Technical field: Truss elements and their mechanical connections used for structural concrete utilizing and as reinforcements for the stnittural concrete members instead of traditional reinforcing bars and stirrupjs or welded joints truss. The produced truss can be used for bearing weight of slabs, fresh concrete and construction working loads without provisional support.

Introduction and Previous Art

Reinforced concrete is one of the widespread building materials all over the world. The advantages of reinforced concrete including low costs; high compressive strength; better resistance to fire than steel; it can be cast to take required architectural shape, and it yields rigid members with minimum apparent deflection.

Reinforced concrete element such as columns, beams, rafts and slabs are reinforced by reinforcing steel bars or bars made of fiber reinforced polymer. Reinforcement is applied mainly for these elements to resist stresses such as tension and shear. Lap splicing has become the traditional method of connecting the reinforcing bars. Lap splicing requires the overlapping of two parallel bars. The overlap load transfer mechanism takes advantage of the bond between the steel and the concrete to transfer the load. The load in one bar is transferred to the concrete, and then from the concrete to the ongoing bar. The bond is largely influenced by deformations on the surface of the reinforcing bar. The lap splice length depends on many parameters. According to ACI 12.2, these parameters include, steel grade, bar surface condition, bar size, design load and others.

ACI R21.3.2.3 states that lap splices are not considered reliable under conditions of cyclic loading into the elastic range. Because lap splices develop their strength from concrete cover, deterioration of concrete will inevitably lead to splice failure. The overlap transfer method generates additional forces in the concrete which tend to push the bars apart, so concrete cover must be strong enough to overcome this "bursting" force. Bursting force can cause spalling of the concrete cover and splice failure. Because of bursting force for larger size reinforcing bars, additional transverse reinforcement is required by most design codes. In addition to disadvantages stated above, the use of lap splices leads a large amount of waste in the reinforcing steel bars.

In summary, there would be massive wastage in reinforcement steel or steel rods because of the space that must be added at the end of stresses area, in addition to lap splices, hooks and rod folding. Besides, reinforcement is applied to cover areas not to cover points of maximum stresses.

On the other hand, the maximum stresses on the structural elements subjected to applied load are at specific points or lines while reinforcements even with or without mechanical couplers, placed to cover areas far outweigh the maximum stress areas.

Therefore, the reinforcements do not follow exactly the stress path which leads to a large amount of waste in the reinforcing steel.

The question is: is it possible via the traditional reinforcement method to place the required reinforcements at each point of the structural element to following the stress path? The answer is no. Stresses have maximum values at a given points then it quickly decreases, and these stresses may convert from tension to compression, so it would be difficult to deliver reinforcement sufficient to each of stress values at each point. In the traditional method, certain amount of reinforcing steel rods are used to cover the maximum stress value in a wide area, compared to the point of maximum stress, in addition to increasing the reinforcing bar lengths behind the selected area as anchorage lengths. Also, wastage may occur because of excessive length of rods which does not match the requirements of reinforcement, and hence there would be more wastage in reinforcement amount applied.

Hence, there would be massive wastage in reinforcement amount, especially when that reinforcement is made using steel, which is considered the most expensive component of the reinforced concrete.

During the last three decades interests were increased in truss reinforcement for concrete beams. Compared to traditional reinforcements, truss shape reinforcement has the following advantages:

i. The trusses reinforcement can bear their own weight and the weight of slabs and fresh concrete without provisional support during a first assembly stage. Therefore, when the concrete reaches its designed strength, the truss reinforcement can sustain the working loads together with the casted concrete.

ii. A large amount of space is available for construction activities,, such as for depository.

The strong reduction of the number of supports implies the elimination of the most part of obstacles which are one of the most important sources of risks and injuries in building sites. The accessibility of the building site is much easier and thus the internal mobility is improved for both machines and workmen. Typically, all these positive features lead to a sensible reduction of the management costs and allow for more rational spaces utilization.

iii. Trusses save significant amounts of material and dead weight.

iv. Easier placement of the truss shape reinforcement saves valuable crane time, and helps to keep labor costs to a minimum while maintaining or accelerating project schedules. v. The placement of the truss girders reinforcements does not require skilled labor for

manually manufacturing the reinforcing structure on the building site.

v. The large prefabrication of the steel reinforcement speeds up the construction activities;i. The risks due to the beam reinforcement working in the building site are strongly

reduced. In fact, the truss structure needs to be mounted by using opportune cranes and only little in situ workmanship is needed.

A number of recent references studied long reinforced concsete beams reinforced with trusses having welded joints. With numerous advantages in using trusses as reinforcements, but the welded joint have some drawbacks, among them:

i. Welding the truss joints requires skilled manpower, inspection, proper temperature and chemical composition of the steel alloy;

ii. Welded joints are highly prone to cracking under fatigue loading. Large residual stresses and distortion are developed in welded connections;

iii. The joints suffer from eccentricity problems and probable failures of the surrounding concrete due to the kinematic behavior of the end connections.

iv. The constantly changing anti-earthquake regulations and seismic design criteria have critically affected the adequacy and reliability of the design and use of such joints.

On the Traditional couplers based on cold metal forming create interlock of the sleeve with rebar deformations by applying external pressure to the sleeve, forcing the walls of the sleeve to formed and penetrate into the deformation shape of the reinforcement. The technique requires special field equipment, sometimes cumbersome. Since the sleeves are manufactured from materials other than rebar and may have different machinability and formability, added quality control procedures are required. The metal forming splice techniques also leave some doubt as to whether proper interlock has been achieved, since they cannot be visually inspected. They are not compatible with epoxy-coated rebar because coating deterioration may be caused by the physical processes required.

The traditional hot forged system is similar to cold metal forged one described above but performed by heating the sleeve till reaching its forging temperature. The hot forged method requires a furnace and fuel source near the immediate work area. The sleeves are heated to about 2000 degrees F, removed from the furnace, and positioned over the bar ends to be spliced. The adjoining bars are positioned in the opposite ends of the splice, and the hot sleeve is forged into the deformations of both bars by a hydraulic ram. Contraction of the sleeve upon cooling improves bond and increases the splice strength.

The applicability of the hot forged technique with these requirements becomes too difficult in practice or even avoided.

Induction Heating Technique

Induction heating is a subfield of the industrially used electric heating techniques. All electrically - conductive materials can be heated quickly and cleanly with pollution-free induction heating. Features of such technique include:

• Selected parts of the work-piece can be heated;

• Heating time and temperature can be precisely controlled;

• There is no smoke or soot pollution;

• Heating operation can be integrated in semi-automatic production sequences;

• Induction equipment can usually be operated by unskilled personnel;

• Induction heat treatment can be used for melting ferrous and non-ferrous metals with temperatures up to 1800°c.

One from many coupling technique presented in this invention is the induction heating which use forging from 750oc and up to 1250oc. This type of heating has the following advantages: very fast partial hardening; high production rates; significant reduction in pollution, distortion, forging scale, energy and space requirements and high degree of reproduction and automation;

Element of Novelty

This work is an attempt towards safer and economic reinforcement for concrete members. The invention relates to trusses reinforcement for the structural concrete members instead of traditional longitudinal and transverse bars and stirrups. The invention provides, a high tensile and compressive strengths mechanical coupler having multiple branches and directions used for assembling the truss members or multi-direction reinforcing bars. The bar ends may be with or without end preparations like threading. The invention provides mechanical couplers with several branches, directions and several closure techniques fasten the straight members or reinforcing rods thereto, either via adhesion, bolting, threading soldering and/or riveting. The coupler may be one or more pieces, and more than one type of couplers can be used in the same truss. The suggested method highly reducing the reinforcement amount of the concrete members reduces its weight, highly improves the structural performance of the produced members, increase its load capacities and completely avoid reinforcement wastage.

Moreover, in traditional reinforcement the concrete members, bending the high strength steel causes stress concentration at the bending points which may greatly reduce the overall strength of the reinforcing bars. A proposed solution for this problem is coupling the two or three bars together instead of bending the bars using the suggested mechanical couplers. This solution is vital in the case of beam-column connections subjected to high tensile stresses. Moreover, the proposed coupler could solve the problem of special bent bars in regions of high shear stress.

Detailed Description

According to the present invention, two-dimensional and space truss reinforcements and joints for the structural concrete members instead of traditional reinforcing bars and stirrups or welded joints truss, comprising:

1-5 Straight members.

11 Coupler body for straight members.

12 Special U-shape bolt.

23 Coupler branches coming out from solid central part.

13 Protruded parts.

14 Holes in protruded parts.

15 Tip threading.

16 Nut.

17 longitudinal protruded flange wing out from the upper portion of the branch

21 Solid central parts of the coupler.

22 Solid part cap joins the tip ends of the straight members to the main body of the coupler.

24 Central hole.

25 Side hole.

26 Central threaded hole.

27 Side threaded hole.

28 Central threaded bolt.

29 Side threaded bolts.,

30 One part solid coupler core.

31 Solid central part of C-Coupler.

32 Solid part cap join the end of the straight member.

33 C-Coupler branch body.

34 Special C-Clamp.

35 Threaded bolt.

36 Engagers digging the straight members.

37 Threaded hole.

38 Slut.

39 C-Clamp strip

40 portion of pipe take special T-shape and L-shape.

41 Solid Coupler part. 2 Internally threaded coupler branch.

3 Internal threading.

4 End straight member threading.

0 Coupler fastened the straight member ends by riveting and bolts..

51 Solid central part. '

52 Solid central part.

53 Coupler branch.

54 Holes in protruded parts.

56 Riveted bolts.

57 threaded bolts.

55 Coupler branch.

58 Cap with two holes strip. ;

59 Solid central part.

60 Coupler with solid central part, portion of pipe branches, packing and rings with

threaded holes.

61 Coupler with solid central part, portion of pipe branch.

63 Ring.

64 Threaded hole.

65 Threaded bolt.

66 Packing.

71 Main portion of solid central part of the coupler.

72 Upper portion at central sold parts.

73 Branch.

74 Portion of coupler ring is apart of coupler branch.

75 Threaded hole.

81 Main portion of Solid central part.

82 Cap portion of solid central part.

83 Branch.

84 Female groves.

85 Male deformation.

91 Central solid part.

92 Coupler branch comprise sleeve with threaded holes.

93 Threaded holes.

94 Threaded bolt.

95 Sleeve.

96 Brazing foil 96.

97 Induction heating coil.

100 Truss reinforcement girder

101 Inclined straight members

102 Central tower attached inclined straight members 101 to the .tower at levels and

connected directly to the truss joint coupler branches.

The invention will now be described by way of examples only, with reference to the accompanying diagrammatic drawings in which:

Fig. 1: Examples of trusses with mechanical joints.

Fig l.a: Example of a plane truss.

Fig l.b: Example of a space truss. Example of a curved space truss.

Exploded views of coupling ends of two axially aligned reinforcing bars (1 and 2) using special U-shaped bolt 12 and a portion of sleeve 11 with protruded parts 15 with a hole in each.

: Exploded view of U-shaped bolt coupler with four branches for coupling four straight members showing radial spaced engagers in each branch.

: Exploded view of U-shaped bolt coupler with four branches and two central solid portions for coupling after assembling the four straight members in place of coupler branches, the figure show also the two solid portion components.

: 3-D views of assembled U-shaped bolt coupler with four'branches and two central solid portions.

: 3-D view of assembled U-shaped bolt coupler with four branches and two central solid portions, the figure shows the bolt heads (28, 29) sheared off at a predetermined torque.

xploded view of C-shaped coupler with five branches and one central solid portion. xploded view of C-shaped coupler with five branches and two central solid portions, cross-section view a-a show detailed shape of coupler branch cross-section and the bolt end.

Exploded views of coupler with four internally threaded sleeve branches and one central solid portion and four straight members.

: Exploded views of coupler with four branches for griping four straight members with different directions. The coupler joins the straight members using rivets which comprise, two symmetric portions of pipes with protruded parts come out from a solid part, special riveted bolts. The two pieces solid part help for fastening the straight members using bolt's.

: 3-D view of riveted technique mechanical coupler for assembling four straight members.

Exploded views of space coupler with multiple branches for griping five straight members with different directions. The coupler comprise, portion of special shape pipes come out from a solid part, backers, rings and bolts.

ssembled five straight members with different directions and before tie the bolts. The coupler comprise, portion of special shape pipes come out from a solid part, backers, rings and bolts.

: Exploded views of space coupler with five branches for coupling five straight members with different directions. Each branch comes out from one half of the central solid part take the shape of a portion of pipe, the said pipe portions has protruded upper rings that allows for placing cylindrical steel packing between the said protruded upper rings and the straight members.

Exploded view of space coupler with five branches for coupling five straight members with different directions. Each branch comes out from central solid part take the shape of a pipe with plurality of threaded holes spaced along the length of the branch; the figure shows also threaded screw or bolts.

Exploded views of space corner C-shaped coupler with four, branches for griping four straight members with different directions. Each branch comes out from one of the two central solid part portions.

a: Exploded views of a coupler for griping inclined straight member with a horizontal one using riveting closure technique. Fig 13.b: 2-D view for assembled two horizontal straight members and an inclined one with two riveted closure technique coupler.

Fig 14: Exploded views of a coupler for griping two aligned and one perpendicular straight members using riveting closure technique.

Fig 15. a: Exploded views of a coupler for griping two aligned and one perpendicular straight members using portion of pipe take special T-shape and L-shape and special strip C-

Clamp.

Fig 15.b: 3-D view of a coupler for griping two perpendicular straight members using portion of pipe take special L-shape and special C-Clamp.

Fig 16.a: Exploded view oftwo straight members 1 and 2 , the foil 96 wrapped around the coupling parts of the two straight members. The sleeve 95 is heated by induction heating coil 97. <

Fig 16.b: The brazing layer 96 welded the inner surface of the deformed sleeve with the outer surface of the reinforcing bars 1,2 and fill any gab that may be formed between them. Fig 17.a: Exploded view of two portion coupler with four branches showing a foil of brazing material (96) of coupler branches (53), which wrapped around the coupling parts in each of the straight member or reinforcing bars (1, 2, 3, 4,). The straight member ends

(1, 2, 3, 4,) are placed one coupler portion branches (53).

Fig 17.b: The coupler portions 1 and 52 with branches 53 is assembled around the ends of the straight member or reinforcing bars (1, 2, 3, 4,), in which the said foil of brazing material is laid between the coupler and the straight members.

Fig 17.c: Heating the coupler branches (53) using coil (97) while the brazing layer will melt to weld the inner surface of the coupler branches (53) with the outer surface of the coupling part of straight members.

Fig 17.d: 3-D view of the coupler showing exploded view of rivets (56) that will passing through the holes (54) in the protruded parts and the holes in the two central solid parts to tightly close the two coupler halves around the straight members (1-4).

Fig 17.e: 3-D view of the coupler after riveting the two coupler portions.

Fig 17.f: shows coupler after griping the straight member ends and riveting the two coupler portions and shows bolts that adding more fastening strengths to the coupler.

Fig 18 Truss reinforcement used for bearing weight of slabs, fresh concrete and construction working loads therefore, no need for provisional support like formwork and scaffolding, the figure shows also two central tower attached inclined straight members to the tower at levels and connected directly to the truss joint coupler branches.

Description of the Figures and Closure Techniques

Fig 1 shows, examples of trusses that may be used as reinforcement in concrete members. From these figures, it can specify example of joint forms in terms of number of branches and directions. Fig l.a, b illustrates examples of plane and space truss respectively, Fig l.c shows an example space truss useful for columns subjected to axial and lateral loads while Fig l.d represent an example of arch truss.

U-Clamp Coupler The first joint methods that couple two or more straight members or reinforcing bars are shown in Figs 2 and 3.

Fig 2 shows a portion of pipe having specific length and thickness (11). The pipe potion (11) is equipped with a plurality of protruded circular shape flange members (13) with designed thickness and area come out from the top surface pipe potion longitudinal sides and spaced along the length of the coupling. Every protruded part (13) is equipped with a hole (14). Plurality of U-shaped bolts (12) is used for fastening two straight members (1) and (2). each U-shaped bolt is formed with two parallel threaded arms joined by an intermediate a flattened interior surface bridge section so as to allow full contact with the said elongate members (1) and (2) when the straight member is fastened by said U-shaped bolt member (12) through tying the nuts (16) with designed torque;

Fig 3. a shows exploded view of multiple branches (23) coming out from a central solid part (21) at the junction of longitudinal branch axes. Each branch configuration and fasting technique is the same that explained in Fig 2. The inner surface of each branch may have radial spaced engagers (36) which are ribbed to dig into the sleeve portion (23) and the straight members at tightening condition. The central solid part half (22) is equipped with a plurality of threaded holes (24, 25) passed through the thickness of the central solid part, while the second solid part half (2f ) is equipped with coincident threaded holes with a design depth. The inner surface of the branches may have grooves (female) or threading identical to the straight members end deformation or threading. The pipe portions are assembled along the ends of the straight members or reinforcing bars to be connected assuring the coincidence of the reinforcing bars male deformations or threading with the coupler branches female grooves.

Fig 3.b shows the assembled straight members or reinforcing bars with or without deformations (1-4) on place of coupler branches (23). Fig 3.c shows the assembled straight members or reinforcing bars (1-4) and fastened using the U-shaped bolts 12 by tying the nuts 16. The central solid part 22 tightly closed on tips parts of the straight members (1-4) by tying the threaded holes 28 and 29. It should be noted that, the bolts (28 and 29) may preferably cap screws and with a reduced shank so that the head shears off at a predetermined torque on screwing them in place. Fig 3.d shows the bolts (28 and 29) are sheared off.

C-Clamp Space Coupler

The closure technique, shown in Fig 4 that tightly closes the coupler connection, with multiple branches (33) over the straight members or reinforcing bars ends (1-5), is done using C-clamp and bolts. In this connection type, each branch comes out from one central solid part (30). Each branch (33) takes the shape of a portion of pipe and may having female grooves in the inner surface. Each branch (33) is formed of a part a pipe sectioned parallel to the longitudinal axis of the pipe so that the remaining cross-section larger than the semicircle of the branch cross-section. Two longitudinal protruded parts wings out from the two sides of the branch. The two protruded parts take a plane surface passing the longitudinal axes of each branch. Each branch is embraced by the C-shape clamp (34) with a threaded hole (37) and between which relative sliding movement in a lengthwise direction of the branch is to be accommodated while intruding the C-shape clamp (34) to hold the straight members (1-5). the C-shape clamp ends (39) formed with lengthwise extending load-bearing surfaces (39) which seats upon and extends in the direction of the load-bearing surface of the aforesaid branch (33), the branch being formed with two lengthwise extending load-bearing surface (38) which extends generally in the direction of the direction of movement between the branch and C-shape clamp; the coupling of the said straight members ends is performed by threaded bolts (35) which are tightened in the threaded holes (37) directly over the straight members (1-5).

The difference between Fig 5 and Fig 4, the central solid portion in Fig 4 is one part (30) while in Fig 5 is two portion (31 and 32).

Multiple branches threaded coupler

Fig 6 illustrates exploded view of a coupler with multiple branches (42) to join straight members or reinforcing bars ends (1-4). Plurality of sleeve branches (42) come out from a central solid part 41 of the coupler at the junction of longitudinal axes branches (42). Each sleeve branch having internal threading (43) conform to the threading of the straight members or reinforcing bars ends (44) when the sleeves segment and the straight members are relatively pressed together. The straight member or bar end segment may or may not with enlarged diameter at one or both of ends, a thread on said segment for engaging an internally threaded coupling sleeve element.

Multiple branches riveted coupler

Another shape of space coupler is shown in Fig 7. Fig 7.a and Fig 7.b shows exploded view of a two portion coupler with four branches. The four branches (53) comes out from two central solid parts (51, 52) at the junction of longitudinal axes of branches (53), each branch (53) having a core void (sleeve) with cross-sectional dimensions identical to the external cross-sectional dimensions of the said straight member, each core void extends for a distance inside the central solid part along the axis of the core void. The solid part half (52) ends press to the end parts of the straight members (1-4) while tying the treaded bolts (28, 29) in threaded holes to (pass from holes 24, 25 to holes 26, 27) to produce a shorter branch. The inner surface of each branch may have radial spaced engagers which are ribbed to dig into the sleeve and the straight members at tightening condition. The coupler with the multiple branches is split into two coincident halves along the longitudinal axes of the branches, each branch half is equipped with a plurality of protruded flange members (13) coming out on both sides of the said branch, each protruded part have a hole (54) matching the similar one in the other branch half upon placing the said straight member between the two said coupler halves as in Fig 7.b. It should be noted that, the plurality of threaded holes (24, 25) passed through the thickness of the upper central solid part half, while the second solid part half is equipped with coincident threaded holes (26, 27) with a design depth, means for fastening the two coupler halves through riveting a plurality of riveting passing through the holes (54) in the protruded parts and the holes in the two central solid parts (24, 25, 26 and 27) to tightly close the two coupler halves around the straight members (1-4). As in Fig 5, the radial spaced engagers (36) are ribbed to dig into the sleeve (53) the straight members (1-4) which help for stronger griping of the straight members (1-4).

Space coupler with rings

Fig 8 shows multiple branches (62) coming out from one central solid part (61) at the junction of longitudinal axe branches, each branch (61) with a portion of pipe shape having a core void cross-sectional dimensions identical to the external cross-sectional dimensions of the straight member (1-5). The inner surface of each branch pipe may have radial spaced engagers which are ribbed to dig into the sleeve and the straight members (1-5) at tightening condition. The coupling of the straight members ends (1-5) is performed by intruding a plurality of outer rings (63) with threaded holes (64) over shallow semi circular halves or longitudinal portion with shallow circular arc cross-section (66) made in one of the said two halves of the pipe portions then, threaded bolts (65) are tightened in the said threaded holes to press the semi circular half of pipe portion or longitudinal portion with shallow circular arc cross-section (66) over the straight member end (1-5) to complete the coupling process. The deference between Fig 9 and Fig 8 is the central solid part (61) in Fig 8 becomes two portions in Fig 9. Fastening the two coupler central parts is done through bolts (65, 66) that press the two coupler central parts around the tip ends of the straight members (1-5) through the threaded holes (24, 25).

The closure technique that tightly closes the coupler over the ends of the straight members (1- 5) in Fig 10 is the same as those mentioned in the Fig 8 and 9 with the following difference: Each branch (73) comes out from one halves of the central solid part (71) take the shape of a portion of pipe and may haying female grooves in the inner surface, the said pipe portions has protruded upper rings (74) with specific breadth, thickness, and an internal diameter that allows for placing cylindrical steel packing (66) between the said protruded upper rings (74) and the straight member (1-5) ends to be connected. The coupling of the said straight members ends (1-5) is performed by threaded bolts (65) which are tightened in the said threaded holes (75) directly over the said straight members (1-5) or over cylindrical steel packing (66) placed between the said ring portions (74) and the straight member (1-5) to complete the coupling process.

Bar-lock space coupler

In this invention, the proposed Bar-lock space coupler is multi-directions coupler while, well known bar-lock coupler produced by the Ancon company coupled two aligned reinforcing bars. Fig 11 shows multiple sleeve branches (92) coming out from a solid part (91) at the junction of branch axes. Each sleeve (92) constructed symmetrically about its midpoint and having plurality of threaded holes (93) to receive correspondingly threaded engagers (bolts) (94) which serve to join and fasten said straight member (1-5) in conjunction with radial spaced engagers which are ribbed to dig into the sleeve (92) and the straight members (1-5).

C-Clamp Corner Space Coupler ·

Fig 12 shows corner space coupler with C-clamp as described in Figs 4 and 5. The multiple branches (84) over the straight members or reinforcing bar ends (1-5), are done using C- clamp and bolts. In this connection type, each branch comes out from one of the two portions central solid (81 and 82). Each branch (84) takes the shape of a portion of pipe and may having female grooves (83) in the inner surface. Each branch (84) is formed of a part a pipe sectioned parallel to the longitudinal axis of the pipe so that the remaining cross-section larger than the semicircle of the branch cross-section.

Fig 13 shows another application of mechanical coupler to be used with traditional reinforcing concrete members to connect two or more reinforcing bars in different directions such as to connect inclined bar with vertical or horizontal bars to overcome the structural problems arising from cold bending of reinforcing bars as shown in Fig 13.a,b or to connect two perpendicular bars, three said reinforcing bars; two of the said three reinforcing bars are axially aligned in one direction, while the third reinforcing bar is located perpendicular or coupling as shown in Fig 13.c. '

Induction heating for producing hot forged coupler

The procedure is performed by placing a metal sleeve with the designed length, thickness and diameter in an alternating magnetic field that creates eddy currents, causing losses through which the metal is heated till the required degree. Skin effects concentrate these currents in the outer layers of the sleeve. The inductor traversed by an alternating current creates a magnetic field, which should be optimally adapted to the sleeve.

The depth of heating can be influenced by varying the AC frequency, but it also depends on the concentration of flux capacity, on the length and cross-section area of specimen material, i.e. its heat - conduction properties.

An advantage of such technique is the small thickness of the coupler sleeve which allows for uniform temperature (and consequently easier forging) distribution along the coupler body. Therefore, smaller thickness, and hollow interior allows for ideal distribution of heating temperature along the sleete body. Medium frequency is used for forging heat treatment of the sleeve.

The main purpose of the mechanical coupler is to join the two steel t»ar ends and transmit safely the bar loads and stresses to the other bar. However, to add more strength to the .

connection formed by hot forging, welding of the interior surface of the deformed coupler with the outer surface of the steel bar ends will add more strength, safety, and may further reduce the required coupler dimension. Such welding is performed by wrapping a thin film of soldering material over the connected steel bar ends as stated

Method of making Hot Swaged Coupler for two or more reinforcing rods Using

Induction Heating

The procedure for making the coupler using tubular sleeve comprises:

a. A foil of brazing material (96), which has melting temperature less than the forged chosen temperature of sleeve (95), is wrapped around the coupling parts of the each straight member or reinforcing bars (1,2).

b. A tubular sleeve pipe branch (95) is heated to the chosen forging temperature according to the carbon content of the coupler material and the melting temperature of the brazing material.

c. The sleeve (95) pipe is assembled over the ends of the axially aligned straight member or reinforcing bar (1, 2) to be spliced and the hot sleeve is forged into the deformations of both reinforcing bars by a hydraulic ram.

d. The brazing layer (96) will melt while the hot sleeve is being deformed around the ends of the two reinforcing bars. The role of the brazing layer is to weld the inner surface of the deformed sleeve with the outer surface of the reinforcing bars. Moreover, it will fill any gab that may be formed between the forged sleeve and the bars, weld the coupler sleeve and the reinforcing bars, and consequently increase the coupler capacity. Contraction of the sleeve upon cooling improves bond and increases the splice strength.

Using Soldering with the other Closure Techniques The soldering is used at the same mechanical coupler in addition to the closure techniques in the U-Clamp coupler, C-Clamp Space coupler, riveted or bolted coupler and space coupler with rings described in the preceding paragraphs. An example of using soldering the riveting closure technique is given in Fig 17 which comprises:

a. a foil of brazing (96) material, the foil have melting temperature less than the chosen temperature of said coupler branches (53), is wrapped around the coupling parts in each of the straight member or reinforcing bars (1, 2, 3, 4,) as shown in Fig 17.a.

b. the straight member ends (1, 2, 3, 4,) are then placed one coupler portion branches (53). c. as shown in Fig 17.b, the other coupler portion (52 with branches 53) is assembled around the ends of the straight member or reinforcing bar (1, 2, 3, 4,), in which the foil of brazing material (96) is laid between the coupler and the straight members.

c. the coupler branches (53) are then heated using coil (97) while the brazing layer will melt to weld the inner surface of the coupler branches (53) with the outer surface of the coupling part of straight members, Fig 17.c.

d. Fig 17.d shows, riveting the two coupler portions to fastening the two coupler halves through a plurality of rivets bolts (56) passing through the holes (54) in the protruded parts and the holes in the two central solid parts (24, 25, 26 and 27) to tightly close the two coupler halves arodnd the straight members (1-4).

e. Fig 17.e shows coupler after griping the straight member ends, while Fig 17.f, shows bolts that adding more fastening strengths to the coupler.