Different methods for splicing reinforced bars

5307
Splicing Reinforced Bar
Splicing Reinforced Bar

The method used to join the reinforcement bars, so that the force is transferred effectively from one bar to the other is called splicing. The method involves joining the bars together and overlapping them, but leaving at least two bar diameters between the bars. The two bar diameters provide space for the concrete to go in, around, and between the bars and increase the strength. When the length of the reinforcement bar has to be extended in reinforced concrete structural member splicing is used. In India, the requirement of reinforcement bar splicing is covered in IS456 cl.25.2.5.

Different methods of Splicing Reinforced Bar

Lap Splicing

This type of splicing is done using a lap splice to join two pieces of rebar overlap to form a continuous reinforcement. This helps transfer loads properly throughout the structure. There are two types of lap splices: contact lap and non-contact lap splices. The lapped sections of contact lap splices are wired together. Lapped sections of non-contact lap splices do not touch and are permitted in practice provided the distance between lap sections meets the specified code requirements.

Where reinforcing bars of two sizes are lap-spliced in tension, it is better to use the larger of the tension lap splice length for the smaller bar. The length of a lap splice varies with concrete strength, type of concrete, the yield strength of the reinforcing bars, bar size, bar spacing, concrete cover, and the number of ties or stirrups.

The total lap length of bars including bends, hooks, etc. in flexural tension should not be less than 30 times the diameter of the bar of the full development length Ld as calculated. Tension splices should be enclosed in spirals made from 6mm bars with a pitch not more than 100mm. Hooks are also to be provided at the end of the tension bars. When two different diameters of bars have to be lapped, the lap length should be calculated based on the diameter of the smaller bar.

Lap Splicing

Mechanical splicing

In this method of splicing, the bars in direct contact are mechanically connected through sleeves or other similar devices. The method is used to create connections between two pieces of rebar that enable the bars to act like continuous lengths of rebar. Mechanical splices join rebar end-to-end, providing many of the advantages of a continuous piece of rebar. Mechanical splicing methods are being adopted in project sites due to their flexibility of use in congested reinforcement places at construction joints.

The mechanical splices also allow structural designers to achieve an ideal balance of steel and concrete by eliminating the additional rebar lap zone by meeting building code requirements in many areas. A continuous reinforcement bar is obtained through this coupler splicing. The wastage of steel is also reduced. Mechanical splices maintain load path continuity of the reinforcement. The mechanical joints will not create any steel congestion as the lapping of bars is eliminated. Today, a range of threaded and non-threaded mechanical splices are available to ensure a precise, reliable connection.

Mechanical splicing

Welded splicing

This method of splicing is done by welding so that the stresses are transferred by weld. Welded splicing is used for special conditions splicing of rebars with a diameter greater than 36mm. It is preferred for rebar congestion wherein greater moment strength is required. The welding processes most commonly used are the shielded metal arc welding process, the gas metal arc welding process, and the thermit welding process.

Welded splicing

Conclusion

The need for a more efficient splicing system is becoming more apparent as a result of the increased construction complexities and design requirements. The use of reinforcement rebar couplers can simplify the design and construction of reinforced concrete and reduce the amount of reinforcement required. Discussed above are different splicing methods, each has its advantages and is used as per project suitability.