The present invention is directed toward a rebar support assembly and, in particular, to a rebar support assembly for reinforced concrete beams.
Concrete beams are structural elements typically utilized to transmit tributary loads from floor slabs to vertical supporting columns or walls, as well as to transmit the weight of a super-structure to the supporting soil. Concrete, while possessing strong compressive strength, is subject to tensile forces that, over the life of the beam, results in beam deflection or creep. Reinforcing the beam accommodates for tensile stresses, minimizing creep as well as minimizing the width of any cracks that develop during the life of the beam.
Typically, concrete beams are reinforced utilizing reinforcement bars (“rebars”). Rebars can be made of metal (e.g., steel, stainless steel, etc.) or nonmetals (e.g., fiber-reinforced polymers (FRP)). A typical system may include main bars running longitudinally (along the length of the beam) and transverse bars running across the beam. The bars are set at predetermined locations, e.g., toward the outer (top/bottom) surface of the beam. In addition, stirrups (closed, U-shaped, or C-shaped rebar segments) are often used to provide tensile strength to the beam. Stirrups may be oriented vertically, or may be inclined, slanting within the beam. For example, conventional rebar systems typically include a rebar segment formed into a U-shaped stirrup with angular returns along its top end (the top of the “U”). The stirrups are fastened to the main (longitudinal) reinforcing rebar with a winding wire and then placed onto a separate support chair to elevate the entire assembly above a supporting surface (e.g., the ground, trench, or concrete pour area, or formwork).
Conventional rebar support systems suffer from several drawbacks. For example, the systems require additional process steps—the stirrups must be formed on-site, and then assembled in the field by a construction worker. Metal wire must be utilized to secure the stirrup to the main bar. That is, the stirrup is secured to the main bar by winding metal wire in several places along the inner perimeter of a U-shaped stirrup. In addition, once the U-shaped rebar stirrup is fastened to the main reinforcing rebar, the entire assembly must be positioned onto the support chair placed within the concrete pour area. This process is very labor intensive.
Another problem with conventional rebar support systems is that when the main reinforcing rebar is wound onto the metal stirrup, the integrity of the wound rebar is completely dependent on the skill of the worker winding the binding wire, yielding a winding junction that is non-repeatable and lacking uniformity from job to job. In addition, the wound wire configuration risks the dislocation of rebar if the metal wires are unwound or broken during the process of pouring concrete.
Still another disadvantage of metal wire stirrups is the rusting/oxidation of the binding wire. Since the binding wire tends to extend from the resulting concrete beam, the wire is exposed to the environment, risking the oxidation of the wire over time.
In view of the above disadvantages, it is desirable to provide an rebar support assembly that can be set up quickly on site, can adequately and uniformly secure the rebar segments within the assembly, and can eliminate the need for additional process steps (and, in particular, the extensive winding of field/binding wire).
The present invention is directed toward a rebar support assembly utilized in the formation of cast-in-situ and precast structural elements and, in particular, in the formation concrete beams. The support assembly may include a frame having chair portion, a stirrup portion, an intermediate portion, and/or a header portion. Each portion may include one or more rebar receptacles designed to support a segment of reinforcement bar in a predetermined location and orientation. For example, the receptacles may be configured to support the rebar in a generally horizontal and/or a generally vertical orientation. The assembly may be configured as a unitary structure, or may be modular, enabling its customization at a job site. In use, the assembly is positioned on the supporting surface of the concrete pour area and the rebar segments are coupled to the receptacles. Concrete is then poured over/around the assembly.
Like reference numerals have been used to identify like elements throughout this disclosure.
The cage portion 120 is configured to support one or more receptacles 130 in predetermined positions, orienting the reinforcement bars in spaced, generally parallel relation (vertically and horizontally). As with the chair portion 110, the cage portion 120 includes an open structure to permit the flow of concrete therethrough. Referring back to
The reinforcement bar receptacle 130 is configured to receive a portion of a reinforcing bar segment, selectively positioning the bar at a predetermined location and in a predetermined orientation within the beam.
The receptacles 130 may be disposed at any suitable location along the chair portion 110 and/or cage portion 120. For example, a first set of receptacles 130 may be disposed in spaced relation along the exterior wall 140 of the cage portion 120. The receptacles 130 may extend distally from the exterior wall, with the receiving section 310 oriented upwards to support the reinforcement bar generally parallel to the supporting surface (i.e., horizontally). Alternatively or in addition to, a second set of receptacles 135 may extend distally from generally vertical support wall 160, with the receiving portions oriented outward to support the reinforcement bar generally perpendicular to the supporting surface (i.e., vertically). In the embodiment shown in
The receptacles 130, 135 may possess any shape suitable for its intended purpose. Referring to
While a generally rectangular rebar support assembly 100 is illustrated, the assembly—and in particular, each of the chair portion 110 and cage portion 120—may possess any desired shape or have any dimensions suitable for its described purpose.
The assembly 100 may be formed from any suitable materials. By way of example, the assembly 100 is formed from a moldable material such as a thermoplastic resin including, but not limited to, acrylonitrile butadiene styrene; polyvinyl chloride; polypropylene (e.g., polypropylene, talc-filled polypropylene, calcium filled polypropylene, and polypropylene copolymers); polyethylene (low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), ultra high molecular weigh polyethylene (UHMWPE)); polyamide, polyester; and polycarbonate. The assembly 100 may be formed utilizing injection molding, co-injection molding, profile extrusion, ram extrusion versus injection molding or co-injection molding, or computer controller cutting or building process such as machines using computer numerical control (CNC), and selective laser sintering (SLS), stereolithography (SLA). When molding processes are utilized, the assembly 100 may be formed into a unitary structure in which each of the chair portion 110, the cage portion 120, and the receptacles 130 being integrated into a single piece unit.
In addition, the assembly 100 may be formed from other, metallic and nonmetallic materials. When metal is used to form the assembly 100, furthermore, the metal may be coated with a thermoplastic resin to provide a layer to inhibit oxidation of the metal.
Operation of the assembly is illustrated with respect to
With this configuration, the rebar support assembly 100 provides a single-piece rebar support that locates the main reinforcing bar in the same location across the spanned rebar, maximizing the reinforcement performance of the concrete poured slab, floor, wall, etc. This configuration further does not require the use of winding to secure the vertical and horizontal rebar segments together/in position.
In the embodiment illustrated, each portion 610, 620, 630, 640 includes a plurality of generally vertical support members or walls 650 intersected by generally horizontal support members or walls 655. The portions 610, 620, 630, 640 may further include a fastener socket 660 operable to guide a fastener toward its corresponding assembly portion. With this configuration, the assembly 600 may be fastened to the walls of a concrete form via the sockets 660 (shown in
Each portion 610, 620, 630, 640 is adapted to mate with a corresponding portion. By way of example, the generally vertical support members 650 of the header portion 630 is adapted to mate with the generally vertical support members of the cage portion 620, which, in turn, is adapted to mate with the generally vertical support members of the chair portion 610. Referring to the embodiment of
Each portion 610, 620, 630, 640 may be single-piece units; alternatively, each portion may be adapted to connect with other segments, making the assembly reconfigurable. Referring to the embodiment illustrated in
The chair portion 610 further includes receptacles operable to support and orient reinforcement bar segments in predetermined positions. Preferably, the chair portion 610 includes a first set of receptacles configured to simultaneously position the reinforcement bar in a first orientation (e.g., generally horizontally) and second reinforcement bar in a second orientation (e.g., generally vertically). By way of specific example, as shown in the embodiment of
The cage portion 620 is disposed above the chair portion 610. Referring to
The header portion 630 is disposed at the top of the assembly 600. Referring to
The rebar support assembly 600 may further include one or more intermediate portions 640 that are selectively positioned within the assembly. In the embodiment of
The intermediate portion 640 may include receptacles configured to position the reinforcement bar in a desired orientation. By way of example, the generally horizontal support member 655 may include one or more horizontal receptacles 820 configured to orient a reinforcement bar generally horizontally (i.e., generally parallel to the supporting surface). While not illustrated, it should be understood the intermediate portions may further include vertical receptacles 810 operable to support a reinforcement bar vertically. Furthermore, the intermediate portions 640 may be formed with no receptacles 810, 820830.
Operation of the device is explained with reference to
In addition, a vertical reinforcement bar 910 may be inserted into the vertical receptacles 810. The vertical reinforcement bar 910 may be configured such that it includes an elongated rod having hooks or bends 930 formed into its terminal ends. The hook 930 may possess an angle of about 90°. Referring to
The vertical reinforcement bars 910, moreover, strengthen the finished concrete beam against shear forces. Utilizing two vertical reinforcement bars 910 (instead of one bar) provides better shear resistance of the concrete beam, increasing the beam's resistance to any accidental torsion that might be applied to the beam (e.g., due to the grid action resulting from any differential settlement). In that case, the torsion can be resisted by the coupling force in the two bars. The hook 930 decreases the probability of anchorage failure. In addition, the hooks 930 permit the reinforcement bars to reach their ultimate tensile strength before having bar slippage. The hook 930 also improves the effectiveness of the reinforcement bar should a shear crack form near the end of the reinforcement bar (the receptacle alone may not be suitable). In operation, the vertical reinforcement bars 910 should be carried as close to the beam face as possible, and the bar may have an extension of at least 6 db after the hook for No. 5 and smaller, and 12 db for No. 8 and smaller.
It is important to note that, in addition to capturing and support sections of reinforcement bar, the receptacles 810, 820830 may be utilized to support other, non-rebar sections. By way of example, the horizontal receptacles 820, 830 may be configured to support other, non-rebar components such as cables, as well as plumbing and electrical conduits (pipes, wires, etc.). This feature is particularly useful during the formation of precast structural elements, where the element is formed off-site and delivered to the work site. Thus, the assembly 600 may support various rebar and non-rebar components, properly supporting the components within the in-situ environment and, consequently, within the finished structural element.
The assembly 600 may be formed from any suitable materials. Preferably, the assembly 600 is formed from a thermoplastic resin including, but not limited to acrylonitrile butadiene styrene; polyvinyl chloride; polypropylene (e.g., polypropylene, talc-filled polypropylene, calcium filled polypropylene, and polypropylene copolymers); polyethylene (low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), ultra high molecular weigh polyethylene (UHMWPE)); polyamide, polyester; and polycarbonate. The assembly 600 may be formed utilizing injection molding, co-injection molding, profile extrusion, ram extrusion versus injection molding or co-injection molding, or computer controller cutting or building process such as machines using computer numerical control (CNC), and selective laser sintering (SLS), stereolithography (SLA). When molding processes are utilized, each portion 610, 620, 630, 640 of the assembly 600 may be formed into single piece units, wherein the receptacles 810, 820, 830, the fastener sockets 660, and support members 650, 655 are part of an integrated frame structure.
In addition, the assembly 600 may be formed from other, metallic and nonmetallic materials. When metal is used to form the assembly 600, furthermore, the metal may be coated with a thermoplastic resin to provide a layer to inhibit oxidation of the metal.
Thus, the present invention provides a rebar support assembly 100, 600 that is able to carry two rows or more of longitudinal flexural reinforcement (top or bottom), as well as the skin reinforcement. The above-described modular configuration enables the use of hooked shear reinforcement bars that would enclose the flexural reinforcement.
Thus, the above-described configurations provide a single piece integrated rebar support system that will overcome the shortcomings of the prior art devices by forming an integrated rebar support system formed from, structurally sound thermoplastic parts, eliminating the need for any field wire winding by construction workers. The described configurations further provide a rebar support system that locates the main reinforcing rebar in the same location across the latitudinal spanned rebar of the assembly to maximize the reinforcement performance of the concrete poured slab, floor, wall, etc. Finally, the described configurations provide a single piece integrated rebar support system that is simple, cost effective and eliminates the possibility of human error from workers' experience and techniques, or lack thereof.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. For example, the assembly 100, 600 may be of any suitable shape and possess any suitable dimensions. Similarly, the portions 610, 620, 630, 640 may possess any suitable shape or have any suitable dimensions. The portions may comprise any number of segments 670A, 670B, 670C, 670D to accommodate wide concrete beams.
The receptacles 130, 810, 820, 830 may be disposed at any suitable locations within the assemblies 100, 600. For example, the receptacles may be disposed within the interior of the cage and/or chair portions. While shown as supporting reinforcement bar segments vertically and horizontally, the receptacles may be configured to support reinforcement bars at any desired angle (e.g., latitudinally or longitudinally inclined with respect to the supporting surface). The positioning of the receptacles 820, 830 along the horizontal bar 655 of a portion 610, 630, 640 may be such that the clear spacing between the longitudinal reinforcement bars in a single row (e.g., at the bottom and at the top) is larger than about 1.4 times the diameter of the reinforcement bar, and not less than about 30 mm.
The above-described rebar support system can be used for cast-in-situ (i.e., on site) concrete, or can be used in precast and/or pre-stressed concrete applications. Precast concrete is performed in a factory. Pre-stressing is a process where internal cables are stretch inside the concrete, such that when the concrete hardens, the cables compress the beams, thus closing the cracks and the tension forces. The resulting beams formed in the precast/prestressed processes may not possess rectangular shapes. For example, the resulting beams may have a bulge along its bottom surface to accommodate more reinforcement bars along the tension side.
It is to be understood that terms such as “top”, “bottom”, “front”, “rear”, “side”, “height”, “length”, “width”, “upper”, “lower”, “interior”, “exterior”, “inner”, “outer” and the like as may be used herein, merely describe points of reference and do not limit the present invention to any particular orientation or configuration. Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of the appended claims and their equivalents.
This application is a non-provisional application of provisional application No. 60/912,524, entitled “Rebar Support System” and filed on 18 Apr. 2007, the disclosure of which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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60912524 | Apr 2007 | US |