Edifice determines development of a country. The aesthetic view of structure leaves an impression of development, use of couplers provides a wide scope as far as building design is concerned. Lapped joints are not continuously suitable means of joining strengthening bars. The use of laps can be time consuming in terms of design and installation and can lead to greater congestion within the concrete because of the increased amount of rebar used[1-2]. Couplers can simplify the design and construction of reinforced concrete and reduce the amount of reinforcement required. Lapped joints are reliant on the concrete aimed at load transmission. For this reason any degradation in the integrity of the concrete could significantly affect the performance of the joint. The vitality of a mechanical splice is autonomous of the concrete in what it is positioned and resolution and retain its strength, despite loss of cover as a result of impact damage or seismic event [3]. The series of reinforcing bar couplers is the greatest existing and contains tapered threaded, parallel threaded, mechanically bolted and grouted couplers. Stainless steel couplers complete the range. Steel is very expensive and construction activities require large amount of steel. Increasing expense of steel is an area of concern. Use of couplers helps to overcome this concern couplers need fewer quantity of steel as associated to lap splicing. About 3%-5% steel is saved per splicing [4-5]. We know that time is also a major parameter in the construction of building. In situation of the high-rise building and highway bridges each day matters. And we know that splicing the bars with the help of wires takes time. In case of couplers this time can be protected. Couplers are the key for numerous difficulties which arise in the building construction.

The split ends of bars to be interconnected are cut square and distended by cold forging to raise their diameter so as to ensure that the joint is tough than the bar. The couplers are usually supplied attached to the reinforcing bar. First we use the upsetting machine to thicken the rebar at its ends as shown in Fig.1.Then use the steel bar threading machine to make thread on the end of rebars. Connect the two rebar ends with the upsetting rebar couplers.

2

is from 12 mm to 40mm. It has High efficiency, simple structure, and small volume, lightweight and easy operation. It is also suitable for hot working environment.

1. Rebar diameter range 10mm to 42mm 2. Oil pump flux 6l/min 3. Electric motor power 4.5kW 4. Piston movement distance 100 mm 5. Out dimensions (mm)

250*550*1200

The cutting threads externally on the outside of element are done on threading machine by chasing technique shown in Fig. 2. HSS tangential chasers are secondhand as cutters. The module leftovers stationery and Die side revolves. Threads which are cutted on this machine it confide in the category of chasers. For given diameter of rebar bar particular pitch is given TABLE III.

1 Rebar diameter range 10mm to 42mm 2. Mains voltage(v) 3 phase 3. Weight 1270 Kg

TABLE III. Rebar diameter vs Thread pitch

10 2.0 16 2.5 24 3.0 30 3.5 36 4.0

The end of the reinforcing bar is swan cut shown in fig 4.1

Vishal. G. Salunkhe1*, Bhushan. S. Walunj2, Amol. K. Ingle3 2

enlarged end and enclosed by plastic caps to shield the thread of rebar. Finally splice the rebar by using threaded couplers shown in fig 4.2

Material used for the production of the couplers is DIN 17200Gr. C45

1. Grade- C45 2. Condition- Rolled, Annealed, water quenched, oil quenched 3. Yield strength (MPa)- Rolled -460 Annealed -330 4. Tensile strength- Rolled -750, Annealed -540, water quenched -2270, oil quenched -1980 5. Elongation A5(%)Rolled -18, Annealed -30 6. Hardness HRC Rolled -58, Annealed- 55 7. Quenching Temperature- Rolled- 820, Annealed- 860 8. Bend ability Min..recommended bending radius (<= 900)

Established procedure of splicing couplers are restricted keen on four parts

(Threaded rebar and coupler) (Turns the rebars into the couplers to connect) that end of bars are threaded upto partial the size of the coupler

(Threaded rebar and coupler) (Turn the coupler onto short threaded rebar) Used where both rebars are not rotatable, then starter bar is threaded for the full coupler length so screw coupler onto the extended threads.

(Threaded rebars of different diameters and coupler) Used to connect rebars of different diameters by using reducing coupler.

(Turn the coupler and the lock nut onto the small threaded rebar) Worn wherever together rebars are not rotable, after starter bar are threaded for the full coupler lock nut length screw coupler and lock nut onto the extended threads.

2

TABLE V. Estimated dimensions of Threaded couplers

16 28 44 M20x2.5 24 34 52 M24x3.0 30 42 64 M30x3.5 36 52 76 M36x4.0 42 64 94 M45x4.0

TABLE VI. Estimated dimensions of pressing couplers

16 33 120 21.0 24 38 132 26.0 30 47 152 31.5 36 58 194 40.8 42 72 242 48.0

16 129 648 TMT bar 188 24 196 630 TMT bar 130 30 336 690 TMT bar 94

B. Cost estimation Cost of the coupler is from 5 Rs to 2000 Rs per piece. It depends on the type of the coupler. If we consider the wastage of the steel in overlapping splicing process after that price of the coupler is of steel will be saved. In same approximate budget only we can use the couplers.

1. Mechanical systems are more reliable than lap systems because they don‟t depend on the concrete for load transfer. 2. Mechanical connections offer greater structural integrity. Mechanical splices offer strength and toughness during man-made, seismic or other natural events. 3. Codes require that mechanical splices distribute advanced recital than distinctive design sizes aimed at lap splices. This is normally 125% to 150% greater capacity provided by the mechanical splice versus the lap splice. 4. Lap splicing upsurges rebar bottleneck at the lap region and is one of the foremost sources for forming rock pockets and voids in the concrete. Mechanical splices eliminate these bottleneck difficulties and resolve the global job additional price definite over minimalized job site difficulties. 5. Building codes stipulate a steel ratio of under 8% and this makes it nearly impossible to achieve a stable design with lap splicing. Mechanical splices permit the fashionable to achieve an perfect balance of steel and concrete by eliminating the additional rebar in the lap zone. 6. Working with “slight” diameter strengthening bars might necessitate the use of greater column proportions to billet a bigger quantity of bars. Using mechanical splices allows the option of larger diameter rebar in a minor column while minimalizing bottleneck. This condensed column size outcomes are more efficient design and an optimum use of floor space. 7. Mechanical splices eliminate tedious lap calculations 8. Mechanical splices are fast and easy to install and require no specialized skilled labor. 9. Mechanical splices are price effective by falling labor prices and fast-tracking job agendas. 10. Dowel bar substitutes reduce labor on site, form- work costs and increase job site

Vishal. G. Salunkhe1*, Bhushan. S. Walunj2, Amol. K. Ingle3 2

and simplify bar placing. 11. Repair splices eliminate the cost of breaking away massive amounts of concrete.

From Table VII we observe that after the application of load and stress on the bar, fracture was observed in the TMT bar spliced with coupler. But even though none of the cases fracture was observed in coupler. So this splices is having greater strength and toughness.

As we ensure that raised use of the coupler is tranquil and design welcoming. Though it is hard and benign to use. Though manufacturing cost of couplers in budget of construction is going to increase, but even 3% to 5% steel is protected which was lost in overlying. The price of saved steel is more than that of the manufacturing cost of couplers. So we can conclude that those couplers are welcome. They are not only unrestricted but they are money-spinning. Due to its rewards and not even any cost this method is more useful than the earlier one.

[1] Bertero V, Miranda E, Thompson C, “Cyclic behaviour of shear wall boundary elements incorporating prefabricated welded wire hoops,” National institute of Standards & Technology, New York, 1990. [2] Cheok S, and Stone C, “Performance of a 1/3 scale model precast concrete beam-column collections subjected to cyclic inelastic loads,” Report no, vol.4, Nistir 5436, June 1994. [3] Saatcioglu M, and Grira M, “Concrete columns confined with welded reinforcement grids,” Ottawa varelton Earthquake research center, Report OCEERC, pp. 96-05, March 1996. [4] Englekirk R. E, “Seismic Design of Reinforced and precast concrete buildings,” John wiley & sons, New Jersey June 2003. [5] Ozbakkaloglu T, Saatcioglu M, “Response of reinforced concrete frame buildings to blast loading,” Proceedings of the CSCE annual conference, Toronto, Dec 2005.