Bracings play a vital role in ensuring the stability and integrity of steel structures. They provide resistance against lateral loads, such as wind and seismic forces, which can pose significant challenges to the structural integrity of buildings. In this blog post, we will delve into the world of bracing systems and explore the different types commonly used in steel structures.
The advantage of bracing is under bending loads compression flange of the main beam tend to buckle horizontally. The Bracing systems resist the buckling of the main beam. Bracing system help in distributing the vertical and lateral loads between the main beams.
Majorly Bracing systems are classified as:
- Horizontal Bracing System
- Vertical Bracing System
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Horizontal bracing system
The bracing at each floor level provides load paths for the transference of horizontal forces to the planes of vertical bracing. Horizontal bracing is needed at each floor level, however, the floor system itself may provide sufficient resistance. Roofs may require bracing.
Vertical bracing system
Bracing between column lines provides load paths for the transference of horizontal forces to ground level. Framed buildings required at least three planes of vertical bracing to brace both directions in plan and to resist torsion about a vertical axis.
It can also be studied in two types namely:
- Concentric bracing
- Eccentric bracing
Concentric braced frames (CBF)?
Concentric braced frames are a type of structural system that resists lateral loads through diagonal braces that are connected to the beams and columns at their joints, forming a truss-like configuration.
They are called concentric because the axes of the braces and the other framing members are aligned at the connections.
Concentric braced frames are commonly used in low-rise buildings because they provide high stiffness and strength. However, they have limited ductility and energy dissipation capacity compared to eccentric braced frames.
Concentric braced frames can have different configurations, such as X, K or one-directional diagonal bracing.
Eccentric braced frames (EBFS)?
Eccentric braced frames are a type of structural system that combines the strength and stiffness of a braced frame with the energy dissipation characteristics of a moment frame.
They are called eccentric because the braces are connected to the beams or columns at points that are not aligned with the joints, creating intentional eccentricities. This allows the beams or columns to deform in shear or flexure, respectively, and dissipate seismic energy.
Eccentric braced frames are commonly used in areas with high seismic activity because they offer more ductility and resilience than concentric braced frames.
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Which is the commonly used bracing in steel structure?
1. X- bracing
Connection for X- bracing are located at beam to column joint. Bracing connection may require large gusset plate at the beam to column joint. The restriction of space in these areas may have an impact on the mechanical and plumbing systems as well as some architectural features.
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| X-bracings |
2. Chevron bracing
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| Chevron Bracings |
The members used in chevron bracing are designed for both compression and Tension. Chevron bracings allows for doorways or corridors through the bracing lines in a structure.
Chevron bracing members use two types of connections. The Floor level connection may use a gusset plate as like in x-braced frame. The bracing members are connected to the beam/girder at the top and converge to a common point.
When gusset plate is used, it is important to consider their size when laying out any mechanical equipment pass through brace bays.
Final Words or conclusion
The bracing systems are necessary for structures that are subjected to lateral loads due to earthquake, wind, etc. They help in minimizing the lateral deflection of the structure. We can say that the beams and columns of the framed structure carry vertical loads while the bracing system carries the lateral loads.