Future Steel Buildings
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range from 190-210 gigapascals.
3.Poisson’s Ratio
It is the ratio between contraction and elongation of the material. Lower the value, lesser the object will shrink in thickness when stretched. Acceptable values for structural steel are 0.27 to 0.3.
4.Tensile Strength
Tensile strength of an object is the determination of limit up to which an object can be stretched without breaking. Fracture point is the point at which an object breaks after application of stress. Structural steel has high tensile strength so is preferred over other materials for construction.
5.Yield strength
Yield strength or yield point is the stress at which an object deforms permanently. It cannot return to its original shape when stress is removed. Structural steel made of carbon has yield strengths of 187 to 758 megapascals. Structural steel made of alloys has values from 366 to 1793 megapascals.
6.Melting point
There is no defined value for melting point due to the wide variations in types of structural steel. Melting point is the temperature at which object starts to melt when heated.
7.Specific heat
Specific heat or heat capacity is the amount of heat which needs to be applied to the object to raise its temperature by a given amount. A higher value of specific heat denotes greater insulation ability of the object. Values are measured in Joules per Kilogram Kelvin. Structural steel made of carbon has values from 450 to 2081 and that made from alloys has values ranging from 452 to 1499.
8.Hardness
Hardness is the resistance of an object to shape change when force is applied. There are 3 types of hardness measurements. Scratch, indentation and rebound. Structural steel made by using alloys has hardness value between 149-627 Kg. Structural steels made of carbon has value of 86 to 388 Kg.
5 | Components of Steel Buildings
Modern steel buildings are made of many individual components that have evolved over time. With the benefit of CAD manufacturers are able to produce more variations in dimensions and format of steel buildings.
Building construction is done using different steel shapes and pieces. In most of the developed countries, standard approved shapes are available.
Small steel buildings are prefabricated and are simple to assemble. The larger steel buildings require skilled workers so that safe assembly of the structure is ensured.
There are five main components of structural steel. They are tension members, compression members, bending members, combined force members and their connections.
Tension members can be found as web and chord in trusses and open web steel joints. They carry tensile and pulling forces preventing force to be applied on the other members used in construction.
Columns, Struts or posts make up the compression members. They are the vertical members in trusses and joists that are in compression.
Beams, joists, girders, spandrels, lintels are known as bending members. Each member has its own application but typically bending members carry moments and shear forces.
Combined force members are also known as beam-columns and are subjected to bending compression. Connecting members bring the entire building together.
Steel beam forms basic skeleton of the building and provides great support and strength. These beams usually hold the floor or the roof. I beams are widely used and come in different sizes. I beam can be used both as a beam and a column.
The girder or I beam is used in construction of nearly all metal buildings. It gives strength in all directions. Every structural component of a steel building can be made by varying sizes of I beam.
Reinforced Bars is a type of steel rod which is used to create reinforced concrete. Steel rods are inserted into concrete to add strength and give flexibility to concrete.
These bars are important in buildings made of concrete or which have substantial amounts of concrete used in construction. Steel joists are used to support floors or ceilings. These are laid in rows across girders. They are attached using joist hangers.
6 | Development of Steel Buildings
Construction Basics
Before proceeding with the building design, figure out the exact purpose of construction. Most of the time greater attention is paid to the final look of the building, not the purpose for which it has to be built. It is important to consider how big and tall a structure needs to stand. The time for which building needs to be used is also an important factor.
If the building needs to be used for long periods, steel is a good choice. It will give greater strength and durability. Steel does not bend, break or twist with increasing load. Changes can be made very easily to the steel structure.
Pre-engineered steel used for construction these days has pre defined points at which bolts need to be fixed.
The most impressive feature of steel is that it is recyclable and is very environmentally friendly.
Most steel buildings used for offices or even apartments are located on busy streets of the city. It becomes more important to consider the safety of the residents and people waking around these structures. Structural flaws need to be avoided at all costs.
Building Design
The design of a modern building involves a team of experts from different disciplines. The team needs to communicate clearly to avoid any undesired outcome at the end of the procedure.
The concept of the final design of the building starts with a drawing. Here the architecture comes into action. Designers (architects) start making new drawings and sketches.
A rough design is made initially. Any problems in the design need to be corrected in the early stages. With support from the structural engineer, the complex procedure of drawing a building structure can become easier.
There are two basic parts of a building design. First is the aesthetic and second is practical. The physical and visual appearance of the building needs to be attractive. It will influence the perception people have of the building.
The practical aspect of the building design is mainly concerned with the space allotment for different activities. It includes entry and exit of people, lighting, acoustics, legal matters and building codes.
Computer Aided Design (CAD) is widely used computer software to create technical drawings. There is no need to make the drawing on paper. A 3D model of the building can be made using CAD. Visuals can be added to the model. Different colors and textures can also be applied. Most appropriate settings can then be finalized.
After the architecture is decided it is important to work out the design of the framework. Beams, columns, bracing are decided by engineering calculations. It is the job of the structural engineer to give a shape to the architect’s idea.
Steel Frame
A steel frame refers to the building technique with a steel skeleton. Vertical steel columns and horizontal I beams are constructed in a rectangular grid. This grid frame supports the attached walls, floors and roof of the building. The development of the steel frame technique has made the construction of sky scrapers possible.
The cross section of steel columns has a shape similar to the letter H. the two flanges of the column are thicker and wider as compared to the flanges on a beam. This makes it better to withstand compression stress on the building structure.
Square or round steel tubules can be also used. They are often filled with concrete. Steel beams are connected to the columns with fasteners and bolts. The steel web in I beam is wider than column web to resist higher bending stress and moments that occur in beams.
7 | Future of Steel Buildings
Talking about skyscrapers automatically brings in mind images of tall buildings steering through the clouds and reaching the stars. The term sky scraper was first applied to steel frame buildings constructed up to 10 floors in the late 19th century.
Today skyscrapers are becoming common in cities where land is expensive. They provide high ratio of floor space per unit area of land. They not only give utilization of space but also are a symbol o
f a city’s economic power.
The list of super tall towers is headed by Burj Al Khalifa (Dubai). This 160 floored building stands over 828m. Empire State Building was the first to have over 100 storeys.
Other tall towers include PETRONAS Twin Towers (Kuala Lumpur), Taipei 101 and Willis Tower in Chicago.
The Idea of skyscrapers dates back to the first iron frame glass curtain walled office building in 1864. It was only 5 floors. Towards the end of 19th century, skyscrapers began to emerge in Chicago, London and Melbourne.
In the early 1960’s, structural engineer Fazlur Khan realized that rigid steel frame is not the only system for tall buildings. This gave the innovation in skyscraper design and construction.
The tube structural system including framed tube trussed tube and bundled tube systems were introduced. This technique allowed skyscrapers to have different shapes from the traditional box shape.
Framed tubes allow fewer interior columns therefore more floor space is available.
The tube structural system is a three dimensional structure composed of 3, 4 or more braced frames or shear walls joined to form a vertical tube system. This system can be constructed using steel, concrete or composite material. This type