Reinforcement and repair of building structures during the reconstruction of the building - Reconstruction of the archive building - course

Introduction

Reconstruction of buildings and structures is a complex complex task, the implementation of which requires special knowledge obtained after studying many disciplines.

The reconstruction of buildings can be divided into several stages:

- feasibility study of reconstruction;

- detailed examination of building structures and engineering equipment, determination of technical condition;

- determination of reserve of load capacity of building structures, calculation of structures for new loads taking into account the results of the survey, structures requiring reinforcement or replacement are identified;

- design of building structures reinforcement is being developed;

- design of works during reconstruction is being developed.

The purpose of the course project is to develop a structural solution for reinforcement of two structures made of different materials, to produce a variety of reinforced structures, to execute working drawings on reinforcement and to describe the rules and procedure for carrying out reinforcement work.

Measures to protect building structures from corrosion.

7.1 Protection of steel structures against corrosion

One of the main conditions of durability and reliability of the structure is protection of steel structures from corrosion during operation and reconstruction. Building structures are characterized by corrosion damage caused by chemical corrosion, direct exposure of metal to aggressive liquids or gases; electrochemical corrosion - the effect of moisture on the surface layer of the metal. Corrosion, depending on the degree of aggressiveness of the medium and the degree of humidity of the air, proceeds in a large range - 0.05... 1.6 mm per year. Corrosion rate from 0.1 mm per year and more dangerous for structures, as it reduces thickness and cross-sectional area by 40... 100% and incapacitates structures.

The reduction of corrosion losses, in addition to secondary protection, is achieved by the use of alloying additives, as well as the use of the concentration principle in the design, i.e., by giving sections of elements of a smaller surface. The structural shape of the sections plays a large role in corrosion damage. In particular, the circular section is the most resistant against corrosion. Corrosion control measures consist in reducing factors contributing to corrosion (exhaust ventilation device, various traps, roof care), as well as in special protection of steel structures.

The main method of protecting steel structures from corrosion in the conditions of used buildings is the use of protective coatings corresponding to an aggressive environment. Atmospheric-chemically resistant paint coatings, thin films, plastics, more resistant metals are applied to the surface of structural elements.

The most important stage of corrosion protection is the preparation of the surface of the elements for coating. Poor quality preparation nullifies any protection, since the corrosion process occurs under the coating, it peels off and practically does not protect the structure from environmental effects. The surface of the elements should be cleaned (by mechanical or chemical method) of rust, old coatings, fat and other contaminants.

After preparation of the surface of structural elements depending on the operating environment in which it operates and in accordance with the requirements of [3], paint coatings are applied.

7.2 Protection of reinforced concrete structures against corrosion

Reinforced concrete is a complex material, in structures of which steel reinforcement usually perceives tensile stresses, and concrete - compressive. In traditional structures, concrete plays the role of protecting reinforcement from corrosion and high temperatures in a possible fire. Thus, concrete is directly in contact with the environment in the reinforced concrete structure. Therefore, many cases of early damage of reinforced concrete structures associated with corrosion of reinforcement are explained by the discrepancy of their resistance to operating conditions, either due to underestimation of operating conditions during design, or due to manufacturing defects, in particular, the displacement of reinforcement beyond the tolerance in the thickness of the protective layer, not sufficient density of concrete or a large dispersion of permeability indicators. The factors under the influence of which concrete loses protective properties are divided into: physical, chemical and physicochemical.

When developing reconstruction projects of buildings, it is necessary to provide means to ensure corrosion resistance of concrete and reinforced concrete structures in specific operating conditions.

Corrosion resistance of reinforced concrete structures is provided by means of primary and secondary protection. Primary protection measures include:

- use of materials of increased chemical resistance; - application of additives that increase corrosion resistance of concrete and its protective ability in relation to steel reinforcement; - reduction of concrete permeability by various technological methods; - establishment of additional requirements for designing structures: according to the category of requirements for crack resistance and the maximum permissible crack opening width, thickness of the protective layer of concrete in reinforcement, ensuring the safety of reinforcement .

Secondary protection measures include :

- paint coatings; - adhesive insulation from sheet and film materials;

- lining and lining with piece or block products made of ceramics, slag steel, glass, stone casting, natural stone; plaster coatings based on polymer binders, liquid glass, bitumen; - sealing impregnation of the surface layer of concrete of structures with chemically resistant materials.

Since the application of secondary protection measures is labor-intensive and expensive, the specified service life of structures should be provided primarily by primary protection measures. Secondary protection is used if the primary protection does not achieve the required durability of the structures. In the conditions of reconstruction, when, according to the results of the examination, defects that arose as a result of corrosion of concrete or steel are revealed, it is necessary first of all to take measures, if possible, to change the operating conditions: exclude humidification of structures, reduce the concentration of aggressive effects.

Primary protection of reinforced concrete structures in reconstructed buildings is carried out during repair .

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