In roll thread rebar coupler, the coupler is threaded by threading machine. To fit the bar in the roll thread coupler in reinforcement, the ends of the TMT bars are threaded in the Roll Thread Machine. After that the rebar coupler installation is done to the both ends of the TMT bar like nut and bolt, for the continuous reinforcement.
Rolling Threaded rebar coupler, also known as the names rebar connector, Steel bar coupler , Reinforcing bar coupler, mechanical rebar coupler is a joint of steel bars on a parallel line which is designed for reinforcement bars and usually used in conjunction with rebar threading machine.
Rebar couplers are used in reinforced concrete structures to replace normal rebar lap joints. The couplers are also suitable for use in reinforced concrete columns and walls.
This type is rolling parallel thread rebar coupler, Belongs to Rib peeling and rolling technology.
There are 3 Kinds of inside thread
1. Inside thread is standard thread (right hand thread).
2. One side is left hand thread, another side is right hand thread.(positional rebar coupler).
3. The inside thread of two sides are different diameters(Reducer coupler).
There are different code specification in India for Rebar Coupler which is given below
1. ACI:- 318-2008
Type 1:- As per this code joint should be required to achieve 1.25Fy as a minimum.
Example :- For Fe500 the tensile strength expected is at least 625 N/mm2.
Type 2:- As per this code Joint should be required to meet the 1.25Fy requirement and also meet the Tensile Strength of the rebar.
For Example :- For Fe500 the ultimate stress expected from the same is at least 700 N/mm2.
2. BS 8110-Part 1, Section 3, 1989
In this Code Specification testing of the rebar coupler of a precise type, the permanent elongation after loading to 0.6fy should not exceed 0.1mm.
For Example :- For grade 460 the tensile strength should exceed 497 N/mm2.
3. IS 1786-2008
In this Specification for Fe500 Rebar is considered acceptable for use anywhere in the structure if meets the ultimate strength of 545 N/mm2 which is much lesser than the 1.25Fy.
In this case, the Condition becomes at least 625 N/mm2 as well.
4. IS 16172-2014
Coupler to be designed for Fe550 grade.
The only tests recommended for acceptance on projects are static tensile tests.
Example :- Fe500 rebar breaking at a stress of 580 N/mm2 is acceptable as per IS 1786 requirement of 545 N/mm2.
