Steel structures do not only include buildings and high-rise towers and may include any type of structure in all industries. Storage tanks and bridges are two familiar types of metal structures that are implemented in different scales. In the following, we talked about the types of steel structures, their advantages and disadvantages.

Type of steel building structures

The portal frame structure has simple power, clear power transmission path and fast construction speed. It is widely used in industrial and civil buildings such as public industrial, commercial, cultural and entertainment facilities.

The metal frame structures of the building are flexible and can form a larger space. It is widely used in multi-story, tall, and super-tall buildings, commercial office buildings, conference centers and other buildings.

The advantage of the steel truss structure is that small cross-section bars can be used to form larger cross-section components, which are often used in industrial and civil buildings such as roofs, bridges, TV towers, mast towers, offshore oil production platforms. . Tower corridors etc. with large openings or elevations in the building.

The steel grid structure is a high-order indeterminate static spatial structure that consists of many bars based on certain rules. This space has small force, light weight, rigid and good seismic resistance. It can be used as sports hall, exhibition hall, rain roof of buildings such as shed and shed.

characteristic of steel structure

Below are the most important characteristics of small and large steel structures.

Strength

In general, strength materials are determined by the structure’s bearing capacity and its holding effect. Relevant national standards can be used to improve the performance of steel structural components, there it lists the materials that the steel structure can use above the standards, such as the building must comply with the CSA standard or the ASTM standard.

Due to the huge change in construction in recent years, the data related to the tensile strength and yield strength used in the structure are all from the CISC record, and now Canada recognizes steel grade 7 and strength 8 for engineering and normal structural steel. has done. The structural steel of the building and the range of yield strength is from 260 to 700 MPa.

But not all steels have full strength rating, therefore, when designing a specific steel structure, it will be very important to select the type and strength grade of steel. In general, the use of steel structure can reduce material consumption. reducing the weight of the structure; Shorten the support component and the size of the foundation and ultimately reduce the cost of the building structure.

Stiffness

Many other functional parameters, such as deformation, are determined by the stiffness component and

The stiffness is determined by the structure system. However, in summary, the hardness of the components is mainly determined by the characteristic geometric cross-section of the material and the modulus of elasticity of the material, the modulus of elasticity of the steel structure is 200Gpa, while the compressive strength of the normal density is in the range of 20-40Gpa.

The modulus of elasticity of concrete is in the range of 40-45Gpa. For this reason, the rigidity of the steel structure is five times that of concrete and is significant

Ductility

Ductility mainly refers to a material that has the capacity of non-plastic fracture deformation

Drawing process In general, ductility is an important characteristic parameter in the design of structures, especially in earthquake design, as buildings that maintain their survival in earthquakes.

Hysteresis energy dissipation of the main structure frame after experiencing inelastic deformation.

It should be noted that the steel structure has become the most widely used and the best engineering material for toughness. But the internal plasticity of the material does not become the internal plasticity of the steel structure. Therefore, to fully realize this feature, reasonable design methods, reliable and stable waste removal system should be used.

In general, if a design wants to have a ductile response, it should be sufficient for the material section, material ductility, structure ductility, and component ductility. However, ductility and demand must be matched for surface ductility, curvature ductility, and displacement ductility.

But even though the steel structure has relatively high ductility, due to the unstable bending under stress, the ductility tends to be lacking in the curvature of the components.

Toughness

Toughness is a major index to judge the energy absorption and fracture capability of plastics

Material Fracture It can resist the formation of unstable notch cracks. In general, toughness means that the steel structure can withstand a relatively large industrial deformation in the manufacturing, installation and use process, which is also an important characteristic of the steel structure.

Due to its toughness, it reduces the possibility of cracking in punch bending, forging and drilling. The steel structure must have adequate fracture toughness, especially in buildings with alternating loads and shock loads.

The fracture toughness of the steel structure is about specific temperature conditions and as

The temperature decreases, gradually decreases. Therefore, to design a metal frame building in cold ground, toughness should be considered first.

Relatively speaking, low carbon niobium steel is more ductile than high carbon steel components. From a general point of view, regardless of hardness and strength, or ductility characteristics, steel structure should be given priority over steel concrete, and steel structure can easily create strange properties.

In general, steel structure can provide the most ideal design, flexibility and use of space. Regarding the steel structure, another advantage is having an ideal construction system.

Reasonable transportation uses bracket and hollow steel component for trepanning, therefore, they should provide the corresponding channel for the pipe and some other lines, then during construction, the construction slag equipped with steel structure should be specially discussed. be placed

The principles to maintain steel structure

Stability is always an important problem in using steel structure. Among various types of steel
structure, one often meets stability problems. Once the problem handled improperly, it would lead to loss.

According to characteristic that stability in actual design, one should implement the following three principles, and ensure the component of steel structure stability design, and would not loss stability.

First, layout of the whole structure must consider the stability requirements of the whole system and components. At present, the structure is based on plane system, like truss and frame.

Ensure the plane structure wouldn’t cause the instability problems; it needs to be solved from overall arrangement structure, that needs to design the necessary supporting artifacts, which means the plane stability calculation of plane structure component should consistent with the structure arrangement.

Second, the brief calculation of steel structure should be consistent with practical brief calculation, this is very important for frame structure stability calculation. At present, in design single or multilayer frame structure, one used to take frame column stability calculation place of frame stability analyze.

Applying this method, it should use the coefficient of column calculation length when calculate the stability of frame column, so that make column stability calculation has effect on frame stability calculation.

But, the actual framework is diversification, in order to simplify the calculation in design, one need to set the corresponding condition.

Third, design detail structure must cooperate with structure stability calculation, and keep consistency. Structure calculation and structure design should conform to each other, which raise attention in structure design.

To whether passing bending moment connection, it should full amount of rigidity and flexibility each other, and reduce the eccentricity of bar for the truss nodes as soon as possible.

Advantages of steel structure

• Cheap and durable
• Strong
• Ductile
• Versatile

Disadvantages of steel structure

• Maintenance cost of a steel structure is very high.
• Steel has very small resistance against fire as compared to concrete.
• Steel cannot be mold in any direction you want.
• steel loses its ductility property, than chances of brittle fractures increase.

Type of steel grade in structure

The steels used to build large and small structures are not only one type and are divided into several types based on their structure and specifications.

Carbon Steels

Carbon steel is actually a type of steel in which another element such as zirconium, cobalt or nickel is not needed and the amount of copper does not exceed 0.4%. This type of steel is divided into three types: medium carbon, high carbon and low carbon.

High Strength Low Alloy Steels

These types of steels are designed to have better mechanical properties and are more resistant to atmospheric corrosion than carbon steels. They contain up to 2.0% manganese. Small parts of other alloying elements such as chromium, nickel, molybdenum, nitrogen, vanadium, niobium and titanium can be used in different combinations to change the properties (3). Weathering steels, which are a subgroup of low-alloy steels with high strength, have a high resistance to atmospheric corrosion by forming a passive layer and rusting on the surface, which is one of the important structural steels. It is mostly used in structural forms and plates.

Forged Steels

Forging is simply the process of shaping metal into a solid state. It is done by applying mechanical and thermal energy to the steel ingot or billet. This process introduces a uniform grain structure to the material, which reduces voids, gas bubbles, discontinuity in the matrix and increases overall strength.

Quenched and Tempered Alloy Steels

A type of structural steel (for example A514) mostly used in building constructions. As it can be understood from its name, this type of steel has undergone quenching and tempering heat treatment steps.

Design methods of steel structures

The design of the metal frame can be done in one of three simple ways, continuous or semi-continuous. To simplify the design calculations, the joints in the structures are considered to be pinned or flexible.

The simple designs of the joints make them ideal as flawless pins. Regardless of the applied moment, continuous innovation assumes that the connections are rigid and that the connected elements cannot rotate relative to each other. Most designs created today rely on one of these two defaults, although a semi-continuous design, a more practical option, is now possible.

The methods of designing the metal frame are as follows:

Simple design of steel structure

The most conventional method is the simple design, which is still frequently used. Bracing or, in some multi-story buildings, concrete cores are commonly used to ensure the flexibility of the structure against lateral and sway loads.

The designer must be aware of the joint response assumptions and ensure that the connections are accurate enough to avoid any moments that could adversely affect the performance of the structure.

The types of details that meet these conditions have been shown through many years of experience, and the designer should pay attention to the typical joints in joints in uncomplicated construction.

Continuous design of steel structures

The joints that transfer the anchors between the parts are in a continuous design. The frame action is what keeps the frame from swaying.

Frame analysis is often done using software because continuous design is more complex than initial design. Continuous frames should be designed considering the actual pattern load combinations.

Depending on whether the frame is designed using an elastic or plastic method, the connections between members must have different properties.

In a flexible design, the connections must have sufficient rotational stiffness to ensure that the forces and moments distributed throughout the frame do not deviate significantly from the calculated values.

The connection must be strong enough to support the anchors, forces and shears resulting from the frame analysis.

Joint strength, not stiffness, is the most important factor in plastic design to calculate maximum load capacity. Finding plastic hinges in joints or members depends on the strength of the joint, which significantly affects how the structure collapses.

If joints are to be hinged, the joint should be specified with sufficient ductility to support subsequent rotations. When calculating sway stability, warp deflection and beam deflection, the stiffness of the joints will be very important.

Semi-continuous design of steel structure

True semi-continuous design is more complex than basic or continuous design because the true response of the joint is represented more accurately. Developing analytical routines that closely track actual joint behavior is very labor intensive and not suitable for routine design.

For both braced and unbraced frames, there are two simple processes that are briefly discussed below. Unbraced frames provide lateral load resistance from bending anchors in columns and beams, while braced frames use a bracing system or a core to provide this resistance.