NZ545571A - Pre-stressed and post-stressed hollow block retaining wall construction - Google Patents

Abstract

To construct a wall a footing 2 is cast and threaded inserts 4 are placed into the footing. Hollow blocks 6 are laid to form the wall on top of the footing and vertical reinforcing rods 5 are inserted through the blocks and screwed into the inserts then the several rows of blocks are compressed by pre-tensioning the reinforcing. Concrete is poured into the spaces of the blocks and allowed to set. Moreover, some of the reinforcing is sleeved so that once the concrete is poured the reinforcing can be post-stressed to put the entire wall structure under compression.

Description

A 5 5 71 *10056732603* PATENTS FORM NO. 5 Fee No. 4: $250.00 . PATENTS ACT 1953 COMPLETE SPECIFICATION After Provisional No: 545571 15 Dated: 27 February 2006 ^ IMPROVEMENTS IN AND RELATING TO THE CONSTRUCTION OF STRUCTURES WE ITW NEW ZEALAND LIMITED, a New Zealand company of 23-29 Poland Road, Glenfield, Auckland, New Zealand hereby declare the invention for which We pray that a patent may be granted to 25 us, and the method by which it is to be performed to be particularly described in and by the following statement: -Intellectual Property— Office of N.Z. 19 MAR 2607 RECEIVED STATEMENT OF CORRESPONDING APPLICATIONS This application is based on the provisional specification filed in relation to New Zealand Patent Application Number 545571, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION The present invention relates to improvements in and relating to the construction of structures, in particular, but not exclusively to the construction of walls and retaining walls.

BACKGROUND ART KNOWN TO THE APPLICANT Many structures include walls. The function of most walls is to keep something in or to keep something out. At the very least a wall will function as a barrier. In addition, walls may be decorative through their design and/or serve additional purposes such as hiding matter such as conduits or wiring within them if they are, for example, an internal wall of a domestic dwelling or office block.

The design of a wall, or the individual building units such as bricks that go into its construction, is usually dependent upon its function. Prison walls for example, are high, thick and, if modern, heavily reinforced with steel. Apartment block external walls may be formed from bricks linked by mortar in an overlying staggered ^ arrangement for eye appeal.

Typical walls found adjacent the front or back of a house, or which may partially or completely surround a building used by the public, such as a hotel or museum, usually define the boundary of these structures. Usually, that is their sole purpose and, as such, they do not tend to require the design features or reinforcement associated with, for example, a retaining wall.

Retaining walls are walls that are built to resist lateral pressure usually on account of the advance of a mass of earth or fluid. These types of wall can be formed from smaller building blocks that can either be linked together by mortar, or if no mortar 232541/53 2 is used, each building block tends to possess some form of integral locking unit like a lip that will enable one row of blocks to lock up against a previous row.

The lateral pressure from the backfill pushing against the blocks will act to further lock the entire wall into place. Such walls may usually be seen on motorways 5 adjacent to hillsides or near railway tracks adjacent to steep hillsides Dams are huge structures that may be considered to be intricate forms of retaining walls and they are designed to be curved and thicker at their base to cope with the pressures of the water against them.

These types of retaining wall are large in comparison to retaining walls that may 10 be required adjacent smaller structures, such as houses or within domestic gardens or larger.landscaped expanses such as a botanic garden.

Such smaller retaining walls still usually need to be reinforced and this is usually through the use of a grid system of metal rods placed within hollow concrete building blocks that are used in the wall's construction, the hollows of which are 15 later filled with cement or concrete.

However, the building of all such retaining walls is a skilled job that is time consuming and usually such a wall has to be built "all in one go". It is an object of the present invention to provide a method of structure construction that tends to alleviate these aforementioned problems or at least provides the public with a /0 useful choice.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy 25 and pertinence of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country. 232541/53 3 It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the 5 listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

STATEMENT OF THE INVENTION According to a first aspect of the present invention there is provided a method of construction for building a structure comprising the steps of: providing a footing for a structure with means to enable a reinforcing material to be placed under a tensile stress; fitting one or more reinforcing materials to the means; forming a structure using a plurality of hollow and/or channelled building blocks so arranged as to accommodate said one or more reinforcing materials within the hollow and/or channel of two or more of these blocks; pre-stressing the structure by placing said one or more reinforcing material(s) 20 under tensile stress and, in so doing, placing at least a plurality of the building blocks under compressive stress; supplying the hollow and/or channelled blocks with a cementitious material; and allowing the material to set or cure whilst maintaining at least part of the structure in its pre-stressed state.

It will be appreciated by those skilled in the art that this process provides a solution to the problems outlined above because it is relatively simple to perform 232541/53 4 and once the structure has been made in the manner described above, it is again a relatively simple matter to build or add to the structure using the same method.

The building blocks may be of differing thicknesses (for example those intended for use towards the base of the structure may be thicker than those at the top of 5 the structure) or they could be of differing sizes, however, preferably the building blocks are generally of substantially uniform dimensions Pre-stressing the structure has the advantage that the structure is locked into its pre-stressed state once the cementitious material has "set". However, there is ^ nothing to prevent part of the structure to be pre-stressed in the manner described 10 and part to be post-stressed in a similar manner if the nature of the reinforcing material is chosen correctly.

For example one may envisage that one level of the structure could be pre-stressed and one level could be post-stressed. Alternatively, one level could be subject to both pre- and post- stressing. This could certainly be the case if the 15 structure were built in stages or capable of being added to. Furthermore, it enables the structure to be stressed to different amounts. One row could be stressed to amount "X", another row could be stressed to amount "Y", and X could be greater or lesser than Y.

Preferably therefore, the reinforcing materials may be selected from the group p) comprising those suitable for pre-stressing a structure or those suitable for post-stressing a structure.

For the avoidance of doubt, the term "structure" throughout this specification is intended to include partially completed structures as well as fully completed structures.

More preferably, the method further comprises the step of post-stressing the structure by placing one or more reinforcing materials suitable for post-stressing under tensile stress and in so doing, placing at least a plurality of the building blocks under compressive stress. 232541/53 Preferably, the method further comprises the step of supplying the structure so formed with means to enable a further reinforcing material to be joined to the structure and placed under a tensile stress, thus enabling an additional structure to be added to the structure already created in a similar manner. Such an 5 arrangement has the advantage that another structure may be added to the first structure or the completion of the original structure can take place and as such this additional structure can be pre- or post- tensioned as well.

Preferably, the means may be selected from the group comprising threaded inserts and threaded collars.

The structure as it is being formed may use some form of bonding mixture (for example mortar) to bond the building blocks together prior to any form of stressing or through the use of a cementitious material.

However preferably, the building blocks are fitted together"without the aid of a bonding mixture. This has the advantage that one step in the "normal" procedure 15 of structure construction can be removed and as the application of a bonding mixture is a relatively skilled job, its absence serves to de-skill the construction process thus making the process more available to the DIY end of the market.

In such an arrangement, the building blocks could be inter-engaged or simply sit and/or lie in a contiguous relationship. ^0 Although the structure could inter alia be a dome or curved dip forming part of a skate board park it could also be a roof, door or arch, however, preferably, the structure is a wall.

More preferably, the wall is a retaining wall.

According to a second aspect of the present invention there is provided apparatus 25 for the formation of a structure that is suitable for use with the method as specified herein comprising: a plurality of hollow and/or channelled building blocks; at least one reinforcing member and 232541/53 6 at least one threaded insert.

Preferably the apparatus forms part of a kit that may form part of a DIY package that will become commercially available.

The invention includes within its scope a structure, wall or retaining wall 5 substantially as herein described with reference to and/or as illustrated in figures 1- 5 of the accompanying drawings.

The invention aiso includes within its scope a structure or land selected from the group comprising stadium, domestic dwelling, office building, hotel, museum, art ^ gallery, domestic garden, botanic garden and a park incorporating within or 10 adjacent to it, a structure, wall or retaining wall as specified herein.

The invention again includes within its scope a method substantially as herein described with reference to and/or as illustrated in any appropriate selection _or combination of figures 1-5 of the accompanying drawings.

The invention yet further includes within its scope a structure, wall or retaining wall 15 formed from the method substantially as herein described with reference to and/or as illustrated in any appropriate selection or combination of figures 1 - 5 of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Further aspects of the present invention will become apparent from the ensuing 20 description which is given by way of example only and with reference to the accompanying drawings in which: Figure 1 illustrates a sectional view from the side of a completed structure in the form of a retaining wall encompassing one embodiment of the present invention.

Figure 2 illustrates a rear view of the embodiment illustrated in figure 1; Figure 3 illustrates a top view of the embodiment illustrated in figures 1 & 2; 232541/53 7 Figure 4 illustrates a top view of a hollow building block typical of the type used to form the wall illustrated in figures 1-3, and Figure 5 illustrates a wall formed using a further preferred embodiment of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION Figure 1 shows a side sectional view of a structure in the form of a completed concrete vertical retaining wall and is generally referenced 1. The structure 1 ^ comprises an elongate horizontal concrete footing 2 having proximal and distal ends. The footing 2 has been reinforced by a plurality of spaced apart straight 10 steel reinforcing bars 3 the majority of which lie in substantially the same plane and are each substantially parallel with the length of the wall 6.

— In cross section, the thickness of the footing 2 is substantially uniform except for a thicker downwardly depending portion 2A provided with its own steel reinforcing bar 3 parallel with the others. This downwardly depending portion 2A is inset a 15 short distance from the proximal end of the footing 2 and travels downwards for a similar distance.

The wall 6 overlies the downwardly depending portion of the footing 2. 0 Inset within the footing 2 substantially midway along the width of the downwardly depending portion of the footing 2 are a plurality of linearly spaced apart steel 20 threaded inserts 4 that run substantially the length of the footing 2. The tops of each respective insert 4 being substantially flush with the top surface of the footing 2.

The procedures for applying the inserts 4 and for ensuring that the footing 2 is level for the application of a first layer of building blocks 9 is known to the person 25 skilled in the art, 232541/53 iciiesuiuai pro Office of N„ 2 6 NOV 2007 [JIecei vedi A line of hollow building blocks 6 in the form of concrete 'knock out bond beam blocks' 9 are then placed in a contiguous row along the footing 2 in such a manner that the hollow portion of each block 9 overlies each of the inserts 4. Once this has been done, a number of steel reinforcing bars 7 are horizontally placed within 5 the hollow 10 (best seen in Figure 4) so as to span the length of the first row of the wall 6 generated thus far.

Of course depending upon the type of knock out bond beam block 9 used some aspects of the block 9 may need to be removed for this to occur. No bonding material in the form of mortar is used to bond the first row to the footing 2.

Once this has happened, a second row of blocks 9 is simply placed on top of the first row in a similar and completely overlying but staggered arrangement (like the bricks in a brick wall) the arrangement of the second row also being such that a ho[low 10 of a block 9 again overlies each of the inserts 4. No reinforcing bar 7 is placed in this second row of the wall 6 and no bonding material in the form of 15 mortar is used to secure the second row to the first.

A third row of blocks 9 spatially arranged in a manner similar to the first row is then added and reinforced with a bar 7. A fourth row of blocks, spatially arranged in a manner similar to the second row is then added. As with the second row no reinforcing bar 7 is placed in this row. Finally, a fifth row of blocks 9 reinforced with bars 7 in the same pattern as the first and third rows is added.

At this point, a number of screw threaded steel reinforcing bars 5 equal to the number of inserts 4 are vertically inserted within the height of the wall 6 through the hollows 10 and one end of each bar 5 is screwed into one of the complementary threaded inserts 4. The length of these bars 5 should be sufficient 25 to ensure that the opposite end to the threaded insert 4 extends to just beyond the height of the wall 6 generated thus far.

An apertured steel plate (not shown) is then slotted over an exposed end of one of the vertical reinforcing bars 5, the dimensions of the plate being such that it overlies the width (but not the length) of the block(s) 9 it is adjacent to. This 30 process is repeated using another similar steel plate until each bar 5 has received 232541/53 0 a plate. Each of the bars 5 is then fitted with a nut (not shown) and the nuts are tightened pre-stressing (or pre-tensioning) the wall 6 formed thus far, preferably to 1.5 tonnes.

A cementitious slurry of material 11 (see Figure 3) is then directed into the hollows 5 10 of the wall 6 formed thus far. The overlying nature of the hollows 10 means that all of the internal cavities of the blocks 9 used to construct the wall 6 can be filled with the cementitious material. Once all of the hollows 10 have been filled and the cementitious slurry 11 is substantially flush with the top of the wall 6 constructed thus far, the material 11 in the wall 6 is allowed to set (usually over the course of seven days) whilst keeping the wall 6 under stress or tension.

After the cementitious material 11 has set, the nuts and plates are removed and screw threaded sleeves (not shown) are fitted to the exposed ends of the . reinforcing_bars 5. The.hei.ght of the wall 6 can now be increased in a manner similar to that just described using appropriately sized bars 5.

To "finish" the wall 6, a top row of blocks 9 need only be applied and, apart from the respective ends, the middle portions of each block 9 can be knocked out (for aesthetics) and the remaining large hollow 10 filled with the same cementitious material 11. As before the concrete so formed after seven days of curing will "bind" around the once exposed ends of the reinforcing bars 5 physically linking 20 the top row to the rest of the wall 6. The ends can be finished with additional bricks suited for such purpose in the manner known to those skilled in the art.

In another embodiment not illustrated, the reinforcing members 5 could be sleeved in some form (e.g. in plastic) to enable post-tensioning (as opposed to pre-tensioning) to take place after filling with concrete but before the concrete is 25 bound to the reinforcing bars.

On the other hand, there could be a mixture of sleeved and un-sleeved reinforcing members (possibly alternate) along the length of the wall to enable some pre- and some post-tensioning of the structure 1 to take place.

Alternatively, the first part of the structure (in this case the first five rows) could be 30 set up for post-tensioning or a mixture of post- and pre-tensioning whilst the next 232541/53 part of the structure (another five rows) could be set up for pre- or post-tension only.

In yet a further embodiment, the wall 6 could be virtually complete after five rows, requiring only a top or "capping" row of blocks 9. Although a straight structure 1 in 5 the form of a retaining wall has been described, it will be appreciated that depending on the shape of the footing 2 and the blocks 9 curved structures can also be formed using this method.

The method of forming the wall 6 could be carried out by first fitting the reinforcing bars 5 to the inserts 4. If such a change in the method were carried out, other 10 structures could be formed as the bars 5 could, either before or after being fitted to the inserts 4, be bent or curved to assist in the formation of a curved or bent structure or wall, the blocks 9 (or the like) being threaded around the bars 5 during - construction.

The nature/shape of the blocks 9 may need to alter to cope with the pre- or post-15 stressing that may need to take place but such redesign and materials can be selected without further inventive thought by the skilled addressee of this specification and as such need not be discussed further here.

A brief description of another embodiment of the present invention will now be ^ described with reference to Figure 5. Referring to Figure 5, vertical starter bars 17 20 are screwed into the base of inserts 13 set into the footing 14 in every second core. Laminated veneer lumbar (LVL boxing, not shown) is levelled and aligned over the footing 14 to ensure the blocks are laid level and in the desired alignment.

Once all the footing 14 is placed and the LVL boxing (not shown) is levelled and 25 aligned, the footing 14 is filled with 17.5mpa concrete. Horizontal bar 15 is set into the footing as it is being poured. Inserts 13 are puddled into the wet concrete using nail plates attached to "puddle in boards" (not shown). When the concrete has set the "puddle in boards" (not shown) are removed leaving the nail plates (not shown) exposed. The nail plates (not shown) are removed and vertical bars 30 16 inserted, torqued and levelled. 232541/53 -|-| Office of n.z. 26 NOV 2007 _E C EI V F n The vertical bars 16 are pre-cut on site to a length that extends 100mm above the anticipated height of the first set of five rows of blocks to allow for the pre-tensioning packer, washer and nut (not shown). A maximum of five courses of blocks are laid with horizontal steel laid and joined with couplers to an engineer's 5 specification, generally at each three courses.

Any level imperfections are corrected using shims 18 that have been cut in half or quarters. Further courses can then be added to the wall 6 in like manner using threaded couplers19 to join additional vertical bar 16 to that already in situ. Once ^ the desired number of courses is laid, the vertical bar 16 reinforcing is screwed 10 and torqued in the manner previously discussed with respect to the embodiment depicted in Figures 1-4.

Specifically, torque nuts (not shown) on metal or wooden plates plus 50mm washers (not shown) are used to tension the vertical reinforcing wall 6 to 1.5 tonnes (100 Newton Metres) with a torque gauge (not shown) seven days after 15 pouring the concrete. The final course is simply laid and filled with concrete and capping blocks 20 glued with Epoxy/Acrylic adhesive if required.

A plastic "horseshoe" (not shown) has also been designed to take up the effect of the 10mm allowance for mortar in the block design when a half block is required for finishing.

» Advantages of the system over conventional masonry wall construction include: • Significant savings in the laying of the blocks in time and materials.

• Pre-tensioned steel has significant advantages over static steel, pre-tensioned steel is already "working". In fact calculations have shown that the pre-tensioned but unfilled wall satisfies retaining wall strength requirements.

• The wail can be built progressively with no loss of reinforcing steel strength integrity.

Intellectual Prooertv Office of N.Z 26 NOV 2007 Received The LVL boxing is re-useable. 232541/53 12 The wall can be built by the amateur builder easily and accurately.

If required or desirable, pillasters can be built into the wall.

For special architectural effects splitstone blocks and/or pre-coloured blocks can be used.

If there is a collapse of the retained material it is very easy to unscrew the Starter Bars, unscrew the horizontal reinforcing steel, dismantle the blocks and clean up the problem.

If pre-tensioned pilasters are used and connected to the wall using back to back threaded inserts every three courses, a significant strength advantage is added to the wall.

By not using mortar, the walj cavities are completely clean for filling with 20 MPa grout.

Aspects of the present invention have been described by way of example only and it should be appreciated by those skilled in the art that modifications and additions 15 may be made thereto without departing from the scope thereof as defined in the appended claims. 232541/53 13 ** — Intellectual Property Office of N.Z. 26 NOV 2007 ,R_ECEI VE Di

Claims (11)

WHAT l/WE CLAIM IS:
1. A method of construction for building a structure comprising the steps of: providing a footing for a structure with means to enable a reinforcing material to be placed under a tensile stress; fitting one or more reinforcing materials to the means; forming a structure using a plurality of hollow and/or channelled building blocks so arranged as to accommodate said one or more reinforcing materials within the hollow and/or channel of two or more of these blocks; pre-stressing the structure by placing said one or more reinforcing material(s) under tensile stress and, in so doing, placing at least a plurality of the building blocks under compressive stress; supplying the hollow and/or channelled blocks with a cementitious material; allowing the material to set or cure whilst maintaining at least part of the structure in its prestressed state and; post-stressing the structure by placing one or more reinforcing materials suitable for post-stressing under tensile stress and in so doing, placing at least a plurality of the building blocks under compressive stress.
2. A method according to claim 1, wherein the building blocks are generally of substantially uniform dimensions.
3. A method according to claim 1, wherein the reinforcing materials are selected from the group comprising those suitable for pre-stressing a structure and those suitable for post-stressing a structure.
4. A method according to claim 1, wherein the method further comprises the step of: /53 14 Intellectual Property Office of N.Z. 26 NOV 2007 RECEIVEE • supplying the structure so formed with means to enable a further reinforcing material to be joined to the structure and placed under a tensile stress, thus enabling an additional structure to be added to the structure already created in a similar manner.
5. 5. A method according to claim 4, wherein the means is selected from the group comprising: threaded inserts; threaded collars.
6. 6. A method according to anyone of claims 1 to 5 wherein the building blocks are fitted together without the aid of a bonding substance.
7. 7. A method according to any one of claims 1 to 5 wherein the building blocks are fitted together with the aid of a bonding substance.
8. 8. A method according to anyone of claims 1 to 7 wherein the structure is selected from the group comprising a: dome; curved dip; roof; door; arch; dam, wall; retaining wa|l; stadium; domestic dwelling; office building; public building.
9. 9. A method according to claim 8, wherein the structure is a retaining wall.
10. 10. A kitset suitable for use in accordance with a method of construction for building a structure as claimed in claims 1 to 9, said kitset including: at least two hollow and/or channelled building blocks for forming said structure; at least one threaded reinforcing member for placing in said structure, and at least one threaded insert for threading on said reinforcing member wherein the said threaded reinforcing member and threaded insert are suitable for post-stressing said structure under tensile stress.
11. 11. A method of construction for building a structure substantially as herein described and illustrated with reference to any one of the accompanying drawings 1 to 5. IINTELLECTUAL PROPERTY OFFICE OF N.Z - 9 l-fctf 232541/53 15 RECEIVED ITW New Zealand Ltd by its authorised agents James & Wells Intellectual Property 232541/53 16 INTELLECTUAL PROPERTY OFFICE OF N.Z. - 9 FEB 2009 RECEIVED