GB2158484A - Stool - Google Patents

Abstract

A stool,which is positioned in an opening (24) in a wall so as to temporarily support an upper part (26) of the wall whilst a beam (33) is cast in the opening (24), has a column (1) which is positioned outside the plane of, whilst substantially abutting the face of, the wall, and an upper support (4) and lower support (3), both of which are mounted on the column (1) to project into the opening (24) to abut against the upper part (26) and a lower part (25), respectively of the wall. The upper support (4) may be located at a number of positions along the length of the column (1) by varying into which of a pair of apertures (2) a pin (5) is inserted. A bar (7) mounted on stirrup arms (8) projecting upwards and backwards from the rear of the upper support (4) extends across the back face of the column (1) to provide the reaction force which prevents tilting of the upper support (4). <IMAGE>

Description

SPECIFICATION Stool Awell known technique of ours, when stabilizing a building orforming a lintel in a building, involves inserting a concrete beam in the wall ofthe building parallel to the plane ofthe wall. The beam may eventually redistribute the load above the beam onto newfoundations, or, in the case of a lintel, the existing wall between the central portion ofthe beam is subsequently cut away to form an opening. Such a beam (hereinafter referred to as ofthe kind described) is constructed by cutting away the wall and inserting stools at horizontally spaced positions. The stools are built in to supporttemporarilythe wall above. With the intervening wall between the stools cut away, reinforcing rods are inserted, formwork is erected, and an in situ concrete beam is cast incorporating the reinforcement.

Conventional stools for this purpose are positioned wholly between the inner and outerfaces ofthe wall, and are hollow so thatthe reinforcement extends through the stools. The stools arethen wholly embedded within the subsequently cast concrete beam and are sacrificed. This loss of a number of stools within each beam contributes appreciably to the overall cost ofthe beam.

More recently, recoverable stools, consisting essentially of upper and lowerflanges extending from one side of a vertical column, which is used offsetfrom the plane ofthewall, have been used. For example, our GB-A-1 599890 discloses two versions of this type of stool.Thefirstversion hasthevertical column touching, whilst being outside, the plane ofthewall, and the stool incorporates a short screwjack mounted on the top of the upper flange, so as to be extendible, after loose insertion of the stool flanges into thewall, to develop the load bearing reaction between the stool and the wall above. However,the stroke of the jack is too shortforthe stool tobe used when more or less than a certain number of brickwork courses are to be cut away.In that event a stool of a different size has to be used. A contractor therefore has to purchase and store stools of different sizes in readinessfordifferent work. The second version hasanabutmentsupport, via which the upper flange is mounted on the column.

The abutment support can be slid up and down the column and pegged art a number of positions, thus providing the large scale vertical adjustment which enables one second version stool to coverthe same range as requires several first version stools. The second version stool also has a shortscrewjackthat moves the upperfiangevertically relatively to the abutment support so as to allow the stool to develop the load bearing reaction between itself and the wall above. However, this screw jack is provided between the column and the plane ofthe wall, thus requiring the column to be stood offfrom the wall.This means thatthe moment arm between the column and wall is biggerthanthatofthefirstversion,which requires the stool to be stronger (and, consequently, heavier and more expensive) if it is to be capable of withstanding the larger bending moment.

The object ofthe invention is to provide a recoverable stool which is readily adaptable for use in wall openings within a wide range of heights and which minimisesthe bending momenttowhich it is, in use, subjected.

In accordance with the present invention, a recoverable stool for use in an opening in a wall to prop the wall above from the wall below, comprises a column which has a front face with a plurality of vertically spaced apertures and which, in use, extends upwards outside one face ofthe wall with the frontface ofthe column substantially abutting and parallel to the wall face; upper and lower supports carried by and extending above one another laterally from the front face of the column, in use, into the opening, with the upperoneofthe supportstakingthe load ofthewall above and the lower one of the supports transmitting the load to the wall below; at least one of the supports being located adjacentto the front face ofthe column in a selected position apartfrom the other support by at least one lug extending into a selected one of the apertures; and the one support also forming part of a stirrup which has arms extending past the sides ofthe column and abutment means at the ends of the arms for engaging the back ofthe column remote from the wall at a level offset along the column from the lug(s) in a direction away from the other support to prevent tiltingoftheonesupporttowardstheothersupport. In the context, the reference to the wall below may include a foundation, if the beam is to be inserted between the bottom of a wall panel and a foundation.

A stool of this construction is versatile in that it may be used in conjunction with wall openings within a wide range of heights, owing tothe possibility of fitting at least one of the supports at a selected position along the column by use of an appropriate one ofthe apertures in the column. The stool may also be of lightweight construction, since it is designed to carry and transmit the load in a most efficient manner.

Thus the one support is fixed in position along the column by at least one lug which acts in shear and cooperateswith one ofthe apertures in the frontface of the column at a position immediately adjacent to the face ofthe wall so that the one support is subjected to the minimum bending moment, the moment arm of which is essentially no morethan half the width of the wall. Also, as the support forms part of the stirrup with abutment means engaging the back ofthe column at a position spaced along the column from the support, an adequate reactionary moment is readily available to prevent tilting of the one support.

After the beam has been cast and set, and the wall above pinned up from the new beam, the stools may be recovered by releasing the compression on the stools, in a mannerwhich will be discussed later, and gently tapping each stool so that the bond between the lower support and the concrete is broken, followed by manipulating the stool outwardly from the wall. To assist removal, the lower support is preferably chamfered towards its free end, both in the vertical and horizontal planes, to assist removal from the cast beam.The chamfering in the horizontal plane may be provided byforming at least one side of the lower support as an arc centred adjacentto the point where the other side of the lower support intersects the plane ofthefrontface ofthecolumn. The stool maythen be swung awayfrom the cast beam by twisting it about a vertical axis through the centre ofthe arc, thus swinging the lower support out ofthe bottom ofthe beam.The beam is not normally cast up to the full heigh oftheopening so that chamfering is not usually necessaryforthe uppersupport.Withdrawal ofthe stool may also be assisted if a screw threaded spindle is provided through a complementary screw threaded aperture extending from backtofrontthroughthe column.Advance ofthe spindle will then cause a part of the leading endofthespindleto engage the cast beam and force the stool awayfromthe beam.

Most simply, the lower support is a shoe fixed to the column andthe uppersupportprovidestheone supportwhich is adjustable along the column.

The stool columns, positioned as they are along the wall adjacentto the face ofthe wall, provide ideal supports forformwork forthe front of the beam to be cast. Such formwork may be plywood or similar panels extending between adjacent stool columns and located in position,forexample againstthe backs of plates forming the frontfaces of the columns, or by means of lugs projecting from the sides of the columns, e.g. pins inserted into holes in rearwardly extending parts ofthe columns.

The one support may be in the form of a horizontal plate, to be used face to face with the wall above or below, usually with an interposed packing. Alterna tively, the support could involve two or more horizontal fingers, in the manner of a liftfork, on or under a plank or other plate may bear for engagement directly or indirectlywith the wall above or below.

The column, incorporating the apertured frontface, may be in the form of a member of I orT section, two of the coplanarflanges of which form the face in which the apertures areformed. The web ofthe member will then extend awayfrom the wall and provide the beam effect to prevent collapse of the column. Preferably, however, the column is hollow of rectangulartubular section andthelugs maythen extend through apertures in both thefrontand backwalls ofthe section. The front face ofthe column may then be constituted by the front wall ofthe section, or by a reinforcing facing plate fixed to the front wall ofthe section.

The arms of the stirrup may have the abutment meansintheform of return portionswhichseparately engage the back ofthe column. Preferably, however, the stirrup arms are connected by a part extending fully across the back ofthe column, so that the stirrup forms an enclosed hoop.

The important interconnection between the support and the apertured frontface ofthe column may take a varietyofforms. For example, each lug which cooperateswith an aperture maybeformed rigidly with the support. In this event it may be difficult to provide a small adjustment ofthe support along the column to develop the load in the stool and, in this case,thestool may be builtin byconventionalpinning up techniques utilizing earth damp mortar.

In an alternative construction, each lug is a separate elementwhich is inserted through one ofthe aper tures and engages, e.g. extends through an aperture in, the one support immediately adjacentto the front faceofthecolumn. Conventional building-in techniques may again be used. However, if the lugs are wedges, they may be driven in to provide a small adjustment ofthe one support away from the other supportto develop the load in the stool. Upon subsequent withdrawal ofthe wedge, the load will be released to enable immediate withdrawal and recovery ofthe stool.

When the lugs are nor wedges, in ordersubsequentlyto release the compressive load on the stool, to enable its removal and recovery, it is desirable to enable the one support to be ableto tilt slightly towards the other support. This may be achieved by providing initiallyawedge orother insert between the abutment means and the back of the column so that when the insert is knocked out, the abutment means is able to move slightly towards the back of the column, allowing the stirrup and one supportto tilt as necessary. Also, when each lug is rigid with the one support, some degree of rocking ofthe support and stirrup on the column is necessaryto bring the support away from the front of the column and allow withdrawal ofthe lug from the column aperture.This involves no difficultysincethe abutment means engages the column along the column from the point at which the lug cooperates with the aperture so that the distance between the lug and abutment means is greaterthanthefrontto back width of the column.

The load may also be developed in the stool by jacking the column and supports upwardsfrom the wall below, so that the upper support comes directly, orwith interposed packing, into full load bearing engagement with the wall above, and pinning up the Iowersupportfromthewall below, priorto removing the jacking means. The jacking may additionally lift the wall abovetotighten any looseness in the wall. A hydraulic, pneumatic, screw, or otherjacking unit may be removably attachable to the bottom of the front face ofthe column, so astotransfera reaction from the wall belowto the column.The unit may have a memberwhich is temporarily bolted onto, or other- wise coupled to, the column and projects into the plane ofthe wall.The lower support may be pinned up fromthewall belowto develop the load quickly, by surrounding the lower support on the wall belowwith a shieldthrough a side ofwhich packing material, such as earth damp mortar, can be rammed between the underside ofthe lower support and the wall below.

Since the packing material is adequately contained, the jacking means can immediately be removed without danger, for application perhaps to the next stool along the wall, even though the packing material has not yet set. Some hours later when the packing material has set, the shield may also be removed prior to casting the beam. The jacking means may be stood on the shield to provide a firm supportforthe jacking from the wall below and within the plane ofthe wall.

An example of a stool according to the present invention, and its use, are illustrated in the accom panying drawings, in which Figure lisa front elevation of the assembled stool; Figure 2 is a plan ofthe assembled stool; Figure 3 is a perspective view of a shield; Figure4isa perspectiveviewofa jack; Figure 5 is a side elevation ofthe stool when in use inserted into an opening of a wall, which is shown in section; Figure 6 is a rear elevation ofthe bottom part of the stool with the jack attached and fitted with the shield; and, Figure 7 is a side view of those parts shown in Figure 6when mounted on a lower wall (shown in section) of an opening.

As shown in Figures 1 and 2, the stool has a column 1 which is of rectangulartubular cross-section and which has pairs of aligned apertures 2 passing through the front and backwalls. A lower support3 having a horizontal flange is welded to the bottom of the column 1. An upper support 4, also having a horizontal flange, isfixed to the column 1 by means of a pin 5 which forms a lug and passes th rough an aperture 6 in the upper support 4 and through one of the pairs of apertures 2, and also by means of a bar7 which extends across the back ofthe column 1. The bar7 isfixed between the ends of stirrup arms 8 welded to, and extending backwards from, the upper support 4 so as to straddle the sides ofthe column 1, thus preventing the upper support4from pivoting about the pins.Also, the bar7 does not abut directly onto the back face of the column 1, but, instead, a tapered wedge 9 (see Figure 5) is inserted between the bar and the backface ofthe column. This arrangement enables small adjustmentsto bemadetothe relative positioning ofthe upper support 4 and the column 1 by moving the tapered wedge 9 to reduce the distance between the bar 7 and the back face ofthe column 1.

Sincethe pin 5 may be inserted in any one ofthe pairs of apertures 2, the separation between the upper support4andthe lowersupport3 may be varied.

The stool also has a jack 10 which is used to raise the column 1 so as to bring the upper support4 into load-bearing engagement with the wall above. The jack 10, shown in Figures 4,6 and 7, has a lug 11 which fits in an aperture 12 on thefrontface ofthe column 1, and an aperture 13 with associated fixed nut 14which receives a bolt 15 which passes through a pair of aligned apertures 16 in the column 1 thus fixing temporarilythejackto the column. The jack 10 has a pair of screw jacks 17 which have bodies 18 fixed to the main partofthejack and feet 19 which are extensible away from the bodies 18.

A shield 20, which is fitted around the lower support 3 so asto inhibitthe escape of mortar rammed thereunder, is shown in Figures 3,6 and 7. The shield 20 has a horseshoe-shaped section 21 which fits around the sides and front ofthe horizontal flange of the lowersupport3. A pairofflanges 22 extend one from each side of the base of the section 21. These flanges 22 extend sufficiently far sideways for the feet 19 of the jack 10, when placed above the shield 20, to be able to sit on top ofthem. The flanges 22 also have lips 23 which, as shown in Figure 7, engagethefront of the wall to preventthe shield 20 being displaced into the wall.

The stool is positioned bythewall and the upper and lowersupportsareoffered into an opening 24inthe wall (see Figure 5) until the front face ofthe column 1 is flush with the front surface ofthewall. The lower support 3 is rested on top of the lower part 25 of the wall, and the upper support 4 is hoved up and down the column 1 unfllthe p & ofapertures 2which brings the support closest to the upper part 26 of the wall has been found. The pin 5 is then inserted through this pair of apertures 2 and through the aperture 6 in the upper support4.The wedge 9 is then inserted in the gap between the bar7 andthe backface ofthecolumn 1, and adjusted until the upper support 4 is approximately parallel with the bottom face of the upper part 26 of thewall. The gap 27 between the upper support4and the upper part 26 of the wall is filled with packing material 28, so as to reduce the size ofthe gap and avoid local pressure points.

The shield 20 is then slid overthe lower support 3 until it is sitting on the upperface ofthe lower part 25 ofthe wall with its lips 23 wrapped around the front edge of the wall.Thejack 1 O is then fitted to the front face ofthe column 1 by fitting the lug 11 in the aperture 12 and inserting the bolt l5throughtheapertures 16 and 13 until it engages with the nut 14, thus fixing firmlythejack 10tithe column 1 . The feet 19 ofthe screw jacks 17 are then advanced down until they touch the flanges 22 oftheshield 20. Further advancement ofthe feet 19 lifts the column and two supports upward.This is continued until the upper support4 has been brought into load-bearing engagement with the upper part 26 ofthe wall, and, if necessary, until the upper part 26 ofthe wall has been lifted far enough to tighten any loosenesstherein.

The jacking operation creates a gap 29 between the lower support 3 and the lower part 25 of the wall.

Whilstthejack 10 is supporting the column 1, the gap 29 is rammed full of earth damp mortar 30. The shield 20 prevents the mortar30from being extruded out from underneath the support 3, and this enables the jack 1 Oto be removed as soon as the gap 29 has been filled fully. The jack 10 may now be used to jack up another column 1. Once the earth damp mortar 30 has fully set, the shield 20 may also be removed.

When the opening has been prepared fully by the insertion ofthe requisite number of stools, formwork is erected. Part of such framework 31 is located against the front ofthe opening 24 in the wall behind by lugs 32 on the column sides. The upper lugs 32 may be provided by removable pegs in holes iffixed lugs would preventthe upper support4from being fixed to a lower part of column 1 bythe pin 5 passing through a lower one of the pairs of apertures 2.

Once theformwork has been erected, a beam 33 is cast in the opening 24. When the beam 33 has set, the gap 34, in the sections between the stools, between the top ofthe beam 33 and the upper part 26 of the wall is filled with earth damp mortar (not shown). When this mortar has set the stools may be removed. The wedge 9 is knocked out, thus releasing the upper support4. However, as the lower support 3 has been cast into the beam 33, its horizontal flange is difficultto remove. Forthis reason, the lower support 3 has chamfered sides 35 and a chamfered upperface 36.

The horizontal flange ofthe upper support 4 is similarly chamfered on its sides 37 and, as shown in Figure 2, each side 37 is in the form of an arc of a circle centered on the end adjacent to the column 1 of the opposite side, i.e. the point 38. With the aid of the chamfers on the upper and lower supports, the stool may be both pulled and wiggled free from the wail.

The gaps above the castbeam,wherethe upperstool supports have been removed may then be grouted up.

Claims (18)

1. A recoverable stool for use in a opening in a wall to prop up the wall above from the wall below, the stool comprising a column which has a front face with a plurality of vertically spaced apertures and which, in use, extends upwards outside one face ofthe wall with thefrontface ofthe column substantially abutting and parallel to the wall face; upper and lower supports carried by and extending above one another laterally from thefrontface ofthe column, in use, into the opening, with the upper one ofthe supports taking the load ofthe wall above and the lower one of the supports transmitting the load to the wall below; at least one of the supports being located adjacent to the front face ofthe column in a selected position apart from the other support by at least one lug extending into a selected one ofthe apertures; and the one support also forming part of a stirrup which has arms extending pastthe sides ofthe column and abutment means atthe ends of the arms for engaging the back of the column remote from the wall at a level offset along the column from the lug(s) in a direction awayfrom the othersupportto prevent tilting ofthe one support towardsthe other support.

2. A stool according to claim 1, wherein the or each lug engages the one support adjacentto the frontface of the column.

3. Astool according to claim 2,whereinthe or each lug extends into an aperture in the one support.

4. Astool according to any one ofthe preceding claims, wherein the abutment means comprises a bar linking the ends ofthe arms whilst passing across the back of the column.

5. Astool according to anyoneofthe preceding claims,furthercomprising a removable wedge positioned between the abutment meansandthe backof the column.

6. Astool according to any one of the preceding claims, wherein the column is hollow and the vertical- lyspaced apertures extend through the front and back walls ofthe column.

7. A recoverable stool according to any one ofthe preceding claims, wherein the lower support is fixed to the column.

8. Astool according to any one ofthe preceding claims, wherein lugs projectfrom the sides ofthe column for supporting formwork.

9. A stool according to any one ofthe preceding claims, further including a removable shield extend ing around the lowersupportwith an opening adjacentto the column.

10. A stool according to claim 9, wherein the shield has horizontal flanges extending laterally in opposite directions, and which rest, in use, on the wall below.

11. A stool according to claim 10, wherein the shield has a vertical lip attached to the horizontal flanges, and, in use, engaging thefrontedge ofthe wall below so as to preventthe shield from slipping into the opening.

12. Astool accordingto anyoneofthepreceding claims,furthe inciuding a jacking unit removably attachable to the bottom ofthe front face of the column.

13. A stool according to claim 12 when dependent upon claim 11 or claim 10, wherein the jacking unit has extensiblefeetwhich are abuttableagainsttheflanges ofthe shield.

14. A recoverable stool substantially as described with reference to the accompanying drawings.

15. A method of casting a concrete beam in a wall, the method comprising cutting awaythewall, inserting into the wall at horizontally spaced positions a plurality of stools according to any one ofthe preceding claimstemporarilyto supportthe wall above, erecting formwork, inserting reinforcement, casting a concrete beam, and removing the stools.

16. A method according to claim 15, wherein a jacking unit is used to raise the column so asto bring the upper support into load bearing engagement with the wall above prior to mortar being inserted between the lower support and the wall below, and the jacking unit being removed priorto casting of the beam.

17. A method according to claim 16, wherein a shield is fitted around the lowersupportto contain the mortar.

18. A method according to claim 17, wherein the jacking unit raises the column whilst pressing down onflangesforming part of the shield.