The lapping of rebars has long been considered an effective, economical splicing method, But Lapped joints are not always an appropriate solution for connecting rebars. Today’s more demanding concrete designs are compelling engineers to consider alternatives to conventional lap splices. Which is mechanical splice or rebar couplers.
In almost all RCC structures, rebars need to be spliced. Splicing is required when the required length of a bar suppresses the available length of steel rod, or the rod may be too long to be delivered conveniently.
For example, suppose we need to build a 30 m long building, but there is not a single 30 m long bar available in the market. In that case, we need more pieces of steel bars that must be spliced together to achieve the desired length.
In projects with small bar sizes such as of number 6 or number 8, relatively low yield stress in steel, and building heights of 15 stories or less, lap splices have performed well over a long time.
RCC framed structural buildings nowadays are being built to 100 stories and more. The bar sizes from number 8 to number 11 with yields of 60 or 75 ksi are used in current design practice for structural framing And the accepted concrete strengths by code vary from 8000 to 12,000 psi. The use of higher-strength concretes permits shorter lap lengths. That’s why rebar couplers are getting more attention.
What Is Rebar Coupler?
Rebar couplers or mechanical splices are used to connect reinforcement bars of various grades and diameters. They eliminate the use of lapping and welding. Rebar couplers can join rebars with full tension capacity.
The ends of steel bars to be joined are provided with threads, and a coupler is used to join rebars end-to-end, which transfers the loads on the rebar across the connection. They are more efficient than lap splices because they do not depend on the concrete for load transfer.
Rebar couplers have all of the essential features required in a rebar joining system. They are designed with unequaled simplicity of installation to join the rebars of the same diameter where one bar is movable and rotatable.
The coupler system is available in various styles to meet virtually any application. They are used in
i) Bar-to-bar connections,
ii) Precaging applications,
iii) Hooked bar applications,
iv) Closure pours,
v) Precast connections, rebar terminations and anchorages,
vi) Transition splices, segmental construction,
vii) Connections to structural steel.
The most popular mechanical splicing systems are Interlock, Quick wedge, Speed sleeve, Terminator, Lock, Form saver, Taper thread splices, and Cad weld splices.
Advantages Of Rebar Couplers/Mechanical Splices:
i) The self-aligning taper-threaded design of mechanical splices maintain load path continuity of the reinforcement, providing full strength in tension and compression stresses.
ii) Mechanical splices do not depend on the concrete for load transfer.
iii) Improved structural integrity.
iv) Rebar couplers eliminate the errors which are caused due to providing the wrong lap length.
v) A common problem during concrete placing is that the concrete can’t be poured well through the rebar cages. The congestion due to lapping restricts the flow and distribution of larger sized aggregates and limits the performance of vibrator. Mechanical splices significantly reduce this congestion.
v) Develops higher tensile strength than lap splicing in RCC structure.
vi) The amount of steel used in reinforcement is less compared to lapping, reducing the material costs.
vi) Eliminates the tidy lap splice calculation.
vii) Inspection of connection is easy.
viii) Great quality control.
ix) Quick and easy to install increasing speed of works.
x) Dowels avoided enabling reuse of form works
xi) Reduced construction cycle time.
xii) Minimal wastages of steel when using rebar couplers.
Couplers Vs Lapping Vs Welding:
|1. Load Path Continuity||Accurate||Not good||Not good|
|2. Load Transfer||Great||Depends on concrete||Depends on concrete|
|3. Structural Integrity||Great||Moderate||Moderate|
|5. Steel Quantity||Less||Requires extra steel for lapping.||Requires extra steel for welding|
|6. Rebar Congestion||Rebar couplers does not create congestion||Creates congestion, Difficulty in concrete pouring and vibration||Creates congestion, Difficulty in concrete pouring and vibration|
|7. Splice Calculation||Not required||Required||—|
|8. Supervising||Easy||Easy||Not easy|
|9. Quality Control||Great||Moderate||Low to medium|
|12. Time||Fast work||Time consuming||Time consuming|
|13. Installation||Very Easy||Easy||Welder Required|
So, from the above comparison, we can see rebar couplers or mechanical splices are far better than lapping or welding. We can use it in any construction effectively.
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