What is coupler in reinforcement?
A rebar is a product that is used when a long length of the bar is required. The primary work of the coupler is to join 2 TMT bars for continuous reinforcement. It is used in all the construction fields like the construction of buildings, bridges, dams, towers, etc.
What is rebar coupler?
Rebar couplers are used in reinforced concrete cement structures to replace the system of lapping & welding in reinforcement. Couplers are used where the long length of the bar is needed or When joining the extra bars to the end of existing bars are tied by wire next to each other.
There is a waste of bars in the welding system & lapping system, alternative system is used called a rebar coupler or coupler in reinforcement that provides an end-to-end connection for the continuous reinforcement of any structure.
The coupler is economical and cost-efficient unlike the lapping system, where some part of the bar is wasted due to lapping. The Couplers are generally known as mechanical splices. It is used in all construction such as the construction of buildings, bridges, dams, towers, etc.
Types of rebar couplers
There are mainly two types of rebar couplers in reinforcement. They are,
- Threaded rebar coupler
- Roll thread coupler
- Cold forged rebar coupler
- Non-threaded coupler
- Crimping rebar coupler
- MBT coupler
1) Roll thread rebar coupler
In this coupler, the coupler is threaded by a threading machine. To fit the bar in the roll thread coupler, the end of the TMT bars are threaded in the roll thread machine.
After that, the coupler installation is done to both ends of the TMT bar such as nut & bolt, for continuous reinforcement.
2) Cold forged rebar coupler
The cold-gorged coupler is also threaded by the threading machine like roll thread rebar coupler. But in this coupler, the end of the TMT bar is forged with the help of a forging machine by hydraulic pressure.
After the process of forging the end of the TMT bar losses, a minimal part of length & rises in thickness & the bar is threaded by the threading machine & is fitted to the coupler. It is passed for big infrastructure projects & other government projects.
3) Crimping rebar coupler
It is also known as the first coupler in reinforcement in construction & after that threaded coupler was introduced. There is no thread in the crimping rebar coupler.
The rebar coupler is fitted in two ends of the TMT bar without thread & the coupler is crimped by a crimping machine. The crimping coupler is not economical & more material is used & the labor cost is also high.
A crimping coupler in rebar cannot be un-crimped after installation. Because of this, the crimping coupler system has failed in the market.
4) MBT rebar coupler
The MBT rebar coupler is designed for the critical conditions of continuous reinforcement.
The MBT coupler is used in reinforcement when there is less lap length & not much of a bar is left for continuous reinforcement. It is also used in retrofitting constructions.
There are six to eight bolts in the top MBT coupler. Its length is more than a threaded coupler. The strength of this coupler depends on the number of bolts present on it & with the help of these bolts the coupler in reinforcement is installed.
Test of rebar coupler
The coupler in reinforcement is processed by various rebar coupler testing. Some tests of coupler are as follows:
- Cyclic tensile test
- Low cycle fatigue test
- High cycle fatigue test
- Static tensile test
- Yield strength of steel
- Slip test
- Chemical test
Advantages of rebar couplers
Some advantages of the coupler in reinforcement are as follows;
- It has great quality control & is easy to supervise.
- The load transferring is proper.
- The coupler does not create congestion.
- The continuity load path is accurate.
- The rebar coupler is very economical compared to all the systems of joints in reinforcement.
- The Coupler increases the work speed by quick installment.
- The connection inspection is easy & simple.
- It increases the use of the bar by not wasting bars like the lapping.
- The coupler reduces the lapping length calculation.
- It improves structural integrity.
Disadvantages of rebar couplers
Some disadvantages of coupler in reinforcement is given below;
- Possibility of misalignment in the attachment of 2 shafts which will create an excessive force on the coupling, bearing & shaft, causing them to wear prematurity.
- It is difficult to available a coupler in the local market whose diameter is more than 32 mm or more.
- Skilled manpower is required for the assembling process.
- It can create structural damage if the grade of the coupler will not equivalent to the reinforcement bars.