DRAINAGE CHANNEL

Abstract: A channel section (13) is of generally U-shaped cross-section and is made from glass fibre reinforced concrete. The section can be thin and light and easily man-handled. In order to provide the section with sufficient rigidity during the setting of a concrete back fill around the section, a framework of reinforcing bars (17) is provided spaced from the reinforced concrete channel member by tie bars (18) or an integral rib (25). The reinforcing bars and tie bars (17,18) or rib (25) form a rigid composite structure with the fibre reinforced concrete member which keeps the member rigid while the concrete back fill is drying and which forms a reinforcing structure in the concrete after drying.

Description: The invention relates to drainage channels including a channel member of fibre reinforced material. Examples of such fibre reinforced materials are glass fibre reinforced concrete or glass fibre reinforced gypsum, or gypsum or concrete reinforced with stainless steel fibres. The use of such fibre reinforced materials is advantageous in that the strength and wear resistance of such materials are superior to unreinforced materials. This allows the dimensions of structural elements formed from such materials to be thinner and lighter than similar elements made of unreinforced materials. Further, it allows elements to be constructed from such materials which, because of weight and size considerations, could not be constructed from unreinforced materials. Water drainage channels have conventionally been made of unreinforced concrete and are formed of sections laid end to end and embedded in a concrete surround. Unreinforced concrete channel sections are necessarily thick and heavy and require mechanical lifting gear to handle them. In principle, channel sections of, say, glass reinforced concrete, could be made sufficiently thin and light to be handled by without mechanical lifting gear. However, when used with a concrete surround, fibre reinforced materials such as glass fibre reinforced concrete can have the disadvantage that they flex and bend and plainly this is unacceptable. It has been proposed, in order to overcome this problem, to make such structural members with two spaced layers of glass fibre reinforced material with a void between the layers filled with an expanded plastics material, such as expanded polystyrene. It has been found, however, that such composite members are liable to fail and for this reason, in some applications, the use has been banned. GB-A-2085502 discloses a building unit incorporating a thin wall concrete base and one or more reinforcing members each having a foot secured in the base and extending above the base. Concrete is poured on the base to form a structural member. According to the invention, there is provided a drainage channel comprising a channel member of generally U-shaped cross-section and formed of fibre-reinforced material, an exterior surface of said channel member having one or more metal reinforcing bars connected thereto but spaced therefrom for anchoring in concrete and maintaining the channel member rigid in such anchorage. Thus, the use of the spaced reinforcing bar or bars allows the channel to be thin and light but at the same time prevents its flexure when set in concrete. In essence, prior to setting in concrete, the metal bar forms a rigid composite structure with the member and, after setting, the bar reinforces the concrete. According to a second aspect of the invention, there is provided a method of manufacturing a drainage channel comprising forming from fibre reinforced concrete an elongate member of U-shaped cross-section with an interior surface defining a passage for the drainage of liquid and an exterior surface and connecting to said exterior surface a plurality of reinforcing bars at positions spaced from said exterior surface. The following is a more detailed description of one embodiment of the invention, by way of example, reference being made to the accompanying drawings, in which:- Figure 1 is a cross-section through a first form of U-shaped channel section of glass fibre reinforced concrete, Figure 2 is a side elevation of the channel section of Figure 1, Figure 3 is a detail showing the connection of a tie bar to the glass fibre reinforced concrete of the channel section, Figure 4 is a similar view to Figure 1 but showing tie bars connected to the glass fibre reinforced concrete member in a different orientation, Figure 5 is a side elevation of a second form of U-shaped channel section of glass fibre reinforced concrete, Figure 6 is a plan view of the channel section of Figure 5, Figure 7 is an end elevation of the channel section of Figures 5 and 6, and Figure 8 is a section on the line VIII-VIII of Figure 7. The channel section shown in the drawings is one of a number of such sections which are laid end to end to form a drainage channel. The open upper end of the channel is covered by an end to end series of perforate covers which provide a load-bearing surface while allowing water to drain through the perforations into the channel. Referring now to Figure 1, the first form of channel section is formed in two main parts, a member 10 of glass fibre reinforced concrete and a framework of reinforcing bars 11 connected to the concrete member 10. The glass fibre reinforced member is of generally U-shaped cross-section with a flat base 12 from which extend diverging lower side walls 13. Parallel upper side walls 14 extend from the lower side walls 13. Outwardly extending stepped flanges 15 provide the upper free ends of the upper side walls 14. The steps 16 in the flanges 15 are for receiving the edges of a cover (not shown). Since the member 10 is made of glass fibre reinforced concrete, it is light in weight and thin in dimensions as compared with a member of unreinforced concrete. Referring now to Figures 1 and 2, the reinforcing framework 11 comprises four U-shaped reinforcing bars 17, tie bars 18 and spacer bars 19. All these bars may be of circular cross-section steel. The steel may be galvanised to resist corrosion. Alternatively, the bars may be of any other suitable material including phospher bronze or other alloys. Each reinforcing bar 17 is of similar shape to the cross-section of the reinforced concrete member 10 but of increased dimension. As best seen in Figure 2, the free ends of each reinforcing bar 17 are provided with portions 20 which extend parallel to the length of the channel section. On each reinforcing bar, these end portions 20 face opposite directions and are connected to respective flanges 15 towards the outer edges of those flanges 15. The tie bars 18 are of generally V-shape (see Figure 3) without outwardly turned ends 21. Six such tie bars 18 are used to connect each of the four reinforcing bars 17 to the concrete member 10. Of course, a greater or lesser number may be used as required. Each reinforcing bar 17 is welded in the angle between the limbs 22 of the six tie bars 18, which are arranged around the reinforcing bar 17 as shown in Figure 1. The end portions 17 of the tie bars 18 are connected to the concrete member 10, as shown in Figure 3. In this way, the reinforcing bars 17 are rigidly connected to the concrete member and form, with the concrete member, a composite structural element. The four reinforcing bars 17 are interconnected by the spacer bars 19. In all, six such spacer bars are used at spaced intervals around the reinforcing bars, as seen in Figures 1 and 2. The spacer bars 19 extend parallel to the length of the channel section and are welded to the reinforcing bars 17. As shown in Figure 1, the tie bars 18 lie in planes generally normal to the cross-section of the channel member 10. However, as shown in Figure 4, at least some of the tie bars 18 may be turned through 90° so that they lie in planes including the plane of the concrete member 10. This may have the advantage of giving a more rigid structure, since, as will be seen from Figure 4, the structure approximates to a truss. In use, a trench is excavated where a channel is required. A plurality of channel sections of the kind described above with a reference to the drawings are then laid end to end and aligned to form a continuous channel. For the purposes of alignment, the channel sections may be provided with interlocking or interconnecting parts (not shown). Alternatively, as the channel sections are laid end to end to form the channel, they can be connected together by the use of bars which extend between adjacent reinforcing bars 17 on the two sections. As shown in Figure 3, the outer reinforcing bars 17 are spaced by some distance from the ends of a channel section. It would be possible, however, to arrange for these outer reinforcing bars 17 to be close to the ends of the associated channel section. With such an arrangement, a butting channel sections would have closely adjacent reinforcing bars 17 which could be tied together using wire. The channel sections described above with reference to the drawings are comparatively light in weight and can be unloaded and positioned without the use of a mechanical lifting device. Their low weight also facilitates their transport. The bases of the sections are then set in concrete and, once this concrete has dried, the remainder of the trench is filled with concrete. The spacing of the reinforcing bars 17 from the reinforced concrete member 10 is such as to ensure that this concrete fills completely the spaces between the reinforcing bars 17 and the exterior surface of the concrete member 10. The forces generated by the wet concrete, which tend to squeeze the side walls of the concrete member together, are resisted by the framework 10, which thus holds the concrete member rigid while the back fill concrete is setting. Once set, the framework 11 provides reinforcement for the back fill concrete, so increasing its strength. In addition, it provides a key which ensures a firm connection between the concrete member 10 and the concrete. The channel sections may be manufactured in the following way. First, a number of reinforcing bars 17, tie bars 18 and spacer bars 19 are formed to shape from steel bar stock. Four reinforcing bars 17 are then arranged at spaced intervals along a former and the tie bars 18 and spacer bars 19 welded to them to form the framework 11. Glass fibre reinforced concrete is then sprayed onto the exterior of a suitably shaped mould to form the reinforced concrete member 10. While this concrete is still wet, the former is brought up to the mould and the ends of the reinforcing bars 17 and the tie bars 18 positioned on the concrete. As seen in Figure 3, further fibre reinforced concrete is then applied over the ends of the tie bars 18 and over the ends of the reinforcing bars 17 and the structure left to dry. Curing may be natural curing or may involve the use of applied heat. Once cured, the mould and the former are removed to leave a completed channel section. An alternative method of manufacture, the reinforcing framework 11 may be constructed as above, but the reinforced concrete member 10 formed as follows. First, glass fibre reinforced concrete is laid over a flat porous sheet. The fibre reinforced concrete is then de-watered and shaped by wrapping around a mould. The manufacture then continues as described above. This alternative method of manufacture has the advantage of better controlling the thickness of the fibre reinforced concrete member 10. Referring next to Figures 5 to 8, the second form of channel section is of a generally U-shaped cross-section similar to that of the channel section described above with reference to Figure 1 to 4 and including a flat base 20, diverging lower side walls 21, parallel upper side walls 22 and flanges 23 provided with steps 24 for receiving the edges of a cover (not shown). The channel section is of glass fibre reinforced concrete. The exterior surface of this channel is provided with three U-shaped ribs 25. Each rib 25 lies in a plane normal to the length of the channel and extends from the upper edge of one flange 23 to the upper edge of the other flange 23 passing, inbetween, over the upper side walls 22, the lower side walls 21 and the base. There is a rib 25 at each end of the channel section and a rib 25 at a position intermediate the ends of the section. Of course, there may only be two ribs 25 or there may be four or more ribs. As best seen in Figure 8, each rib 25 is reinforced by a correspondingly shaped reinforcement bar 26. As also seen in that Figure and in Figure 5 each rib 25 is provided with five spaced holes 27 extending through the rib 25 in a direction parallel to the length of the channel and spaced around the rib 25. The holes 27 of the ribs 25 are in register. The use of the holes 27 will be described below. The second form of drainage channel is manufactured by arranging the reinforcement bars 26 in a suitably shaped mould (not shown). Glass fibre reinforced concrete is then sprayed and/or poured and vibrated into the mould to form the channel section. The holes 27 are then formed by, for example, drilling. In use, a trench is excavated where a channel is required. A plurality of channel sections of the kind described above with reference to Figures 5 to 8 are laid end-to-end and aligned to form a continuous channel. For aiding alignment the channel sections may be provided with interlocking or interconnecting parts (as shown). Next reinforcement bars 28 (see Figure 8) are inserted through the aligned holes 27 and are wired together to form continuous bars extending generally parallel to the length of the channels and parallel to, but spaced from, one another. This wiring also helps to draw the channel sections together. The channel sections are then set in concrete as described above with reference to Figures 1 to 4. Of course, the bars 28 need not be filled on site, they could be supplied filled to the channel sections and then wired together on site. Although four such bars 28 are described, there could be more or less bars as required. It will be appreciated that any reinforced material may be used. For example, the material may be gypsum and the reinforcement need not be glass fibres, it could be stainless steel fibres or other fibres.

Claims: A drainage channel comprising a channel member (13) of generally U-shaped cross-section and formed of fibre-reinforced material, an exterior surface of said channel member having one or more metal reinforcing bars (17, 28) connected thereto but spaced therefrom for anchoring in concrete and maintaining the channel member (13) rigid in such anchorage. A drainage channel according to claim 1 characterized in that the or each reinforcing bar (17) is of generally U-shape and lies in the plane of the U cross-section of the channel member (13), the or each reinforcing bar (17) being connected to the exterior surface of the channel by tie bars (18). A drainage channel according to claim 2 characterized in that at least two U-shaped reinforcing bars (17) are provided, interconnected by one or more spacer bars (19) extending parallel to the length of the channel. A drainage channel according to claim 2 or claim 3 characterized in that the channel (13) includes outwardly extending flanges (16) from upper free ends of the channel, the flanges being connected to respective ends of the or each U-shaped reinforcing bar (17). A drainage channel according to any one of claims 2 to 4 characterized in that each tie bar (18) is of V-shape, with the associated reinforcing bar (17) connected in the angle of the V and the two free ends (21) of the limbs of the V connected to the channel member (13). A drainage channel according to claim 1 characterized in that a plurality of reinforcing bars (28) are provided, each reinforcing bar extending generally parallel to the length of the channel (21) and parallel to, but spaced from, one another. A drainage channel according to claim 6 characterized in that the exterior surface of the channel (21) is provided with at least two ribs (25) lying in respective planes normal to the length of the channel, said reinforcing bars (28) extending between, and being carried by, said ribs (25). A method of manufacturing a drainage channel comprising forming from fibre reinforced concrete an elongate member of generally U-shaped cross-section with an interior surface defining a passage for the drainage of liquid and an exterior surface and connecting to said exterior surface a plurality of reinforcing bars (17, 28) at positions spaced from said exterior surface. A method according to claim 8 comprising forming the elongate section by spraying the fibre reinforced material on to a mould or by spraying the fibre reinforced material on to a flat sheet and then shaping the material prior to drying.

Inventors: MONKS, DAVID WILLIAM
Applicants: HODKIN & JONES (SHEFFIELD) LIMITED
Application year: 1990
Main classification: E03F3
IPC codes: E02B13, E03F3, E02B5