Rebar trusses and their supporting systems for reinforcing concrete members and strengthening cold-formed sections

Abstract

The patent application No WO / 2016 / 138912 presented two-dimensional and space trusses for structural utility and for reinforcement the structural concrete members instead of traditional reinforcing bars and stirrups or welded joints truss comprises from: a) straight members, with or without end preparations as threading or deformations, b) mechanical couplers, each one is formed from one or several portions and having plurality of branches and multiple directions according to the said truss design, composition and shape and c) means for tightly closing the said mechanical coupler over the ends of axially aligned said straight members. The drawbacks of these trusses are: 1- Each truss joint connects several discontinuous reinforcing bars, even if two of them are in axially aligned, as the bars are separated but coupled by the mechanical coupler joint. 2- The proposed system will need large numbers of these mechanical joints for each concrete element, which will make its implementation costly. This application overcomes the shortcomings of the previous truss joints and provides even simpler and more cost-effective rebar truss systems with simplified mechanical joints that meet the required mechanical requirements. Among the truss systems presented, the locations of the truss joints at the ends of the diagonals and / or along the rebar chords and are shaped to form nodes. Each node prepared with a hole created by forging, and these nodes are assembled using mechanical fasteners according to the shape of the truss. The application recommends using these rebar and hybrid rebar truss systems to reinforce concrete elements, strengthen cold-formed steel sections, composite reinforced concrete sections, and reinforces the beam-column joints.

Description

[0001] Rebar trusses and their supporting systems for reinforcing concrete members and strengthening cold-formed sections

[0002] Technical field: The current invention introduces more cost-effective, simpler, and practical rebar trusses and their supporting systems with mechanical joints to reinforce the concrete elements. Furthermore, it introduces a simplified version of the truss mechanical joints outlined in patent application WO / 2016 / 138912 and European patent EP15883847.

[0003] Background:

[0004] The reinforcement of semi-precast or conventional lattice girder comprises mainly from three parallel reinforcing bars one of them is in the upper chord (101) while the other two reinforcing bars (102) and (103) are used lower chord, Fig l.a. The three reinforcing bars are connected to each other by V-shaped truss webs (104). The horizontal projection of the upper chord centered between the two lower chord bars. The upper and lower chords are assembled with the webs using welding (108). The lattice girder is also known as filigree slab and developed in 1960s, example Grebner 1965 an example of this type of slabs is shown in Fig l.b. Newell, and Goggins, 2018 studied the structural capacities of the lattice girder slab at construction stage prior to the pouring of in-situ concrete with particular emphasis on deflection and stress capacities. They concluded that, the modeling of a lattice girder system is difficult to achieve. Also, it was found that the tall girder systems were well represented by the axial deformations method while the shallower trusses were more accurately described with the beam bending method in case the structural behaviors within the slab are governed by bending behaviors. Furche and Bauermeister 2011 presented an experimental work to study the flexural and shear resistance of the lattice girder during erection. The element consisted of a concrete base with lattice girders protruding from the top surface of the concrete. The study checked the required safe upper chord and diagonal diameters for safe erecting spans of various slab thicknesses.

[0005] Figure 2 shows another reinforced concrete girder system which named as hybrid steel trussed concrete beam. The reinforcement of this system comprises of an upper chord (101) reinforcing bar, a continuous steel plate or a precast concrete slab represents the lower chord and two lattice web bars which connect the upper and lower chords by welding (108), Fig 2. The web bars could be a repeated two bars take a V-shape or composed of two bars; everyone takes the shape of a zigzag or sinusoidal wave. The bending portions are welded to the top and to the bottom chords. Fig 2.a shows the reinforcement of composite beams having a steel truss welded to a continuous lower steel plate while Fig 2.b shows a truss with a precast concrete bottom chord.

[0006] Quaranta et al. 2011 presented design procedures consequential with the European standards for steel structures, reinforced concrete structures and mixed steel -concrete structures. Tullini and Minghini 2013 presented a nonlinear finite element formulation based on Newmark's classical model to analyze the composite beams constituted by a concrete -encased steel truss welded to a continuous steel plate. The use of this mathematical model was due to the web bars behavior as the result of loading the composite beam. For the shear connection, elastic -perfectly plastic models are calibrated using load-slip curves obtained from push-out tests. Trentadue et al. 2014 presented a closed-form equation for calculating the equivalent bending stiffness along with a corresponding parametric formula that represent rapid design tool for designers. Colajanni et al. 2018 presents the state of the art on laboratory tests and analytical modeling of the steel-to-concrete stress transfer mechanism investigated by push-out tests. The study summarized the shear behavior in the literature regarding the experimental investigation. Although several tests proved the significant effect of this system on the shear strength of the beam, the available models do not adequately reflect this effect as they do not consider the collaboration of the added rebars, and steel plate ensured by the welds. Also, it must be emphasized that there is a lack of knowledge on the connection capacity and shear behavior of beams with precast prestressed concrete bottom chord.

[0007] With the numerous advantages in using trusses with welding joint as reinforcements in the above literature, the attendance for cracking under fatigue loading, eccentricity problems and probable failures of the surrounding concrete due to the kinematic behavior of the end connections are the most drawbacks of the welded joint truss. The constantly changing anti -earthquake regulations and seismic design criteria have critically affected the adequacy and reliability of the design and the use of such welded joints.

[0008] The patent application No WO / 2016 / 138912 presented two-dimensional and space truss for structural utility and for reinforcement the structural concrete members instead of traditional reinforcing bars and stirrups or welded joints truss comprises from: a) straight members, with or without end preparations as threading or deformations, b) mechanical couplers, each one is formed from one or several portions and having plurality of branches and multiple directions according to the said truss design, composition and shape and c) means for tightly closing the said mechanical coupler over the ends of axially aligned said straight members.

[0009] The drawbacks of this system are:

[0010] 1- Each truss joint connects several discontinuous reinforcing bars, even if two of them are in axially aligned, as the bars are separated but coupled by the mechanical coupler.

[0011] 2- The proposed system will need large numbers of mechanical couplers for each concrete element, which will make its implementation costly.

[0012] The present invention presents more economic, easier, and applicable mechanical joints for rebar trusses to reinforce the concrete and composite elements.

[0013] In the following explanation, the term hybrid-rebar truss is synonymous with composite rebar truss. Also the term rebar is synonymous with reinforcing bar.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS:

[0015] Fig l.a: Three parallel reinforcing bars one of them behave as an upper chord (101) while the other two reinforcing bars (102) and (103) are used lower chord.

[0016] Fig l.b: Filigree slab system composite of three conventional lattice girder, lower thin precast slab and then cast in situ concrete.

[0017] Fig 2: Hybrid rebar trussed beam: a) a steel truss welded to a continuous lower steel plate; and (b) a truss with a precast concrete bottom chord, (c and d) connection within the beam-to-column joint. Fig 3. a: Exploded view of two parallel rebar trusses (10), each one comprises of, continues bars (1, 2) behave as an upper, a lower chords, and diagonal bars 12, all nodes (13, 15) and holes (14) are shaped using forging.

[0018] Fig 3.b: Fastener types for the truss joints.

[0019] Fig 4.a: Truss (20) comprises two laminated vertical trusses (270, 280) with a continuous rebar (1) as the upper chord in each, a plate (9) as the lower chord for the trusses, and diagonal bars (12), with all nodes (13, 15, 19) and holes shaped through forging.

[0020] Fig 4.b: A type of two rebar diagonals (12) formed from one rebar, the node (13) as well as the end portion (19) is shaped by forging.

[0021] Fig 4.c: Pieces of a plate (11), prepared with one or two holes (14).

[0022] Fig 4.d: Upper chord with eyes and steel plate lower chord with diagonal wings. Fig 5. a: The components of a truss (30) are diagonal bars (12) with forged ends, plate (9) acting as a lower chord, continuous, rebar upper chord without machining (1), and joint (201).

[0023] Fig 5.b: A type of diagonal rebars (12) with two end nodes (13) each shaped by forging, and a hole in each.

[0024] Fig 5.c: The joint (210) is made up of a plate (18) with two holes (14) emerging from a tubular portion, the bolts (201) function of is to secure the upper chord 1.

[0025] Fig 5.d: A type of diagonal rebars featuring an enlarged lower end portion and a node (13) by forging.

[0026] Fig 6.a: Rebar truss (40) comprises an upper chord (4) that is broken near to both ends, a straight lower chord (2), non-straight diagonal (38, 39), joints (24) that couple the upper or lower chords with the diagonals, and joints (25) connecting the diagonals subjected to tensile forces with the diagonals subjected to compressive forces.

[0027] Fig 6.b: The two non-straight rebar diagonals (28, 29) intersect at a joint (36), and the upper chord (26) breaks down at its free end to meet the lower chord (27), which likewise breaks upward at its free end (37).

[0028] Fig 6.c: Explode the set of hangers (22) and a set of arch (23), which together forms the truss.

[0029] Fig 6.d: The two non-straight diagonals (38, 39) are coupled at node 25, where they intersect. One diagonal is exposed to tension (38), while the other is exposed to compression (39). Both diagonals have three nodes and a hole formed in each node.

[0030] Fig 7. a: A tubular sleeve piece 101 that have a hole 102 inserted in the place of the node on the upper chord (1).

[0031] Fig 7.b: Formed node (104) created on the upper chord 1 having the hole (105).

[0032] Fig 8: High stiffness truss (50) comprises two rebar upper chords and likewise two in lower chord, each one of them connected with two V-shaped repeated diagonal trusses (223) and a plurality of joints (210). Each joint connects a chord in one plane to two chords in another plane. Each diagonal member (223) of the diagonal trusses is similar to diagonal (12) that illustrated in trusses 10, 20, and 30.

[0033] Fig 9: Details of rebar truss 240 used for strengthening the cold formed sections (Fig 9.b and 9.d), as well as for reinforcing the composite steel concrete elements (Fig 9.c).

[0034] Fig 10: Using the truss joints with the rebar to reinforce the beam-column-connection.

[0035] Fig 11 : Load transfer reinforcement system for the rebar truss to the supporting column.

[0036] DETAILED DESCRIPTION:

[0037] Formation of truss rebars nodes using forging or rolling:

[0038] An aspect of this innovation is the formation of rebar truss rebars nodes using hot forging. The hot forging is better for cost-effective, ease of shaping the material and because it can be done quickly and with proper accuracy. Moreover, the rebar steel alloy does not harden while it is formed as usually results from cold forging, and thus the hardening problems are avoided through the recrystallization process.

[0039] Rebar truss system I:

[0040] An aspect of the invention is the beam or joist rebar truss system (10), Fig 3, the rebar truss system (10) comprises two laminated vertical rebar trusses (270, 280) with a continuous rebar (1) as the upper chord in each, a rebar (2) as the lower chord for each laminated truss (290). The beam (10) manufacturing process begins with cutting the reinforcing bars with specified lengths representing an upper chord, lower chord, and diagonals. Certain sections of these rebar are shaped through the process of hot forging, resulting in nodes with a hole in each individual truss member. Manufacturing nods in the chords (1, 2) and in the ends of the diagonals (13), and when changing the directions of the diagonal sections (Fig 6), requires enlarging the size of the locations of those nodes in their initial stage and before making them flat and forming the hole in their middle, so that the cross-sectional area at any section in these nods along the longitudinal axis of the reinforcing bar is not less than the cross-sectional area of the reinforcing bars.

[0041] These members are then assembled together to construct the truss skeleton, which takes on the desired shape of the designed truss. This formation is better produced using closed compression dies. The temperature used to shape the required parts of the reinforcing bars is above the material's recrystallization temperature (hot forging).

[0042] Another aspect of this invention is to manufacturing the rebar upper or lower chord using rolling. The upper or lower rebar chord, a continuous reinforcement bar, has nodes formed at intervals along its longitudinal length, these nodes have two flat, parallel, and opposite surfaces, and a hole is formed at the center of each node, the rebar chord is manufactured through the rolling process.

[0043] For more explanation, as shown in Fig 3, the ends of the diagonal bars (12) are shaped flat (13) and then the holes (14) are formed within each flatted end (13). Specific repeated nodes (15) along the upper and / or lower chord’ bars are shaped to become flat then holes (16) corresponding to those (14) formed within the ends of the diagonals (12) are formed within them. All these shaping is done using localized compressive forces of specific parts that are preheated in reinforcing bars. The diagonal bars are then assembled with the upper and lower chords (1, 2) using fitted bolts or solid rivets (17) to produce the required truss (10) with the designed shape. The shape of this truss may call: forged eye nodes rebar trusses.

[0044] Composite rebar truss system II

[0045] Another aspect of the invention is the composite truss system (20), Fig 4, composite truss system (20) comprises two laminated vertical rebar trusses (270, 280) with a continuous rebar (1) as the upper chord in each, a plate (9) as the lower chord for the trusses instead of the reinforcing bars (2) in truss type I in Fig. 3, and diagonal bars (12), with nodes (13, 15, 19) and holes shaped through forging. In this truss, pieces of a plate (11), prepared with one or two holes (14) in each corresponding to the holes shaped in the diagonal bars (12) to be assembled, are welded to the bottom plate (lower chord 9). These pre-holed plate pieces serve as bolting points for the diagonal bars and the lower chord (steel plate 9). These pieces of pre -holed plates are welded to predetermined places along the length of the bottom plate (lower chord) according to the truss design. The diagonal bars (12) are then assembled with the upper chord (1) and the lower chord (plate 9) to form the final shape of truss. Figure 3 shows the details of the truss components including the diagonals as well as the upper and lower chords. Fig 4.d illustrates the rebar upper chord with eyes and steel plate lower chord with diagonal wings.

[0046] Another innovative aspect of this section is the simplification of the connection of the diagonals (12) to the bottom chord (9) as shown in Fig 4.b. The end portion of the diagonal (12) is formed by forging to make it slightly larger in size so that it has a base to rest on and the welding area between it and the bottom chord (9). This lower chord portion (19) is increased by hammering the end of the diagonal or pressing in a mold while still there is hot. The diagonal is assembled with the lower chord by welding between the enlarged portions (19) and the lower chord (9). Fig. 4.b shows the diagonal (12) with the enlarged lower portion. As shown in Fig. 4.b, the diagonal (12) and bottom chord (9) can be assembled by attaching them to the threaded bolt (8) that passes through the bottom plate (9) and engages a threaded hole in the bottom of the enlargement part (19). This type of truss may call: truss with forged eye nodes in upper chords and steel plate with diagonal wings bottom chord.

[0047] When the beam or joist is constructed from multiple laminated vertical rebar trusses with continuous rebar (1), the upper chords are parallel and spaced apart, as shown in Fig 3 and 4. In such cases, the diagonals are more prone to lateral buckling compared to the upper chords that are adjacent or formed from a single bar as depicted in Fig l.a and Figure 2. This results in the joist or beam section being perpendicular to the beam's longitudinal axis, forming a triangular shape. To address this issue and capitalize on the benefits of a joist or beam made up of laminated vertical rebar trusses, the upper chords are braced to the lower chords (228), as illustrated in Figure 4.e. The bracing is mainly positioned in the areas most vulnerable to lateral buckling, including at the joist supports and under concentrated loads that the joist may bear.

[0048] Composite rebar truss system III

[0049] When there is a difficulty in forming parts in the rebar upper and / or lower chord using hot or cold forging, another aspect of this invention, the composite rebar truss reinforcement system (30) presents in Fig 5. The continuous reinforcing bar, either upper or lower chord, may path through and attached to a tubular sleeve portion of the mechanical coupler joint that coupled the one continuous bar as well as the diagonal bars. Thus, continuous straight member (upper or lower rebar) in this case passes through the tubular sleeve portion (210) of the mechanical joint and fastened to it by bolts (201). These bolts pass through threaded holes intended for this purpose in the sleeve portion of the mechanical coupler joint.

[0050] The composite rebar truss system (30) comprises of upper chord reinforcing bars (1), lower chord steel plate (9) and inclined webs (diagonals) (12). The upper chord mechanical coupler joint comprises: a tubular sleeve portion (210) welded with a portion of a plate (18) with predetermined dimensions having one or two holes corresponding to the diagonal end holes (14), the plate piece (18) comes out from the outer surface of the tubular portion (210) and parallel to the longitudinal axis of the truss. As shown in Fig 5, this mechanical coupler joint is repeated at equal distances on the upper chord. Bolts or rivets (17) attach an inclined webs (12) to the plate (18) as the reinforcing bar (1) passes through the tubular portions (210). To secure the upper chord (1) within the tubular portion (210) tighten multiple bolts (201) that pass through the tubular portion wall and press the upper chord ( 1 ) to the tubular portion's lower inner serrated surface.

[0051] Another innovative feature of this section is the simplification of the connection of the diagonals (12) to the bottom chord (9) as shown in Fig 5.d. The end portion of the diagonal (12) is formed by forging to make it slightly larger in size so that it has a base to rest on and the welding area between it and the bottom chord (9) is increased by hammering the end of the diagonal or pressing in a mold while still there is hot. While the diagonal (12) is fastened to the plate (18) using bolts or rivets, the upper rebar chord (1) passes through and is fastened to the tubular portions (210). The diagonal is assembled with the lower chord by welding between the enlarged portions (19) and the lower chord (9). Fig. 5.d shows the diagonal with the enlarged lower portion. As shown in Fig. 5.e, the diagonal (12) and bottom chord (9) can be assembled by attaching them to the threaded bolt that passes through the bottom plate (9) and engages a threaded hole in the bottom of the enlargement part (19). Rebar truss reinforcement system IV

[0052] The upper and lower chords of the reinforcing bar trusses used by the specialized companies11, also referred to as filigree slabs or hybrid rebar trusses, are connected to one another by V-shaped truss webs connected with straight upper and lower chords (Warren Truss), also known as diagonal bars. One of the problems faced by these truss skeletons before the concrete is poured and intended to support the dead load of slabs and the construction working loads is the diagonal bars, which are subjected to compressive stresses. Since the longer they are, the more likely they are to buckle in the direction of its longitudinal axis. Therefore, the longer the diagonals subjected to compressive stresses, the larger the cross-sectional dimensions of these elements, which increases the weight of the materials used to build the rebar trusses. Therefore, there seems to be an urgent need to change the composition of the truss components and the skeleton shape to obtain elements that weigh less and perform better.

[0053] Therefore, another aspect of this invention, the optimized truss system (40) according to the applied load (5), which lengthens the diagonals subjected to tension and reduces the diagonals subjected to compression, is shown in Fig. 6. a. This illustration shows several hanging bottom chord with the diagonals (22) as well as a series of arches (21) as shown in Fig 6.c. Fig 6.c shows explode the set of hangers (22) and a set of arch (23), which together form a truss, and works.

[0054] The special thing about this rebar truss form (40) is that the truss joints (25), which connect the diagonals subjected to tension (38) and compression (39) forces, run along the central longitudinal section of the truss. As a result, unlike earlier conventional rebar trusses reported in the literature and those explained above for trusses form (10 and 20), not all truss joints connect the top or bottom chord to the diagonals; instead, new truss joints are created connecting the diagonals to each other in specific locations (25, 36). The two non-straight diagonals (38, 39) are coupled at node 25, where they intersect. One diagonal is exposed to tension (38), while the other is exposed to compression (39). Both diagonals have three nodes and a hole formed in each node.

[0055] Although there are more truss joints in the proposed new shape and may be more expensive, but because these truss joints (24 and 25, 31, 36) are made by forging and the truss members are assembled using bolts (31) or rivets (32), the proposed manufactured truss is the most affordable in terms of cost and performance.

[0056] Another aspect of this invention is that, in contrast to conventional cantilever truss systems, the diagonals, the upper and the lower chords in Figure 6.b are not straight members. This cantilevered truss’ system (41) has a top chord (26) subjected to tension forces which breaks at node (31) and slopes downward, to couple the bottom chord at truss joint (37), rather than a straight line. The bottom chord (27) breaks upwards to couple the top chord at truss joint (37). At the truss joint (36), the diagonal tension bar (28) and the diagonal compression bar (29) come together to intersect. Hence, the Figure 6.b depicts the upper chord (26) that breaks down at its free end to meet the lower chord (27), which likewise breaks upward at its free end (37). The two non-straight rebar diagonals (28, 29) intersect at a truss joint (36).

[0057] Strengthen the node region to prevent a decrease in its cross-sectional area due to forging processes

[0058] Another aspect of invention is to strengthen the node section to make up for the reduction in cross-sectional area due to the forging process. The issue with creating nodes through forging along the reinforcing bar representing the upper or lower chord is that it impacts their strength against tension or compression. This decrease in strength becomes evident during tensile testing on a reinforcing bar with a node in the middle length and a hole at the center of the node; it was observed that the tensile strength may decrease up to 40% of the ultimate strength. This decrease is due to elongation caused by forging, which reduced the cross-sectional area in the middle of the node.

[0059] To address this challenge and maintain the strength of the upper or lower chord with perforated nodes depicted in Fig 3 and 4, the following solution is proposed:

[0060] Prepare sleeves with circular of square cross-section and of suitable thickness with a length slightly exceeding that of the node length in Fig 7. a and b. The inner diameter of each sleeve piece should be slightly larger than the diameter of the rebar upper or lower chord to allow easy insertion along them. The thickness of the sleeves is calculated to compensate for the resistance loss from forging. Each sleeve piece is pierced with a hole in the middle of its length, perpendicular to its longitudinal axis, passing through both the two wall thicknesses of the sleeve. sleeve pieces (401) of suitable thickness, each with a length slightly exceeding that of the node length, the inner diameter of each sleeve piece is slightly larger than the diameter of the rebar upper or lower chord to allow easy insertion along them, the thickness of the sleeves is calculated to compensate for the resistance loss node cross-sectional area from forging process, each sleeve piece is pierced with a hole in the middle of its length, perpendicular to its longitudinal axis, passing through both the two walls of the sleeve.

[0061] Each sleeve piece is inserted near each position to create the node on the reinforcing bar that represents the upper or lower chord, both the node location of the reinforcing bar and the sleeve piece inserted close to the node location are then heated to the appropriate temperature for forging, Fig 7. a.

[0062] The sleeve is then placed around the node location, ensuring that, the center of the two sleeve piece' holes aligns with the hole to be made in the node along the chord's length; the shaping process is carried out, creating the node (401) and a hole (402) aligning with the diagonal (12) end hole for connecting the chord with the selected diagonals at this node as shown in Figure 7.b.

[0063] The nodes at the ends of the diagonals (12, 38, 39) will be connected to the upper or lower chord using a screw or rivet that goes through the holes at the ends of the diagonals and the hole (405) in the node (404) formed by the forge.

[0064] Another aspect of this innovation involves adding a welding material or weld layer between the inner surface of the sleeve portion and the reinforcing bar representing the upper or lower chord prior to heating. Upon heating, the welding material or layer melts. Following the hammering process to create the node and central hole, as well as the cooling process, the welding material or layer transforms into a bond between the reinforcing bar and the inner surface of the sleeve. This bond helps the forged node, consisting of the reinforcing bar and the sleeve portion, to work together to withstand the tensile or compressive stresses that the truss joint experiences when integrated into the truss. Therefore, the sleeve pieces (401) of suitable thickness, each with a length slightly exceeding that of the node length, the inner diameter of each sleeve piece is slightly larger than the diameter of the rebar upper or lower chord to allow easy insertion along them, the thickness of the sleeves is calculated to compensate for the resistance loss from forging, each sleeve piece is pierced with a hole in the middle of its length, perpendicular to its longitudinal axis, passing through both the two walls of the sleeve. Then a soldering layer is wrapped around the upper or lower chord at the location of the node before inserting the sleeve piece above this soldering layer. Thereafter, insert the sleeve pieces around and along the upper or lower chord to be positioned at the node locations. Ensure the center of the two sleeve piece' holes aligns with the hole to be made in the node along the chord's length, heat each node's location to the appropriate temperature, then forge it to form the node (404) and a hole (402) aligning with the diagonal (12) end hole for connecting the chord with the selected diagonals at this node, the soldering layer acts as a bridge between the chord and the sleeve portion, allowing them to increase bond between them.

[0065] Rebar truss system V

[0066] The proposed beam or joist truss system (50) illustrated in Fig 8. a composite of four parallel longitudinal rebar, two of which represent the upper chord (211) and two represent the lower chord (212). The horizontal projection of each upper chord is located above one lower chord bar. Also, each upper chord is connected the two lower chords by two V-shaped trusses webs (223). Therefore, each upper chord attached with the two lower chords by two multiple V-shaped truss diagonals (223). The tubular sleeve portion in the truss joint (210), Fig 8. a, and b, is similar to that in the upper chord joints presented in Fig. 5. The distinct feature is that every joint has two plate pieces or a solid pyramid-shaped (217) piece protruding out of the joint tubular sleeve (210), Fig 8.b. The shaped steel piece (217) to which the diagonals (223) attached is coming out and attached with the tubular sleeve (210) by welding while the diagonals are attached to this joint by bolts (218).

[0067] Composite rebar truss system VI

[0068] Another feature is utilizing suggested trusses to strengthen the structural components constructed from light steel plate, improving its structural performance and boosting its load-bearing capabilities.

[0069] As well known, the light steel elements like cold formed members are usually thin with respect to their width. Therefore, they are likely to buckle at lower stress than yield point when they are subjected to compression, bending, shear or bearing forces. The deformed modes of these sections were summarized by Rui et al., 2008 as shown in Fig 9. a.

[0070] A method for reinforce these light steel structural elements using reinforcing members such as the suggested rebar truss shape skeletons is shown in Fig 9.b. The role of these skeletons is to strengthen the light steel elements against the local and distortional buckling, enhance the overall structural behavior and increase its load capacity. The trusses are made from reinforcing bars. Therefore, the place where the buckling may occur, a designed truss skeleton members exists. One of the most important places of this truss is to attach the two longitudinal walls (121) from the free edges (246) of element. Other places of the truss skeleton members are also placed diagonally inside the light steel element attaching the corners of the steel section perpendicular to the longitudinal direction of the joist element. However, each open joist elements may strengthen with two longitudinal trusses (240) placed beside the walls (121) and plurality of cross diagonals (241 and 244). The role of the diagonal members (244) is to prevent the side wall from buckling. With the present strengthening technique, no need for stiffened process to be carried out.

[0071] To demonstrate the current feature, Fig 9.b displays an exploded view of two parallel trusses (242, 243) joined to function collectively as strengthening and / or reinforcement for the structural components crafted from cold formed steel thin plate. This aims to improve its structural performance and boost its load capacities. In this Figure, the assembled light weight folded thin plate joist (120) strengthened by truss system (240). The two side walls (121) are connected by two horizontal rows of bars with threaded ends (245) passing through holes (247) with nuts securing them around the bars' threaded ends (245) from outside the walls (121). By the same way, the role of the upper horizontal members (241) is to attach the two longitudinal walls near the free edges of element and horizontal lips (248).

[0072] Another feature is to use the system that comprises of the cold formed element and the inside trusses as a reinforcement of concrete elements such as beams to be a composite element as shown in Fig 9.c. The fastening connections of the truss with the cold-formed joist in the design form shown in Fig 9.b keep the concrete from separating or sliding from the cold-formed steel element. On the other word, the suggested reinforcement system, the separation will decrease significantly between the poured concrete and the cold formed element. In addition, the cold formed element and the inside trusses will behave with the concrete medium as a single object as exposed to the applied loads.

[0073] DELTABEAM® (which is one of Peikko Company’ products) is designed to be used as a structural element combined with all general concrete slab types: hollow-core slab, Filigran slabs, composite steel decking, trapezoidal steel decking slabs, and cast-in-situ concrete slabs. It enables the usage of shallow element structures and strengthens the frame structure inside the slab. Fig 9.d depicts a 3-D view of another cold formed joist strengthened with truss shape reinforcement (240) used with concrete to form a composite beam instead of the brand DELTABEAM®. If the proposed hybrid model (Fig 9.d) is used, it will eliminate the problems of concrete cohesion with the steel plates, make the reinforced concrete section more consistent, and improve its load-bearing performance while also being less expensive.

[0074] Another feature of the present system is to use the thin steel plates as a temporary reinforcement and scaffolding at the same time to help for bearing the beam own weight, the weight of the slabs and the fresh concrete while the inside truss reinforcements continue inside the concrete as a permanent reinforcement. This means that the steel plates will remove after the concrete element becomes with its internal truss reinforcement able to bear the permanent dead and live loads.

[0075] Rebar truss system for beam-column connection VII

[0076] In the reinforced concrete structures, the sufficient load capacity and ductile behavior are crucial aspects for the RC beam column connection to avoid complete structure collapse in case of a localized failure in adjacent members. The reinforcement detailing plays a vital role in enabling the connection to meet these requirements. In contrast to traditional reinforcement methods, trussshaped reinforcement allows the truss members and joints to function as a unified entity. This results in forces being concentrated at the truss joints and distributed in accordance with the truss skeleton system. Consequently, each joint and member operates as an integral part of a unified truss structure. As a result of the extensive experimental work presented by Nilsson (1973) and Nilsson and Losberg (1976), the reasons of failure of corner connections were set as: diagonal tension crack failure, splitting crack failure, failure due to yielding of the reinforcement, anchorage failure, and failure due to crushing of the concrete. In this section, a cost-effective reinforcement system is proposed to enhance the strength, performance, and resistance to dynamic loads of reinforced concrete corner connections exposed to closing and opening moments.

[0077] Another aspect of this innovation is the use of the presented truss types to reinforce the beam- column-connection. Fig 10. a shows the column-beam connection reinforced by truss shape reinforcement with truss mechanical joints (210, 300, 410). Fig lO.b displays the upper reinforcement bar bending to act as an external vertical reinforcement bar in the column, and Fig lO.c shows the reinforcement detail of the other joint reinforcement bars including diagonals, lower and vertical inner bars. The truss system (400) described in this section (Fig 10) is cost-effective, enhances the performance of these connections under various loads, and significantly improves their resistance to dynamic loads.

[0078] The truss reinforcement system for concrete beam-column connection comprises of upper and lower reinforcement bars (7, 43), diagonal bars (12), and internal vertical reinforcement bars (44), the upper reinforcement bar bending to act also as an external vertical reinforcement bar in the column, the process of constructing the beam-column joint reinforcement truss system involves: a. Creating a node (42) on the upper reinforcing bar following similar steps used to create node (404), except that the reinforcing bar is bent after heating to the appropriate temperature, and then a hole (45) is made, similar to the process for hole (14), b. Forming nodes (404, 13) on the lower reinforcing bar (43) and node (13) on the vertical inner bar (44) in the same manner as in the upper bar. c. Assembling and securing the beam-column joint reinforcement skeleton by connecting nodes (13) in the diagonals (12) with their corresponding ones in the upper, lower, and vertical reinforcement bars (42, 404, 13) using bolts or solid rivets (17) to achieve the truss reinforcement configuration depicted in Fig lO.a.

[0079] Load transfer reinforcement system for the rebar truss to the supporting column

[0080] Fig 2.c and Fig 2.d show the column connection with a simple and a continuous hybrid trussed beam in the prior art. In both cases, one or two large diameter reinforcing bars of suitable length are welded longitudinally to the lower plate, which acts as the lower chord of the beam. Additionally, a third piece of bar is welded perpendicular to these two bars, with the ends of the bars and the third piece resting on the column. In Figure 2.d, extra lower and upper reinforcing bars are included when the beam is continuous.

[0081] Fig 11 illustrates another aspect of this innovation, showcasing a more consistent reinforcement system for transferring reactions from the two rebar trusses to load-bearing column in a precise and clear manner that aligns with the truss system. In Figure 11. a, two rebar trusses (10) are depicted on the right and left sides, supported in the column (510) in the center. The reinforcement transferring system (500) of the two rebar trusses (10) comprising of the upper chord (505), which can be a continuation of the upper chords of the rebar truss (10), along with the lower chord (502), diagonals (503) and (504). Their primary function is to carry loads from the two upper joint of the beams (506) and (507) to the foundation connection at the joint (508). The reinforcing rod (501) plays a crucial role in transmitting and distributing the loads from the truss supporting joint (508) to the surrounding concrete of the column. Additionally, at the base of rod (501), there is an end piece of steel plate designed to enhance stress distribution within the column.

Claims

CLAIMS1. Rebar and hybrid-rebar truss systems (10, 50, 20, 30, 40, 41, 240, 400) and their supporting reinforcement system (400, 500) utilized for structural purposes to reinforce concrete elements, beam-column joints, and strengthen cold-formed steel joists, the truss joints feature nodes in the diagonals or along with the top and / or bottom chord comprises: a. a continuous upper chord of reinforcing bar, either with forged nodes of the same reinforcing bar, each having a central perforated hole located at intervals along the length of the upper chord, or with mechanical devices attached to it. b. a rebar or a steel plate constituting the lower chord, c. rebar diagonals with at least two end nodes in each diagonal bar, and a hole in each node created by forging, d. means of assembling and fastening truss elements by combining nodes in the diagonals with their corresponding ones in the upper and lower chords and mechanically fastening them to create truss system with the designed shape.

2. As stated in claim 1, the nodes are shaped by hot forging or rolling to create two flat, parallel, and opposite surfaces, each with a central hole.

3. As stated in claim 1, the upper or lower rebar chord, the continuous reinforcement bar, has nodes formed at intervals along its longitudinal length, these nodes have two flat, parallel, and opposite surfaces, and a hole is formed at the center of each node, the rebar chords with its nodes are manufactured through rolling process.

4. The rebar truss system (10) as stated in claim 1, and 2 or 3 comprises: upper and lower rebar chords with identical shapes (1, 2), each having nodes (15) and a hole in every node (16), and rebar diagonals (12), each diagonal have two end nodes, the assembly of the rebar truss components is achieved using mechanical fasteners (31 or 32) for each rebar truss joint, each mechanical fastener has a head (33, 43) on one side and a smooth shaft with a threaded end (46) or buck -tail, these fasteners pass through corresponding holes in the nodes of the upper or lower chord and two diagonals (13, 15, 13) based on the truss design, securing the truss component involves creating a head (34) through forging or tightening a nut (44) to a specified torque on each nut (44) on the opposite side of the fastened truss members.

5. The hybrid rebar truss system (20) according to claims 1, and 2 or 3 comprises: a. a plurality of rebar upper chords (1) with nodes (15) positioned at predetermined intervals along the upper chord, b. a steel plate (9) constituting the bottom chord, to which pieces of plate (11) are welded in two longitudinal rows, with one or two holes in each piece (11),C. rebar diagonals (12), each with two end nodes (13), have a hole in each node corresponding to similar holes - one in the top chord and the other in the plate welded to the bottom chord, d. Assembling the truss elements occurs through 31 or 32 mechanical fasteners per truss joint to construct the intended truss.

6. According to claims 1, and 2 forming the nodes of the chords (1, 2, 4, 26, 27) and in the ends of the diagonals (12, 28, 29, 38, 39), as well as the nodes at changing the diagonal the directions making knee nodes (31, 25, 36), requires enlarging the size of the node locations in their initial stage before flattening them and forming holes in their centers, this ensures that the cross-sectional area at any section within these nodes along the longitudinal axis of the reinforcing bar is not less than the cross-sectional area of the reinforcing bars.

7. According to claims 1, 2, forming strengthened nodes (404) in the chords (1, 2, 4, 26, 27) and strengthened knee nodes (31, 25, 36) at changing the diagonal the directions, comprises, a. sleeve pieces (401) of suitable thickness, each with a length slightly exceeding that of the node length, the inner diameter of each sleeve piece is slightly larger than the diameter of the rebar upper or lower chord to allow easy insertion along them, the thickness of the sleeves is calculated to compensate for the resistance loss node cross-sectional area from forging process, each sleeve piece is pierced with a hole in the middle of its length, perpendicular to its longitudinal axis, passing through both the two walls of the sleeve; b. each sleeve piece is inserted near each position to create the node on the reinforcing bar that represents the upper or lower chord, both the node location of the reinforcing bar and the sleeve piece inserted close to the node location are then heated to the appropriate temperature for forging, c. the sleeve is then placed around the node location, ensuring that, the center of the two sleeve piece' holes aligns with the hole to be made in the node along the chord's length; d. the shaping process is carried out, creating the node (104) and a hole (102) aligning with the diagonal (12) end hole for connecting the chord with the selected diagonals at this node.

8. According to claims 1, 2, and 7 forming strengthened nodes (104) in the chords (1, 2, 4, 26, 27) and strengthened knee nodes (31, 25, 36) at changing the diagonal the directions, comprises, a. sleeve pieces (101) of suitable thickness, each with a length slightly exceeding that of the node length, the inner diameter of each sleeve piece is slightly larger than the diameter of the rebar upper or lower chord to allow easy insertion along them, the thickness of the sleeves is calculated to compensate for the resistance loss from forging, each sleeve piece is pierced with a hole in the middle of its length, perpendicular to its longitudinal axis, passing through both the two walls of the sleeve; b. a soldering layer is wrapped around the upper or lower chord at the location of the node before inserting the sleeve piece above this soldering layer, c. insert the sleeve pieces around and along the upper or lower chord to be positioned at the node locations; d. ensure the center of the two sleeve piece' holes aligns with the hole to be made in the node along the chord's length; e. heat each node's location to the appropriate temperature, then forge it to form the node (104) and a hole (102) aligning with the diagonal (12) endhole for connecting the chord with the selected diagonals at this node, the soldering layer acts as a bridge between the chord and the sleeve portion, allowing them to increase bond between them.

9. According to claims 1 and 5, each pair of diagonals in the truss is formed using a reinforcing bar that is initially enlarged in the middle through hot forging, then bent and flattened also via hot forging to create an inverted V-shape with a node (222) containing a central hole at the vertex of the V-shaped diagonal (223), the two lower end sections of the diagonals (19) are enlarged through hot forging to provide a stable base for resting on the lower plate chord 9 by welding them to the bottom plate (9) or by using screws to connect the enlarged lower part to the bottom plate (9).

10. The hybrid-rebar truss system (30) according to claims 1 and 5 comprises, an upper rebar chord (1), lower chord steel plate (9) and inclined rebar diagonals (12), and upper and lower mechanical joint which are evenly spaced along the longitudinal axis of the hybrid rebar truss system (30), the upper chord mechanical joint include a tubular sleeve portion (210) welded to a plate section (18) having one or two holes aligning with the diagonal end holes (14), the plate piece (18) extends from the outer surface of the tubular part (210) parallel to the truss's longitudinal axis, assembly involves using bolts or rivets (17) to connect the inclined webs (12) to the plate (18), while a reinforcing bar (1) passes through the tubular sections (210), securing the upper chord (1) inside the tubular part (210) is achieved by tightening multiple bolts (201) that traverse the tubular part' (210) wall and press the upper chord (1) against the lower inner serrated surface of the tubular part.

11. The rebar truss systems (40, 41) according to claims 1, 2 comprising diagonal bars (38, 39, 28, 29), an upper chord (4, 26), a lower chord (2, 27), truss joints (24, 25, 31, 36, 37) that join the truss elements, each diagonal in the truss is broken at a location along that diagonal forming a knee node, each of the truss elements has at least two nodes, and forging creates both the nodes and the hole in each node, assembly takes place via a mechanical fasteners (31or 32) for each truss joint (24, 25, 31, 36, 37).

12. The rebar truss (50) as stated in claim 1 and 9 comprises four parallel longitudinal reinforcing bars, two of which represent the upper chord (211) and two represent the lower chord (212), the horizontal projection of each upper chord (211) is located above one lower chord bar (212), each upper chord (211) is connected with the two lower chords by two multiple V-shaped truss webs (223) by the joint (210), every truss joint has two plate pieces or a part of pyramid-shaped piece (217) protruding out of the truss joint tubular sleeve (210), the diagonals (223) are attached to the joint by bolts (218).13.The rebar truss (240) according to claims 1, 2, 10 is used to strengthen the open, thin, cold-formed joist against deformation, localized, and distorted buckling, the truss is placed within the cold formed element, attaching the two longitudinal walls (121) and the bottom plate together to prevent movement or deformation, other elements (244) of the rebar truss (240) perpendicular to the longitudinal axis of the joist inside of the open, cold-formed joist element are used to strengthening the side walls as well as the bottom plate.14.The rebar truss (240) and the cold formed joist according to claims 1, 9 are used to reinforce concrete elements such as beams, resulting in a hybrid-truss that behaves as a single object when exposed to applied loads.

15. The rebar truss (240) with the cold-formed joist according to claim 1, 13 is intended to be used simultaneously as temporary reinforcement and scaffolding to support the selfweight of the beam, the weight of the slabs and the fresh concrete, while the internal rebar truss (240) remain in the concrete element as permanent reinforcement, while the cold- formed steel joist is removed as soon as the concrete element with its internal rebar truss is able to bear the permanent dead and live loads.16.Truss system for concrete beam-column connection according to claims 1 and 7 comprises of upper and lower reinforcement bars (7, 43), diagonal bars (12), and internal vertical reinforcement bars (44), the upper reinforcement bar bending to act also as an external vertical reinforcement bar in the column, the process of constructing the beamcolumn joint reinforcement truss system involves: a. Creating a node (42) on the upper reinforcing bar following similar steps used to create node (404), except that the reinforcing bar is bent after heating to the appropriate temperature, and then a hole (45) is made, similar to the process for hole (14), b. forming nodes (404, 13) on the lower reinforcing bar (43) and node (13) on the vertical inner bar (44) in the same manner as in the upper bar. c. Assembling and securing the beam-column joint reinforcement skeleton by connecting nodes (13) in the diagonals (12) with their corresponding ones in the upper, lower, and vertical reinforcement bars (42, 404, 13) using bolts or solid rivets (17) to achieve the truss reinforcement configuration depicted in Fig lO.a.

17. The load transfer reinforcement system for the two rebar trusses (10) to the supporting column (500) according to claim (1) comprising: upper chord (505), which is a continuation of the upper chords of the rebar truss (10), along with the lower chord (502), diagonals (503) and (504) that transfer the loads from the two upper rebar truss joints (506) and (507) to the joint (508) in the center of column (510), the rebar (501) connects to bottom chord (502) at the joint (508), extending in concrete of column (510) and terminating with an end plate.

Images