GB2078823A - Jacking-up of buildings - Google Patents

Abstract

A method of jacking-up a building involves casting an in situ reinforced concrete beam section (15) in a wall (16) of the building, attaching a bracket (14,19,20) to the end of the beam section, and raising the bracket, and hence the beam section and wall by means of a jack (13) in line with the end of the beam section. <IMAGE>

Description

SPECIFICATION Jacking-up of buildings In the jacking-up of buildings which have been subject to subsidence, it is known to provide a beam in the plane of at least one wall of the building, adjacent to the bottom of the wall, and to apply a jacking reaction, for example by means of an hydraulic jack, to the beam. The building is consolidated in its raised position, usually by flooding concrete between the underside of the beam and the original foundation and if necessary by means of a final dry packing step.

When the beam is a cast in situ reinforced concrete beam, it has been usual to dig a hole in the ground beneath the beam to accommodate each jack. This requires a great deal of labour, particularly if the hole is to be large enough to enable ready insertion, manipulation and removal of the jack, and if room has to be provided in the bottom of the hole to cast a pad on which to stand the jack. The digging of the hole is made more difficult by the fact that the hole will frequently have to be dug through the original foundation.

In an alternative method, brackets are fitted to opposite sides of the beam and separate jacks are applied to each bracket. The duplication of brackets and jacks at each of the opposite sides of the beam is necessary to avoid the production of a tiiting moment on the wall. However this has the disadvantages that, firstly, twice the equipment is used than would otherwise be necessary; the fixing of the brackets to the sides of the beam usually involves drilling holes in the beam which in itself weakens the beam; and the provision of the bracket and jack on the inner side of the beam is inconvenient in disturbing the fittings and decoration within the building.

In accordance with the present invention, in a method of jacking-up a building, a section of reinforced concrete beam is formed in situ in the plane of and adjacent to the bottom of a wall of the building, a bracket being fitted to an end face of the beam section; and the wall is raised by applying to the bracket an upward reaction by means of a jack which is positioned substantially in the central vertical longitudinal plane of the beam section at a level which intersects the central horizontal longitudinal plane of the beam section.

With this arrangement, since the jack is accommodated beyond the end of the beam section, it is unnecessary to dig to any significant depth, if at all, into the brick work or foundation beneath the beam to accommodate the lower part of the jack. Also, since the original foundation is not disturbed, it may not be necessary to provide a new pad on which to seat the jack, at least unless the jack is positioned at an end of the wall where no foundation exists.

The bracket may be of various constructions but in most cases will incorporate a vertical member which is secured to the end face of the beam section and a horizontal member carried by and extending transversely away from the top of the vertical member in the longitudinal direction of the beam away from the beam section. The jack will then be accommodated beneath the horizontal member and the extensible part of the jack will engage the underside of the horizontal member level with an upper part of the beam.

The vertical member of the bracket must be fitted to the end face of the beam section sufficiently securely for the jacking reaction to be transmitted through the bracket to the beam and hence to the wall. The secure fitting may be provided by securing the bracket to the metal reinforcement of the concrete beam. This could be done in a variety of ways but in one example end portions of longitudinal reinforcing wire rods of the beam project from the end face of the beam and are provided with screw threads. These projecting portions act as integral studs which, when the bracket is fitted to the end face, pass through aligned holes in, for example the vertical plate, or the bracket and receive nuts whereby the bracket is effectively bolted to the beam section.This is a convenient arrangement when the end face of the beam section to which the bracket is fitted is exposed at an end of the wall. In such case the bracket may consist merely of the vertical member a horizontal plate forming the horizontal member, and, at each side of the bracket, a fillet plate interconnecting the perpendicular edges of the vertical and horizontal plates, one at each side of the bracket.

An alternative manner of fitting the brackets securely to the end face of the beam section involves providing the bracket at the time of casting the beam whereby an end portion of the beam is cast onto a portion of the bracket. For example the bracket may incorporate a shoe which forms a part of the framework for the end of the beam section, the concrete filling the shoe during the casting. An end of the reinforcement may also extend into the shoe to protect the end of the beam section against crumbling during the jacking-up. This arrangement is suitable in a case in which a single jack and a single bracket are used between the adjacent ends of a pair of substantially longitudinally aligned beam sections. The bracket will then have a pair of shoes facing in opposite directions, or other means for uniting the bracket to the end portions of both beam sections.In this case the common horizontal member beneath which the jack will be positioned may be a box or other beam section which can accommodate continuous longitudinal reinforcing rods extending from one beam section to the next. When the jacking-up has been completed and the building consolidated in its raised position, the jack may be recovered and the gap between the adjacent ends of the two beam sections filled with concrete.

The advantage of providing a jacking point between two initially separate beam sections is that jacking of the other ends of the two beam sections may be carried out to a different extent whereby a hinge, extending transversely to the wall, is effectively provided between the adjacent ends of the two beam sections. In this manner two parts of a wall which have parted in the plane of the wall may be brought together again.

The beam section itself may be constructed by a method involving cutting awaythewall and inserting at horizontally spaced positions stools which temporarily support the wall above, and with the intervening wall between the stools cut away, inserting reinforcement, erecting formwork, and casting the in situ concrete beam section incorporating the reinforcement and at least part of the stools. If the stools incorporate screw jacks, local tightening up of the wall above the stools can be carried out prior to jacking-up of the whole wall.

Two examples of a method of jacking-up a building in accordance with the invention are illustrated in the accompanying drawings, in which: Figure 1 is a diagrammatic central vertical section through part of one wall incorporating beam sections; Figure2 is a diagrammatic plan ofthe beam sections and adjacent parts of Figure 1; Figure 3 is a section corresponding to Figure 1 but showing the second example; and, Figure 4 is a view partly in elevation from the left in Figure 3 and partly on the section line IV-IV in Figure 3.

In the first example, illustrated in Figures 1 and 2, two reinforced concrete beam sections 5 and 6 are built into the plane of the wall, some courses above the foundation. Each section is built in generally conventional fashion by cutting a hole in the wall and inserting at spaced positions along the wall screw jacks 7 which are seated on the wall below and extended upwards to take temporarily the weight of the wall above. The intervening wall between the stools is then cut away to form a continous slot along the wall.A shoe assembly consisting of two shoes 8 supporting a horizontal box section 9 which spans between the shoes is inserted with the shoes resting on the wall below and at each side of a central gap to accommodate an hydraulic jack 10, which in this case is shown resting on the wall below where an extra course of brickwork has been cut away, and beneath the horizontal member 9. Reinforcement 11 for each beam section is then wired to the stools 7 with its ends projecting into the shoes 8 and through the horizontal member 9. Formwork is erected at each side of the wall and the concrete poured and allowed to set to form the beam sections 5 and 6. The beam sections are cast just short of the wall above and the gap packed with just damp mortar 12.When the beam sections and mortar packing have finally set, the wall above can be raised by means of the jack 10, and possibly jacks provided at the outer ends of the beam sections 5 and 6.

Differential extension of these jacks enables a hinging effect at the jack 10. The beam sections are then packed up from the wall below in their final positions and when the packing has set, the jack 10 and any similar jacks, may be removed and the gap between the ends of the beam sections 5 and 6 filled with concrete including, if necessary, reinforcement.

In the second example, illustrated in Figures 3 and 4, an hydraulic ram 13 is shown acting on a horizontal member 14 of a bracket fixed to the end of a beam section 15 (which may be an end of one of the beam sections 5 or 6 in the first example), at a corner of a building where a wall 16 meets a cross cavity wall 17. The cross wall is provided with a similar beam section 18 and both beam sections may be constructed substantially in a similar manner to the sections 5 and 6. One difference however is that a vertical member 19 of the bracket, which is connected to the horizontal member 14 bytwo triangular fillets 20, is secured to the end of the beam section 15 by means of nuts 21 screwed onto screw threaded ends of reinforcement bars 22 which extend through holes in the member 19. The ram 13 stands on a foundation 22 built up from an existing foundation 23 ofthe building.

After appropriate lifting of the beam sections 15 and 18 by means of the ram 13, the ram and bracket may be recovered.

Claims (8)

1. A method of jacking-up a building, wherein a section of reinforced concrete beam is formed in situ in the plane of and adjacent to the bottom of a wall of the building, a bracket being fitted to an end face of the beam section; and the wall is raised by applying to the bracket an upward reaction by means of a jack which is positioned substantially in the central vertical longitudinal plane of the beam section at a level which intersects the central horizontal longitudinal plane of the beam section.

2. A method according to claim 1, wherein the bracket incorporates a vertical member which is secured to the end face of the beam section and a horizontal member carried by and extending trans versely away from the top of the vertical member in the longitudinal direction of the beam away from the beam section, the jack being accommodated beneath the horizontal member and engaging the underside of the horizontal member.

3. A method according to claim 2, wherein the bracket is secured to metal reinforcement of the section.

4. A method according to claim 3, wherein end portions of longitudinal reinforcement wire rods of the beam section project from the end faces of the beam section and are provided with screw threads, these projecting end portions passing through aligned holes in the bracket and receiving nuts whereby the bracket is bolted to the beam section.

5. A method according to claim 2, wherein the bracket is provided at the time of casting the beam whereby an end portion of the beam is cast onto a portion of the bracket.

6. A method according to claim 5, wherein the bracket incorporates a shoe which forms part of the formwork for the end of the beam section, the * concrete filling the shoe during the casting of the beam section.

7. A method according to any one of the preceding claims, wherein a single jack and a single bracket are used between the adjacent ends of a pair of substantially longitudinally aligned beam sections.

8. A method according to claim 1, substantially as described with reference to either one of the examples illustrated in the accompanying drawings.