What is Bracing in construction?
Bracing is used in construction to support a structure against lateral stresses such as wind and seismic pressure. It contributes to the building’s stability and resistance to the impacts of earthquakes. It strengthens the building and makes it earthquake resistant. Steel members are used to strengthening braced constructions, enhancing their tensile and compressive strength.
Columns and beams carry the vertical loads of the building in frame construction while bracing bears the horizontal load. The basic goal of bracing in any construction is to keep it stable and prevent it from collapsing. All horizontal loads are transferred from the frame to the foundation.
Types of Bracing System
There are two types of bracing systems used in building construction:-
Horizontal Bracing System
- Bracing is provided on each floor (in horizontal planes) to offer load paths for the transference of lateral forces to the vertical bracing planes.
- It is necessary to provide bracing on every floor. The floor system itself can provide sufficient resistance, but the roof may require bracing.
- Horizontal bracing systems are intended to transmit horizontal loads from columns at the structure’s perimeter to vertical bracing planes.
- The pressure of wind forces on the cladding of the structure causes horizontal forces on the columns near the structure’s edge.
- Horizontal bracing has two types, which are used for multi-story steel structures:
1. Diaphragms Bracing 2. Discrete triangulated Bracing.
Vertical Bracing System
- The bracings in the vertical planes are located between the column lines, providing load channels that are utilized to transmit horizontal forces to the ground level, and this system will transfer horizontal loads to the foundations.
- Framed buildings need at least three vertical bracing planes to withstand torsion about a vertical axis and brace both directions in the layout.
Types of Bracing
- Single Diagonal Bracing
- Cross Bracing or X Bracing
- K Bracing
- V Bracing
- Chevron Bracing
- Eccentric Bracing
- In a rectangular frame, the braces are placed diagonally to stabilize the structure and resist tension as well as compression.
- Sufficiently resistant to tension and compression.
- Here bracing is placed at an angle of 45° for an efficient system, and this type of arrangement is strong.
- Vertical bracing is specially designed to resist high wind loads and horizontal forces acting on it.
- If we increase the bracings at the vertical plane, then it will automatically improve the structural stability.
Cross or X Bracing
- Cross bracing used two diagonal members intersecting each other, which was suitable to resist tension only.
- Cross bracing can interfere with the position and operation of door and window openings, causing higher bending in the floor beams.
- Connects to the columns at mid-height.
- These frames are more flexible and they have provisions to provide openings in the outer face, which results in the least bending in floor beams.
- K bracing is not used in seismic areas due to the danger of column failure if the compression brace buckles.
- This bracing consists of two diagonal members moving down, from the two corners of the horizontal member and meeting the center point of horizontal members, which forms the shape of the letter V.
- V bracings are also known as chevron bracing (it is just the inverse of V bracing. Look at the figure below.)
- It is commonly used in seismic regions.
- It is similar to V-bracing but its bracing members don’t meet at the center, they are slightly far from each other.
- This is done so that the ‘link’ between the bracing members absorbs seismic energy through plastic deformation.
- Eccentric single diagonals can be utilized to support a frame as well.
Uses of Bracing
- Bracings are used to stabilize the structures
- Used in bridges to support frames.
Advantages of Bracing
- Used to resist the bulking of the main beam in the structure.
- To provide strength to the existing structure.
- Helps in distributing lateral and vertical loads equally to the structure.
- Resist wind and seismic force in an excellent way.
- It is cost-effective and flexible to design.
Disadvantages of Bracing
- When reinforced, the length of the span of the structures is limited to 40 feet.
- It requires skilled workmanship.
- Seismic region changes that rely on altitude.