What’s rebaring? And how does it differ from bar bending?
Concrete is a material that is very strong in compression, but relatively weak in tension. To compensate for this imbalance in concrete’s behaviour, rebar is cast into it to carry the tensile loads. Most steel reinforcement is divided into primary and secondary reinforcement, but there are other minor uses:
- Primary reinforcement (Main Steel) refers to the steel which is employed to guarantee the resistance needed by the structure as a whole to support the design loads.
- Secondary reinforcement(Distribution Steel), also known as distribution or thermal reinforcement, is employed for durability and aesthetic reasons, by providing enough localized resistance to limit cracking and resist stresses caused by effects such as temperature changes and shrinkage.
Steel Reinforcement in Slab
Rebar
- Rebar is employed to confer resistance to concentrated loads by providing enough localized resistance and stiffness for a load to spread through a wider area. Rebar be used to hold other steel bars in the correct position to accommodate their loads.
- They are usually provided at the junctions where formwork is closed and new element of the structure needs to form a bond with the previous one.
Rebar’s surface is often patterned to form a better bond with the concrete.
Placing rebar
Steel wire used to secure rebar before concrete is poured over it
Rebar cages are fabricated either on or off the project site commonly with the help of hydraulic benders and shears. However, for small or custom work a tool known as a Hickey, or hand rebar bender, is sufficient. The rebars are placed by steel fixers “rod-busters” or concrete reinforcing iron workers, with bar supports and concrete or plastic rebar spacers separating the rebar from the concrete form-work to establish concrete cover and ensure that proper embedment is achieved. The rebars in the cages are connected either by spot welding, tying steel wire, sometimes using an electric rebar tier or with mechanical connections. For tying epoxy coated or galvanised rebars, epoxy coated or galvanized wire is normally used.
Stirrups
Stirrups form the outer part of a rebar cage. Stirrups are usually rectangular, and are placed at regular intervals along a column or beam to prevent shear failure.
Steel wire used to secure rebar before concrete is poured over it
Rebar cages are normally tied together with wire, although spot welding of cages has been the norm in Europe for many years, and is becoming more common
Mechanical connections
Also known as “mechanical couplers” or “mechanical splices”, mechanical connections are used to connect reinforcing bars together. Mechanical couplers are an effective means to reduce rebar congestion in highly reinforced areas for cast-in-place concrete construction. These couplers are also used in precast concrete construction at the joints between members.
Safety:
To prevent injury, the protruding ends of steel rebar are often bent over or covered with special steel-reinforced plastic “plate” caps. “Mushroom” caps may provide protection from scratches and other minor injuries, but provide little to no protection from impalement
Steel tie bars can constrain and reinforced masonry structures. They tie the main and distribution bars.
Yellow bars are tie bars
Simply bending the reinforcement bars mechanically
These are bended bars.
The bars which comes out of the formwork from the other side, which are welded or anchored or chemically bonded with concrete are the rebars.