Man is always engaged in the construction of objects for various purposes. Buildings to be built must be strong and durable. To do this, it is necessary to ensure the stability of the structure. Read about it in the article.
What is sustainability?
This is the ability of a structure or its individual elements to maintain one of two states: equilibrium or movement in time when exposed to small disturbances. In other words, the ability to maintain the shape or original position of a structure is called stability.
Instability - the ability of a structure, characterized by obtaining large displacements with minor vibrations.
Stability Loss
This phenomenon is very dangerous for the structure as a whole and for its individual elements in particular. If a structure changes from a stable state to an unstable state, this phenomenon is called buckling. It happens that the reason for the destruction of structures and structures should not be sought in violation of their strength. This happens when there is a loss of stability of the structure. knowncases where entire structures were destroyed because of this. The cause of such a major catastrophe may be the loss of stability of individual elements.
Reason for buckling
The stability of structures and structures tend to lose sheet elements, as they have the ability to compress. Therefore, before using them, it is imperative to determine whether or not the stability of structural elements will be lost after welding. If this is not done, the compressive stress left after welding may be the reason why the welded plate structural members become unstable.
Elements of structures have the original form of equilibrium. If the stability of the building structures is lost, then the balance of the elements is also disturbed, and this entails the loss of their performance and further leads to an accident of the entire structure. There are many such cases in construction practice.
Viscoelastic elements present in the structure tend to deform and sag. Such characteristics are usually called functions of time. In this regard, the stability of the structure is divided into instant and long-term. Therefore, in the requirements for structural elements, in addition to its mass, load on it, the service life is indicated.
Stability can occur due to compressive stress in structural members. This is relevant for aviation technology with supersonic speed, since the skin of the aircraft is heated differently. This leads touneven temperature distribution.
Stability of the structure is broken when exposed to a critical load. In most cases, this leads to its destruction. Therefore, when erecting a structure, it is very important to calculate structures for stability, and not just for the strength of elements and assemblies.
Local sustainability
This is the stability of structural elements. If they buckle as a result of exposure to compressive or tangential stresses, this phenomenon is said to be a loss of local stability.
Strength of the structure is reduced when the stability of the wall is lost. If it is located next to the support, then shear stress acts on it. Under its influence, the wall warps. It contracts along shortened diagonals, and stretches along elongated ones. There is swelling of the wall, the formation of waves. This phenomenon can be prevented by installing vertical stiffeners. They will cross bulges, straightening the wall.
The stability of the structure, namely the walls and the belt, can be lost not only from shear stresses. They have little effect on the wall of the middle of the beam, here it is affected by normal stresses, which can become a loss of stability of the structure.
Calculation of building structures
The purpose of the calculation is to ensure the specified operating conditions of the structure in compliance with its strength and minimal costs. The calculation takes into account the impact of force and otherimpacts on structural elements, taking into account the limit states, which are divided into two groups. The first is when the bearing capacity of the structure is lost or it is completely unusable; the second - when the normal operation of the facility is difficult.
Impacts and loads
During operation, any structure experiences certain loads and impacts on it. The operation of the entire structure is affected by the nature, duration and nature of the impacts. The stability of the structure depends on them.
Loads happen:
- From the weight of the structure itself.
- From the weight of equipment, people, materials, pressure of gases and liquids.
- Atmospheric loads - wind, snow, ice.
- Temperature and seismic effects.
- Biological (the process of decay), chemical (corrosive phenomena), radiation effects, as a result of which the properties of materials change. This affects the life of the structure.
- Emergency loads that occur if the technological process is disrupted, equipment breaks, power lines, etc.
Reinforced concrete structures
Reinforced concrete is a complex material for construction, which includes concrete and steel. Using the natural properties of substances, a material is obtained that is able to perceive compressive and tensile forces.
Reinforced concrete structures are used in constructionas basic structures. They have high strength, durability, resistance. For their production, you can use the building materials of the local area, they are easy to form the desired shape, do not require large expenditures.
Reinforced concrete structures have a number of disadvantages. They have high density, high heat and sound conductivity. With shrinkage of the structure and force impact, cracks may appear over time.
Precast concrete structures
Reinforced concrete structures and elements are monolithic and prefabricated. Monolithic ones are produced directly at the construction site, and prefabricated ones are produced at factories using special equipment. Structures with external reinforcement with metal profiles stand out as a special group.
Prefabricated reinforced concrete structures are used for the construction of premises for various purposes, landscaping, pipes, piles, sleepers, power line supports and much more.
Monolithic reinforced concrete structures (prefabricated) are used for the construction of hydraulic structures, in transport and underground construction, in low-rise and high-rise construction of residential buildings and office buildings.
Advantages and disadvantages
Prefabricated building structures have an undeniable advantage - their production is carried out in factories equipped with special equipment. Due to this, the terms of manufacturing of manufactured structures are reduced, and theirquality. It is only possible to manufacture prestressed reinforced concrete structures at the factory.
Building structures are not so perfect. Their disadvantage is that it is impossible to produce them in a wide range. This applies, first of all, to the diversity of forms. The factories produce structures for mass use. Therefore, in cities and other settlements, many similar structures appear: residential and administrative. This leads to the fact that the architecture of the building region is degrading.
Production of reinforced concrete structures and their elements is carried out using the following technologies:
- Conveyor, when the execution of technological processes occurs sequentially.
- Flow-aggregate. This technology provides for the implementation of technological operations in separate rooms, forms with structures or elements are moved by cranes.
- Bench technology. Here everything happens the other way around. Products remain stationary, while aggregates move.
Structures from monolithic structures
Construction using this technology is a laborious process, but very understandable. Monolithic structures can be made by hand.
Construction stages:
- The rebar frame is being installed.
- Formwork is being arranged, reinforcement is placed inside it.
- A mixture of concrete is poured, which is compacted with special vibrators. This is done so that voids do not form in the formwork.
- Concretebeing cleared.
- Formwork removed.
Monolithic buildings: advantages
Recently, more and more often, when building a residential building, they use technology developed for the construction of monolithic buildings, which have a number of advantages:
- No need to use heavy machinery, in particular cranes. For work, concrete pumps are needed, with the help of which concrete will be poured into molds and placed in the right place. The landscape will be preserved on the site where the house is being built.
- The method of monolithic construction allows you to build structures of any shape and number of storeys. Ceilings and walls are ready for finishing, construction time is reduced.
- The load-bearing walls of a monolithic house are 2.5 times thinner than brick ones, although they are not inferior to them in terms of thermal conductivity. Heating costs are reduced by 4 times. By reducing the thickness of the walls, the area of \u200b\u200bthe internal space increases.
- Monolithic buildings are durable and rigid. Loads on the foundation are reduced due to the small thickness of the walls.
- In monolithic construction it is allowed to use fixed formwork and traditional materials. This allows developers to implement the project in any style.
- There are no joints in such houses, they are not affected by precipitation, they can be built at any time of the year.
- Shrinkage of the foundation is carried out evenly.
- No cracks on walls and ceilings.
- Door and window openings are not deformed.
- Monolithic buildings are soundproof.
Monolithic buildings: disadvantages
Havingmany advantages, such structures have disadvantages:
- Building a house requires additional labor.
- Creating a project for a monolithic house is an expensive service.
- Concrete must be poured continuously, otherwise it will thicken.
- In the process of living in such a house without a tool, it is impossible to make a hole in the right place on the wall.
