What is a Bracing System in the Steel Structure?
Steel structure buildings are developing rapidly in the construction industry. It not only has good structural strength but also has good seismic performance, fire performance, sound insulation and thermal insulation performance. The bracing system is a secondary part of the steel structure system, but it is also an essential part.
In the portal rigid frame steel structure, the bracing system has important functions, mainly ensuring the stability of the overall structure and individual components, transmitting the horizontal action to the foundation and auxiliary installation works, etc.
For a structure with a complex plane layout, the bracing system is also conducive to the adjustment of the structural rigidity, so that the force of the structure is uniform and reasonable, and its integrity is improved.
Bracing system in steel structure refers to the use of steel pipes, H-beams, angle steels, etc. to enhance the stability of the engineering structure. Generally, it is an inclined connecting member, and the most common are herringbone and cross shapes. Because the steel bracing can be recycled and reused, it has the characteristics of economy and environmental protection.
Further Reading: Steel Building Plans and Specifications
Different Types of Bracing Systems
Roof Bracing System
The roof horizontal support and the inter-column support are a whole, which together maintain the stability of the structure, and transmit the longitudinal horizontal load through the roof horizontal support and through the inter-column support to the foundation.
In order to ensure that the transmission path of the longitudinal load on the structural gable is short and fast, the lateral horizontal support of the roof should be arranged in the bays at both ends of the building temperature section, so as to directly transmit the gable load. If it cannot be installed in the first bay, it can be set in the second bay.
But it must be noted that the rods in the first bay that transmit horizontal loads should be designed as compression rods. When the building or temperature expansion section is long, one or more horizontal supports should be added, and the spacing should not be greater than 60m.
When the structure is simple and symmetrical, and the heights of each span are the same, the horizontal support of the roof is relatively simple, that is, it can be set only in the end openings under the condition that the length of the temperature section is satisfied.
In a building, when the columns have different column spacing, or when the building has a change in height and span, vertical horizontal supports should be installed to improve the integrity of the structure, and the distribution of lateral stiffness of the structure should be adjusted to reduce the size of each rigid frame.
The difference in the lateral horizontal displacement of the column makes the force of the structure uniform and reasonable. When the layout of the building is irregular, such as when there are local protrusions and concave, pull out columns, etc., in order to improve the overall lateral resistance of the structure, it is necessary to set up a continuous horizontal support system closed longitudinally and transversely in the above areas.
When setting up the support system, it is necessary to set pressure rods at the roof ridge and column top and pay attention to the structure of the nodes to ensure the transmission of horizontal force.
Column Bracing System
The inter-column support is generally arranged in the middle of the column row. For this reason, the horizontal tie rod at the top of the column needs to be designed as a rigid tie rod, so as to transfer the load borne by the horizontal support of the roof to the inter-column support. If the building is long, inter-column support can be added.
The supports between the two columns are placed at 1/3 of the longitudinal direction. When the inter-column support cannot be set in the ideal position required by the structural design due to the requirements of the building, it can also be set off from the middle of the column. The inter-column supports can be designed in a cross shape, a figure-eight shapes, a door shape, or even a rigid frame.
It is better to use one type of inter-column bracing in the same building, and it is not advisable to mix several types of inter-column bracing. If due to functional requirements such as opening doors, windows or other factors, rigid frame support or truss support can be used. When the support system must be used in combination, the rigidity should be as consistent as possible. If the rigidity cannot be met, the longitudinal horizontal force borne by each support should be analyzed in detail to ensure the stability and safety of the structural symmetry.
The inter-column support can form a solid longitudinal frame to ensure the longitudinal rigidity and stability of the steel structure workshop; The inter-column support can withstand the wind load, longitudinal horizontal load and temperature stress of the gable wall of the steel structure workshop;
The inter-column support of the steel structure workshop can be used as the fulcrum of the frame outside the frame to reduce the calculated length of the frame outside the frame, thereby reducing the overall stability calculation of the steel structure workshop.
Angle braces are unique to solid-web portal rigid frame light steel structure buildings. The angle brace is arranged between the lower flange of the rigid frame inclined beam and the purlin or between the inner flange of the rigid frame side column and the wall beam. It supports the stability of rigid frame inclined beams and rigid frame side columns. The angle brace is an auxiliary member that does not become a system independently.
The function of the rigid frame inclined beam angle brace is to prevent the lateral instability of the inclined beam when the lower wing is compressed.
Angle iron is generally used for corner bracing, and the angle between the corner bracing and purlin or wall beam should not be less than 35°, and the minimum angle steel L40*4 can be used. Corner braces are bolted to beams or side columns and purlins or wall beams.
In general, the angle brace should be installed in the full span of the rigid frame inclined beam, mainly considering the possibility of the flange of the beam being compressed under the action of wind load, it can be installed only in the area where the lower flange of the beam is compressed near the support.
Bracing System Setting Principles
- Clearly, reasonably and simply transmit the longitudinal load, and shorten the force transmission path as much as possible;
- Ensure the out-of-plane stability of the structural system, and provide lateral support points for the overall stability of the structure and components;
- It is convenient to install the structure;
- Meet the necessary strength and stiffness requirements and have reliable connections.
Further Reading: Steel Structure Installation & Design
- How to Design Steel Building Components & Parts
- How Much Does a Steel Building Cost
- Pre-Construction Services
- What is a Steel Portal Framed Construction
- How to Read Structural Steel Drawings
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K-home Steel Structure Co., Ltd covers an area of 120,000 square meters. We are engaged in the design, project budget, fabrication, and installation of PEB steel structures and sandwich panels with second-grade general contracting qualifications. Our products cover light steel structures, PEB buildings, low-cost prefab houses, container houses, C/Z steel, various models of color steel plate, PU sandwich panels, eps sandwich panels, rock wool sandwich panels, cold room panels, purification plates, and other construction materials.