GB2403736A

GB2403736A - Shroud for a bolt to be set in concrete

Info

Publication number: GB2403736A
Application number: GB0315915A
Authority: GB
Inventors: Saul Tristan Charlton; Simon Nicholas Johnson
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-07-08
Filing date: 2003-07-08
Publication date: 2005-01-12
Also published as: GB0315915D0

Abstract

A shroud for a bolt to be set in concrete comprises a first chamber 7 for enclosing and retaining a first end 12 of the bolt and a second chamber 2 for the shank 10 of the bolt, and adapted to allow movement of the bolt relative to the longitudinal axis of the shroud. In use a bolt, and a washer 14 is inserted into the shroud via the first chamber, which is then closed by slidable lid 9. The other end of the shroud may be closed by a lid 4. The assembly is placed in a foundation and concrete poured around it. The bolt can be moved within the shroud to accommodate tolerance variations in e.g. structural steel to be bolted to the foundation, and when this has been fixed in place, the shroud may be filled with grout.

Description

SHROUD FOR A BOLT

Field of the Invention

This invention relates to a shroud into which a bolt is placed during a procedure where the bolt is set in concrete.

Background to the Invention

In the construction industry there is often a requirement to set bolts into concrete. This is particularly the case in the construction of steel framed buildings, such as warehouses, of lice blocks, multi-story car parks, sports stadiums, etc. In such constructions, a concrete foundation is laid and bolts are set into the concrete. The steel constructional members are then fastened to the bolts, thereby anchoring the building to the foundation.

The setting of bolts into concrete cannot be done to great accuracy. The usual method of locating the bolts in a desired position in the concrete is to make a jig from a wooden frame to which the bolts are attached and place this jig in position in the foundation prior to pouring the concrete.

The problem with this method is that steel constructional members arrive at the building site with the holes, in which the bolts are to locate, pre-drilled. Whilst the tolerances to which the bolt holes are drilled are relatively tight, the jig is not built to the same tolerances, and the concrete pouring process tends to move the bolts away from their desired positions. It is then necessary to crack the bolts away from the concrete in which they are set, so that they can be aligned with the bolt holes.

This cracking procedure is usually carried out whilst the concrete is still curing, and therefore relatively weak. Concrete "goes of P', i.e. cures to a degree where cracking the bolt away from the concrete is not feasible, within about twelve hours. The cracking off procedure must therefore be completed during this short period.

In order to facilitate the cracking off of the bolt from the concrete, it is desirable to set the bolt and any associated washer in as little concrete as possible.

One widely used means of achieving the above end involves placing a paper cone over the shank of the bolt. The cones are of a diameter great enough to allow sufficient degree of movement of the bolt shank to crack the bolt head and any washer from the concrete. When the bolts have been located in the holes of the steel constructional member, and their corresponding nuts tightened, a grout is poured into the void formed by the paper cone, thereby re-setting the bolt into the concrete foundation. The paper cone mmains in place in the foundation after the final setting of the bolt into the foundation.

Another known means of setting the bolt and its associated washer into as little concrete as possible involves using a polystyrene tube, which surrounds the bolt. Prior to cracking offof the bolt head and its associated washer, the polystyrene tube must be removed. This is achieved by pouring a chemical onto the tube to dissolve it. The diameter of the resulting bore in the concrete allows sufficient movement ofthe bok shank to crack offthe bolt head and any associated washer from the concrete.

The cracking off of bolt heads is a time consuming and arduous task. Furthermore, the task can be made more time consuming by the contamination of voids around the bolts by concrete overspill occurring during the pouring procedure, rubble and other materials often found on a building site.

Other problems associated with the known devices concern water. Since water corrodes steel, the ingress of water into the region of the bolt head and its washer is clearly undesirable. Also, a jig having bolts mounted thereon with paper cones shrouding the bolts may be set up in a foundation some time before the concrete is poured. If there is considerable rain this can cause the paper cones to collapse, particularly if they have been cut, a necessary procedure to create the correct length of cone, since this exposes paper which would otherwise be protected by wax.

A further problem associated with the known devices concerns the filling of the void with the cement based slurry, and the difficulty in ensuring that the slurry passes around the bolt head and washer, as opposed to sitting on top of the washer or forming bridges. Clearly, any weakness at the foundation of a building could result in catastrophic consequences, and therefore should be avoided.

The invention seeks to provide an improved shroud for use in setting a bolt into a concrete foundation.

Summary of Ille Invention

One aspect of the invention provides a shroud for a bolt as specified in Claim 1.

Another aspect of the invention provides an assembly comprising a bolt and a shroud as specified in Claim 13.

Another aspect of the invention provides a method of construction as specified in Claim 15.

Brief Descnpdon of the Drawings In the drawings, which illustrate preferred embodiments of shrouds according to various aspects of the invention, and which are for exemplary purposes: Figure 1 is a schematic representation of a shroud according to an aspect of the invention; Figure 2 is a side view of the shroud illustrated in Figure 1 in cross- section, Figure 3 is a schematic representation of the base of the shroud illustrated in Figures 1 and 2; Figure 4 is another schematic representation of the base of the shroud illustrated in Figures 1 and 2; Figure 5 is a schematic representation of a shroud and bolt assembly in assembled form; and Figure 6 illustrates a jig set up for securing bolts into a concrete foundation.

Demiled Descnpdon of the Preferred Embodiments Referring now to Figure 5, there is shown a shroud and bolt assembly, designated generally by the numeral 1, in assembled form. The assembly 1 comprises a shroud 2, which in the example is formed from a strong plastics material. The shroud 2 has a conical portion, which includes an upper end 3 and a lower end 6. A lid 4 fits into the upper end 3 of the conical portion, and comprises an orifice 5 through which the threaded portion 11 of a bolt 10 passes.

The shroud 2 includes a base 7 in the form of a substantially square box extending from the lower end 6 of the conical portion of the shroud 2. The box comprises a box body 8 which is formed integrally, with the conical portion as a single plastics moulding. A lid 9 fits to the box body 8, and win be described in greater detail below with particular reference to Figures 3 and 4.

An anchor bolt 10 fits inside the shroud 2, the bolt comprising a threaded portion 11 and a bolt head 12. A substantially square washer 14 having an orifice 15 located substantially in the centre thereof is located in the base 7, with the bolt passes through the orifice 15. The diameter of the bolt head 12 is greater than the diameter of the orifice 15. In the assembled illustrated in Figure 5, the nut 13 co-operates with the threaded portion 11 of the bolt 10 to secure the lid 4 in place on the upper end 3 of the shroud 2.

Referring now to Figures 3 and 4, it can be seen that the base 7 comprises a box body 8, and that in the region of the lower edge of the box body 8 on opposing sides thereof, there is provided a pair of inwardly extending projections 20, which are spaced apart so as to form a groove 22. The groove is substantially ['-shaped in its internal cross- section, and receives correspondingly T-shaped edge portions 21 of the lid 9. The grooves 22 locate the lid 9 in the box body 8. The shape of the edge portions 21 and the grooves 22 serve to lock the lid to the box body, preventing the downwardly depending wads of the box body from splaying.

The perspective view shown in Figure 4 illustrates the base 7 with the lid 9 removed therefrom. The lid 9 includes a planar base and a smaD side was extending substantially perpendicularly to the planar base. The side was makes the lid easy to handle.

In Figure 1 to 4, four ribs 23 extend between the upper surface 24 of the box body 8 and the lower end 6 of the conical portion of the shroud 2. The ribs 23 strengthen the shroud 2 in the region where the lower end 6 of the conical portion of the shroud 2 joins the upper surface of the box body 8.

In Figure 2, concentric lobes 25 extend from the underside of the upper surface 24 of the box body 8. These lobes 25 serve to space slightly the washer 14 from the underside of the upper surface 24 of the box body 8. The lobes 25 could be replaced by other mechanical equivalents. For example, the upper surface of the washer 14 may be provided with similar lobes, or another type of spacer might be used. The purpose of this feature will be described in more detail below with reference to the use of the shroud and bolt assembly.

Tuming now to Figure 6, there is shown a jig 50 comprising spaced apart upper and lower plates 53, 54. Each plate is substantially square and in the corner regions thereof is provided with an aperture 58. The jig 50 mounts four shroud and bolt assemblies 1, the bases of which sit above and spaced apart from a reinforcementgrid 60. The space between the base ofthe shroud and the reinforcement grid is determined by the specification of the foundation.

The threaded portions 11 of the bolts pass through aligned apertures 58 of the upper and lower plates 53 and 54 with each of the shroud and bok assemblies 1 being fastened to the lower plate 54 by means of a nut 13 which screws onto the threaded portion 11 of the bolt 10.

Passing between the plates 53, 54 are a pair of elongate timbers 51, 52 the opposite ends of which sit on unexcavated ground, and in Figure 6 rest on the upper edge of shattering 59. The plates 53, 54 are attached to the elongate timbers 51, 52 by means of a threaded bob 56, which passes through both of the plates and a nut 57 which clamps a square washer 55 against the upper plate 53.

In use, in the example shown in Figure 6, concrete is poured onto the foundation grid 60 until the level of the concrete reaches the underside of the lower plate 54. When the concrete has set, the nuts 13 are removed, and the plates 53, 54 and elongate timbers 51, 52 and associated clamping means are removed to leave the threaded portions 11 of the bolts 10 protruding above the surface of the concrete. The nuts 13, removed from the threaded portions 11 to pemmit removal of the lower plate 54 are re-attached to the threaded portions 11 of the bolts 10 to fasten the lid 4 to the conical portion of the shroud 2.

When the time for attaching a steel constmctional member to the foundation arrives, the workman removes the nuts 13, and the lids 4. Each bolt is free to move within the confines of the conical portion of its shroud 2. When the bolts have been aligned with holes in the steel constructional member, nuts 13 are once again threaded onto the threaded portion 11 of the bolt 10, and tightened. A grout is pumped into the inside of each shroud to set the bolt fast. The grout runs down into, and fills, the base 7.

Referring again to Figure 2, the concentric lobes 25 ensure adequate space between the washer 14 and the underside of the upper surface 24 of the box body 8 for the cement based slurry to run into and fill the base 7.

Assembly of the bolt in the shroud is a relatively simple operation. A workman places the washer 14 onto the bok 10, and inserts the bolt 10 into the lower end 6 of the conical portion of the shroud 2. When the washer 14 and bolt head 12 are located within the base 7 of the shroud 2, the workman slides the lid 9 into the box base 8. The lid 4 is put in place, closing the upper end 3 of the conical portion of the shroud 2.

In order to facilitate the use of bolts having different lengths, the conical part of the shroud may be provided with lines of weakness at locations corresponding to common lengths of bolt, thus enabling one shroud to be functional with a range of different lengths of bolt.

The invention also provides a method of foundation construction in which a plurality of bolt and shroud assemblies 1 are mounted on a jig 50, and set in concrete.

The invention provides a number of advantages over the known prior art devices. First, the bolt head 12 and washer 14 are free to move within the base 7. Therefore, there is no requirement to crack offpartially set concrete.

The full enclosure of the bolt, barring the threaded portion which necessarily protrudes through the lid, protects the bolt and associated washer from the weather, with ingress of water to the inside of the shroud being substantially prevented.

The provision of the lid stops the type of waste materials found on a building site, such as rubble, soil, pieces of wood and metal from finding their way into the shroud. Therefore, time is not wasted cleaning out shrouds to permit movement of the bolt.

The shroud remains in place in the foundation permanently. There is no requirement to introduce chemicals to dissolve the shroud, thereby avoiding any possible chemical damage either to the concrete or the bolt and its associated washer.

Claims

Claims 1. A shroud for an elongate bolt having first and second ends, the

shroud comprising a first chamber for receiving and substantially enclosing a first end of the bolt and a second chamber for surrounding a substantial portion of said bolt, wherein, in use the second end of the bolt protrudes from a first end of the second chamber, and wherein the second chamber is so dimensioned as to permit movement of the elongate bob within the said shroud relative to a longitudinal axis thereof
2. A shroud according to Claim 1, wherein the shroud further comprises lid closing the second chamber, the lid including an aperture through which the second end of the bolt may pass.
3. A shroud according to Claim 2, wherein the said lid is removably mounted on the shroud.
4. A shroud according to any of Claims 1 to 3, wherein the first chamber includes a removable lid.
5. A shroud according to Claim 4, wherein the said lid is slidably mounted in the first chamber.
6. A shroud according to Claim 5, wherein the first chamber comprises at least two walls, each of the walls including rails in which the said lid slides, and wherein the rails and the lid are so shaped and dimensioned such that movement of the lid in a first direction is permitted, but movement of the lid in a direction perpendicular to said first direction is prevented.
7. A shroud according to any preceding claim, wherein the first chamber is wider than the bolt.
8. A shroud according to any preceding claim, wherein the said first chamber includes spacer elements arranged to space an element mounted on the first end of the bolt away from an internal surface of the said first chamber.
9. A shroud according to Claim 8, wherein the first chamber is so shaped an dimensioned as to receive and retain a washer, in use, said bolt passing through an aperture in said washer.
10. A shroud according to any preceding claim, wherein the first chamber consists of a box, and the second chamber consists of a cone, said box including an opening into said cone.
11. A shroud according to (claim 10, wherein the cone is substantially circular m cross-secton.
12. A shroud according to any preceding claim, wherein the first and second chambers are formed as a single plastics moulding.
13. An assembly comprising a shroud as claimed in any preceding claim and a bolt having a first end located in said first chamber, and a second end protruding from the second chamber.
14. An assembly according to Claim 13, when dependent on Claims 7 and 9, wherein a washer is arranged on the first end of the said bolt, and said spacer means separate the washer from the inner surface of the first chamber.
15. A method of constructing a foundation comprising the steps of i. mounting at least one assembly according to Claim 13 or 14 on a jig, ii. mounting the jig so that the upper surface of the second chamber is substantially aligned with a desired upper level of a foundation; iii. pouring a setting aggregate mixture into the foundation until said mixture reaches the desired upper level of the foundation; iv. removing the jig; v. aligning the bolt of or each assembly with an aperture in a constructional element; vi. fastening a nut onto the threaded portion ofthe bolt; vii. tightening the nut to fasten the constructional element to the foundation; viii. pouring a setting aggregate mixture into the said shroud.
16. A method as claimed in Claim 15, wherein the said setting aggregate mixture poured into the foundation is a concrete mixture.
17. A method as claimed in Claim 15 or 16, wherein the said setting aggregate mixture poured into the shroud is a grout.
18. A method as claimed in any of Claims 15 to 17, wherein the said aggregate mixture poured into the shroud is a cement based slurry.
19. A foundation comprising at least one assembly according to Claim 13 or 14.
20. A foundation according to Claim 19, and constructed according to the method of any of Claims 15 to 18.
21. A shroud substantially as described with reference to, and as shown in, Figures 1 to 5 ofthe drawings.
22. An assembly substantially as described with reference to, and as shown in, Figure 6 of the drawings.