A person is always engaged in the construction of objects for various purposes. Constructed structures must be strong and durable. To do this, 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 motion in time when exposed to small disturbances. In other words, the ability to maintain the shape or initial position of the structure is called stability.
Instability - the ability of the structure, characterized by obtaining large displacements with slight fluctuations.
Buckling
This phenomenon is very dangerous for the structure as a whole and for its individual elements in particular. If a structure passes from a stable state to an unstable one, this phenomenon is called loss of stability. It happens that the reason for the destruction of structures and structures must not be sought in violation of their strength. This happens when structural stability is lost. There are cases when, due to this, entire structures were destroyed. The reason for such a major disaster may be the loss of stability of individual elements.
Causes of buckling
The stability of structures and structures tend to lose sheet elements, since they have the ability to compress. Therefore, before using them, it is necessary to determine whether or not the stability of structural elements after welding will be lost. If this is not done, the compressive stress left after welding may be the reason why sheet welded structural members lose stability.
Structural elements have an initial form of equilibrium. If the stability of the building structures is lost, then the balance of the elements is disturbed, and this entails the loss of their performance and subsequently leads to an accident of the entire structure. In the practice of building such cases a lot.
Viscoelastic elements present in the structure tend to deform and bend. Such characteristics are commonly called time functions. In this regard, the structural stability is divided into instant and long-term. Therefore, the requirements for structural elements, in addition to its mass, load on it, indicate the service life.
Loss of stability may occur due to compressive stress in structural members. This is true for aircraft with supersonic speeds, as the skin of the aircraft heats up differently. This leads to an uneven distribution of temperatures.
The stability of the structure is violated when exposed to a critical load. In most cases, this leads to its destruction. Therefore, it is very important when constructing a structure to make the calculation of structures for stability, and not just for the strength of elements and assemblies.
Local sustainability
This is the stability of structural elements. If their buckling occurs as a result of exposure to compressive or tangential stresses on them, this phenomenon is said to be a loss of local stability.
Structural strength decreases when wall stability is lost. If it is near the support, then shear stress acts on it. Under its influence, the wall warps. It is compressed along shortened diagonals, and elongated along elongated diagonals. There is an expansion of the wall, the formation of waves. This phenomenon can be prevented by installing vertical stiffeners. They will cross the swollen places, straightening the wall.
The stability of the structure, namely the walls and the belt, can be lost not only from shear stresses. They slightly affect the wall of the middle of the beam, here it is affected by normal stresses, which can become a loss of structural stability.
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 minimum cost. The calculation takes into account the effect of force and other influences on structural elements, taking into account the limiting states, which are divided into two groups. The first is when the bearing capacity of the structure is lost or it is completely unsuitable for use; the second - when the normal operation of the structure is difficult.
Impacts and loads
During operation, any design experiences certain loads and effects on it. The operation of the entire structure is affected by the nature, duration and nature of the effects. The stability of the structure depends on them.
Loads are:
- 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 exposure, as a result of which the properties of materials change. This affects the life of the structure.
- Emergency loads that occur if the process is disrupted, equipment breakdown, 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 capable of absorbing compressive and tensile forces.
Reinforced concrete structures are used in construction as basic structures. They have high strength, durability, resistance. For their production, you can use the building materials of the area, they are simple in the formation of the desired forms, do not require large expenses.
Reinforced concrete structures have several disadvantages. They have a high density, high heat and sound conductivity. When the structure shrinks and the force is applied, cracks may appear over time.
Prefabricated reinforced concrete structures
Reinforced concrete structures and elements are monolithic and prefabricated. Monolithic are produced directly at the construction site, and prefabricated - at factories using special equipment. A special group stands out structures with external reinforcement with metal profiles.
Reinforced concrete structures manufactured in the factory are used for the construction of premises for various purposes, landscaping, the manufacture of pipes, piles, sleepers, supports for power lines 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 manufacturing time for manufactured structures is reduced, and their quality is increased. It is possible to make prestressed structures from reinforced concrete only at the factory.
Building structures are not so flawless. Their disadvantage is that it is impossible to produce them in a wide range. This applies primarily to the diversity of forms. The factories produce structures for mass use. Therefore, in cities and other settlements there are many similar structures: residential and administrative. This leads to the fact that the architecture of the building region is degrading.
The manufacture of reinforced concrete structures and their elements is carried out according to 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. The products remain stationary, and the units move.
Monolithic structures
Building on this technology is a laborious process, but very understandable. Monolithic designs can be done with your own hands.
Stages of construction:
- The frame is made of reinforcement.
- Formwork is equipped, 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.
- Concrete is scraped.
- The formwork is 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 several advantages:
- There is no need to use heavy equipment, in particular cranes. For work, concrete pumps are needed, with which concrete will be poured into molds and laid in the right place. At the site where the house is being built, the landscape will be preserved.
- The technique of monolithic construction allows you to erect structures of any shape and number of storeys. Ceilings and walls are already ready for decoration, construction time is reduced.
- Bearing walls of a monolithic house are 2.5 times thinner than brick ones, although they are not inferior to them in thermal conductivity. Heating costs are reduced by 4 times. By reducing the thickness of the walls increases the area of the internal space.
- Monolithic buildings are durable and stiff. The foundation loads are reduced due to the small wall thickness.
- In monolithic construction, it is allowed to use fixed formwork and traditional materials. This allows developers to implement the project in any style.
- In such houses there are no joints, 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 form on walls and ceilings.
- Door and window openings are not deformed.
- Monolithic buildings are soundproof.
Monolithic buildings: disadvantages
Having a lot of advantages, such structures have disadvantages:
- For the construction of the house requires additional labor.
- Creating a monolithic house project is an expensive service.
- Concrete must be poured continuously, otherwise it will thicken.
- While living in such a house without a tool, it is impossible to make a hole in the right place on the wall.