In reinforcement of steel bars, splicing technique is generally used to produce a single large reinforced steel bar by joining two similar length reinforced bars and wiring them. Splicing is used in situations that demand the use of reinforced steel bars that have lengths higher than the standard specified length. Even though in theory it is possible for reinforced bars to have a length up to 40 feet, in practice, it is not feasible.
Types of splices for reinforced bars
Splicing in reinforced bars mainly consists of three types. Each splicing type is determined by the design engineer based on certain criteria such as the diameter of the reinforced bar, skilled labourers etc. The three splicing techniques are:
- Lap splicing
- Mechanical splicing
- Welded splicing
One of the most common and economic splicing technique implemented in construction is the Lap splicing. It requires the overlapping of two parallel bars. Lap splicing is commonly preferred because the other splicing types namely mechanical splices and welded splices require more skill and labour force. When performing lap splices, reinforcement bars should always be staggered. The reinforced bars should be provided either horizontally one beside the other or vertically one above the other. When two different diameters of rebars have to be lapped, then the lap length should be calculated based on the diameter of the smaller reinforced bar.
Reinforced bar having a diameter more than 36mm is not used for lap splicing. In those scenarios, the rebars are joined using welded splicing. When a bundle of reinforced bars are to be spliced by lapping, then lap splicing is performed one bar at a time. The length of a lap splice varies with concrete strength, type of concrete, grade of the reinforced bars, size, bar spacing, concrete cover, and the number of ties or stirrups. Lap splices get necessary strength from the concrete cover and deterioration of concrete will inevitably lead to splice failure.
Mechanical splicing or butt splicing is a technique in which two pieces of reinforced steel bars are joined by mechanical connections such as couplers. This provides many of the advantages of a continuous piece of rebar. They are more reliable than lap splices because they don’t depend on concrete for load transfer. Furthermore, these splices provide superior strength than lap splicing during load transfer.
This is a new type of splicing technique in the Indian construction sector. When compared to lap splicing technique, mechanical splicing has several benefits such as
- A single continuous reinforced bar is obtained.
- The errors caused by wrong lap length in the conventional methods are avoided.
- Using a mechanical joint helps to avoid lap length.
- Steel wastage is decreased.
- Mechanical joints don’t create any sort of steel congestion as lapping of the bars are eliminated.
- Couplers provide more flexibility for designers.
Couplers are commonly used for mechanical splicing of the reinforced bar. Mechanical couplers consist of two types which are Threaded Couplers and Non Threaded couplers. Threaded couplers are further classified into Tapered Threaded Couplers and Roll Threaded Couplers. Similarly, the Non-threaded Couplers are also classified into Bolted Couplers, Friction weld couplers, Welded Couplers and Swage Couplers.
Welded splicing is a technique which is done by joining two reinforced bar by electric arc welding. Before performing welded splicing on the reinforcement a proper chemical analysis of the rebars, field inspection, quality of the steel and proper supervision is necessary. Compared to the previous two splicing types, welded splicing is only preferred under special conditions and rules such as the diameter of the reinforced bar must be greater 36mm. Also, it is preferred only for areas that require, avoiding rebar congestion and high moment strength.