A 20m x 50m prefabricated warehouse building is a type of structure that is manufactured off-site and then transported and…
Steel Structure detail shows the specification of the rigid frame, multi-floor frame, and truss structure, which is the most common use building structure for warehouses, workshops, multi-floor buildings, venues, stations, and Aircraft Hangars.
The steel structure is mainly made of steel, and it is one of the main types of building structures. The characteristics of steel are high strength, lightweight, excellent overall rigidity, and strong deformability. So it is especially suitable for large-span, super-high, and super-heavy buildings. The steel structure is a steel beam, column, truss, and other components made of section steel and steel plate, and welds, bolts, or rivets connect each component or part.
The steel used in structural steel mainly includes steel plate, section steel, and C/Z section steel.
1. Steel plate
Steel plates include thin steel plates (thickness 0.35~4mm), thick steel plates (thickness 4.5~60mm), extra thick plates (thickness>60mm), flat steel bars (thickness 4~60mm, width 12~200mm), etc.
2. Section steel
The commonly used metal structure are angle steel, I-shaped steel, channel steel, H-shaped steel, steel pipe, etc. Except for H-shaped steel and steel pipe, which are hot-rolled and welded, the rest are hot-rolled.
(1) Angle steel
There are two types of angle steel: equilateral and unequal angle steel.
There are two types of I-beams: ordinary I-beams and light I-beams.
(3) Channel steel
Channel steel is also divided into ordinary channel steel and light channel steel.
(4) H-shaped steel
H-shaped steel is divided into two types: hot rolling and welding. There are four types of hot-rolled H-shaped steel: wide flange (HW), medium flange (HM), narrow flange (HN), and H-shaped steel column (HP).
(5) steel pipe
There are two types of steel pipes: hot-rolled seamless and welded steel.
3. C/Z shape steel
Mainly used as purlin or wall girt to fix roof and wall panels, the thickness is generally 2~3mm.
FAQs On Steel Structures
1. What is a steel structure?
A steel structure is a steel-made framework used to construct buildings, bridges, and other structures.
2. What are the benefits of using steel in construction? Steel is strong, durable, lightweight, and versatile, making it a popular choice for construction. It is also resistant to fire, pests, and natural disasters and requires less maintenance than other materials.
3. How is steel manufactured for construction?
Steel is manufactured by melting iron ore and scrap metal in a furnace, removing impurities and adding elements to produce specific steel grades. The steel is then shaped into various forms, such as beams, columns, and plates.
4. What is the difference between hot-rolled and cold-rolled steel?
Hot-rolled steel is produced by heating it above its recrystallization temperature and then rolling it into the desired shape. Cold-rolled steel is produced by rolling the steel at room temperature. Hot-rolled steel has a rougher surface and is typically used for structural purposes, while cold-rolled steel has a smoother surface and is used for cosmetic finishes.
What is the typical lifespan of structural steel?
The lifespan of structural steel can vary depending on factors such as its location, the quality of materials and construction, and maintenance. However, a metal structure can last for decades or even centuries with proper care and maintenance.
Steel Structure Detail for Rigid Frame Structure:
The rigid frame is a single-story steel building with rigidly connected beams and columns. It has the advantages of a simple structure, is lightweight, and all the components manufactured in the factory are easy to assemble on site.
The rigid frame structure is widely used for Industrial, commercial, and agricultural buildings, such as steel warehouses, workshop buildings, Storage, Poultry building, and aircraft hangar.
The rigid frame can divide into single-span (Figure a), double-span (Figure b), multi-span (Figure c), cantilever steel frame (Figure d) ) and steel frame with the adjacent frame (Figure e).
The connection between the column and the roof beam is generally hinged in the multi-span rigid frame and in the multi-span rigid frame, single-slope roof (Figure f).
The multi-span rigid frame consisting of multiple double-slope roofs can also be used (Figure g). The beam-column cross-section can be equal or variable, and the base of columns is hinged or rigid connected.
Length and Width of Steel Building :
Generally speaking, according to the principle that the long side is greater than the width, the amount of steel used in the rigid frame can be reduced, and the support between the columns can be reduced, thereby reducing the amount of metal used in the support system.
Example 1: The size of the building is 60x50m; 60 m should use as the length and 50m as the width, that is: 60 (L) x50 (W), not 50 (L) x60 (W).
The most economical column distance under standard load is 7.5-9m. When it exceeds 9m, the steel consumption of roof purlin and wall girt will increase too much, and the overall cost is not economical. The standard load here refers to 0.3KN / m2 for live roof load and 0.5KN / m2 for essential wind pressure. When the loading is more significant, the economic column distance should reduce accordingly. As or workshop building with more than 10 tons of crane, the financial column spacing should be 6-7m.
When arranging column spacing, if unequal column spacing is required, try to arrange the end-span column spacing to be smaller than the center span. The wind load at the end span is larger than the center. Besides, when using a continuous purlin design, The deflection of the end span and the mid-span bend is always more significant than other spans. Using smaller end spans can make roof purlin design more convenient and economical.
Example 1: Building length = 70m
Economical column distance is available: 1 @ 7 + 7 @ 8 + 1 @ 7 or 1 @ 8 + 6 @ 9 + 1 @ 8
Example 2: Building length = 130m, with a 10-ton crane
Economical column distance is preferable: 1 @ 5.5 + 17 @ 7 + 1 @ 5.5 or 20 @ 6.5
Determination of a reasonable span
Different production processes and use functions largely determine the span of the metal building. Some owners even require steel building manufacturers to determine a more economical span based on their useful features. A reasonable span should decide according to the height of the steel building. When the column height and load are constant, the span increases appropriately. The increase in steel consumption of the rigid frame is not apparent, but it saves space, the foundation cost is low, and the comprehensive benefits are considerable.
Through a large number of calculations, it finds that when the eaves height is 6m, the column distance is 7.5m, and the load conditions are entirely consistent, the steel consumption of the rigid frame (For Q345B steel) width is between 18-30m is 10-15kg / m2. The amount of metal used for rigid frame units between 21-48m is 12-24kg / m2. When the eave height is 12m and the width exceeds 48m, a multi-span rigid frame (sway column set in the middle) should use. The frame saves more than 40%, so when designing the rigid portal structure, you should choose a more economical span according to specific requirements and not pursue a large span.
Steel Structure Detail-Roof slope
The roof slope decides according to comprehensive factors, including the roof structure, the drainage slope length, and the columns’ height. Generally, it is 1/10 ~ 1/30. Studies have shown that different roof slopes significantly impact the amount of steel used in rigid steel frames. The following results from the calculation and analysis of the steel consumption under different roof slopes with a single span of 42m and an eave height of 6m.
When the roof slope is 0.5: 10, the weight of a frame is 3682 Kg; when the roof slope is 1: 10, the amount of a frame structure is 3466 Kg. When the roof slope is 1.5: 10, the frame’s weight is 3328 Kg. When the roof slope is 2: 10, the amount of a frame structure is 3240 Kg.
So for a single-span rigid frame, a better way to reduce the weight of the rigid frame is to increase the roof slope. The larger the hill, the less steel is used. However, the situation is different for a multi-span frame. A large slope will increase the amount of metal used in the frame. It is because a large hill will increase the length of the inner column.
When the span of the building is large, increasing the incline can reduce the deflection of the roof steel beam. Through research and calculation, the more economical slope is: multi-span buildings: 1:20 single span, span less than 45 m: 0.5: 10 single span, span less than 60m: 1.5: 10 single span, more than 60 m span : 2: 10
The roof slope is also related to whether the building has a parapet wall, and the large hill will increase the cost of the parapet wall.
Steel Structure detail-Eave Height
The eave height has a significant impact on the cost, which is mainly manifested in the following aspects:
- Increasing the height of the prefab steel building will cause the wall cladding to grow, the wall girt to grow, and the amount of steel used for columns will increase.
- If the steel column has no lateral bracing (such as the center column or the side column without a brace), the influence of the eave height on the frame weight will be more prominent; An increase in eave height will result in an increase in wind load on the frame. If the height/building width is> 0.8, changing the column foot from hinged to rigid is sometimes necessary to control the lateral displacement.
The following factors determine the height:
- The height requirements at the eave;
- When there is a mezzanine structure, the net height of the mezzanine and the height of the mezzanine beam;
- Height of crane beam and crane hook when the crane is available.
According to the code of prefab steel building, the maximum length is not more than 300m, and the width is not more than 150m. The first temperature-segmented expansion joint can be set with a double-column arrangement (Figure 2a) or a single-column expansion joint with slotted holes connected to the purlin (Figure 2b).
Steel Structure Detail-Bracing
(A) the use of the Bracing
In the longitudinal structure of the portal frame, a complete bracing system should arrange to form a whole spatial structural system. The rigidity of the frame ensures the lateral stability of the lightweight portal frame in the width direction to resist the lateral load.
Due to the weak stiffness of the longitudinal structure in the length direction, it is necessary to set bracing in the longitudinal direction to ensure its longitudinal stability. The bracing forces are mainly longitudinal wind load, crane braking force, earthquake action, and temperature action. When calculating the internal strength of the brace, the joints are generally assumed to be hinged, and the effect of eccentricity ignores. The general support is considered according to the tie bean. Therefore, a two-way arrangement is suitable.
(B) Common types of bracing
Figure 3-3 shows the general arrangement of roof bracing and the force transmission path of wind loads acting on the gable wall. Figure 3-4 shows the common support types between columns for portal frames. Due to building function and appearance requirements or process equipment layout, when the above supports are not allowed to use, consider using a longitudinal structure. At this time, the bending stiffness of the weak axis of the column needs to use.
Stee Structure Detail-Basic principles of bracing settings
- The column bracing should be on the same span as the roof bracing. When it cannot be installed due to the door opening on the wall, the column bracing can be set on the adjacent span;
- The distance between bracing should not exceed five spans; 30 ~ 45m should be taken when there is no crane, and the distance should not be greater than 60m when there is a crane;
- The roof bracing needs to divide into the ridge. (See Figure 3-3)
The following situations need to consider the installation of vertical-horizontal roof bracing
(1) When there is a removing column(In the column net, one or more columns are removed), such as a local removing column, only longitudinal bracing is required, as shown in Figure 3-5a;
(2) When the column distance is large, and the side column adopts the scheme of a false wall frame column, see Figure 3-5b;
(3) The tonnage of the crane is greater than 15 tons.
When the building width is bigger than 60m, it is appropriate to increase the column bracing. When cross bracing cannot be arranged, the bracing forms shown in Figures 3-4b and 3-4c can be used. It is also possible to increase the section size of the roof bracing or the column bracing without increasing the internal inter-pillar support. At this time, the internal force calculation needs to be strictly performed to ensure the bracing is safe.
In the same column, different types of bracing should not be mixed; otherwise, the bracing with slight stiffness will have less force and will not function as it should, and the bracing with high rigidity will be damaged due to overload work. The columnBracing should preferably choose to use cross braces.
In the following cases, the column bracing needs to be layered.
(1) When there is a high-low span (or with a large rain canopy), the upper and lower bracing between the columns need to be layered at the high-low span (or the large rain canopy) (see 3-6a);
(2) When the eave height exceeds 9m, double-layer column bracing can be set according to the included bracing angle. The angle between the cross-bracing and the horizontal plane is preferably 45 °, and it should not exceed 55 °. The upper and lower bracing are set between the columns. The end-opening room may not be provided with a lower bracing to reduce the temperature stress of the crane beam (see 3-6b).
Round steel, angle steel, or round (square) pipe can be used for Column Cross Bracing.
When the internal force of column bracing is large, or the lifting tonnage of the crane is more than 5 tons, round steel support is not suitable. At this time, it should use angle steel Or round (square) pipe as column bracing.
Steel Structure detail – use and setting of the flange bracing.
The function of the flange bracing is mainly to prevent the instability of the beam’s lower flange and the column’s inner flange. The brace is connected to the lower flange of the beam on one side and the purlin on the other. Refer to Figure 3-7 for the practice of bracing.
Steel Structure detail for Multi-floor Steel Frame Structure
The multi-layer steel frame structure differs from the traditional brick-concrete and concrete structures. During the construction process, the steel structure is mainly used as the load-bearing system, and the steel frame structure is used to form the load-bearing system of the building.
The steel frame structure comprises frame beams, frame columns, beam-column connection components, profiled steel plate composite floors, and foundations, and it is a pure steel frame structure system.
The floor structure adopts the primary and secondary beams and the profiled steel plate composite floor. Therefore, the installation of the profiled steel plate, the binding of the floor reinforcement, and the concrete pouring must be completed on-site.
Connection Type for Steel Frame Structure
The connection of steel frame structure includes various connection methods such as rigid connection, bolt connection, and welding connection. As a result, the on-site construction speed is fast, and the quality is easy to guarantee; the primary and secondary beams are generally connected by a combination of hinges and welding, which can improve the stability of the structure.
Node type mainly includes beam-to-column, beam-to-beam, column-to-column, and connection nodes at the foot of a column.
Steel Structure Detail for Truss Structure
The truss structure is a relatively common structural form in metal structures. It is often used in large public buildings such as venues, stations, and airports. In recent years, the rapid development of high-speed railways and intercity rail transit stations often adopt this structural form. It has a large span, many shapes, and other characteristics.
Steel truss structures generally consist of chords, webs, and gusset plates. Due to the different materials used for structural members, there are various types, such as steel pipe trusses, H-shaped steel trusses, box-section trusses, and angle steel trusses.
1. Angle Steel Truss
Angle steel trusses are primarily used in roof structure systems and are often used in industrial buildings, such as factories and warehouses. Angle steel truss mainly adopts a T-shaped section welded by double-angle steel.
2. Steel pipe truss:
The structural member materials of the steel pipe truss include round pipes, square tubes, and rectangular tubes. The connection of steel pipe through Intersecting.
3. H-shaped steel truss:
The H-shaped steel truss has chords and webs that are all H-shaped steel or chords that are H-shaped steel, and the webs are round steel pipes, square steel tubes, or rectangular tubes.
4. Box-shape steel truss:
The box-shaped steel truss is in the form of chords and webs, both box-shaped or the chords are box-shaped, and the webs are round steel pipes, square steel tubes, or rectangular tubes.
When the web is round steel pipe, square steel pipe, or rectangular pipe, there is an intersecting connection between the web and chord.
Structural steel is a type of construction that uses steel as a primary material in building structures such as buildings, bridges, and towers. Steel has been used in construction for over 150 years and is considered one of the most versatile and durable materials.
Advantages of Metal Structures:
Strength: Steel is a very strong material capable of supporting heavy loads. This makes it ideal for use in high-rise buildings, bridges, and other structures where the structure’s weight must be supported.
Durability: Steel is resistant to many forms of damage, including corrosion, fire, and seismic activity. This makes metal structures ideal for use in harsh environments and for structures that must last for a long time.
Versatility: Steel can be shaped into any form and easily fabricated, making it suitable for use in a wide range of structures, from simple single-story to complex multi-story buildings.
Ease of Construction: Metal structures can be prefabricated, reducing construction time and cost. This makes metal structures popular for large construction projects, such as stadiums and office buildings.
Disadvantages of Metal Structures:
Cost: Metal structures are generally more expensive to construct than other structures, such as those made of wood or concrete.
Maintenance: Metal structures require regular maintenance to prevent corrosion and other forms of damage.
Environmental Impact: Steel production requires large amounts of energy and can result in significant environmental impacts, including air and water pollution.
In conclusion, metal structures are widely used in construction due to their strength, durability, versatility, and ease of construction. While metal structures have some disadvantages, such as cost and environmental impact, the benefits of steel structures generally outweigh these drawbacks. Metal structures continue to be a popular choice for construction projects worldwide and will likely remain so in the future.