Discussion
12. Discuss the pros and cons of metallic structures in construction.
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1. __________________________ 2. __________________________ 3. __________________________ 4. __________________________ … |
1. ________________________ 2. ________________________ 3. ________________________ 4. ________________________ … |
Project work
Make reports on the topics.
The analogues of metallic structures.
The future of metallic structures construction.
Unique metallic structures in construction.
Metallic structures construction in Chelyabinsk.
Unit 4. Frameworks
LEAD-IN
Match the terms and their Russian equivalents.
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multi-span framework
частично несущий каркас
single-span framework
несущий каркас
uncompleted framework
многопролетный каркас
wooden frameworks
металлический каркас
completed framework
однопролетный каркас
metallic frameworks
деревянный карскас
W hat types of frameworks do you know? What types of frameworks (by number of spans) are given in the pictures?
a. _______________________ b. ________________________
3
.
What
materials are used for building framework? What types of frameworks
(by type of material) are given in the pictures?
________________________ b. ________________________
4.Name the advantages of frameworks.
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1. __________________________ 2. __________________________ 3. __________________________ …__________________________ |
Text 1. Frameworks
A
framework is a load-bearing structure, consisting of vertical
constructions (columns) and horizontal ones (longitudinal girders)
and links. A framework carries all vertical and horizontal loads and
transmits them to a foundation. It performs only bearing function for
a building.
There are various classifications of frameworks. For example, by structure it is possible to differ frame, linking and frame-linking frameworks. A frame structure is applied for low buildings where all vertical and horizontal loads acting on a building are carried by cross and longitudinal frames formed with rigid joints of columns and girders. A linking structure has columns and girders of less cross compared to a frame structure. The joints in such structure are hinged but not rigid. The columns take vertical loads and the system of longitudinal and cross links between the columns takes horizontal loads. A frame-linking structure combines frames and diaphragms of stiffness. Both frames and diaphragms take vertical and horizontal loads.
Frameworks can be classified by the location of columns. The buildings with a completed framework exist when the columns are installed inside all the area of a building. In this case the columns carry all the loads from coverings, floors and walls. There are buildings with an uncompleted framework when the columns are erected only inside a building but the bearing walls with separate foundations are installed on the perimeter of a building. According to the number of storeys there are one-storeyed and multi-storeyed frameworks. By the number of spans single-span and multi-span frameworks are used. The former are applied for single-storeyed public or industrial buildings with huge inner volumes such as cinemas, stadiums or industrial shops. The latter are traditional for multi-storeyed dwelling, public and industrial buildings. Frameworks can be prefabricated, monolithic and prefabricated-monolithic frameworks. Prefabricated structures are used for dwelling, public and industrial buildings. Monolithic structures are more laborious under installing but they allow to erect various architectural forms which are impossible under prefabricated frameworks. Prefabricated-monolithic frameworks are needed under buildings reconstruction and extensions.
According to material frameworks are divided into metallic and wooden frameworks. Wooden frameworks are designed for single-storeyed industrial buildings. Metallic framework has a number of advantages before reinforced concrete structure. It is lighter, more technological than reinforced concrete framework. Such type of framework is used for industrial buildings designing which are over 18 meters high. But this type of frameworks has a limited application because of temperature dependence. Alloy frameworks are easily subjected to temperature fluctuations, they change their properties. A wooden framework is used for one-storied industrial and civil buildings. The constructive elements of such framework are made of multi-layered wood, timber, boards and logs. Among the advantages of such type of framework are lightness, small thermal conductivity, easy production and processing, resistance to aggressive chemical mediums. Among the main disadvantages are low fire resistance and moisture resistance.
Under the projecting of industrial buildings mixed framework can be used. It combines reinforced concrete, metallic and wooden elements. In this case the columns are made of reinforced concrete as this material works well in compression. And covering is made of steel or wooden trusses or beams as these materials work well in bending. The choice of a framework material is made after the complex analysis of all positive and negative qualities which must provide strength, reliability, durability and technological ability of a building.
Tasks