Some useful construction tips on splicing reinforcement bars
Splicing is essential to combine two reinforcement bars to deliver the force from one bar to the joining bar if the length of reinforcement bar should have been expanded in reinforced concrete structural member.
The forces are delivered from one bar to the other via bonds in concrete. Initially force is transmitted to the concrete via bond from one bar and then it is transmitted to the other bar and develop the splice with bond among it and concrete. Therefore, concrete at the point of splicing is dependent on high shear and splitting stresses which can result in cracking in concrete.
Splicing of reinforcement bars is done with the following processes:
1. Lapping of bars
2. Mechanical joint
3. Welded joints
In India, the requisite of reinforcement bar splicing is described in IS456 cl.25.2.5. The code also defines that the splicing of flexural members should not be performed at sections where the bending moment is over 50% of the moment of resistance, and less than 50% of reinforcement bars are spliced at any specified section. The splicing of bars should be accomplished for substitute bars if above one bar has to be spliced.
Lap Splicing of Reinforcement Bars: When arranging lap splices in reinforcement bars, focus should be given on the following points:-
1. Laps in reinforcement is staggered at all times. The center to center distances of laps should be above 1.3 times the necessary lap length of the bars. The bars which have to be lapped should be placed either perpendicularly one above the other or parallel one beside the other.
2. The total lap length of bars along with bends, hooks etc. in flexural tension should be greater than 30 times the diameter of the bar of the complete development length Ld as measured, whichever is higher.