US20070251169A1

US20070251169A1 - Grouted rebar dowel splice

Info

Publication number: US20070251169A1
Application number: US11/410,651
Authority: US
Inventors: Kjell Dahl
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-04-26
Filing date: 2006-04-26
Publication date: 2007-11-01

Abstract

Disclosed herein is a grouted rebar dowel splice by which first and second rebars to be embedded within adjacent concrete sections are coupled to one another to hold the concrete sections together and resist tension and compression forces that are typically encountered during an earthquake. The rebar splice includes a hollow cylindrical splice body. One end of the hollow splice body is flattened, and a reinforcing sleeve is pressed into surrounding engagement with the flattened first end. The first rebar is received through axially aligned holes formed in the flattened first end and the reinforcing sleeve. A coiled compression spring is engulfed by a solidifier (e.g., an epoxy or a grout) at the hollow interior of the splice body. The second rebar is received through an opening at the opposite end of the splice body to be surrounded by and coaxially aligned with the coiled compression spring. The hole through the flattened first end of the splice body has a longitudinal axis which is perpendicularly aligned with the longitudinal axis of the opening at the first end of the splice body such that the first and second rebars extend in different directions.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to a grouted rebar dowel splice by which to couple a first rebar embedded within a first concrete section or block to a second rebar embedded within an adjacent concrete section or block so as to function as a continuous casting joint therebetween, when the first and second sections are not cast at the same time. The dowel splice has particular application during the erection or retrofitting of buildings, subways, airports, bridges, and other large construction projects.
2. Background Art
It is common in the construction industry, during the erection and retrofitting of buildings, parking structures, bridges, subways, airports, and similar large construction projects, to add a new contiguous concrete structure or section to an existing concrete structure or section. At other times, the construction project requires that a series of adjacent concrete sections be poured at different times. In either case, care must be taken during construction to ensure that the sections and/or structures are interconnected so that they will not shift relative to one another, particularly as a consequence of a seismic event or during earth movement. The foregoing has typically been accomplished by means of splicing together modified steel rebars that are embedded in and project from an existing concrete structure or section to a new structure or section, whereby both the original structure or section and the new structure or section will be capable of withstanding earthquake strength forces without separating.
Couplers that are filled with cement grout are known in the art by which to splice together opposing rebars that extend from one concrete section or structure to the next. Such grout filled couplers typically include a relatively long cylindrical pipe body to prevent the separation of one rebar from the other. A majority of the stress experienced by a cement grout filled coupler is concentrated along the interface of the rebar with the cement grout with which the pipe body of the coupler is filled. Consequently, the rebars can be undesirably loosened from or pulled out of their coupler under compression and tension forces, such as those generated during an earthquake. To overcome this problem, I have added a stress distributing, coiled reinforcement wire or spring at the interior of the coupler body such that a rebar is received within the coupler body in coaxial alignment with the coiled reinforcement wire. Examples of my patents which show a high strength grouted pipe coupler including such a coiled reinforcement wire are identified below:

- Patent No. Issue Date
- U.S. Pat. No. 6,192,646 Feb. 27, 2001
- U.S. Pat. No. 6,679,024 Jan. 20, 2004

What is now desirable is a grouted coupler by which adjacent concrete sections at a construction site can be reliably held together by means of rebars which require no modification when the concrete sections are poured at different times. In addition, it would also be desirable to be able to splice a bent rebar to a straight rebar or to a plurality of straight rebars which are not axially aligned with one another when they are embedded within the concrete sections to be joined together.

SUMMARY OF THE INVENTION

In general terms, a grouted rebar dowel splice is disclosed by which to hold together large sections or blocks of concrete that are cast at different times. The dowel splice herein disclosed has particular application at large construction sites during the erection of buildings, bridges, subways, airports, and the like, that must withstand earthquake strength forces. The dowel splice includes a hollow cylindrical body that is preferably manufactured from steel. A first end of the splice body is compressed and flattened. A (e.g., steel) sleeve is pressed around the first flattened end of the splice body to provide structural reinforcement and a shear pin is inserted through the sleeve and the splice body. Axially aligned holes are formed through each of the sleeve and the flattened end of the splice body surrounded by the sleeve. A first curved or straight rebar to be embedded within a first section of concrete is inserted through the axially aligned holes formed in the sleeve and the splice body.
A flat plate is welded across the opposite end of the hollow body of the rebar dowel splice. An opening formed in the flat plate communicates with the hollow interior of the splice body. A coiled compression spring is located at the hollow interior of the splice body past the opening in the plate. A set of holes is formed through the plate to receive respective fasteners. In this regard, when the first rebar attached to the dowel splice at the flattened first end thereof is embedded within the first section of concrete, nails, or similar fasteners, are located through the holes in the flat end plate to detachably connect the dowel splice to a wooden form. After the first section of concrete within which the first rebar is embedded has cured, the wooden form is stripped off the rebar dowel splice and pulled away from the flat end plate thereof. The hollow splice body is then filled with a solidifier (e.g., an epoxy or a cement based grout), and a first end of a second rebar is pushed into the solidifier via the opening in the flat plate such that the second rebar is surrounded by and coaxially aligned with the compression spring. The solidifier hardens to form a solid core at the interior of the splice body to encase the second rebar. The second concrete section is then poured adjacent the first concrete section with the opposite end of the second rebar embedded therewithin. The compression spring surrounding the first end of the second rebar distributes the stresses through the solid core and thereby helps to reinforce the solid core within the splice body so as to prevent the second rebar from pulling out of the splice. Accordingly, the rebar dowel splice reliably couples the first rebar to the second rebar to establish a continuous casting joint between the first and second concrete sections so as to hold the sections together during tension and compression forces of the type that are generated during an earthquake

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the rebar dowel splice according to a preferred embodiment of this invention for coupling first and second rebars to one another;
FIG. 2 is a top view of the rebar dowel splice shown in FIG. 1;
FIG. 3 is an end view of the rebar dowel splice;
FIG. 4 is a side view of the rebar dowel splice;
FIG. 5 shows a cross-section of the rebar dowel splice having a coiled wire and being detachably connected to a wooden form when the first rebar is embedded within a first concrete section that is being cured;
FIG. 6 shows the rebar dowel splice of FIG. 5 that is loaded with a solidifier to surround the coiled wire after the first section of concrete has cured and the wooden form has been removed;
FIG. 7 shows the rebar dowel splice of FIG. 6 with the first and second rebars embedded within adjacent first and second concrete sections; and
FIG. 8 shows a plurality of the rebar dowel splices of this invention for coupling a single first rebar extending in a first direction to a plurality of parallel aligned second rebars extending in a different direction.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the grouted rebar dowel splice 1 which forms the present invention is described while referring concurrently to FIGS. 1-4 of the drawings. As will soon be disclosed, and as is best shown in FIG. 1, the rebar splice 1 functions as a coupler between a first rebar 3 and a second rebar 5 at large construction sites during the erection of buildings, bridges, subways, airports, and the like. More particularly, the splice 1 has particular application as a continuous construction joint where large sections or blocks of concrete are to be joined and held together, but where such concrete sections or blocks are not cast at the same time.
The rebar dowel splice 1 includes a hollow cylindrical or tubular body 7 that is preferably manufactured from steel. One end 9 of the cylindrical body 7 is compressed and flattened. To maximize the coupling strength of the splice 1, a steel sleeve 10 is pressed into surrounding engagement with the flattened first end 9 of splice body 7. A shear pin 12 extends through the sleeve 10 and the flattened first end 9 to prevent sleeve 10 from sliding off the splice 1 at those times with the splice is stressed, such as during an earthquake or at other times when the ground shifts or settles.
Axially aligned holes 14 and 15 are formed through the sleeve 10 and the flattened end 9 of splice body 7 surrounded by the sleeve. The holes 14 and 15 are sized to accommodate the first rebar 3. In the case of FIG. 1, the first rebar 3 is shown having a bent shape. However, a straight rebar (shown in FIG. 8) may also be located through the holes 14 and 15 of dowel splice 1, particularly in those cases where a plurality of such splices are arranged in spaced, parallel alignment. By virtue of the sleeve 10 surrounding the compressed first end 9 of splice body 7, the dowel splice 1 is capable of achieving the full tensile strength of the second rebar 5 that is coupled to the first rebar 3.
Extending across the opposite end of the hollow cylindrical body 7 of the rebar dowel splice 1 is a flat (e.g., steel) plate 16. The plate 16 is affixed to the splice body 7 by means of a suitable weld 18. An opening 20 (best shown in FIGS. 1 and 3) is formed through end plate 16 to communicate with the hollow interior of splice body 7. The longitudinal axis of the opening 20 through plate 16 is aligned perpendicular to the longitudinal axes of the holes 14 and 15 through the flattened end 9 of splice body 7 and the reinforcing sleeve 10 in surrounding engagement therewith. The hollow splice body 7 and the opening 20 through plate 16 are sized and aligned with one another to accommodate therewithin the second rebar 5 to be coupled to the first rebar 3. The end plate 16 includes a set of (e.g., four) holes 22 that are sized to receive respective fasteners (designated 36 in FIG. 5) therethrough for a purpose that will soon be described.
A compression spring 32 is located at the hollow interior of the splice body 7 via the opening 20 through end plate 16. In a preferred embodiment, the compression spring 32 is wound as a coil and is manufactured from stiff steel wire.
Turning now to FIG. 5 of the drawings, the rebar dowel splice 1 is shown embedded within a first section 25 of concrete. The first rebar 3 is mated to the first end 9 of the hollow cylindrical splice body 7 of dowel splice 1 at the axially aligned openings 14 and 15 through the reinforcing sleeve 10 and the flattened end 9 of body 7 surrounded by sleeve 10.
As the first section 25 of concrete cures, and prior to the time when an adjacent concrete section is cast, the rebar dowel splice 1 is attached to a wooden form 34. The foregoing is accomplished by means of nails 36 or similar fasteners being driven into form 34 by way of the holes (designated 22 in FIGS. 1 and 3) in the flat end plate 16 that is welded across the splice body 7.
Once the concrete section 25 within which the rebar dowel splice 1 is embedded has cured, and referring to FIG. 6 of the drawings, the wooden form 34 is stripped off the splice 1 and separated from the end plate 16 thereof. The hollow interior of the splice body 7 is then filled with a suitable solidifier 38 so as to engulf the compression spring 32. By way of example, the solidifier 38 is an epoxy or cement based grout. After the hollow body 7 of rebar dowel splice 1 has been loaded with solidifier 38, one end of the second rebar 5 to be coupled to the first rebar 3 is pushed inwardly of the splice body 7 such that the rebar 5 and coil spring 32 are coaxially aligned. It is important that the wound compression spring 32 float within the solidifier 38 so as to be spaced radially from the second rebar 5. When the solidifier 38 has hardened, a solid core will be established within the splice body 7 in which the compression spring 32 and the second rebar 5 are encased.
In the example of FIG. 6, the first rebar 3 is curved and the second rebar 5 is straight. When the solidifier 38 has hardened to a solid core to retain the second rebar 5 at the interior of the splice body 7, and referring now to FIG. 7 of the drawings, the second concrete section 30 is poured so as to lie adjacent the first concrete section 25. By virtue of the coiled compression spring 32 that is encased in the solidifier core 38 within the splice body 7 of rebar dowel splice 1, the stresses that are applied to the rebars 3 and 5 during a seismic event are more uniformly spread out along the length of the rebars. Moreover, the coiled compression spring 32 reinforces the core formed from solidifier 38 and anchors the core within the confines of the splice body 7 to resist the tension and compression forces that are applied to the rebars 3 and 5 during an earthquake. What is even more, the coiled compression spring 32 avoids a concentration of stress at the interface of the solidifier core 38 and the second rebar 5 by transferring the load to the splice body 7. Accordingly, the rebar dowel splice 1 develops a load capacity substantially equal to that of the first and second rebars 3 and 5 by which the adjacent concrete sections 25 and 30 can be reliably held together by means of a continuos casting joint in the event of earth movement. In this same regard, it may be appreciated that neither one of the first nor second rebars 3 or 5 requires any special modifications (e.g., screw threads or upset heads) before they are coupled to one another.
While FIG. 7 shows a single curved rebar 3 coupled to a single straight rebar 5 at the opposite ends 9 and 16 of the splice body 7, FIG. 8 of the drawings shows a single straight rebar 3-1 coupled to a plurality of rebars 5-1 and 5-2 projecting from a corresponding plurality of spaced, parallel aligned rebar dowel splices 1-1 and 1-2. In this case, the rebar 3-1 is held in perpendicular alignment to the plurality of rebars 5-1 and 5-2. Although a pair of rebars 5-1 and 5-2 are shown mated to a pair of splices 1-1 and 1-2, it is to be understood that the straight rebar 3-1 can be coupled to any number of rebars 5-1, 5-2 . . . 5-n, depending upon the length of the rebar 3-1 and the size of the concrete sections 25 and 30 within which the splices will be embedded.

Claims

1. A rebar splice for coupling a first rebar to be embedded within a first section of concrete to a second rebar to be embedded within a second section of concrete, said rebar splice including a splice body and said splice body having first and opposite ends with respective openings formed therethrough for receiving said first and second rebars, said first and second openings having longitudinal axes that are aligned perpendicular relative to one another.

2. The rebar splice recited in claim 1, wherein said splice body has a hollow interior and the first end of said splice body is flattened, the first opening being formed in said flattened first end to receive the first rebar therethrough.

3. The rebar splice recited in claim 2, also including a sleeve surrounding the flattened first end of said splice body and having an opening formed therethrough, the openings formed through said sleeve and said flattened first end being axially aligned to receive the first rebar therethrough.

4. The rebar splice recited in claim 2, wherein the second rebar is received at the hollow interior of said splice body.

5. The rebar splice recited in claim 4, also including a compression spring located at the hollow interior of said splice body.

6. The rebar splice recited in claim 5, wherein said compression spring is a coiled wire surrounding the second rebar at the interior of said hollow splice body, such that said coiled wire and the second rebar are arranged in spaced coaxial alignment.

7. The rebar splice recited in claim 6, wherein the hollow interior of said splice body is filled with a solidifier, said compression spring and the second rebar being surrounded by said solidifier and encased therewithin when said solidifier hardens.

8. The rebar splice recited in claim 7, wherein said solidifier is an epoxy.

9. The rebar splice recited in claim 7, wherein said solidifier is a grout.

10. The rebar splice recited in claim 7, also including a plate extending across the opposite end of said splice body and having an opening formed therethrough to communicate with the hollow interior of said splice body, the second rebar being received at the hollow interior of said splice body by way of the opening through said plate.

11. The rebar splice recited in claim 10, wherein said plate extending across the opposite end of said splice body has a set of holes formed therein for receip therethrough of respective fasteners.

12. The rebar splice recited in claim 1, wherein said splice body is a hollow cylinder that is manufactured from steel.

13. A rebar splice for coupling a first rebar to be embedded within a first section of concrete to a second rebar to be embedded within a second section of concrete, said rebar splice including a cylindrical splice body having first and opposite ends and a hollow interior, the first end of said splice body being flattened and having an opening formed therethrough, said rebar splice also including a reinforcing sleeve surrounding said flattened first end and having an opening formed therethrough which is axially aligned with the opening formed through said flattened first end so as to receive the first rebar, and the opposite end of said splice body having an opening through which the second rebar extends for receipt at the hollow interior of said splice body, such that the first and second rebars extend in different directions through the respective openings formed in said first and opposite ends of said splice body.

14. The rebar splice recited in claim 13, also including a shear pin extending through each of the first flattened end of said splice body and the reinforcing sleeve to retain said reinforcing sleeve in surrounding engagement with said first end.

15. The rebar splice recited in claim 13, also including a coiled wire surrounding the second rebar at the hollow interior of said splice body, said hollow interior being filled with a solidifier such that said coiled wire and the second rebar are surrounded by said solidifier and encased therewithin when said solidifier hardens.