GB2608809A

GB2608809A - Bolt assembly

Info

Publication number: GB2608809A
Application number: GB2110026.8A
Authority: GB
Inventors: Richardson James
Original assignee: Individual
Current assignee: JAMES RICHARDSON
Priority date: 2021-07-12
Filing date: 2021-07-12
Publication date: 2023-01-18
Also published as: GB202110026D0

Abstract

A bolt assembly (200) for embedding in concrete, includes a bolt (101) having a shaft (113) and a bolt head (112) at a first end (104) of the bolt (101). A washer plate (103) has a hole (114) configured to allow passage of the shaft (113) of the bolt (101) to secure the bolt head (112) to the washer plate (103). A cover (201) has a sealing surface configured to seal against a planar surface of the washer plate (103) and being sized to surround the bolt head (112).

Description

BOLT ASSEMBLY

Field of the Invention

The invention relates to a bolt assembly for embedding in a concrete structure, a method for embedding a bolt assembly in concrete and a concrete structure having an embedded bolt assembly.

Background

When fabricating a concrete structure or foundation, attachments typically need to be made to secure components such as steel columns and beams to the concrete structure. This may be done using bolts that are embedded in the concrete prior to setting. To ensure the bolt is securely anchored to the surrounding concrete, a washer plate is embedded in the concrete, through which the bolt passes. To ensure that the bolt can be located within holes in a beam or column connection plate to be secured to the concrete, some lateral movement is required in the free end of the bolt after the concrete has set to allow for tolerances in positioning of the bolt. A schematic illustration of an example arrangement for an embedded bolt is shown in Figure 1. The bolt 101 is held in place in the concrete 102 by means of a washer plate 103 embedded in the concrete 102 at an embedded end 104 of the bolt 101 and a free end 105 of the bolt 101 is held in place to a temporary mould wall or template that is typically only present until the concrete has set and is removed thereafter. The mould wall or template 106 is held in place with a nut 107. A shaft 113 of the bolt 101 passes through a hole 114 in the washer plate 103, which is sized to allow for some lateral movement of the bolt 101. A cavity 108 between the mould wall 106 and the embedded plate 103 is formed by a hollow cone 109 surrounding the shaft 113, the cone 109 having a narrow end 111 proximate the embedded washer plate 103 and a wide end 110 proximate the mould wall 106. The cone 109 may for example be formed from waxed card and is removed once the concrete 102 is set. A head 112 of the bolt 101 secures the bolt 101 to the washer plate 103 to allow tension to be applied for securing the bolt 101 to a structure such as a steel beam or column once the concrete 102 has set. The cavity 108 formed by the cone 109 allows for some lateral movement of the free end 105 of the bolt 101 once the concrete 102 is set so that the free end 105 can be aligned with a hole in the structure.

A problem with the arrangement as shown in Figure 1 is that, to allow for lateral movement of the free end 105 of the bolt 101, the head 112 must be free to rotate by the shaft 113 moving within the limits of the conical void 108 within the set concrete 102.

This may be done by forcing some lateral movement of the free end 105 before the concrete has fully set. This process relics on timing and skill, and is often not carried out correctly or at all, resulting in the bolt 101 having zero positional tolerance and requiring remedial work, thereby adding time and cost.

Summary of the Invention

in accordance with a first aspect of the invention there is provided a bolt assembly for embedding in concrete, the bolt assembly comprising: a bolt having a shaft and a bolt head at a first end of the bolt; a washer plate having a hole configured to allow passage of the shaft of the bolt to secure the bolt head to the washer plate; and a cover having a sealing surface configured to seal against a planar surface of the washer plate and being sized to surround the bolt head.

An advantage of the bolt assembly is that the cover allows the bolt head to be kept apart from the surrounding concrete while setting and thereby allows for movement of the bolt head after the assembly has been embedded in concrete without requiring an additional step of releasing the bolt prior to setting.

The cover may comprise an internal cavity or void sized to surround the bolt head, thereby allowing movement of the bolt head within the internal cavity after setting of the surrounding concrete. In alternative arrangements, the cover may comprise or be formed of a resilient material such as a foam or rubber that allows for movement of the bolt head within the material after setting of the concrete.

The sealing surface of the cover may be a planar surface configured to seal against the planar surface of the washer plate. Sealing the cover to the planar surface of the washer plate prevents concrete from entering the cavity, allowing for movement of the bolt head after setting.

The portion of the cover that surrounds the bolt head, for example the internal cavity, may be hemispherical.

The planar scaling surface of the cover may be the same size at the washer plate.

The cover may comprise a c-section rim on opposing parallel edges of the planar sealing surface, each c-section rim being sized to fit around a corresponding edge of the washer plate. In some examples, each c-section rim may define a channel having a minimum width smaller than a thickness of the washer plate such that each c-section rim is arranged to resiliently clamp around the washer plate.

The planar surface may be rectangular. The cover may comprise a c-section rim on three out of four sides of the planar scaling surface.

The cover may comprise foldable leaves extending from each edge of the planar surface, the foldable leaves arranged to fold over on to a side of the washer plate opposing the sealing surface.

The sealing surface of the cover may comprise an adhesive for securing the cover to the planar surface of the washer plate.

The assembly may further comprise a hollow cone having a narrow end sized to fit around the shaft of the bolt. The hollow cone may be provided as part of the assembly or may be provided separately. The hollow cone defines the range over which the free end of the bolt may move laterally once the bolt assembly is embedded. The hollow cone may for example be made from waxed cardboard, which is commonly used in conventional embedded bolt assemblies to enable removal after the concrete has set.

The assembly may further comprise a nut sized to fit to a threaded section of the bolt In accordance with a second aspect of the invention there is provided a method of embedding a bolt in a concrete structure, the method comprising: providing a bolt having a shaft and a bolt head at a first end of the bolt, a washer plate having a hole configured to allow passage of the shaft of the bolt to secure the bolt head to the washer plate and a cover having a sealing surface configured to fit against a planar surface of the washer plate and being sized to surround the bolt head; providing a hollow cone having a narrow end sized to fit around the shaft of the bolt.

attaching the bolt to a wall of a mould by passing the shaft of the bolt through the washer plate, hollow cone and a hole in the wall and securing the bolt to the wall by attaching a nut to a second end of the bolt; attaching the cover to the planar surface of the washer plate to surround the bolt head: and casting the concrete structure.

The steps of attaching the bolt to the wall of the mould and attaching the cover to the washer plate may be carried out prior to casting the concrete structure such that the concrete structure is cast around the assembly comprising the bolt, washer plate, cover, wall and nut. In some cases, for example when embedding one or more bolts in concrete for securing a column, the assembly may be embedded after casting the concrete structure by sinking the assembly into the concrete prior to setting.

The sealing surface of the cover may be a planar surface sealed against the planar surface of the washer plate. Sealing the cover to the planar surface of the washer plate prevents concrete from entering the cavity, allowing for movement of the bolt head after setting.

The bolt may be attached to a bolt group template as part of attaching the bolt to the wall of the mould, for example when a plurality of bolts is embedded as a group for attaching to a column. The bolt group template ensures that the bolts are laterally accurately positioned relative to each other.

The planar sealing surface of the cover may be the same size at the washer plate. The cover may comprise an internal cavity.

The portion of the cover sized to surround the bolt head, for example the internal cavity, may be hemispherical.

The scaling surface of the cover may be secured to the planar surface of the washer plate by adhesive, thereby preventing movement of the cover during filling of the mould and while the concrete is setting.

In accordance with a third aspect of the invention there is provided a concrete structure comprising a bolt assembly according to the first aspect embedded in the concrete structure, wherein the cover is attached to the planar surface of the washer plate and surrounds the bolt head, the shaft of the bolt passing through the hole in the washer plate and through a conical cavity in the concrete structure, the conical cavity having a narrow end proximate the washer plate and a wide end at an outer surface of the concrete structure.

The concrete structure may further comprise a hollow cone defining the conical cavity, however the hollow cone is typically only present until the concrete is set and is removed thereafter. Once the concrete is set, the bolt secures a further structure, for example a steel structure, to the concrete structure. The conical cavity may be filled with a flowable cementitious grout once the further structure is secured.

Other features relating to the first aspect may also apply to the invention according to the third aspect.

Detailed Description

The invention is described in further detail below by way of example and with reference to the accompanying drawings, in which: figure 1 is a schematic sectional diagram of a conventional embedded bolt assembly; figure 2 is a schematic sectional diagram of an example embedded bolt assembly; figure 3 is a schematic drawing of an example cover for an embedded bolt head; figure 4 is a schematic sectional drawing of an example alternative cover for an embedded bolt head; figure 5 is a schematic drawing of a further alternative example cover for an embedded bolt head; figure 6a is a schematic sectional side view of a further alternative example cover for an embedded bolt head; figure 6b is a schematic perspective view of the example cover of figure 6a; figure 7a is a schematic plan view of a further alternative example cover for an embedded bolt head; and figure 7b is a schematic perspective view of the cover of figure 7a.

Figure 1 has been described above in relation to the background to the invention. This arrangement illustrates a typical assembly in place after concrete casting, with the bolt 101 embedded in the concrete 102 and secured to a temporary mould wall 106, typically formed of plywood. The mould wall 106 may be part of a mould into which the concrete is cast or may be a template with one or more bolts attached that is embedded in the concrete immediately after casting while the concrete is still fluid. The conical cavity 108 is defined by the hollow cone 109 that also fixes the position of the bolt 101 and washer plate 103 in place while the concrete 102 sets.

After casting, but before the concrete 102 is fully set, the nut 107 is removed and the mould removed from the outer surface of the concrete 102. The bolt 101 must then be cracked", typically by the frcc end 105 being struck laterally with a hammer, to frcc the bolt head 112 from the surrounding concrete 102 that is not yet fully set. Free movement of the bolt 101 must be allowed within the range defined by the cavity 108, otherwise it may not be possible for the bolt 101 to be aligned with a structure to be attached to the concrete 102 after setting. After the cracking process, the cavity 108 may need to be covered again to prevent ingress of material and the nut 107 may be replaced to avoid loss and to secure the bolt in place while the concrete 102 sets. These operations add cost to the process and are required to take place at specific times relative to when the concrete was poured. A problem is that the cracking operation may not be carried out at all or may be partially ineffective, requiring remedial work after full setting of the concrete 102. Such remedial work may for example involve what is known as "slotting" or elongating securing holes in the steel structure to attain the required fixed position.

Figure 2 illustrates a bolt assembly 200 in which the above problems are solved by introduction of a cover 201. The cover 201 comprises a cavity or void 202 that surrounds the bolt head 112 and protects the bolt head 112 from being fixed in place due to setting of the surrounding concrete 102. The cover 201 as shown in figure 2 is hemispherical in shape with a surrounding planar flange 203 allowing the cover 201 to be sealed against the washer plate 103. A further illustration of an example cover 201 is provided in figure 3. The planar flange 203 may be of the same or similar size as the washer plate 103 to maximise the sealing surface to prevent ingress of concrete during casting into the cavity 202. The cover 201 may be sealed against the washer plate 103 by adhesive, for example by the use of an adhesive layer 204 provided on the sealing surface 205 of the planar flange 203. A removable backing sheet may be provided to protect the adhesive prior to attaching the cover 201 to the washer plate 103. The adhesive layer 204 may be provided in the form of a gasket having an adhesive on opposing faces. As an illustrative example, a neoprene gasket of between around 1 and 2 mm in thickness having a high tack adhesive on both faces may be used. The gasket may be applied to the planar flange 203 either as part of a manufacturing process for the cover 201 or before attachment of the cover 201 to the washer plate prior to embedding. A backing sheet over the gasket may be removed to expose an adhesive layer to secure the cover 201 to the washer plate.

In the examples illustrates in figures 2 and 3, the washer plate 103 and planar flange 203 are rectangular in shape, although these may be of other shapes such as circular, hexagonal or other shapes. The shape of the cavity 202 is shown as being hemispherical, but other shapes may also work as effectively, provided the cavity is sufficiently sized to allow for movement of the bolt head after casting. The cavity may be empty, i.e. air fined, or in some cases may be filled with a resilient material such as a rubber or foam such as a low density foam or a high viscosity gel to prevent ingress of concrete and cement while still allowing for movement of the bolt head after casting.

In a typical example implementation, the cover 201 may have a cavity of around 40 mm in diameter. A typical bolt may be an M20 x 450 bolt, i.e. having a shaft 20 mm in diameter and 450 mm in length. A washer plate may typically be a 150 mm square 20 mm thick plate with a single hole to allow the bolt to pass through. Such dimensions are, of course, only provided by way of example and the invention is not intended to be limited to such dimensions.

The cover 201 may be formed by injection moulding or vacuum forming or a polymeric material. The polymeric material may be selected a range of materials such as polypropylene, polycarbonate, polyvinylchloride and many others. The cover 201 may advantageously be formed from a recycled polymeric material. The cover 201 may have a wall thickness that is sufficient to withstand pressure from the surrounding concrete during casting, for example a thickness of between 100 micrometres and 1 millimetre.

In some examples, the cover 201 may further comprise a rim on two or more edges for securing the cover 201 to the washer plate 103. In the case of a rectangular shape planar flange 203, a c-section rim on two parallel sides may be sufficient to secure the cover 401 to the washer plate 103, as shown schematically in figure 4. This may further prevent the cover 401 from being dislodged during casting and allows the cover 401 to be easily attached, optionally without the use of an adhesive layer if the fit between the cover 401 and the washer plate 103 is tight. With sufficient flexibility, the cover 401 may be snapped into place around the washer plate 103 over the bolt head during assembly, the opposing c-section portions 402, 403 allowing the cover 401 to grip securely to the washer plate 103. Other arrangements for securing the cover 201, 401 to the washer plate 103 may be envisaged, such as an arrangement in which pairs of triangular leaves fold over the washer plate to hold the cover in place. An example of such an arrangement is illustrated schematically in figure 5, in which the cover 501 comprises foldable leaves 502a-d that are arranged to fold over on to a side of the washer plate opposing the sealing surface. Each leaf 502a-d may have a circular cut out 503a-d that fits around the shaft of the bolt once folded against the washer plate. Once folded and secured in place the cover 501 provides a more secure seal against ingress of concrete or cement. The number of leaves 502a-d may correspond to the number of sides of the washer plate, which in the example in figure 5 is four in the case of a rectangular or square washer plate but may vary in alternative examples.

The cover 201, 401, 501 may also or alternatively be secured to the washer plate 103 to achieve grout tightness by applying tape, e.g. duct tape, on all sides prior to casting. In practical applications, particularly where the components may be greasy and/or wet where adhesives may be less practical, duct tape may be a preferred vvay of securing the cover to the washer plate.

Figures 6a and 6b illustrate an alternative cover 601 comprising a c-section rim 602a, 602b on two opposing parallel sides of the cover 601, each c-section rim 602a, 602b defining a channel 603a, 603b having a minimum width 604a, 604b that is smaller than a thickness of the washer plate around which the cover 601 is configured to fit. The minimum width 604a, 604b is between an inner edge 605a, 605b of a curved upper flange 606a, 606b of each c-section 602a, 602b. The upper flanges of the cover 601 are sufficiently elastic so that the cover 601 can be secured to the washer plate by clamping around the washer plate. With the cover 601 formed from a flexible material such as a polymer, the flexibility of the cover 601 and the flanges 606a, 606b may allow the cover to be secured to the washer plate without adhesive or may allow the cover to be sufficiently securely held in place while an adhesive to bond the cover to the washer plate cures or sets.

Figures 7a and 7b illustrate a further alternative cover 701 comprising a c-section rim 702a, 702b, 702c on three out of four sides of the cover 701. With the cover 701 formed from a sufficiently flexible material the washer plate can slide into the cover, which is then held in place around the washer plate with the bolt head within the cavity 703.

Other embodiments are intentionally within the scope of the invention as defined by the appended claims.

Claims

CLAIMS1. A bolt assembly for embedding in concrete, the bolt assembly comprising: a bolt having a shaft and a bolt head at a first end of the bolt; a washer plate having a hole configured to allow passage of the shaft of the bolt to secure the bolt head to the washer plate; and a cover having a sealing surface configured to seal against a planar surface of the washer plate and being sized to surround the bolt head.
2. The bolt assembly of claim 1, wherein the cover comprises an internal cavity sized to surround the bolt head.
3. The bolt assembly of any preceding claim, wherein a portion of the cover sized to surround the bolt head is hemispherical.
4. The bolt assembly of any preceding claim, wherein the sealing surface of the cover is a planar surface configured to seal against the planar surface of the washer plate.
5. The bolt assembly of any preceding claim, wherein the planar sealing surface of the cover is the same size at the washer plate.
6 The bolt assembly of claim 4 or claim 5, wherein the cover comprises a c-section rim on opposing parallel edges of the planar sealing surface, each c-section rim sized to fit around a corresponding edge of the washer plate.
7. The bolt assembly of claim 6, wherein each c-section rim defines a channel having a minimum width smaller than a thickness of the washer plate such that each c-section rim is arranged to resiliently clamp around the washer plate.
8. The bolt assembly of claim 6 or claim 7, wherein the planar sealing surface is rectangular and the cover comprises a c-section rim on three out of four sides of the planar sealing surface.
9. The bolt assembly of claim 4 or claim 5, wherein the cover comprises foldable leaves extending from each edge of the planar surface, the foldable leaves arranged to fold over on to a side of the washer plate opposing the sealing surface.
The bolt assembly of any preceding claim, wherein the sealing surface of the cover comprises an adhesive for securing the cover to the planar surface of the washer plate.
11. The bolt assembly of any preceding claim, wherein the assembly further comprises a hollow cone having a narrow end sized to fit around the shaft of the bolt.
12. The bolt assembly of any preceding claim, wherein the assembly further comprises a nut sized to fit to a threaded section of the bolt.
13. A method of embedding a bolt in a concrete structure, the method comprising: providing a bolt having a shaft and a bolt head at a first end of the bolt, a washer plate having a hole configured to allow passage of the shaft of the bolt to secure the bolt head to the washer plate and a cover having a sealing surface configured to fit against a planar surface of the washer plate and being sized to surround the bolt head; providing a hollow cone having a narrow end sized to fit around the shaft of the bolt.attaching the bolt to a wall of a mould by passing the shaft of the bolt through the washer plate, the hollow cone and a hole in the mould wall and securing the bolt to the wall by attaching a nut to a second end of the bolt; attaching the cover to the planar surface of the washer plate to surround the bolt head; and casting the concrete structure.
14. The method of claim 13, wherein the sealing surface of the cover is a planar surface sealed against the planar surface of the washer plate.
15. The method of claim 14 wherein the planar sealing surface of the cover s the same size at the washer plate.
16. The method of any one of claims 13 to 15, wherein the cover comprises an internal cavity.
17. The method of any one of claims 13 to 16, wherein a portion of the cover sized to surround the bolt head is hemispherical.
18. The method of any one of claims 13 to 17, wherein the sealing surface of the Cover is secured to the planar surface of the washer plate by adhesive and/or by adhesive tape.
19. A concrete structure comprising a bolt assembly according to any one of claims 1 to 10 embedded in the concrete structure, wherein the cover is attached to the planar surface of the washer plate and surrounds the bolt head, the shaft of the bolt passing through the hole in the washer plate and through a conical cavity in the concrete structure, the conical cavity having a narrow end proximate the washer plate and a wide end at an outer surface of the concrete structure.
20. The concrete structure of claim 19, further comprising a hollow cone defining the conical cavity.
21. The concrete structure of claim 19, wherein the bolt secures a further structure to the concrete structure.
22. The concrete structure of claim 21 wherein the conical cavity is filled with a cementitious grout.