BS 8110 PI : 1997 Clause 3.12.8.16.2
The only form of full strength butt joint for a bar in tension comprises a mechanical couple satisfying the following criteria.
ACI 318-95 Clause 12.14.3.4
A full mechanical connection shall develop in tenision or compression, as required, at least 125% of specified yield strength of the steel bar
IS 16172:2014 ICS 77.140.15
The Indian standard for Reinforcement Couplers for mechanical splices of bars inconcrete.
When a test is made of a representative gauge length assemble comprising reinforcement of the size, grade and profile to be used, and the couplers of a precise type to be used, the permanent elongation after loading to 0.6 fy should not exceed 0.1 mm.
The tensile strength of the coupled bar should exceed
518.0 N/mm2 : for grade Fe415,
625.0 N/mm2 : for grade Fe500,
682.0 N/mm2 : for grade Fe550.
Thread characteristics | Standard Metric thread |
Preservation of re-bar cross section area | 100% |
Built-in safety factor | 40% above required thread area |
Minimum designed yield stress of coupler assembly | 575N/mm2 |
Minimum ultimate tensile stress of coupler assembly | 800N/mm2 |
Cutting
The end of reinforcing bar is squarely cut by circular blade cutting machine for perpendicularity.
Thread Rolling
Now the parallel threads are formed by cold rolled process at the end of the bars.
Increases tensile and compressive capacity of columns, long columns and long beams, where the designed tensile loading is greater than normal situations.
Tension couplers is so far the best solution for tension columns and tension piles.
Eliminates congestion of steel bars in heavily reinforced columns and core wall of building, thus reducing formation of “HONEY-COMB” in concrete structures.
Facilitates speedier concrete casting due to bigger space available between reinforcements.
Reduces cost and increases speed of slip and jump from work system in the construction of core walls and towers.
Avoids strains, corrosion and breakage of starter bars left for future extension of building and bridges.
Allows constant flow of traffic in construction of structures like bridges, where the structure could be constructed in stages.
Provides connections for starter bars for underground slab and beams in the construction of diaphragm wall. This prevents breakage of precast starter bars during the process of bending-up to avoid tedious concrete hacking.
Enables construction of micropiles, where spacing between bars is insufficient for lapping.
Reduces size of concrete section and ensures maximum usage of expensive floor space in office towers.
Enables connecting precast members to cast-in-site members, where a full tension splice is required.