EP3106583B1

EP3106583B1 - Rebar anchorage device and method for connecting same to a rebar

Info

Publication number: EP3106583B1
Application number: EP15172152.9A
Authority: EP
Inventors: Christian L. Dahl
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-06-15
Filing date: 2015-06-15
Publication date: 2018-05-09
Anticipated expiration: 2035-06-15
Also published as: EP3106583A1; ES2672354T3

Description

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates to a mechanical anchorage device and to a method for connecting the device out in the field to the upstanding end of a rebar which may be embedded within and project from a section of concrete. The anchorage device forms a wide head on the rebar which will be covered with concrete to create one or more bearing surfaces and thereby enable the rebar to better withstand forces applied thereto through the concrete.

2. Background Art

Steel reinforcement bars (i.e., rebars) are well known to be embedded within a reinforced concrete structure (e.g., a wall, panel, or the like) so that the structure will be less likely to shift or suffer damage caused by physical forces, such as those generated during an earthquake. In some cases, the rebars can become prematurely separated from their concrete structure as a consequence of tensile loads applied to the rebar.
In order to stabilize and better hold the rebars in place within the concrete structure so as to more reliably withstand tensile loads, a relatively wide head is often formed to establish a wide bearing surface at the end of each rebar. The headed end is then covered over with additional concrete. However, it is sometimes difficult to form a wide head out in the field on a rebar that is already installed and embedded in a concrete structure with one end projecting from the structure to be subjected to a heading process. While it may be simpler to head the rebar prior to its installation in the field, the precise length of the rebar that will project from the concrete structure is often difficult to predict. That is to say, the end of the rebar may need to be cut and shortened in the field resulting in the preformed head being cut off the end. In other cases, the end of each rebar is bent over to form a hook so as to increase the bearing area thereof. Alternatively, a plate has been welded to the end of the rebar. In any case, special equipment and/or tools may have to be transported into the field for post-installation treatment of the top ends of the rebars to better resist tensile loads. The requirement for special equipment and tools slows the construction project and increases cost.
Accordingly, it would be desirable to be able to quickly and reliably connect a mechanical anchor to and increase the bearing surface at the upstanding end of a rebar that projects from a concrete structure out in the field without the cost or inconvenience of having to use such special equipment and tools and without stressing or loading the rebar during the connection of the anchor.
US 6,513,287 B1 discloses a method and apparatus for forming an anchorage of a post-tension system in which a tendon is positioned within a cavity of an anchor such that an end of the tendon extends outwardly of the cavity, a plurality of wedges are mechanically inserted within the cavity between the tendon and a wall of the cavity, and pressure is applied to an end of the tendon such that the tendon and the wedges are in interference-fit relationship with the cavity. A compression mechanism is used having a cylindrical member and a plunger extending in a channel of the cylindrical member. The wedges are attached to the cylindrical member and the cylindrical member is moved toward the cavity such that the wedges enter a space between the tendon and the wall of the cavity. The plunger applies a compressive force to the end of the tendon when the end of the tendon is in the channel of the cylindrical member.

SUMMARY OF THE INVENTION

In general terms, this invention relates to a mechanical anchor and to a method for connecting the anchor to the upstanding end of a steel reinforcement bar (i.e., a rebar) that projects from a concrete structure. Once it is connected, the rebar anchor will be embedded within concrete so as to create a large bearing surface by which to enable the rebar to better withstand tensile forces such as those which are generated during an earthquake and applied to the rebar through the concrete.
According to the present invention, a method for connecting an anchorage device to a steel rebar is provided as set forth in claim 1, and a combination is provided as set forth in claim 8. Preferred embodiments of the present invention may be gathered from the dependent claims. According to a preferred embodiment, the rebar anchor includes a cylindrical barrel to surround the upstanding end of the rebar. A tapered bore runs longitudinally through the barrel within which to receive the end of the rebar. A disk-shaped resistance lid extends across the top of the barrel over the end of the rebar. The diameter of the lid may be greater than the diameter of the barrel to create a bearing surface below the lid. Located inside the tapered bore through the barrel is a tapered segmented jaw that is split into a plurality of wedges. The angle of the wedges matches the angle of the tapered bore. The wedges of the jaw are laid end-to-end and seated against the tapered bore. The wedges of the jaw are configured to surround and grip the rebar. To this end, the wedges are provided with teeth or sharp threads adapted to bite into and prevent a displacement of the rebar relative to the barrel of the rebar anchor. A helically-wound spring is positioned at the top of the tapered bore of the barrel to lie between the lid and the relatively wide top end of the tapered segmented jaw of the rebar anchor.
As an important feature, a threaded bolt is moved through a correspondingly threaded bolt hole formed through the lid so as to apply an axial pushing force against the end of the rebar surrounded by the barrel. Accordingly, the rebar is pushed downwardly through the tapered bore and outwardly relative to the barrel to cause the segmented jaw to slide therealong so that the correspondingly angled wedges of the jaw close tightly around and are locked against the rebar, regardless of the diameter of the rebar. Thus, the rebar anchor is quickly and positively connected in surrounding engagement with the rebar out in the field to create a wide head thereon without requiring the use of special tools or machinery. When the rebar anchor is covered with concrete, the bottom of the cylindrical barrel creates an additional bearing surface by which to hold the rebar in place embedded in the concrete so as to be advantageously adapted to withstand tensile loads applied thereto. However, the rebar anchor of this invention does not add tension to or load the rebar to which it is connected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plurality of rebars installed within and projecting from a concrete structure so that mechanical anchors can be affixed to the upstanding top ends thereof in accordance with a preferred embodiment of this invention;
FIG. 2 is a cross-section of one of the rebar anchors taken along lines 2-2 of FIG. 1; and
FIG. 3 is an exploded view of the rebar anchor shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 of the drawings shows a plurality of conventional rebars 1 (i.e., steel reinforcement bars) protruding from a concrete structure. The rebars 1 are particularly useful to reinforce the concrete structure so as to be able to withstand physical forces such as those generated by an earthquake. Any number of rebars 1 may be embedded within the concrete structure. FIG. 1 also shows a corresponding plurality of mechanical anchors 3 attached to upstanding ends of the embedded rebars 1. The rebar anchors 3 can be advantageously installed in the field, without requiring special tools or equipment, and without tensioning the rebars 1 to which the anchors 3 are attached. That is, the rebar anchors 3 are adapted to be connected after the rebars 1 are already installed and embedded in concrete and without requiring that the upstanding ends thereof first be prepared (i.e., headed or bent). Once the post-installed rebar anchors 3 are attached to the upstanding ends of the rebars 1, the anchors and rebars are covered by and embedded within additional concrete.
Details of the mechanical rebar anchor 3 and a preferred embodiment by which the rebar anchor is connected to a rebar are now explained while referring concurrently to FIGs. 1-3 of the drawings. A (e.g., carbon steel) barrel 5 of the rebar anchor 3 is initially pushed or hammered onto the upstanding end of the rebar 1 so that the upstanding end 1 is surrounded by barrel 5. The barrel 5 of anchor 3 has a cylindrical outside wall 7 and a tapered inside wall 9. A correspondingly tapered or angled inner bore 10 (best shown in FIG. 3) runs longitudinally through the barrel 5 for receipt therewithin of the rebar 1.
A disk-shaped resistance lid 12 is connected over the upstanding end of rebar 1. The lid 12 is preferably welded to or rotated into surrounding mating engagement across the top of the barrel 5 of rebar anchor 3 so that the upstanding end of the rebar 1 moves upwardly towards the inside of the lid 12 when the barrel 5 is attached. The lid 12 has a peripheral lip 14 extending downwardly therefrom. In the case where the lid 12 will be rotated into such surrounding mating engagement with the barrel 5, the inside edge of the lip 14 of lid 12 is provided with a set of threads 16 running therearound. The top of the barrel 5 is provided with a complementary set of threads 18 running therearound. The threaded top of barrel 5 may be recessed with respect to the cylindrical outside wall 7 thereof at which the threaded lip 14 will be received when the lid 12 is rotated around the top of barrel 5 and the sets of threads 16 and 18 are mated to one another. As best shown in FIG. 2, the diameter of the lid 12 is greater than the diameter of the barrel 5. By virtue of the recessed threads 18 of barrel 5, a secondary bearing surface 20 is created along the bottom of the lip 14 of the lid 12 after the lid 12 has been connected across the top of barrel 5.
Located within the bore 10 running through the barrel 5 of rebar anchor 3 is a tapered, segmented jaw 24. As is best shown in FIG. 3, the segmented jaw 24 is split into a plurality of independent wedges 26 that are disposed end-to-end one another and angled in order to be seated against the tapered inside wall 9 of barrel 5. A set of teeth or sharp threads 28 are formed inside the segmented jaw 24. In the assembled configuration of FIG. 1 with the rebar anchor 3 connected to the upstanding end of rebar 1, the wedges 26 of the jaw 24 are configured to surround and grip (i.e., bite into) the rebar 1 to prevent a displacement thereof relative to barrel 5 regardless of the diameter of the rebar located in the bore 10 of barrel 5.
A (e.g., steel or rubber) O-ring 30 is received by a peripheral groove formed in the wide (i.e., thickest) top ends of the wedges 26 of the jaw 24 so as to hold the wedges 26 together. Laying on top of the O-ring 30 and surrounding the rebar 1 is a disk-shaped spring support 32. A helically-wound spring 34 is located above the jaw 24 at the top of the bore 10 of the barrel 5 of rebar anchor 3. The spring 34 is sized to surround the upstanding end of rebar 1 and positioned to lie between the inside of lid 12 and the spring support 32.
As an important feature of the rebar anchor 3 disclosed herein, a threaded bolt hole 38 is formed completely through the lid 12. A correspondingly threaded fastener (e.g., a bolt 40) is rotated completely through the bolt hole 38 and into contact with the top end of the rebar 1 which is surrounded within the bore 10 of barrel 5 by the spring 34. The bolt 40 is axially advanced through the bolt hole 38 towards and into contact with the rebar 1 by means of a torque wrench or the like.
The bolt 40 applies a downward pushing force directly against the top of the rebar 1 to force the rebar downwardly through the bore 10 and slightly outward from the barrel 5 of the rebar anchor 3. The helically-wound spring 34 is compressed by the lid 12 to exert a pushing force against the spring support 32 and thereby urge the wedges 26 of the tapered and segmented jaw 24 to slide downwardly along the tapered inside wall 9 of the bore 10 of the barrel 5. As it moves through the tapered bore 10, the segmented jaw 24 will automatically close around the rebar 1. More particularly, the angled wedges 26 of jaw 24 are forced radially inward towards rebar 1 by the matching tapered bore 10 so that the teeth 28 of wedges 26 bite into and are locked against the rebar. Accordingly, the rebar anchor 3 is quickly and positively connected to the top of the rebar 1 with minimal slippage to create a relatively wide head thereon after the rebar is already installed out in the field and without requiring the use of special tools or heading machines. The axial pushing force applied by the bolt 40 takes up any slack within the barrel 5 and thereby enables the rebar anchor 3 to be snugly held in surrounding engagement with the top of rebar 1. In other words, the combination bolt 40 and resistance lid 12 cooperate to eliminate internal movement (i.e., slippage) in both tension and compression to enable the post-installed anchor 3 to replicate a pre-installed rebar having an integral head that is formed by forging or welding.
Once the rebar anchor 3 is connected to the rebar 1 to form a head at the upstanding end thereof, the anchor is covered by concrete. The relatively wide bottom of the barrel 5 of anchor 3 creates a primary bearing surface (designated 42 in FIG. 2) that will be embedded within the concrete. Moreover, in the event that the peripheral lip 14 of the lid 12 is not flush with the top of the barrel 5 in the manner shown in FIG. 2, the aforementioned secondary bearing surface 20 is also created below the lip 14 and around the barrel 5. By virtue of the mechanical rebar anchor 3 and the primary bearing surface created thereby, the rebar 1 will be reliably held in place because the forces applied to the rebar will be transferred into multi-axial stresses in the concrete below the anchor. What is more, and unlike conventional tendon and wire anchorages that are surrounded and gripped by wedges inside a barrel, the rebar anchor 3 of this invention does not require the rebar to be stressed or tensioned to ensure a tight connection thereto. In addition, the rebar anchor 3 is capable of functioning under compressive and cyclic tension-compression loading.

Claims

A method for connecting an anchorage device (3) to a steel rebar (1) having first and opposite ends and being subject to tension and compression loads, said anchorage device including a barrel (5) having a top, a bottom and a tapered bore (10) running longitudinally between the top and the bottom of said barrel (5), a lid (12) connected to and extending across the top of said barrel (5), said lid (12) having a threaded opening (38) formed therein which extends completely through said lid (12), and a tapered jaw (24) located within and slidable through the tapered bore (10) of said barrel (5), wherein the first end of the rebar (1) is surrounded by the barrel (5) of said anchorage device (3) such that the rebar (1) is received within the tapered jaw (24) located within said barrel (5) and the lid (12) of said barrel (5) lies adjacent and covers the first end of the rebar (1), said method comprising the steps of:
locating a threaded fastener (40) at the top of said lid (12) for receipt within the threaded opening (38) that extends completely through the lid (12) connected to the top of said barrel (5) so that said threaded fastener (40) lies in axial alignment with the first end of the rebar (1) within the tapered jaw (24) that is located within the tapered bore (10) of said barrel (5); and

applying a rotational force to the threaded fastener (40) from above the lid (12) for advancing the threaded fastener (40) completely through the threaded opening (38) which extend completely through said lid (12) into end-to-end contact with the first end of the rebar (1) for applying an axial pushing force directly against said first end and thereby causing the rebar (1) to move through the tapered bore (10) of said barrel (5) and said tapered jaw (24) to slide through said tapered bore (10) and into locking engagement with the first end of the rebar (1) by which said anchorage device (3) is connected to the rebar (1); and

covering the barrel (5) of said anchorage device (3) with concrete such that said barrel (5) forms a bearing surface on the rebar (1) for holding the rebar (1) in place within the concrete.
The method recited in Claim 1, wherein said threaded fastener (40) is a threaded bolt.
The method recited in Claim 1, comprising the additional step of embedding the opposite end of the rebar (1) in concrete prior to the step of surrounding the first end of the rebar (1) with the barrel (5) of said anchorage device (3).
The method recited in Claim 1, wherein the lid (12) of said anchorage device (3) has a first set of threads and the top of the barrel (5) of said anchorage device (3) is surrounded by a second set of threads (18), said method comprising the additional step of rotating the first set of threads of said lid (12) into mating engagement with the second set of threads (18) surrounding said barrel (5) for connecting said lid (12) across the top of said barrel (5).
The method recited in Claim 1, wherein the barrel (5) of said anchorage device (3) has a cylindrical shape and the lid (12) of said anchorage device (3) attached across the top of said barrel (5) has a disk shape, said lid (12) having a longer diameter than the diameter of said barrel (5), such that the bearing surface formed on the rebar (1) is established underneath said lid (12).
The method recited in Claim 1, wherein said tapered jaw (24) that is located within the tapered bore (10) through said barrel (5) comprises a plurality of wedges (26) lying end-to-end one another and each of said wedges (26) having a set of teeth (28), said tapered jaw (24) sliding through said tapered bore (10) for causing the plurality of wedges (26) of said tapered jaw (24) to close against the first end of the rebar (1) and the teeth (28) of said wedges (26) to bite into the rebar (1), whereby said anchorage device (3) is connected to the first end of the rebar (1) in response to the step of advancing the threaded fastener (40) completely through the threaded opening (38) which extends completely through said lid (12) and into said end-to-end contact with the first end of the rebar (1) for applying an axial pushing force thereto.
The method recited in Claim 6, wherein said anchorage device (3) also includes a spring (34), said method comprising the additional step of locating said spring (34) within the tapered bore (10) through said barrel (5) atop said tapered jaw (24), such that said spring (34) urges said tapered jaw (24) to slide through said tapered bore (10) and the plurality of wedges (26) of said tapered jaw (24) to close against the first end of the rebar (1), whereby the teeth (28) of said wedges (26) bite into the rebar (1) to connect said anchorage device (3) to the first end of the rebar (1).
A combination, comprising:
a steel rebar (1) having first and opposite ends, the first end of said rebar to be embedded in concrete; and

an anchorage device (3) to be connected to the first end of said rebar (1) prior to said first end being embedded within the concrete and without tensioning the rebar (1), said anchorage device (3) including:
a barrel (5) having an open top, an open bottom and a tapered bore (10) running between the top and the bottom thereof in which to receive the first end of said rebar (1) so that said barrel (5) surrounds said rebar (1);

a tapered jaw (24) located within and slidable through the tapered bore (10) through said barrel (5) such that said tapered jaw (24) surrounds the first end of said rebar (1) within said tapered bore (10);

a lid (12) connected across the open top of said barrel (5) so as to lay adjacent and cover the first end of the rebar (1), said lid (12) having a threaded opening (38) formed therein which extends completely through said lid (12); and

a threaded fastener (40) responsive to a rotational force applied thereto from above the lid (12) so as to cause said threaded fastener (40) to move completely through the threaded opening (38) which extends completely through said lid (12) connected across the open top of said barrel (5) and into end-to-end contact with the first end of said rebar (1) to apply an axial pushing force to said first end to cause the rebar (1) to move axially through the tapered bore (10) of said barrel (5) and thereby cause said tapered jaw (24) to slide through said tapered bore (10) and into locking engagement with the first end of the rebar (1) by which said anchorage device (3) is connected to said first end to form a bearing surface to hold said rebar (1) in place after said first end and said anchorage device (3) connected thereto are embedded within concrete.
The combination recited in Claim 8, wherein said threaded fastener (40) is a threaded bolt, said threaded bolt being rotated completely through said threaded opening (38) which extends completely through said lid (12) and moved into said end-to-end contact with the first end of said rebar (1) to apply said axial pushing force thereto.
The combination recited in Claim 8, wherein said lid (12) has a first set of threads and said barrel (5) is surrounded by a second set of threads (18), the first set of threads of said lid (12) being rotated into mating engagement with the second set of threads (18) surrounding said barrel (5) for connecting said lid (12) to the top of said barrel (5) to cover the first end of said rebar (1).
The combination recited in Claim 8, wherein said barrel (5) has a cylindrical shape and the lid (12) connected across the open top of said barrel (5) has a disk shape, said lid (12) having a longer diameter than the diameter of said barrel (5), such that said bearing surface is created around the first end of said rebar (1) underneath said lid (12) after said first end and said anchorage device (3) connected thereto are embedded within the concrete.
The combination recited in Claim 8, wherein the tapered jaw (24) that is located within the tapered bore (10) through said barrel (5) comprises a plurality of wedges (26) lying end-to-end one another with each of said wedges (26) having a set of teeth (28), said tapered jaw (24) sliding through said tapered bore (10) for causing the plurality of wedges (26) of said tapered jaw (24) to close against the first end of the rebar (1) and the teeth (28) of said wedges (26) to bite into the rebar (1), whereby said anchorage device (3) is connected to the first end of the rebar (1) in response to the axial pushing force applied by said threaded fastener (40) to said first end.
The combination recited in Claim 12, wherein said anchorage device (3) also includes a spring (34) located within the tapered bore (10) through said barrel (5), said spring (34) urging said tapered jaw (24) to slide through said tapered bore (10) and the plurality of wedges (26) of said tapered jaw (24) to close against the first end of the rebar (1), whereby the teeth (28) of said wedges (26) bite into the rebar (1) to connect said anchorage device (3) to the first end.
The combination recited in Claim 13, wherein the opposite end of said rebar (1) is embedded in concrete prior to the first end of said rebar (1) being embedded in concrete.