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More than Steel: Explore the key role of structural steel in modern architecture

Date :2024-03-07 Author :Zhishang StructureView : 81

Structural steel is designed for a variety of building uses. It has high ductility, a property that allows for stress redistribution. Because of the high ductility of structural steel, it can be customized to a variety of shapes, sizes and thicknesses. Most countries have strict standards to regulate the shape, size, chemical composition and mechanical properties of steel.


The shape design of structural steel usually has a good strength-to-weight ratio, which enables it to support extremely heavy loads without deformation, so steel becomes an excellent reinforcement material. These include a variety of shapes, such as I-beams, Z-shaped steel, hollow structure cross sections also known as HSS-shapes, which are very common around the world, but specific standards vary from region to region.


In many countries, such as the United Kingdom and the United States, I-beams are referred to as universal beams (UB) or universal columns (UC), respectively. In Europe, sections such as IPE, HE, HL and HD are included. The United States includes wide flanges (WF or W shape) and H-profiles. All construction industries usually use I-beams, which are very effective for bearing bending loads.


In addition, there are such as C-beam or C-section, also known as structural channel steel, T-section is also known as tee, track profile asymmetric general beams, metal plates, open web steel joists and so on.


Structural steel products can be manufactured by hot rolling, cold rolling or by welding profiles together. In the past few decades, "Angle iron", "trough iron" and "iron plate" have been used to describe wrought iron. Today, however, steel has replaced iron, but the terms are still used informally, but it is incorrect to use these old terms to refer to steel. The correct terms are Angle, groove and plate.


Structural steel standard


European standards of discovery


There is an official European Committee for Standardization called CEN.


When it comes to steel manufacturing, there are many current national standards, and most steels used in Europe comply with the European standard EN 10025.


For example, S275J2 and S355K2W are typical names for steel grades, where S indicates that they are structural steels, followed by three numbers describing the yield strength in Newtons per square millimeter or mpa, followed by an alphanumerical combination that is the toughness grade classification. The second letter W in the last example indicates that the product is composed of weathering steel. The name may also include letters for fine-grained steel (N or NL), tempered steel (Q or QL), etc.


The shape of a set of standard structural profiles is defined by five European standards:


European I-beam: IPE - Euronorm 19-57

European I beam: IPN - DIN 1025-1

European flange beam: HE -- Euronorm 53-62

European Channel: UPN - DIN 1026-1

Cold forming in Europe IS IS 800-1


American standard


In the United States, alloy steels used in the construction of buildings are certified and specified by ASTM International. The name of the building material begins with A, followed by two to four numbers. Four-digit names are commonly used for mechanical engineering. Steel used in machines and vehicles has a separate naming system.


The most commonly used types of structural steel include:


Carbon steel

A36 - for structural shapes and plates.

A53 - For structural pipes and tubes.

A500 - for structural pipes and tubes.

A501 - For structural pipes and tubes.

A529 - for structural shapes and plates.

A1085 - For structural pipes and tubes.

High strength low alloy steel

A441 - for structural shapes and plates - (replaced by A572)

A572 - for structural shapes and plates.

A618 - For structural pipes and tubes.

A992 - Suitable for applications such as W or S I-beams.

A913 - For hardening and Self-tempering (QST) W shapes.

A270 - for structural profiles and plates.

Corrosion resistant high strength low alloy steel

A243 - for structural shapes and plates.

A588 - for structural shapes and plates.

Tempered alloy steel

A514 - for structural shapes and plates.

A517 - For boilers and pressure vessels.

Eglin steel - Used in low-cost aerospace and weapons equipment.

Forged steel

A668 - For steel forgings


What is the CE Mark?


The European Directive Construction Products Directive (CPD) introduced the CE marking for all steel and construction products. CPD ensures harmonization of classification and description, facilitating the free movement of products and materials throughout the EU. A factory's factory Production control (FPC) system must be evaluated by a suitable certification body approved by the European Commission before it is allowed to add the CE marking to articles and/or materials. This ensures that these "safety critical" items actually meet the quality specified on the label. For example, CE marking on products such as prefabricated steel structures and bolts can verify that the manufacturing and final properties of the product meet the relevant harmonized standards (see below).


When it comes to steel construction, the standard is indicated by the following descriptive names:


For sections and plates, it is: EN 10025-1

For hollow profiles: EN 10219-1 and EN 10210-1

For pre-tightening bolts, it is: EN 14399-1

For non-preloaded bolts: EN 15048-1

For fabricated steel, it is: EN 1090-1

The CE marking standard for steel structures is EN 1090-1.


As of the end of 2010, the standard covering the CE marking of steel structures is EN 1090-1. After a two-year transition period, the CE mark became an EU standard in 2014.


Concrete or steel?


Of course, steel and concrete are not the only materials used in construction, but they are among the most abundant and widely used materials in most modern buildings. Steel of various grades and properties, concrete of various grades and properties, and other materials such as clay, mortar, ceramics, wood, and masonry are commonly used.


For load-bearing purposes, such as structural frames and load-bearing beams, materials commonly used include some combination of structural steel, concrete, masonry and/or wood. Depending on the conditions of the structural components and the desired performance, different combinations, grades and designs will be used. By far the most common and abundant building materials in these cases are reinforced concrete and steel. The optimal grade, material mix and design are determined by the engineer. Factors that influence these decisions include weight, strength, constructability, sustainability, availability, life, fire resistance, appearance, and cost.


Let's look at some of these factors in more detail:


cost


This will depend on several factors, such as construction location, order size, transportation costs, support machinery, components, and availability and cost of skilled and unskilled labor. For example, reinforced concrete requires formwork before pouring, which accounts for about half of the final cost. The preparation is demanding, but once this work is done correctly, the concrete can be poured and allowed to cure. They form a strong solid material that conforms to the desired shape in pre-cured liquid form. Precast concrete has become a popular way to reduce costs (through factory manufacturing methods) and maintain greater regularity in shape and form. Manufacturing is fast, so, assuming transportation is available and efficient, using the prefabricated method can also speed up other aspects of construction, resulting in cost savings. Since steel (used to reinforce concrete) is sold by weight, structural designers determine the lightest and least amount of steel that can still produce the strength and other properties required for a component. Buying the same components in bulk (even though some may be over-engineered for their purpose) can significantly reduce costs compared to buying every component with properties specific to the job at hand.


Strength-to-weight ratio


Strength-to-weight ratio or specific strength is a useful way to classify building materials. Strength divided by density, the resulting rating is used to indicate how useful a material is in a given situation or for a given purpose. For example, the compressive strength of concrete is ten times the tensile strength, so the strength-to-weight ratio is much higher in cases where compressive strength is the main required attribute.


Sustainable development


As environmental issues become increasingly important and urgent, many construction companies and material suppliers list sustainability attributes as the main feature of their products. The use of sustainable and sustainably manufactured materials usually does not significantly affect the performance or cost of the structure, and some of these materials are actually cheaper. For example, more than 80% of structural steel members are currently made from recycled materials (A992 steel). It is cheaper and has a higher strength-to-weight ratio compared to grade A36 steel members. The concrete, which uses primarily natural materials as components, is now made permeable, which reduces the need for drainage and overflow infrastructure as water can move through the surface on its own. Disposing of old concrete is also less harmful to the environment because it can be used as an aggregate for other construction projects rather than simply thrown into a landfill.


Fire resistance


For buildings and the people who live and work in them, fire can be one of the scariest and most dangerous risks. In dry and windy conditions, fires can mean raging blazes within minutes, and wooden structures are particularly vulnerable to this danger. In this case, even structural steel may be at risk of failure. The use of reinforced concrete, both as a major part of the structure and as a firebreak or protective layer for other materials, is one way to mitigate these risks.


corrosion


Exposure to corrosion in water, heat, moisture, salt, and other substances can cause long-term problems for some building materials, not only damaging the appearance of the material, but also damaging the integrity of the structure. When installing certain materials, special measures must be taken to ensure protection from these potentially harmful elements, and these materials need to be maintained regularly and recommended care procedures followed. Structural steel may rust if exposed to water, wood may rot, and mold may seep into cracks and cavities in the structure, posing a danger to those who live and work near the structure. However, these are well-known risks, and both material manufacturers and construction companies take steps to reduce the risks and educate users on best practices to ensure safety and extend the useful life of these products and structures

Structural steel is an indispensable material in the construction industry, which is known for its excellent physical properties and flexible construction performance. This material has extremely high compressive and tensile strength, which means that it can withstand significant pressure and tension, maintaining its robustness. The excellent toughness and ductility of structural steel enable it to remain stable under a variety of environmental and functional requirements, while its high stiffness ensures the straightness and shape stability of the structure. These properties make structural steel the material of choice when constructing Bridges, tall buildings and other infrastructure.


In terms of construction, the plasticity of structural steel is extremely high, and it can be processed into various shapes required by forging, forming, bending and other ways. It is connected in a variety of ways, and can be connected with other parts by bolts, welding, cutting and forming to adapt to different design and construction needs. Compared with concrete that needs to be mixed, poured and cured on site for a period of time, structural steel can be used immediately after arriving at the construction site, greatly shortening the construction period and improving the construction efficiency, which is crucial for the progress control of engineering projects.


Although structural steel performs well in fire resistance because it is itself non-combustible, its strength and stiffness are affected at high temperatures, which can lead to structural failure. Therefore, in order to meet the requirements of international building codes, steel structure components usually need to be wrapped in refractory materials, which undoubtedly increases the overall construction cost.


In terms of corrosion resistance, structural steel is prone to corrosion when in contact with water, especially in saline environments. To prevent corrosion, protective paint or other protective measures are usually applied and steel components are placed away from water sources.


Mold problems are generally more common in porous surface materials such as wood, and less so in steel structures. This is because mold tends to grow on porous surfaces, and the closed nature of steel limits mold growth.


In modern urban construction, skyscrapers and super high-rise buildings mostly use steel structure, because structural steel has high strength, rigidity, and can be quickly put into use, making the construction progress more controllable. Due to the high strength-to-weight ratio of structural steel, it is particularly suitable for use in tall buildings where structural integrity needs to be maintained from the underground foundation to the tip.


For some low-rise buildings, because they do not require such a high strength-to-weight ratio and have fewer floors, it is more economical to use concrete as a building material. Although structural steel and reinforced concrete are both preferred building materials, builders often also consider economic factors when selecting materials. They need to make a trade-off between maintaining a profitable business and choosing cheaper materials.


In actual building design, engineers and designers often combine the advantages and disadvantages of steel and concrete and use them for different purposes. For example, steel is used in the structural frame of the building, while reinforced concrete is used in the floor slab. This design not only gives full play to the advantages of the two materials, but also enables rapid alternate construction between floors during construction.


In short, the design and construction of structural steel is a comprehensive consideration of material characteristics, cost effectiveness, safety and aesthetic process. With careful design and material selection, it is possible to create building works that are both affordable and safe to use.


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