EP0699805A1

EP0699805A1 - Reinforcement device

Info

Publication number: EP0699805A1
Application number: EP95306099A
Authority: EP
Inventors: David Peter Mckittrick; Gary Joseph Hall
Original assignee: Ec Civil Engineering Ltd
Current assignee: Ec Civil Engineering Ltd
Priority date: 1994-08-31
Filing date: 1995-08-31
Publication date: 1996-03-06
Also published as: GB9417507D0

Abstract

A reinforcement device for connection to a structure (4), comprising:
a reinforcement member (18) having a hook portion (22) for engagement around a coupling element (10,28) secured to the structure (4); and
a connector (26) having spaced-apart openings (46,48) receiving opposite limbs of the hook portion (22), thereby to prevent displacement of the limbs away from each other and to provide a tight connection. The coupling element (10,28) may comprise a pair of spaced-apart loops (10) of reinforcement element embedded at their ends in the structure (4). When the hook portion (22) is aligned with the loops (10) a removable bar (28) is inserted through the loops (10) and the hook portion (22) to secure the hook portion (22) to the structure (4). The connector (26) is then fixed to the reinforcement member (18) to hold the two limbs of the hook portion (22) together. In this way, the reinforcement member (18) is securely connected to the structure (4). A plurality of reinforcement members (18) may be connected to a structure (4) using a single removable bar (28) which runs through respective pairs of loops (10) and corresponding hook portions (22).

Description

This invention relates to a reinforcement device for connection to a structure.
In the construction of reinforced soil retaining walls, it is necessary to anchor reinforcing elements embedded in the backfill, to the facing panels of the retaining wall. This is necessary to transfer the tensile loads in the reinforcing elements into the facing panels. The connection may comprise one or more loops of reinforcement wire cast into each facing panel and corresponding loops formed on the ends of the reinforcement bars by bending over the end of each bar and welding it back on itself. The loops are aligned and a steel bar pushed through them to secure the reinforcement bars to the facing panel. To avoid reducing the tensile capacity of the loops on the end of the reinforcement bars their radius must be no less than four times their diameter. In practice, the reinforcement bars need to be formed from steel wire of at least 8 mm diameter. Thus, the cost of forming the loops and then welding them to the bars is high. Furthermore insertion of the steel bar through the loops in the facing panels and the loops on the ends of the reinforcement bars can be extremely difficult if the ends of the reinforcement bars are not bent and welded accurately. In general the use of a welded connection is expensive and requires a great deal of quality control. In the case of strip reinforcement, a bolted connection is generally used, which reduces the tensile capacity of the strip. Other types of connector are known, but these all rely on a welded joint as part of the connection.
According to the present invention there is provided a reinforcement device for connection to a structure, comprising a reinforcement member having a hook portion for engagement around a coupling element secured to the structure, the reinforcement device also comprising a connector having spaced-apart openings receiving opposite limbs of the hook portion thereby to prevent displacement of the limbs away from each other, and to provide a tight connection.
The coupling element preferably comprises a loop, the sides of the loop may comprise a pair of reinforcement elements anchored to and projecting from the structure in parallel and the end of the loop may comprise a third element which interconnects the reinforcement elements. The third element is preferably a removable bar. A plurality of pairs of reinforcement elements may be interconnected by a single removable bar. The coupling loops may comprise bent lengths of reinforcement bar having a diameter at least half that of the reinforcement member.
Alternatively, each loop may comprise a single reinforcement element anchored to the structure.
The connector may comprise a plate provided with a pair of spaced apart slots in one edge, which preferably extend for approximately /₃ of the width of the connector. In use, the connector is simply pushed onto the opposite limbs of the hook portion of reinforcement member. Alternatively, the connector may comprise a plate provided with a pair of spaced apart holes. Before the reinforcement member is connected to the coupling element the first limb is threaded through one of the holes in the plate and the plate is pushed along the reinforcement member beyond the hook portion onto the second limb. Once the reinforcement member is engaged with the coupling element, the plate is slid back such that the other hole engages the first limb.
Preferably the diameter of the openings in the plate is slightly greater than the outside diameter of the reinforcement member, such that the plate can slide freely onto the reinforcement member. Preferably, if the reinforcement member is of round cross-section, the separation of the openings is equal to approximately four times the diameter of the reinforcement member.
Preferably the width of the plate is at least two times the diameter of each opening.
The reinforcement member may comprise standard ladder wire. Alternatively, the reinforcement member may comprise strip reinforcement.
For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1A is a diagrammatic representation of an initial stage in the construction of a reinforced soil retaining wall;
Figure 1B is a later stage in the construction of a reinforced soil retaining wall;
Figure 2 is a plan view of the retaining wall and reinforcement arrangement of Figure 1A;
Figure 3 is an elevation of the retaining wall and reinforcement arrangement of Figure 1A;
Figure 4 is an enlarged view of a connector plate shown in Figures 2 and 3;
Figure 5A is a top view of a high adherence reinforcement strip;
Figure 5B is a side view of the high adherence reinforcement strip shown in Figure 5A;
Figure 6 is a plan view of an alternative embodiment of connector for use with strip reinforcement;
Figure 7 is an elevation of the strip reinforcement connector of Figure 6; and
Figure 8 is an enlarged view of the reinforcement connector plate shown in Figures 6 and 7.

Figure 1A shows a reinforced soil retaining wall 2 during construction. The retaining wall 2 comprises two rows of facing panels 4, 5 located one above the other on a levelling pad 6. A temporary timber framework 8 holds the facing panels 4, 5 in position during construction. Reinforcement brackets 10, 11 are cast into each facing panel 4, 5. When the level of backfill 12 reaches the height of the first brackets 10 it is compacted and a reinforcement framework 14 of ladder bars is laid onto it. The reinforcement framework 14 is then connected to the respective brackets 10 on each of the first row of facing panels 4.
Referring to Figure 1B, backfill 12 is then placed over the reinforcement framework 14 and again compacted. When the backfill 12 reaches the level of the brackets 11 of the second row of facing panels 5, a second layer of reinforcement bars (not shown) is laid and connected to the respective facing panels 5. By supporting further rows of facing panels (not shown) one above the other and backfilling, compacting , reinforcing and backfilling again, the desired height of wall is attained.
Figures 2 and 3 show in detail how the reinforcement framework 14 is connected to the first row of facing panels 4. The brackets 10 each comprise a pair of steel reinforcement bars bent back on themselves to form loops 16, 17 which project at right angles from the plane of the respective facing panel 4. The ends of the reinforcement bars forming the loops 16, 17 are extended and are anchored in the facing panel 4, such that they lie substantially parallel to the plane of the facing panel 4.
The reinforcing framework 14 comprises a ladder bar arrangement of longitudinal and transverse reinforcement bars 18, 19 welded together where they intersect. The longitudinal bars 18 are each bent over at their free end 20 to form a hook portion 22. To avoid weakening the longitudinal bars 18 the radius of the bend is generally not less than four times the diameter of the longitudinal bars 18.
Prior to connection of the hook portions 22 of the longitudinal bars 18 to the brackets 10 in each facing panel 4, the free end 20 of each longitudinal bar 18 is inserted through an opening 24 of a connector plate 26 (see Figure 4). The connector plate 26 is then pushed along the longitudinal bar 18 beyond the position of the hook portion 22.
To connect the longitudinal bars 18 to the brackets 10, the hook portions 22 of the longitudinal bars 18 are inserted between respective pairs of loops 16, 17 and a steel bar 28 is inserted through the hook portions 22 of the longitudinal bars 18 and through of the loops 16, 17 of the brackets 10.
At this stage each connector plate 26 is swung up and is located over the free end 20 of the respective longitudinal bar 18 by means of a second hole 30 formed in the opposite end of the connector plate 26 to the opening 24. The plate 26 is then pushed along the bar 18, in the direction of arrow A in Figure 3, towards the facing panels 4.
Once all of the longitudinal bars 18 have been secured to their respective brackets 10 on the respective row of facing panels 4, the reinforcing framework is pulled, in the direction of the arrow B, away from the facing panels 4 to remove the play in each connection. In this way each steel bar 28 is gripped firmly between the loops 16, 17 of each bracket 10 and the corresponding hook portion 22 of the respective longitudinal bar 18. Slight distortion of the reinforcing framework 14, when it is pulled, accommodates misalignment of the connections which may be present due to construction or site tolerances.
Figure 4 shows an enlarged view of the connector plate 26 having first and second openings 24, 30 at its opposite ends. The separation of the openings 24, 30 is determined by the radius of the bend of each hook portion 22. Thus, generally the separation of the openings 24, 30 will be not less than four times the diameter of the longitudinal bars 18. As will be appreciated, the size and shape of the connector plate will be determined by the particular application and by the loads which it must resist. However, as a general rule, the width of the plate should be not less than two times the diameter of the holes 24, 30. Typically, the longitudinal bars 18 may be of 10 mm minimum diameter, so that the spacing of the holes 24, 30 is approximately 40 mm. The thickness of the plate is typically at least 3 mm.
As an alternative to the longitudinal bars 18 described in the previous embodiment, strip reinforcement may be used. Figure 5A and 5B show a length of high adherence strip 32 having equidistantly spaced ridges 34 on its upper and lower surfaces to improve adherence in soil. As shown in Figure 7, the free end 36 of the strip 32 is bent over to form a hook portion 38 which engages directly in a bracket 40 formed from a bent length of reinforcement wire cast into each facing panel 4. In this embodiment, connection of the reinforcement strip 32 to the bracket 40 does not require the insertion of a steel bar 28 (see Figure 2 or 3). Instead, the length L of the hook portion 38 is shorter than the length of the open loop of the bracket 40, so that the strip 32 may simply be lifted and the hook portion 38 dropped through the loop of the bracket 40. The strip 32 is then pulled, in a direction B, away from the respective facing panel 4, to secure the hook portion 38 to the bracket 40.
In this embodiment, the connection is completed by means of a connector plate 42 shown in detail in Figure 8. The connector plate 42 comprises a rectangular steel plate 44 provided with a pair of spaced apart slots 46, 48 in one edge. The slots extend for approximately /₃ of the width of the plate 44. To complete the connection of each strip 32 to the respective bracket 40, the connector plate 42 is slid on to the strip 32 from one side. The first slot 46 engages a first limb 39 of the hook portion 38 and the second slot 48 engages a second limb 41 of the hook portion 38, thereby maintaining the bend in the strip 32 when a withdrawing force is applied to the strip 32 in a direction B away from the facing panel 4.
Since respective strips 32 are not connected together like the ladder bar reinforcement 18 of the previous embodiment, the position of the strips 32 can be adjusted independently, such that simply by pulling on the strips 32 in the direction B away from the facing panels 4, abutment can be achieved between the hooked portion 38 of each strip 32 and the end of the loop of the respective bracket 40. This ensures good and consistent transfer of load from the strips 32 to the facing panels 4.
As with the previous embodiment, the size and general proportions of the reinforcement strips 32 and connector plate 42 are dependent on the application and the loads to be resisted. The width of the slots 46, 48 in the connector plate 42 will be slightly greater than the thickness of the strip 32 and the depth of the slots 46, 48 will be approximately equal to the width of the strip 32. Typically, the width of the strip would be 40 to 75 mm and the thickness 3.5 to 12 mm.

Claims

A reinforcement device for connection to a structure, comprising:
a reinforcement member having a hook portion for engagement around a coupling element secured to the structure; and
a connector having spaced-apart openings receiving opposite limbs of the hook portion, thereby to prevent displacement of the limbs away from each other.
A reinforcement device as claimed in claim 1, in which the coupling element comprises a loop of reinforcement material.
A reinforcement device as claimed in claim 2, in which each side of the loop comprises a bent bar fixed to the structure at its ends and the end of the loop comprises a third element which interconnects the bent bars.
A reinforcement device as claimed in claim 3, in which the third element comprises a removable bar.
A reinforcement device as claimed in claim 4, in which a plurality of reinforcement members are connected to the structure by a single removable bar.
A reinforcement device as claimed in any one of claims 2 to 5, in which the loops comprise reinforcement bar having a diameter at least half that of the reinforcement member.
A reinforcement device as claimed in any one of the preceding claims, in which the connector comprises a plate provided with a pair of spaced-apart openings.
A reinforcement device as claimed in claim 7, in which the openings comprise slots provided in one edge of the plate.
A reinforcement device as claimed in claim 7 or 8, in which the separation of the openings is equal to approximately four times the diameter of the reinforcement member.
A reinforcement device as claimed in any one of claims 7 to 9, in which the width of the plate is at least two times the diameter of each opening.