the original structure, taking into account the application of new technologies, new processes, and the selection of new materials.

What method is used to structural strengthening and reinforcement

Common methods: According to different situations, adopt different methods to achieve safety and economic results. The basic methods are:

(1) Replacement method: The original structure has poor toughness and low-strength materials are replaced with materials with good toughness, which is mainly suitable for places where the concrete in the compression zone has serious defects. It has the advantages of small space occupation, simple process and low cost, but the construction time is long, and safe support and unloading must be ensured before the reinforcement concrete finally sets.

(2) Increasing the cross-section: According to the actual force of the original structure, add an outer layer of concrete in the compression zone or the tension zone for pouring. This method is suitable for the reinforcement of general structures such as walls. The application range is relatively broad, and the practicability is relatively strong, mainly because the construction is relatively simple. However, the maintenance cycle is long and the workload is relatively large, which certainly affects the appearance and clearance of the structure.

(3) Increase the fulcrum: reduce the span of the flexural member, thereby reducing the load of the reinforced structure, in order to improve the bearing level, this method is applied to beams and slabs and other structures. The main reason is that this method is simple and reliable, but it also easily damages the construction function and original appearance of the original building and reduces the space used by the owner.

(4) Pre-stressing: applying higher-strength steel bars, pre-stressing struts outside the body to be reinforced, etc., applying pre-stressing so that the two can be stressed together. Overcome the excessive forward stress of the original construction, change the section force, and improve the rigidity and bearing capacity of the structure. For this technology, the requirements are high and the construction is difficult. However, this work occupies a small space, can shorten the construction period, and the reinforcement effect is quite obvious.

(5) Externally bonded steel: flat steel and hoop are mostly used for round components. It not only increases the load-bearing capacity of the structure, but also does not lead to an increase in seismic action caused by the stiffness. However, this method is not suitable for use in places with high temperature exceeding 60~C, because the construction difficulty is relatively high and it is difficult to guarantee the quality.

(6) Pasting steel plate: for concrete compression. The tension members are reinforced. This work requires a professional team to operate, the effect and quality of the reinforcement are related to the process, and special fire prevention treatment is also required. However, his construction was fast, and the appearance and clearance of the original structure were slightly affected.

(7) Wire winding method: This is a reinforcement construction method, the most important thing is to improve the displacement ductility. After this method is implemented, its own weight will be relatively small, other things will not change much, and the construction environment is not demanding. However, its effect is not very obvious, and the bearing capacity of steel reinforcement components is not significantly improved.

New reinforcement material-FRP

Fiber reinforcement. The application of high-strength carbon fiber has high tensile properties of its own material and its own weight is relatively small. Generally, it can reach about 10 times the tensile strength of ordinary steel. The stiffness of carbon fiber of high elastic modulus is 2 to 3 times that of ordinary steel, while glass fiber is only one-fifth of steel. Carbon fiber has high corrosion resistance and long-lasting resistance. Its maintenance cost is relatively low, the materials are not easily corroded, and the construction is relatively light, and there will be no obvious changes to the exterior dimensions of the building.

The necessity of structural reinforcement and strengthening

The development path of the construction industry in modern times can be roughly divided into such several periods. The first stage is a large scale of new construction, and the second stage is the joint development of maintenance, renovation and new construction. Our country is officially in this period. In order to meet the needs of society, new buildings are constantly increasing. However, due to human life and production requirements, the aesthetic level of buildings has increased, and the buildings in the past few years have not fully met the needs of residents. Therefore, the building must be externally repaired, reinforced and transformed. In order to successfully transition to the second stage, it has greatly promoted the improvement of the enterprise's level of building appraisal, which is conducive to the correct implementation of the verification, and also invested a lot of manpower and material resources in the research of reinforcement projects. A few days ago, our country is gradually moving towards the second stage. At present, the development of maintenance and renovation abroad is accelerating. This project has become an indispensable part of the construction industry. Western countries have gone through these stages, and our country must also go through this period of transition. . Now, our country is paying attention to the renovation of the old urban area together with new development projects. With the introduction of the rules and regulations for the maintenance, modification and reinforcement of old buildings, it further emphasizes that this project is getting the attention of the country and the people. At the same time, my country's emphasis on the reinforcement industry has also increased, and this industry has gradually become a part of the construction industry.

With the continuous improvement of the level of urbanization in my country, the demand for building maintenance is also increasing. In recent years, many cities have been repairing and protecting the buildings in the old city to beautify the urban environment. Nowadays, although my country's economy is developing rapidly, the per capita level is low, and the living cannot only rely on newly built buildings, so the maintenance of the old city is inevitable. In the future development, we should focus on the maintenance and construction of the old city.

Concluding remarks

In recent years, my country’s construction industry has developed too fast, and people’s requirements for buildings have become higher and higher. Not only are they required to live comfortably, but they also require beautiful appearance. For these requirements, we only need to continuously innovate our construction technology and construction. Method, selecting appropriate materials and strengthening the building will meet the needs of customers. For a specific structure, there is no fixed pattern for reinforcement. Therefore, under the conditions of compliance with the reinforcement specifications, the appropriate Hong Kong style can be selected according to the actual situation, and special treatment can also be carried out according to the actual situation to achieve the best effect.