GB2270535A - Methods of reinforcing walls - Google Patents

Abstract

A method of reinforcing a wall including the step of raking out a bed joint 20 and grouting a flat bar 13 preferably of deformed or apertured austenitic steel into the joint 20 to form a reinforced beam. A similar step is then be repeated at a lower point in the wall or where the wall is a double skin wall an aperture is made below the beam formed, to permit access to the inner skin 12 of the wall so that a flat reinforcing bar may be similarly incorporated into the inner skin. A reinforced concrete beam may alternatively be formed in the apertured so formed, and a damp proof course or cavity tray may be incorporated into the wall. A variety of bars and reinforcing arrangements suitable for use in any of the methods is described. <IMAGE>

Description

METHODS OF REINFORCING WALLS AND REINFORCEMENT FOR USE IN SUCH METHODS This invention relates to methods of reinforcing walls such as solid or cavity walls of brick, masonry or concrete and to reinforcement means suitable for use in such methods.

Buildings may suffer from a variety of structural failures both above and below ground level, for example lintel failure, subsidence, thermal movement, differential movement and design faults. Since underpinning and partial rebuilding are both very expensive solutions to such problems, there is a need for less radical but nonetheless effective ways of preventing or remedying structural failures.

There have been a number of proposals for repairing walls which involve raking out a bed joint in a wall, inserting a reinforcing steel rod or the like and regrouting and repointing the wall. Such methods are normally limited to the reinforcement of solid walls or the outer skins of cavity walls, and involve reinforcing the wall at a single level only.

According to a first aspect of the invention there is provided a method of reinforcing and/or repairing a wall which comprises the steps of: raking out a bed joint in the wall; inserting a reinforcing bar in the joint and regrouting the joint to link a plurality of bricks or blocks to form a reinforced masonry beam resistant to vertical loads; and repeating the above steps at a lower point in the wall.

According to this first aspect of to the present invention there is also provided a method of reinforcing and/or repairing a cavity wall having inner and outer skins, which comprises the steps of: raking out a bed joint in the outer skin; inserting a reinforcing bar in the joint and regrouting the joint to link a plurality of bricks or blocks and form a beam resistant to vertical loads; forming an aperture below the beam thus formed to gain access to the inner skin; similarly inserting a reinforcing bar into a raked out bed joint of the inner skin, and filling in the said aperture.

When the inner skin has been reinforced and its bed joint regrouted, the aperture below the beam originally formed can be closed off and the outer skin repointed so as to leave almost no visible sign of a repair.

Using the above method relating to a cavity wall, the bar or bars inserted into the outer skin can allow apertures up to 4 metres in length to be formed below the beam for access to the inner skin. In the vent of an aperture of over 4 metres being required, additional support systems such as temporary jacks may be used. The method can be easily adapted to be applied to any configuration of double skin wall.

The method may also include the step of forming a reinforced support (such as a reinforced concrete support) in the aperture formed below the beam. The support may extend into the inner skin so as to support both skins of the wall. The reinforced concrete support may extend entirely round a walled structure to form a ring beam.

According to a second aspect of the invention there is provided a reinforcing bar which is particularly suitable for use in the above method. The bars are of flat cross section, and can thus be inserted into narrower joints than the round bars previously used and also enable the bed joint to be adequately reinforced by means of a single bar. The flat form of the bar will facilitate the even distribution of grout or other fixing material around the bar allow it to be positioned centrally within the joint and provide a bar having a higher surface area to volume ratio than round reinforcing bars customarily used in building construction. The reinforcing bars are preferably made from a metal such as steel, typically deformed austenitic stainless steel. High tensile plastic such as polyethylene may also be used.The width of the bar is preferably at least four times the thickness of the bar so as to provide a large enough surface area to volume ratio.

The bars may be machined and or provided with some form of surface roughening treatment in order to increase adhesion between the grout and the bar. Surface roughening includes blasting with granular material such as sand.

Machining may include deforming parts of the bar out of its substantially flat form eg by forming dimples therein or may involve forming the bar with a slight undulating form along its length. The machining may alternatively include through apertures in the form of circular or elongate holes. Such apertures provide a convenient means by which one bar may be joined to another to form a lap joint, by passing fixing bolts through a pair of overlapping bars.

Bars may however be joined by riveting or welding.

Alternatively or in addition to providing apertures in the bar, the edges of the bar may be notched. In order improve stress distribution in a bar when in use such notches are preferably longitudinally offset from through apertures in bars.

The second aspect of the invention also extends to a method of reinforcing and/or repairing a wall using one or more bars having a flat cross section and optionally have the other characteristics of the bars described above.

The method comprises the steps of raking out a bed joint in a wall, inserting a flat reinforcing bar into the joint and regrouting the joint to link a plurality of bricks or blocks and form a reinforced masonry beam resistant to vertical loads.

According to a third aspect of the invention there is provided a reinforcing arrangement comprising a reinforcing bar connected to one or more supplementary reinforcing members at least one of which is positioned substantially perpendicularly to the reinforcing bar and others of which may be positioned substantially parallel .~ and spaced from the reinforcing bar. The reinforcing bar and some of the supplementary reinforcing members may advantageously be of the type described above. Such a reinforcing arrangement may furthermore advantageously be used in one of the methods discussed above in order to link one bed joint in a wall with adjacent vertical joints.

Where one of the supplementary reinforcing members is substantially parallel and spaced from the reinforcing bar the reinforcing arrangement may be used to link two vertically spaced (normally adjacent) bed joints.

The reinforcing bars and reinforcing arrangements discussed above provide a particularly efficient transfer of load between the structure of the wall and the reinforcement used. In particular flat bars suitably dimensioned to fit in a bed joint as discussed above may be designed to have a specific surface (surface per unit volume) up to 50% greater than round section bars having an equivalent cross sectional area. The efficiency of the bond is increased still further when the bars are deformed, apertured, notched or surface roughened.

Preferred embodiments of the intention will now be described with references to the accompanying drawings wherein: Figure 1 shows in cross section a part of a cavity wall to which the method according to the first aspect of the invention is being applied; Figure 2 is a perspective view of part of a cavity wall reinforced by means of the methods according to the invention; Figure 3 is a cross sectional view through the cavity wall of Figure 2; Figure 3a shows a cross sectional view through a cavity wall reinforced by means of the method according to the second aspect of the invention showing how a damp proof membrane or damp proof course can be inserted as part of the method; Figure 4 is a perspective view of one type of reinforcing bar in accordance with the second aspect of the invention which may be used in the inventive repair methods;; Figure 4a is a perspective view of a further bar in accordance with the second aspect of the invention which may be used in the inventive repair methods; Figure 5 is an edged view, partly in cross section, of part of a bar in accordance with the second aspect of the invention which may be used in the inventive repair methods; Figure 6 is a perspective view of part of the bar of Figure 5.

Figures 7 to 11 show further reinforcing bars in accordance with the second aspect of the invention which may be used in the inventive repair methods; Figure 12 is a vertical cross section through a wall in a region where two overlapping reinforcing bars are joined together; Figure 13 is a perspective view showing how two bars may be joined end to end; Figure 14 is a perspective view showing how two bars may be joined at a corner of a building; Figures 15 to 17 show various forms of reinforcing arrangement in accordance with the third aspect of the invention which may be used in the inventive repair methods; Figures 18 to 20 are three vertical cross-sections through cavity walls which have been reinforced by the method according to the first aspect of the invention in which an extra reinforcing support has been incorporated into the wall;; Figures 21 and 22 are vertical cross-sections through cavity walls which have been reinforced by the method according to the second aspect of the invention in which extra reinforcing support has been incorporated into the wall.

Referring to Figure 1, a cavity wall comprises an outer skin 10 of bricks and inner skin 12 of breeze blocks or the like, with a cavity 19 between them.

To reinforce the wall in accordance with the first aspect of the invention, a bed joint 11 between two courses of bricks is first raked out to a predetermined depth, typically 5 to 8cm in the case of standard size bricks.

A reinforcing bar 13, which may be a substantially flat bar of crimped austenitic stainless steel having a width of 1 to 10cm and a thickness of 1 to 10mm, typically having a rectangular cross section of 25 x 3mm, is inserted centrally into the gap formed by raking out the bed joint, preferably after insertion of some new grout. With the reinforcing bar in position, the bed joint is regrouted, preferably with an expanding cementitious grout.

Alternatively, a resinous grout such as an epoxy resin can be used.

The insertion of the reinforcing bar 13 binds the courses of bricks above and below it into a beam of high rigidity capable of withstanding of considerable vertical loads and the resulting stresses. A course of bricks below the reinforcement can thus be removed, leaving a longitudinal gap 15 which may be 4 metres or greater in length although it may be desirable to leave one or two bricks of this course in position or insert jacks depending on the length of gap needed to carry out the next stage of the process.

Through the gap 15 a bed joint 16 of the inner skin can be raked out in the same way as in the outer skin.

Another reinforcing bar 24 is then inserted into the gap 18 thus formed, and this gap also can then be regrouted. The aperture 15 can then be closed off, to leave a substantially invisible repair.

Referring to Figure 2 a typical repair pattern is illustrated. Two reinforcements are incorporated into each of the inner and outer skins 10, 12. First, a reinforcement 20 is inserted as described in connection with Figure 1, below an upper course of bricks 25. This reinforcement could well extend over the whole length of wall shown in Figure 2, or indeed over a greater length.

With the reinforcement 20 in position, bricks can be removed below it to give access to the inner skin, for the purpose of inserting reinforcements 24, 26. In the course of closing of the outer skin, a further reinforcement 22, can be inserted. The reinforcements 20, 22 form between them a very substantial and rigid beam, which has considerable resistance to vertical stresses, and thus greatly strengthens the wall against subsidence and the like. The inner skin 12 is similarly strengthened, without the need for any opening up on the inside of the building, and when the outer skin has been repointed there need be no external sign of any repair having been carried out at all. The repair shown in Figure 2 is shown to an enlarged scale, and in more detail, in Figure 3.

It should be noted that the method according to the first aspect of the invention may also be applied to a single skin wall. The result would be a wall such as the outer skin 10 only, reinforced as shown in Figure 3.

Figure 3a shows how a damp proof membrane 30, suitably of plastics or metal, can be inserted below one of the lower courses of bricks in the outer skin. The membrane shown is in the form of a longitudinally folded strip of which one half forms a membrane between two courses of bricks in the outer skin 10 while the other half forms a cavity tray 32.

The invention thus provides a simple method for reinforcing cavity walls involving no disturbance to the interior of the building or its occupants, which can be carried out by removing only a minimum of the existing structure and following which only a minimum of making good is required to render the repair invisible.

Figure 4 shows a bar 40 according to a second aspect of the invention which has been machined or otherwise formed with a pattern of grooves extending transversely of the bar on either of its sides. Figure 4a shows an alternative bar 40a to which short rods 40b have been welded so as to extend substantially perpendicularly therefrom. Such bars have been found useful in the process according to the first aspect of the inventions. The configuration of the bars increases the bond between the grout and the bar.

An alternative configuration for the reinforcing bars is that shown in Figures 5 and 6. This bar is also made of austenitic stainless steel, and is crimped in alternating directions at intervals of 2 to 4cm, so that each side of the bar has alternating humps and recesses formed centrally along the length of the bar. The upper side of the bar so as shown in Figures 5 and 6 has alternating humps 52 and recesses 54.

The crimping again imparts greater rigidity and enables the bars to be held more firmly by the expanding cementitious grout and also allows the interlocking of overlapped ends of adjacent bars to form a continuous reinforcement.

Figures 7 to 11 show a variety of alternative reinforcing bars 60 to 64 according to the second aspect of the invention, which can advantageously be in the method according to the first aspect of the invention. Each bar has regularly spaced through holes 70 to 76. The function of the holes is to allow easy joining of the bars by means of appropriate fasteners such as bolts, rivets or studs and also to provide a good bond between the bar and grout or similar material used to fix the bar in the bed joint of a wall. Bars 60 to 63 shown in Figures 7 to 10 respectively have regularly spaced edge notches. The purpose of these notches is to control the distribution of stress in the bar when the bar has been incorporated in a wall using the method described above. Stress concentrations will occur where grout (or similar material) passes through a hole or notch in the bar.All of the bars shown in Figures 7 to 11 have a width 77 of 25mm and a thickness of 3mm.

The bar 64 shown in Figure 11 has been found to be of a particularly advantageous design. The spacing of holes provides particularly adaptable joining means. The holes 75 and 76 etc... occupy approximately 13% of the area of the bar. This provides an optimum transfer of load between the bar 64 and the grout (or similar material) for a bar having the dimension as described above.

The bars 60 to 64 are all made of austenitic steel so as to reduce adverse reaction with the wall into which they are incorporated. The surfaces of the bar are cold worked in order to increase the strength of the bar and roughen the surface to improve the bond between the bar and the material used to fix the bar.

Straight and angled joins between the reinforcing bars of the general type shown in Figures 7 to 11 may be affected as shown in Figures 12, 13 and 14. A straight joining bar 84 or an angle joining bar 86 both of which include regularly spaced taped holes 92, may be bolted to straight reinforcing bars 88 in overlapping relationship.

Fixing bolts 82 are passed through aligned holes to fix the straight reinforcing bars 88 to the joining bars. A selection of joining bars 84 and 86 will be provided with different hole spacings in order to provide adjustability in the way in which the straight reinforcing bars are joined. Where such a joint is formed it will be necessary to form an enlarged portion 80 in the raked out joint as shown in Figure 12.

Reinforcing arrangements 94 to 96 according to the third aspect of the invention which are suitable for use in the method according to the first aspect of the invention are shown in Figures 15 to 17 respectively. All of these arrangements permit a reinforcing bar to be securely linked to portions of a wall above or below a joint in which the bar is located.

In the reinforcing arrangement shown in Figure ;5, supplementary angled members 99 are bolted to a straight reinforcing member 100 with bolts 97. The advantage of such an arrangement is that legs 98 of the angled members which project outwardly from the reinforcing member 100 may be grouted into raked out vertical joints between bricks or into vertical slots cut into a wall.

In the reinforcing arrangement shown in Figure 16 two reinforcing bars 102 and 104 are vertically separated by the distance between two adjacent bed joints in a wall and joined at regular intervals by supplementary reinforcing members in the form of vertical rods 105 (only one shown). Nuts 106 located on either side of each reinforcing bar hold the arrangement rigid. As in the embodiment shown in Figure 15 the rods 105 may be grouted into raked out vertical joints between bricks or blocks or into vertical slots cut into the wall. When the arrangement 95 has been grouted into a wall with the bars 102 and 104 located in vertically adjacent bed joints and rods 105 located in vertical joint or slots, a rigid beam will be formed, which is capable of supporting a very high vertical load.Where the reinforcing arrangement is incorporated into a double skin wall a third reinforcing bar 102a may be connected to the reinforcing bar 102 by means of adjoining member 105a. When each bar 102 and 102a are incorporated into outer and inner skins of a double skin wall, lateral as well as vertical support of the wall skins will be provided.

Figure 17 shows four examples of supplementary reinforcing members which can be connected to a reinforcing bar 96. The supplementary reinforcing member may be in the form of a sinuous hanger 110 engageable in a hole 114 in the reinforcing bar 112 and able to depend therefrom. The hangers may be grouted into vertical joints between bricks or blocks or into vertical slots cut into the wall. Tbis will connect the reinforcing bar 96 to its underlying course of bricks or blocks more securely. Three other examples of supplementary reinforcing members 110a, 110b, 110c, are also shown in Figure 17. Member 110a will be bolted to the bar 96 and comprises a C shaped body. From the back of the body, projections 110d are provided which can be grouted into joints between facing bricks attached to the outer surface of a wall being repaired.Member 110h includes a hooked bar for engagement with the bar 96 and a plate connected perpendicularly to a lower end of the bar.

The plate can act to support an item located below the courses of bricks or blocks being reinforced. Finally member 110c comprises an open loop reinforcing bar which may depend from the bar 96 and be grouted into a vertical joint or slot in the same way as the legs 98 of the angled members 99.

Figures 18 to 20 show three ways in which a cavity wall strengthened by the method according to the first aspect of the invention (described with reference to Figures 1 to 3) may be further strengthened by the incorporation of a reinforcing support member 120, 122 or 124 into the wall. The incorporation of these support members is a relatively straight forward task when included in the reinforcing method described above. In each case the reinforcing member will be formed below the reinforcing bars 125 to 130 once they have been securely grouted in place. By reinforcing a wall in discrete 3m to 4m sections and subsequently joining adjacent reinforcing members a complete ring beam extending around a structure may be formed.

In the embodiments shown in Figures 18 and 20 the reinforcing member is constituted by a concrete body 132, 133 accommodating steel reinforcing bars 134, 135 respectively. The reinforcing member is cast in the customary manner. The reinforcing member may support only one skin of the wall as shown in solid lines in Figure 18 or may extend across and support both skins as shown in Figure 20 and in broken lines in Figure 18. Any space 136 between the skins and below the reinforcing member 124, as shown in Figure 20, is preferably filled with concrete before the reinforcing support member is formed. This will obviate the necessity of providing a soffit shutter for the casting of the reinforcing member 120 or 124.

Figure 19 shows an alternative form of reinforcing member 122. Horizontal reinforcing bars 138 link reinforcing bars 128 and 146 in the inner skin 150 with reinforcing bars 139 and 148 in the outer skin, by bolts or any other suitable means. A shaped member 140 which is positioned in the gap between the skins is bolted with vertically disposed bolts (not shown) to the horizontal reinforcing members 138. An expanded polystyrene layer 142 is located between the shaped member 140 and the inner skin 150. The gap between the shaped member 140 and the outer skin 152 is filled with grout, preferably by injecting grout after the outer skin 152 has been bricked up.

Figures 18 and 20 show ground beams accommodating reinforcement. These beams may in turn be supported by piles or pads.

In Figures 21 and 22 like numerals are used to designate like parts,these figures show walls having a inner skin 200 and an outer skin 202 into which a flat reinforcing bar 208 has been grouted. Below the reinforcing bar in each case a reinforced concrete support beam 204 has been formed which is connected by rods 212 to adjacent floor joists 210. A layer of expanded polystyrene 206 is incorporated next to each support beam 204. Facing bricks 214 are used to cover the aperture in which the beam is formed so as to obscure the fact that any remedial work has taken place. Above or below the support beam a cavity tray 207 may be incorporated into the wall.

Claims (20)

1. A method of reinforcing and/or repairing a wall which comprises the steps of: raking out a bed joint in the wall; inserting a reinforcing bar in the joint and regrouting the joint to link a plurality of bricks or blocks to form a reinforced masonry beam resistant to vertical loads; and repeating the above steps at a lower point in the wall.

2. A method of reinforcing and/or repairing a cavity wall having inner and outer skins, which comprises the steps of: raking out a bed joint in the outer skin; inserting a reinforcing bar in the joint and regrouting the joint to link a plurality of bricks or blocks to form a beam resistant to vertical loads; forming an aperture below the beam thus formed to gain access to the inner skin; similarly inserting a reinforcing bar into a raked out bed joint of the inner skin, and filling in the said aperture

3. A method according to claim 1 or claim 2 wherein the reinforcing bars are of flat cross section.

4. A method according to claim 3 wherein the width of each bar is at least 4 times its thickness.

5. A method according to claim 3 or claim 4 wherein the reinforcing bars are of rectangular cross section having a width of 1 to 10cm and a thickness of 1 to 10mm.

6. A method according to any preceding claim wherein the reinforcing bars are made of stainless steel.

7. A method according to claim 6 wherein the reinforcing bars are made of austenitic stainless steel deformed by crimping at intervals along the length of each bar, to form alternating humps and recesses along each major side of the bar.

8. A method according to claim 7 wherein two said bars are linked in an overlapping end to end formation, at least one said hump on one bar being received in a corresponding recess of the other bar.

9. A method according to any one of claims 1 to 5 wherein the reinforcing bars are made of plastics material.

10. A method according to any preceding claim wherein the reinforcing bars are embedded in an expanding cementitious grout.

11. A method according to any preceding claim wherein a damp proof membrane is installed in the wall below the beam formed by insertion of the first said reinforcing bar.

12. A method according to any preceding claim wherein the reinforcing bars are deformed or apertured.

13. A method according to claim 10 wherein the apertures represent between 10 and 40% of the horizontal cross sectional area of the bars.

14. A method according to claim 12 or claim 13 wherein the reinforcing bars have notched edges.

15. A method according to any preceding claim wherein at least one reinforcing bar is part of a reinforcing arrangement including supplementary reinforcing members extending substantially perpendicularly to the said reinforcing bar.

16. A method according to claim 13 wherein the reinforcing arrangement includes two interconnected substantially parallel reinforcing bars spaced apart so as to be insertable into vertically spaced bed joints in a skin of the wall.

17. A method according to any preceding claim further comprising the step of incorporating an additional reinforcing support member which extends across one or both of the skins of the wall below reinforcing bar or bars in the inner and outer skins.

18. A method according to claim 17 wherein the additional support member is made of reinforced concrete.

19. A method according to claim 17 or claim 18 wherein the additional support member extends round an entire structure so as to form a ring beam.

20. A method of reinforcing an/or repairing a cavity wall, substantially as herein described with reference to the accompanying drawings.

21 A reinforcing bar or reinforcing arrangement substantially as hereinbefore described with reference to the accompanying drawings.