GB2080360A - Post-terminal Wall for Tanks - Google Patents

Abstract

Enclosure walling made up of a series of interconnected building blocks 1 at least some of which have an open-ended recess 5 in the front face which communicates with a corresponding recess on adjacent blocks. Reinforcement, for example steel bar reinforcement 12, extends along these recesses and is in a tensioned state around the enclosure thereby exerting a force on the walling which places the wailing in compression to resist pressure from material contained within the enclosure. The blocks are preferably recessed in a rounded manner in order to reduce localized stress build-up. Adjacent blocks are connected by a torque 4 and groove 3 connection, the groove 3 containing reinforcement bars. A through-bore may be provided for the front to back of the blocks for receiving a pipe or other service. <IMAGE>

Description

SPECIFICATION Enclosure Walling This invention relates to enclosure walling, a method of constructing it and a building block for use therein.

There are considerable advantages in constructing walling and the like of precast blocks, especially when the building material is concrete, as this avoids the need to use complicated site shuttering, reinforcement details and in situ concrete mixing and handling. Precast blocks also allow a uniform appearance and standard of structure to be achieved.

However, in the construction of enclosure walling, for example for liquid-retaining tanks, it has previously proved inconvenient and timeconsuming to fit reinforcement necessary to withstand the pressures exerted by the retained liquid. Concrete is strong in compression but weak in tension, and without reinforcement a concrete tank wall is subject to cracking murder the tension loads exerted from within the tank.

It has previously been proposed to reinforce the walling by inserting bar reinforcement between rows of concrete blocks lying on top of one another so that the reinforcement runs around the walling in the joint between the rows.

The reinforcement then takes effect once the pressure exerted by the liquid retained within the tank causes distortion of the walling to place the reinforcement under tension. Thus slight cracking of the reinforcement is necessary for its effectiveness.

It would be preferable to pre-tension the reinforcement before filling the tank with liquid, but this has been difficult to accomplish effectively with prior arrangements.

According to the present invention there is provided enclosure walling comprising interconnected preformed building blocks having open-ended recesses in their outer faces, and tensioned bar or strip reinforcement extending around the walling within the recesses of adjacent blocks.

Further according to the present invention there is provided a method of forming enclosure walling, comprising interconnecting preformed building blocks having open-ended recesses in a face thereof so that the recesses of adjacent blocks around the walling communicate with one another in an outer face of the walling, placing bar or strip reinforcement within the communicating recesses and tensioning the reinforcement around the walling.

Still further according to the invention there is provided a building block having a body, a first face of which has an open-ended recess for receiving bar or strip reinforcement, and complementary means on second and third faces of the block for interconnecting the block with adjacent such blocks.

The block of the invention is provided with means for interconnection with similar blocks in two dimensions. For example, the means may be in the form of corresponding projections and recesses at opposite edges of the block, and preferably such projections and recesses are of rounded profile, for example part-circular, to avoid build-up of localised stresses at sharp corners.

The recesses in the blocks are preferably of rounded profile, for example part-cylindrical or part-circular.

The block may have a hole extending through it, preferably of tapering cross-section, in order to minimise the weakness plane at the hole bounding near the tangents points of interconnected blocks; this reduces core withdrawal problems during manufacture of the blocks and increases the inherent strength of the structure. The hole may be elliptical in section to minimise stress.

The block may have its opposite side edge faces disposed at an angle to one another to facilitate interfitting of adjacent blocks in the construction of non-linear structures, for example tanks or reservoirs. In this respect the block itself may be arcuate, or it may be linear with angled edge faces.

Although the precast concrete form of the block is especially useful it can alternatively be made of for example light-weight aggregate and/or random fibre elements and/or conventional aggregate and cement and/or fibre cement and resin and/or special mixes and additives, as required for specific uses.

If the walling defines a tank for liquid, the greatest pressure exerted by the liquid will be at the lowest portion of the walling, and for this purpose it is preferable that reinforcement be provided close to the base of the wailing, most preferably within the lowest 10% of the height of the walling. Further, additional recesses may be provided in spaced parallel relationship, especially within that area, to receive reinforcement to combat the pressure exerted by retained liquid.

The reinforcement may be for example lengths of steel rod which are interconnected at their adjacent ends so as to overlap to some extent.

The interconnection can be through screw connections which can be easily tightened when the reinforcement is in position in the recesses to tension the reinforcement against the walling.

For aesthetic and protection purposes it is preferable for the recesses containing the reinforcement to be filled in with weather-proof material. This prevents corrosion of the reinforcement.

Embodiments of this invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a front elevation of a block of this invention; Figs. 2 (a) & b) are respectively sections on the lines A-A and B-B of Fig. 1; Fig. 3 is a top plan view of the block of Fig. 1; Figs. 4 (a)8(b) are respectively front and crosssectional view of an alternative block of the invention; Fig. 5 is a view corresponding to Fig. 2 (a) of a still further alternative block of the invention; and Fig. 6 is a front view of a section of walling of the invention.

Referring now to Figs. 1 to 3, the building block is precast in concrete and is an arcuate member (Fig. 3) one face 1 of which has two dished portions 2, each of rounded profile. The upper face of the block has a deep recess 3 whose inner extremity is semi-circuiar in cross-section for receiving steel or other reinforcement bars 10 along it. The lower face has a rounded projection 4 of a size designed to fit within the recess 3 of a similar adjacent block, thereby to provide positive location between them.

A semi circular groove 5 having spaced raised nodes 1 3 along its base extends along the face 1 of the block below the dished portions 2, for receiving further steel reinforcement bars 11 in use. When the bars 11 are in place, concrete grouting 12 is applied to fill the groove 5 thereby protecting the bars 11 from the weather. The bars 11 bear against the nodes 13 thus reducing frictional forces between the bars 11 and the block.

One end face of the block carries a projection 6 of semi-circuiar cross-section while the other end face has a correspondingly-shaped recess, these being disposed so as to provide positive location between adjacent blocks in use.

A tapered vertical hole 7 of elliptical crosssection extends into the block from its upper face, this hole 7 being formed at the mid-point of the block.

The block of Fig. 5 is of similar construction to that of Figs. 1 to 3, but has two grooves 5 each carrying steel bar reinforcement 11 for additional strength.

In use, a wall can be formed from the blocks of these embodiments of the invention by interfitting adjacent blocks in a horizontal and vertical direction to the desired shape and size of the wall.

Circular or other enclosure walls can thus be built by continuing the curved line of each block around the circle arc, and once a suitable length of wall has been constructed the steel reinforcement bars 10 and 11 can be fixed along the recesses 3 and 5. Obviously, the bars 10 are located in the recess 3 before a second row of blocks are laid on top of the first row, thus closing off the recess 3. These blocks can be quickly and easily assembled into walling, and in that form are subject to very little stress concentration in view of the rounded recesses and projections which avoid the localised stress build-up at corners of conventional rectilinearly-recessed blocks.

Once the bars 11 have been placed in the grboves 5 they are interconnected end-to-end as shown in Fig. 6 by screw connections 14 to form a continuous length of reinforcement. They are then tensioned by tightening the screws 14, thus exerting an inward force on the walling.

When the walling is used to retain liquid or discrete material, therefore, the pressure exerted by that material is opposed by the force exerted by the reinforcement, thus relieving the concrete walling of substantial stresses. Provided the tension of the reinforcement produces a greater force through the walling than the material retained by the walling, the walling itself will be under compression rather than tension.

Figs. 4(a) and (b) illustrates an embodiment of the invention wherein the block is apertured from front to back at 8 through the centres of the dished portions 2. Pipes 9 and other appurtenances can be passed through these apertures 8, which thus provide passageways for services through a constructed wall. This again avoids the occasion of a stress crack flow in the form of a yield line generating towards the corners of a square or rectilinearly-recessed block.

Conventional precast concrete block systems currently in use require either a form of bolted connection between blocks, which considerably increases risks of localised stressing and concrete failure in its weakest form i.e. tension conditions, or other grouted block or panel systems. Such other grouted block systems have disadvantages such that the recessed blocks are of a rectilinear nature, thus attracting a concentration of unsatisfactory stresses.Further disadvantages of conventional systems are (1) they do not provide for reinforcement at the base level of the block where the tension condition is greatest; and (2) they do not incorporate elliptical tapered core holes such that internal stress conditions can be generated for rectilinear core holes; (3) they have core holes running in parallel to the vertical face of recessed panels providing inherent weakness in; the panels; (4) they incorporate recessed grooves of either a rectilinear for example squared or trapezoidal nature, and these rectilinear shapes attract stress conditions at corners; (5) square or rectilinear panels may suffer failure at hole cutting operations of such recessed panels due to the attraction of stress failure conditions to corners.

The blocks of these embodiments of the invention avoid such problems of rectilinear dished panels, square or rectilinear vertical grout holes, and rectilinear or grooved reinforcement channels, and these blocks allow for the establishment of an external base level semi-circular channel to accommodate reinforcement for the maximum tension condition, which can have the effect of reducing the foundation costs associated with wall construction.

The provision of reinforcement in the grooves 5.

affords the ability to construct a precast segmental wall in such a fashion that post tensioning can be carried out totally on the structure before the placing of protective concrete. This then has the advantage that the tensioning of the reinforcement ensures that the tension generated within the steel reinforcement in turn transmits a tensile hoop compressive stress into the concrete wall such that the structure is in total compression, which is the best mechanism for a concrete unit. Whenever concrete is placed around the post tensioned steel, this concrete is placed at a theoretical "no stress" condition into a compression structure.

Thus under load conditions on the structure (internal load within the tank generating tensile load to the concrete structure) the structure is in an ideal situation as all induced compression forces resist the imposition of tensile actions.

Additionally, before tensile forces can be induced with infill concrete surrounding the post tensioned reinforcement, such tensile forces would require to be of such magnitude as to overcome the post tensioning effect in the steel before direct transmission to the cover concrete.

Such conditions represent the ideal mechanism for concrete sustaining tensile forces.

An additional advantage of such a mechanism whereby precast concrete panels have induced compression due to post tensioning actions is that it affords the opportunity of reducing the cross-sectional thickness of the wall compared with prior art arrangements, since the mechanism utilises the compressive qualities of concrete.

Such a reduction in cross-section thickness results in reduced material usage and cost savings, handling and construction costs.

Modifications and improvements may be incorporated without departing from the scope of the invention.

Claims (28)

Claims

1. Enclosure walling comprising interconnected preformed building blocks having open-ended recesses in their outer faces, and tensioned bar or strip reinforcement extending around the walling within the recesses of adjacent blocks.

2. Walling according to claim 1 , wherein at least some of the blocks have two or more vertically-spaced recesses each containing bar or strip reinforcement.

3. Walling according to claim 2, wherein the blocks are arranged in side-by-side rows and the blocks forming the lowest row have two or more recesses.

4. Walling according to claim 1, 2 or 3, wherein bar or strip reinforcement is provided in the block recesses within the lowest 10% of the height of the walling.

5. Walling according to any one of the preceding claims, wherein the reinforcement comprises interconnected lengths of reinforcement material which are tensioned by screw connections between them.

6. Walling according to any one of the preceding claims, wherein the recesses containing the reinforcement are filled with weather-proof material.

7. Walling according to any one of the preceding claims, wherein the recesses are of rounded profile.

8. Walling according to any one of the preceding claims, wherein the blocks have complementary formations on opposed faces for interconnecting adjacent blocks.

9. Walling according to claim 8, wherein said formations are of rounded profile.

10. Walling according to any one of the preceding claims, wherein the blocks are arcuate.

11. Walling according to any one of the preceding claims, wherein nodes are provided at intervals along the base of the recesses, the reinforcement bearing against the nodes so as to be spaced from the recess base.

12. Walling according to any one of the preceding claims, wherein the blocks are of precast concrete.

1 3. Enclosure walling substantially as hereinbefore described with reference to and as shown in Fig. 6.

14. A method of forming enclosure walling, comprising interconnecting preformed building blocks having open-ended recesses in a face thereof so that the recesses of adjacent blocks around the walling communicate with one another in an outer face of the walling, placing bar or strip reinforcement within the communicating recesses and tensioning the reinforcement around the walling.

1 5. A method according to claim 14, wherein the reinforcement is provided by interconnecting bars or strips of reinforcement material which are then tensioned by tightening screw connections between them.

1 6. A method according to claim 14 or 15, wherein the recesses having the reinforcement along them are subsequently filled with weatherproof material.

17. A method according to claim 14, 15 or 16, wherein the reinforcement is placed in recesses within the lowest 10% of the walling height.

18. A method of forming enclosure walling, substantially as hereinbefore described with reference to and as shown in the accompanying drawings

1 9. A building block having a body, a first face of which has an open-ended recess for receiving bar or strip reinforcement, and complementary means on second and third faces of the block for interconnecting the block with adjacent such blocks.

20. A block according to claim 19, wherein the block is of precast concrete.

21. A block according to claim 19 or 20, wherein the interconnection means are a projection on the second face and a corresponding recess in the third face.

22. A block according to claim 21, wherein the projection and recess are of rounded profile.

23. A block according to any one of claims 19 to 22, wherein the open-ended recess in the first face includes spaced raised nodes along the base of the recess for bearing against said bar or strip reinforcement to space it from the base of the recess.

24. A block according to any one of claims 19 to 23, wherein a plurality of spaced parallel recesses are formed in the first face.

25. A block according to any one of claims 19 to 24, wherein a hole extends through the body, opening through fourth and fifth faces thereof, the hole tapering in cross-section.

26. A block according to claim 25, wherein the hole is of rounded cross-section.

27. A block according to any one of claims 19 to 26, wherein the second and third faces are disposed at an angle to one another.

28. A building block substantially as hereinbefore described with reference to and as shown in Figs. 1 to 3, or Fig. 4, or Fig. 5 of the accompanying drawings.