[0001] This application is a non-provisional of United States Provisional Patent Application Serial No. 62/719,318 filed August 17, 2018, the disclosure of which is incorporated by reference in its entirety for all purposes.

[0002] The present disclosure relates to concrete systems comprising load transfer devices and methods for eliminating the pour strip, a common feature used in reinforced concrete slab design.

[0003] Reinforced concrete is an important construction material. It offers strength, durability and can be formed into a variety of shapes. Concrete structures are designed with expansion and contraction joints to allow movement. Pour strips are the standard method to mitigate undesirable restraint-to-shortening cracks in concrete construction. These pour strips have an open gap or strip intentionally left out of a newly constructed concrete slab. This open strip allows the newly poured concrete to shrink and shorten during curing. Once most shrinking and shortening in the adjoining concrete sections has occurred, which typically takes several weeks to months, the strip is poured to complete the slab.

[0004] Despite their benefits and wide usage, pour strips disrupt construction. By leaving the slabs unconnected, the complex and costly shoring and support system installed beneath the elevated slab must remain in place until the pour strip is completed. The support system prevents construction trades from working who would otherwise work on the completed floors below the open pour strips. Pour strips increase the risk of injury resulting from the open gap in each constructed floor of a new structure. An additional concern is needing to remobilize the concrete production team to pour the strip many weeks or months later. Thus, although a pour strip in a concrete slab mitigate the restraint-to-shortening cracks, this method is costly, time-consuming, hazardous to safety, and inefficient.

[0005] In these respects, the concrete system and related methods disclosed herein substantially depart from the conventional concepts and designs of the prior art, and in doing so provide a design methodology primarily developed for eliminating the pour strip while transferring loading in the vertical, horizontal and tensile directions.

DRAWINGS

[0006] FIGS. 1-2 are prior art examples of conventional pour strips (black arrow).

[0007] FIG. 3 is a prior art example of a shoring system, which causes congestion but must support uncompleted floors. [0008] FIG. 4 depicts a lockable dowel, which locks to provide tension and good vertical shear capacity but has no horizontal shear capacity and is very expensive.

[0009] FIGS. 5 and 6 depict a double shear dowel, which carries a similar vertical shear capacity as the lockable dowel of FIG. 4, but has no tension capacity and does not lock. The double shear dowel can be installed on its side; that is, rotated 90° to provide a horizontal shear capacity, and it is less expensive than the lockable dowel.

[0010] FIG. 7 depicts a section of an embodiment of the system 700. Two concrete bodies 710, 720 disposed next to each other, defining an access channel 730. A lockable dowel 750 is disposed along the access channel 730 to provide tension to the two concrete bodies 710, 720. A plurality of double shear dowels 741, 742, 743, 744 is disposed along the access channel 730 to provide shear loading capacity to the two concrete bodies 710, 720. In this embodiment, the plurality of double shear dowels 741, 742, 743, 740 is greater than the plurality of lockable dowels 750.

[0011] FIG. 8 depicts a section of an embodiment of the system 800. Two concrete bodies 810, 820 disposed next to each other, defining an access channel 830. A plurality of lockable dowels 850, 855 is disposed along the access channel 830 to provide tension to the two concrete bodies 810, 820. A plurality of double shear dowels 841, 842 is disposed along the access channel 830 to provide shear loading capacity to the two concrete bodies 810, 820. In this embodiment, the plurality of double shear dowels 841, 842 is equal to the plurality of lockable dowels 850, 855.

SUMMARY

[0012] In light of the above-mentioned disadvantages, the present disclosure provides a concrete system and method for addressing the common problems of pour strips, using a combination of shear transfer systems. The concrete system eliminates the need for a conventional pour strip while addressing the shear and tensile load transfer across the construction joint, including the loading requirements in all three directions across a post tension construction joint. In certain embodiments, a double shear dowel is the primary source of vertical shear transfer across a post-tension construction joint. Contrary to industry practice, the systems and methods disclosed herein use locking dowels to develop only tension across the construction joint, rather than for all vertical shear loading. In certain embodiments, horizontal shear loading is restrained by installing a double shear dowel in its horizontal orientation. [0013] Provided herein is a concrete system, comprising two or more concrete bodies disposed next to each other, defining an access channel; a plurality of lockable dowels disposed along the access channel to provide tension to the two or more concrete bodies; and a plurality of double shear dowels disposed along the access channel to provide shear loading capacity to the two or more concrete bodies; wherein the plurality of double shear dowels is greater than the plurality of lockable dowels. In certain embodiments, the concrete system further comprises a second plurality of double shear dowels installed along the access channel with an 90° rotation to provide horizontal shear transfer to the two or more concrete bodies. In certain embodiments, the two or more concrete bodies are concrete slabs. In certain embodiments, one of the two or more concrete bodies is a wall and one of the two or more concrete bodies is a slab.

[0014] Also provided herein is a method for constructing a concrete system. A plurality of lockable dowels is disposed along an access channel defied by two or more concrete bodies, wherein the plurality of lockable dowels provides vertical loading capacity and pull-apart resistance to the two or more concrete bodies. A plurality of double shear dowels is disposed along the access channel to provide shear loading capacity to the two or more concrete bodies. The plurality of double shear dowels is greater than the plurality of lockable dowels.

[0015] The present disclosure further provides a method for constructing a concrete system, comprising quantifying vertical shear loading capacity and pull-apart resistance needed for the concrete system; disposing a plurality of lockable dowels along an access channel defined by two or more concrete bodies, wherein the plurality of lockable dowels is based on the quantified pull-apart resistance needed for the two or more concrete bodies; and disposing a plurality of double shear dowels at a 90° rotation along the access channel, wherein the plurality of double shear dowels is based on the quantified horizontal shear loading capacity needed for the two or more concrete bodies.

DETAILED DESCRIPTION

[0016] In post tension building construction, a common design requirement is the“pour strip” or“closure strip,” a long strip of the floor left open (not poured) during the concrete pouring process. This open strip allows for the two open and unconnected slabs that have been poured to cure and shrink. Once the desired time has passed and shrinkage has occurred, the strip is poured, completing the construction of the floor slab. This process, although effective, is incredibly disruptive and costly; however, engineers and builders use it because it greatly reduces the cracking in the concrete that would occur if the floor were poured continuously or monolithically.

[0017] Provided herein is a concrete system, comprising two or more concrete bodies disposed next to each other, defining an access channel; a plurality of lockable dowels disposed along the access channel to provide tension to the two or more concrete bodies; and a plurality of double shear dowels disposed along the access channel to provide shear loading capacity to the two or more concrete bodies; wherein the plurality of double shear dowels is greater than the plurality of lockable dowels.

[0018] Dowels transfer shear across construction and movement joints in concrete. They are often either cast or drilled into the concrete. A single row of short thick dowels provides reasonable shear transfer but demands additional accuracy during construction. Skewed installation of dowels can concentrate stress, spalling the concrete. Where dowels are used across expansion and contraction joints, half the length of the bar is debonded to allow movement. Dowelled joints either require formwork to be drilled for the dowels to pass through, or concrete to be drilled for dowels to be resin-fixed in one side. At movement joints, dowels are accurately aligned in both directions to permit movement; otherwise cracking is likely. Plain dowels are not effective across joints wider than 3/8".

[0019] Several dowel systems transfer shear loads in concrete construction, such as the lockable dowel (for example manufactured by Ancon, UK and distributed by Meadow Burke USA). While this product generally operates to mitigate pour strips, it does not transfer common loadings in concrete construction.

[0020] Lockable dowels are used at temporary movement joints, most commonly found in post-tensioned concrete frames. These dowels allow initial shrinkage of the concrete and are then locked in position with a mechanical plate and epoxy resin, generally between 28 and 120 days. The locked dowels continue to transfer shear but prevent further movement.

[0021] Lockable dowels save considerable time and materials over other construction methods. Lockable dowels improve site access, minimize formwork, and accelerate the rate of construction. With a lockable dowel, slabs are propped less or a support corbel is not needed, as shear load is transferred by the dowel. The time saved by early removal of slab props can be significant. In addition, engineers have found the lockable dowel is a solution for pin-ended joints. Although U-bars or other rebar continuity systems are customary at these connections, these options are not hinges, so slab rotation under load induces cracking at the wall-to-slab interface with potential integrity issues. The lockable dowel is closer to a true pin-ended joint and, often being manufactured from stainless steel, provides additional corrosion protection over systems using carbon steel reinforcement.

[0022] In certain embodiments, the lockable dowel comprises a guide tube and a dowel, the guide tube being arranged to receive an end of the dowel, characterized by the end passing through the guide tube into a fixing chamber (void former) via an orifice. In certain embodiments, the guide tube has a width and is disposed adjacent to a joint between adjacent blocks of building materials, such as one or more concrete bodies. In certain embodiments, the dowel passes between the adjacent blocks of building materials and has a width, a first end, and a second end. In certain embodiments, the second end of the dowel is configured to be received by the guide tube and to allow longitudinal movement of the dowel in the guide tube. In certain embodiments, the sleeve is configured to receive the guide tube and to allow for lateral and rotational movement of the dowel. In certain embodiments, the sleeve has a lateral sleeve width in excess of the width of the guide tube. In certain embodiments, a fixing chamber is coupled to the sleeve. In certain embodiments, an open end is configured to receive a fixing means adapted to restrict motion of the dowel within the guide tube. In certain embodiments, the orifice is configured to receive the second end of the dowel.

[0023] In certain embodiments, the fixing chamber is arranged to receive a fixing means. The fixing means is arranged to restrict the motion of the dowels within the guide tube. The lockable allows initial motion of the dowel within the guide tube while restricting, and in some embodiments preventing, motion of the dowel once the fixing means is received in the fixing chamber, and, where applicable, conditioned or positioned into a fixing configuration.

[0024] In certain embodiments, the lockable dowel is modified such that the dowel has at least one end provided with a guide tube and fixing chamber assembly to allow the initial motion of the dowel within the guide tube while restricting motion of the dowel once the fixing means is in place. The other end is retained in a fixed relationship within a building material during use, for example buried within or in fixed relation to a surface. Thus, in certain embodiments, the dowel has a first end adapted to be so retained in a fixed relationship with a building material and a second end provided with the guide tube and fixing chamber assembly.

[0025] In one embodiment, the first end is adapted with a fixing formation retained directly in fixed relation with a building material. In certain embodiments, the first end is structured to be retained within a building material. In certain embodiments, a formation keys within a setting concrete or like structure. In certain embodiments, the first end comprises mechanical fixing means to fix in or upon the surface of a building material. Thus, the first end may be initially fixed in situ, and initial motion of the dowel at the second end only is enabled.

[0026] In certain embodiments, the fixing chamber is formed integrally with the guide tube. Here, providing the fixing chamber integrally with the guide tube simplifies installation of the lockable dowel into a structure under construction.

[0027] The fixing chamber may extend perpendicularly to the longitudinal axis of the guide tube. In one embodiment, the fixing means comprises a fixing member selectively mechanically engageable with the dowel in the fixing chamber. In certain embodiments, the fixing member may be configured such that fixing is effected simply by its insertion into the fixing chamber. In certain embodiments, the fixing member requires a secondary fixing or locking action. In certain embodiments, the fixing means comprises an insert structured to engage with a suitably shaped formation on the dowel in the fixing chamber, for example a portion of the insert and a portion of the dowel is complementarily shaped and

complementarily threaded.

[0028] In certain embodiments, the fixing member comprises a locking device. In certain embodiments, the locking device is selectively positionable between a first unlocked position where the dowel is free to move and a second locked position, whereas the locking device engages the dowel in such manner as to restrict or prevent motion of the dowel. In certain embodiments, a locking device may be configured to lock the dowel once placed in position.

[0029] In certain embodiments, the fixing means comprises a fixing medium introduced into the fixing chamber. In certain embodiments, the fixing medium comprises a fluid introducible to the fixing chamber in fluid form and curable to a less fluid or set form, thereby fixing the dowel to restrict or prevent motion of the dowel. For example, in certain embodiments, the fixing medium is a curable or settable material capable of being introduced into the fixing chamber in fluid state and curable or settable in situ. In certain embodiments, the fixing medium is introduced to substantially fill residual space in the fixing chamber once the dowel is in situ.

[0030] In certain embodiments, the lockable dowel may comprise an intermediate sleeve located between the guide tube and the sleeve. In certain embodiments, the intermediate sleeve is fabricated from a compressible material, for example a plastics foam material. When present, the intermediate sleeves limits the egress of a fixing medium, such as a grout or resin, down the sleeves and into the region of the joint between adjoining blocks of construction material. [0031] In certain embodiments, the fixing chamber comprises a box having an open end, the open end being arranged to receive the fixing medium. In certain embodiments, the fixing chamber comprises a cap arranged to releasably seal the fixing chamber. In certain embodiments, the orifice is remote from the open end. In certain embodiments, the fixing chamber comprises a tube arranged to engage an opening of the box. In certain embodiments, the fixing chamber is removable from the shear lockable dowel. A removable fixing chamber is particularly advantageous by allowing the fixing chamber to be a removable form, so that the fixing medium bonds directly with the building structure in which it is retained rather than to the fixing chamber. Such a removable fixing chamber provides better adhesion of the fixing medium to the structure under construction. In certain embodiments, the fixing chamber comprises a plastics material.

[0032] In certain embodiments, the dowel passes through the guide tube and into a section of the sleeve. In certain embodiments, the fixing chamber is formed integrally with the sleeve. In certain embodiments, the dowel may pass through the section of the sleeve and into the fixing chamber. When present, such sleeve allows for lateral and rotational movement before a fixing means is introduced.

[0033] In certain embodiments, the dowel comprises a keyed section comprising a keying formation arranged to pass into the fixing chamber. In certain embodiments, the keyed section is arranged to engage with the fixing medium and/or with the fixing member. In certain embodiments, the keyed section is located at the second end of the dowel. In certain embodiments, the keying formation comprises one or more features chosen from groove, step, channel, sawtooth, waisted section, frustoconical section, frustoconical keying, screw- thread, and nut arrangement. In certain embodiments, the keying formation extends laterally about the second end of the dowel. In certain embodiments, the second end of the dowel comprise a screw thread arranged to receive a nut. When present, the keying formation may improve the engagement of the dowel with a fixing medium and thereby improves the locking of the dowel into position. In certain embodiments, the keying formation provides direct mechanical engagement with a fixing member.

[0034] In certain embodiments, the lockable dowel may comprise a locking device. In certain embodiments, the locking device engages the keying formation. In certain embodiments, the locking device may comprise a plate. In certain embodiments, the plate may be arcuate, for example comprising sectors of a circle, rectangular, hexagonal or otherwise polygonal. [0035] In certain embodiments, the length of dowel extending into the fixing chamber is sufficiently long so that grooves cut into the dowel to accept the locking device are wide enough to handle a locking device. The locking device may be a locking plate. The thickness of the locking plate may be adjusted, such to be twice as thick as the locking plate commercially available devices.

[0036] In certain embodiments, a locking device may be used with a fixing medium. In such a combination, the locking device transfers any longitudinal tensile and lateral forces from the dowel into the fixing medium within the fixing chamber and aids to restrict movement. In certain embodiments, the fixing medium comprises a grout or a resin. In certain embodiments, the fixing medium is pourable before setting. Without wishing to be bound by theory, tension capacity increases substantially when the fixing means extends below the bottom of the dowel. This configuration allows the locking plate to also extend below the dowel, thus resulting the locking device, such as a locking plate, pulling against a mass of an fixing medium, such as an epoxy resin, underneath the dowel.

[0037] In certain embodiments, double shear dowel (for example manufactured by Ancon, UK and distributed by Meadow Burke USA) and the shear dowel (for example manufactured by Ancon, UK and distributed by Halfen USA) efficiently transfer loadings in the horizontal and vertical directions. These dowels do not lock or restrict movement in the longitudinal direction, an attribute of the lockable dowel. The double shear dowel allows permanent joint movement. It works in beams crossing the intended pour strips or access channels. With the double shear dowel, the pour strip is reduced across the entire depth of the slab.

[0038] As disclosed in the concrete systems and methods herein, the double shear dowel complements the lockable dowel. The double shear dowel offers significant advantages over plain dowel bars. They are more effective at transferring load and accommodating movement. The double shear down costs about half as much as the lockable dowel while providing nearly identical shear capacity.

[0039] Due to their two-part construction, double shear dowels are simpler to install than are plain dowels. Each connector is a two-part assembly comprising a sleeve and a dowel component. Installation is fast and accurate. Drilling formwork or concrete is not required. The sleeve is nailed to the formwork ensuring subsequent alignment with the dowel for effective movement. These connectors are often manufactured from stainless steel to ensure high corrosion resistance with no requirement for additional protection. The dowel component can move longitudinally within the sleeve to accommodate movement. The connector is available in 10 standard sizes and has design capacities from approximately 4,500 lbs. (2,045 kg) to more than 214,000 lbs. (97,300 kg). The larger connectors can be used in joints up to 60 wide, while larger joints can be accommodated using special dowels.

[0040] In certain embodiments, higher strength capacities are obtained by increasing the distance between the dowels in the double shear dowel to the maximum allowable distance, so that the double shear dowel still fits within the concrete body. For example, the concrete body may be a concrete slab that is 7 inches thick. In this example, the distance between the dowels in the double shear dowel are set to the maximum allowable distance for a 7-inch thick slab. This adjustment improves structural performance without increased effort or cost.

[0041] Because the lockable dowel locks, it provides tensile capacity, which the double shear dowel cannot. Plans for building structures of reinforced concrete typically provide a page of“loading conditions,” reporting basic dead load and live load parameters for the shear forces on each floor. It is not typical or customary for these plans to recognize or define the tensile force needed across the access channel. As a result, engineers typically add as many lockable dowels as needed to handle the shear across the joint. The engineers do not determine tension requirements. This approach typically results in the needed shear capacity with hundreds or thousands of times more tension across the joint than is required.

[0042] In some embodiments, the system comprises one lockable dowel. In some embodiments, the system comprises at least one lockable dowel. In some embodiments, the plurality of double shear dowels is equal to the plurality of lockable dowels. In some embodiments, the plurality of double shear dowels is greater than to the plurality of lockable dowels.

[0043] Turning to FIG. 7, system 700 has comprises two concrete bodies 710, 720 disposed next to each other, defining an access channel 730. A lockable dowel 750 is disposed along the access channel 730 to provide tension to the two concrete bodies 710, 720. A plurality of double shear dowels 741, 742, 743, 744 is disposed along the access channel 730 to provide shear loading capacity to the two concrete bodies 710, 720. These double shear dowels are installed on their sides, rotated 90° to provide horizonal shear capacity. In this embodiment, the plurality of double shear dowels 741, 742, 743, 740 is greater than the plurality of lockable dowels 750.

[0044] Turning to FIG. 8, system 800 comprises two concrete bodies 810, 820 disposed next to each other, defining an access channel 830. A plurality of lockable dowels 850, 855 is disposed along the access channel 830 to provide tension to the two concrete bodies 810, 820. A plurality of double shear dowels 841, 842 is disposed along the access channel 830 to provide shear loading capacity to the two concrete bodies 810, 820. These double shear dowels are installed on their sides, rotated 90° to provide horizonal shear capacity. In this embodiment, the plurality of double shear dowels 841, 842 is equal to the plurality of lockable dowels 850, 855.

[0045] Also provided herein is a method for constructing a concrete system. A plurality of lockable dowels is disposed along an access channel defied by two or more concrete bodies, wherein the plurality of lockable dowels provides vertical loading capacity and pull-apart resistance to the two or more concrete bodies. A plurality of double shear dowels is disposed along the access channel to provide shear loading capacity to the two or more concrete bodies. The plurality of double shear dowels is greater than the plurality of lockable dowels.

[0046] Applying the methods disclosed herein, tension for the concrete system is calculated. If an engineer requires more tension, more lockable dowels are substituted for double shear dowels. That is, a large plurality of lockable dowels is used in the concrete system to provide the needed tension. In certain embodiments, the substitution can also be applied to a section of the concrete system requiring additional tension. Elsewhere in the concrete system, the ratio between lockable dowels and double shear dowels can remain unchanged.

[0047] In certain embodiments, the method further comprises determining the shear and tension loads across the access channel. In certain embodiments, the method further comprises selecting a plurality of lockable dowels sufficient to satisfy the tension load and selecting a plurality of double shear dowels to satisfy the balance of the shear load. In certain embodiments, the method further comprises quantifying the vertical shear loading capacity and pull-apart resistance needed for the concrete system. In certain embodiments, the method further comprises quantifying the horizontal shear loading capacity needed for the concrete system. In certain embodiments, the method further comprises determining the plurality of lockable dowels based on the quantified pull-apart resistance needed for the concrete system. In certain embodiments, the method further comprises determining the plurality of double shear dowels based on the quantified vertical shear loading capacity needed for the concrete system.

[0048] In certain embodiments, the method further comprises determining the second plurality of double shear dowels to be disposed at a 90° rotation based on the quantified horizontal shear loading capacity needed for the concrete system. In certain embodiments, the method further comprises disposing a second plurality of double shear dowels at a 90° rotation to provide horizontal shear transfer to the two or more concrete bodies. [0049] Referring again to FIG. 7, a plurality of lockable dowels 750 is disposed along an access channel 730 defied by two or more concrete bodies 710, 720. The plurality of lockable dowels 750 provides vertical loading capacity and pull-apart resistance to the two or more concrete bodies 710, 720. A plurality of double shear dowels 741, 742, 743, 744 is disposed along the access channel 730 to provide shear loading capacity to the two or more concrete bodies 710, 720. The plurality of double shear dowels 741, 742, 743, 744 is greater than the plurality of lockable dowels 750.

[0050] Referring now to FIG. 8, a plurality of lockable dowels 850, 855 is disposed along an access channel 830 defied by two or more concrete bodies 810, 820. The plurality of lockable dowels 850 provides vertical loading capacity and pull-apart resistance to the two or more concrete bodies 810, 820. A plurality of double shear dowels 841, 842 is disposed along the access channel 830 to provide shear loading capacity to the two or more concrete bodies 810, 820. The plurality of double shear dowels 841, 842 is greater than the plurality of lockable dowels 850.

[0051] The following Exemplary Embodiments are included to illustrate the invention: Embodiment 1. A concrete system, comprising

two or more concrete bodies disposed next to each other, defining an access channel;

a plurality of lockable dowels disposed along the access channel to provide tension to the two or more concrete bodies; and

a plurality of double shear dowels disposed along the access channel to provide shear loading capacity to the two or more concrete bodies;

wherein the plurality of double shear dowels is greater than the plurality of lockable dowels.

Embodiment 2. The system of Embodiment 1 , further comprising a second plurality of double shear dowels installed along the access channel with an 90° rotation to provide horizontal shear transfer to the two or more concrete bodies.

Embodiment 3. The system of Embodiments 1 or 2, wherein the two or more concrete bodies are concrete slabs.

Embodiment 4. The system of Embodiments 1 or 2, wherein one of the two or more concrete bodies is a wall and one of the two or more concrete bodies is a slab.

Embodiment 5. A method for constructing a concrete system, comprising disposing a plurality of lockable dowels along an access channel defied by two or more concrete bodies, wherein the plurality of lockable dowels provides vertical loading capacity and pull-apart resistance to the two or more concrete bodies; and

disposing plurality of double shear dowels along the access channel to provide shear loading capacity to the two or more concrete bodies;

wherein the plurality of double shear dowels is greater than the plurality of lockable dowels.

Embodiment 6. The method of Embodiment 5, further comprising disposing a second plurality of double shear dowels at a 90° rotation to provide horizontal shear transfer to the two or more concrete bodies.

Embodiment 7. The method of Embodiments 5 or 6, further comprising quantifying the vertical shear loading capacity and pull-apart resistance needed for the concrete system.

Embodiment 8. The method of Embodiment 7, further comprising quantifying the horizontal shear loading capacity needed for the concrete system.

Embodiment 9. The method of any of Embodiments 5-8, further comprising determining the plurality of lockable dowels based on the quantified pull-apart resistance needed for the concrete system.

Embodiment 10. The method of any of Embodiments 5-9, further comprising determining the plurality of double shear dowels based on the quantified vertical shear loading capacity needed for the concrete system.

Embodiment 11. The method of any of Embodiments 5-10, further comprising determining the second plurality of double shear dowels to be disposed at a 90° rotation based on the quantified horizontal shear loading capacity needed for the concrete system.

Embodiment 12. The method of any of Embodiments 5-11, wherein the two or more concrete bodies are concrete slabs.

Embodiment 13. The method of any of Embodiments 5-11, wherein one of the two or more concrete bodies is a wall and one of the two or more concrete bodies is a slab.