GB2055130A - Method of raising buildings - Google Patents

Abstract

A method of raising a building and securing it at the new height involves building into the walls of the building reinforced concrete beams (15), erecting lifting devices (21) having suspension members (26) the lower ends of which are fixed to the beams (15) by brackets (31). The lifting devices are operated to pull upwards on the suspension members (26), thereby raising the building after which new wall sections (34) are built in between the beams (15) and foundations (30, 36). <IMAGE>

Description

SPECIFICATION Method of raising buildings The invention is concerned with the problem of raising a building, such as a domestic house, bodily, through a height of up to 1 m. or more, and securing the building at the new height, prior for example to raising the local surrounding ground level. Existing underpinning techniques are not suitable for this purpose and no simple technique exists for raising buildings bodily through an appreciable height. For example in one conventional underpinning procedure, a beam is inserted in the plane of an external load bearing wall of the building and one or more jacks are applied to the underside of the beam to lift the beam and adjacent parts of the building, and the beam is pinned up on existing or new foundations, for relevelling the building.However, it would be dangerous to use this technique for raising a building bodily through a significant height owing to the inherent instability of the building whilst supported on the jacks which may have an appreciable height of packing above or below them.

In accordance with the present invention, in a method of raising a building bodily, in situ cast reinforced concrete beams are built into the planes of at least the external walls of the building adjacent to ground level and united with one another to form a rigid frame, firm load bearing surfaces are created adjacent to ground level and outside or at least partly under the external walls of the building, lifting devices are mounted on the surfaces and the beams are connected by suspension members to raisa ble parts of the lifting devices, the raisable parts of the lifting devices are jacked up relatively to the load bearing surfaces whereby the suspension members act in tension to pull the beams upwards and hence raise the building, and a load bearing infill is built in between the underside of the beams and foundations.

With this procedure, the suspension members and frame formed by the beams act as a stable cradle for the building which can accommodate and automatically compensate for any tendency of the building to topple. The suspension members will preferably have an inbuilt flexibility, as a result for example of pivotal interconnections at their ends, but more conveniently as a result of the suspension members being formed by cables, such as steel cables conveniently used for prestressing concrete.

The beams which are built into the planes of the wall are most simply formed by the well known "Pynford" (Registered Trade Mark) technique of inserting stools in the wall at horizontally spaced positions to provide a temporary support for the wall above, and with the intervening wall cutaway, inserting reinforcement, erecting formwork, and casting an in situ concrete beam containing the reinforcement. The frame which is created from the beams in the method according to the invention may, in the simplest case of a rectangular building, consist of four of the beams, one inserted in each of the four external walls of the building. However, if there are significant internal walls of the building, it may be necessary to insert additional beams in the internal walls, these additional beams being united with those in the external walls to form a more complex frame.

The infilling which is built in between the underside of the Pynford beams and the foundations will normally consist of a new section of wall supported on the original foundations, or on new foundations.

The firm load bearing surfaces on which the lifting devices are mounted may be simple plates resting on hard packed consolidated earth. However, when new foundations are required for the building, the load bearing surfaces may be provided by pile caps formed on the top of new piles which are put down adjacent to the external walls of the building, and the pile caps may also provide the discontinuous support for beams formed on the edge of a new site slab. The new lower wall section will then be built on the site slab edge beams. In the case of a simple rectangular building, it may be sufficient to provide one new pile and pile cap at each corner of the building and one midway along each of the two longer sides of the building.

Each lifting device may consist of a trestle resting on a pile cap or other load bearing surface and supporting at its top an hydraulic jack carrying a lifting beam. Extension of the jack then raises the lifting beam relatively to the top of the trestle.

Suspension members as such, particularly, suspension cables, may then be anchored to the lifting beam and extend down through the trestle to a temporary jacking bracket fixed to the external surface of the adjacent Pynford beam or other temporary extension such as a rolled stee! joist cast into the Pynford beam. A climbing effect can be achieved to raise the building by a multiple of the jack stroke in conventional fashion by the use of adjustable cable anchors where the cables pass through the lifting beam and through the top of the trestle. Thus in a cycle of operation the cables are anchored to the lifting beam and the jack is extended whereafter cable anchors secure the cables to the top of the trestle, the jack is retracted with the lifting beam, the cable are re-anchored to the lifting beam and the cycle repeated.Naturally the lifting will have to be carried out substantially evenly at all the lifting devices around the building. This can best be achieved by metering the flow of high pressure oil to the various jacks so that the amount of oil passed into each jack lifts the various jacks equal amounts irrespective of the volume of the jack or the load applied to it through the lifting cables.

The level of the building can be monitored by normal optical levels and corrected as necessary from time to time or the levelling can be controlled by a water level device which senses the level of the building close to each jacking point. Such a device can be used to generate a small electric current when one part of the building has been lifted relatively more than the neighbouring parts of the building. This electric current can be amplified and used to control the hydraulic valves which meter the flow of oil to the jacks so that, when an electric signal is received, the oil to the jack which has advanced more than neighbouring jacks is temporarily cut off thus allowing the building to remain substantially level at all times during the lifting operation.

An example of the raising of a building in accordance with the invention is illustrated in the accompanying drawings, in which: Figure lisa diagram showing the height through which the building, and the level through which the surrounding ground, are to be raised; Figure 2 is a composite vertical section through the building showing one half at an early stage in the raising operation and the other half after the building has been secured in the raised position; Figure 3 is a diagrammatic vertical section through one wall of the building after it has been secured in the raised position, and taken on the line Ill-Ill in Figure 4; Figure 4 is a diagrammatic plan showing the frame of beams inserted into the building; and, Figures 5A, 5B and 5C show successive stages in the operation of a lifting device.

The illustrated example concerns a building 6 which is to be raised through a height of about 1.5 m.

from the position shown in solid lines to the position shown in dotted lines in Figure 1, to allow the surrounding ground 7 adjacent to a dyke 8 to be raised from the level shown in solid line to the level shown in dashed line.

The building may have external load bearings walls 9 built on old foundations 9A, floor 10 supported by existing walls above the level at which the Pynford beams are to be inserted, upper ceiling 11, and roof 12. As an initial step new foundations are put down, in this case in the form of six piles 13, each with a pile cap 14.

In situ reinforced concrete beams 15 are then cast, by the "Pynford" technique, into the external walls 9, adjacent to ground level. The beams are united to form a rigid frame. Further similar beams 16 may if necessary be built into internal walls of the building at the level of the beams 15 and united with the rigid frame as shown in Figure 4. A cross section through one ofthe beams 15 is shown in Figure 3, in which longitudinal steel reinforcing rods 17 and steel stirrups 18 will be seen to be embedded within the concrete matrix 19. The wall 9 above the beam is pinned up from the beam by packing 20.

The next step involves the erection of lifting devices 21 on each of the pile caps 14. Each of the lifting devices incorporates a trestle 22, hydraulic jack 23, and upper lifting beam 24. As shown in Figure 5 the jack 23 acts between an upper part 25 of the trestle and the upper lifting beam 24. Steel cables 26, provided with three sets of anchors 27, 28, and 29, pass down through the upper beam 24, the trestle part 25, and a lower lifting beam 30 which supports a bracket 31 fixed to the adjacent beam 15.

The building is then raised away from the old foundations 9A from the remnants of the walls 9 below the beams 15, 16 by operating the jacks 23 of the six lifting devices simultaneously. The building can be lifted through a multiple of the stroke of each jack 23 by repeatedly extending and contracting the jack through the cycle shown in Figurs 5A, 5B and 5C, while repeatedly moving the anchors 27 and 28 downwardly into engagement with the upper lifting beam 24 and trestle part 25, as shown in the drawings and as already described.

Finally, a new concrete site slab 32 may be cast to provide a floor for a newly formed cellar 33, the slab incorporating integral reinforced concrete edge beams 36 to act as a support for a new lower wall section 34 which is built in under each beam 15 (or 16) in alignment with the original wall 9 to secure the building in its new raised position. Packing 35 may be necessary between the top of the new wall section 34 and the bottom of the beam 15. The load is transmitted from the new wall sections 34 to the pile caps 14 and piles 13 via the thickened edge beams 36 of the slab 32.

The lifting devices 21 and brackets 31 may then be dismantled leaving the building secure in its raised position.

Claims (6)

1 A method of raising a building bodily, wherein in situ cast reinforced concrete beams are built into the planes of at least the external walls of the building adjacent to ground level and united with one another two form a rigid frame, firm load bearing surfaces are created adjacent to ground level and outside or at least partly under the external wails of the building, lifting devices are mounted on the surfaces and the beams are connected by suspension members to raisable parts of the lifting devices, the raisable parts of the lifting devices being jacked up relatively to the load bearing surfaces whereby the suspension members act in tension to pull the beam upwards and hence raise the building, and a load bearing infill is built in between the underside of the beams and foundations.

2. A method according to claim 1, wherein the suspension members are cables.

3. A method according to claim 1 or claim 2, in which the infilling comprises a new section of wall.

4. A method accordng to any one of the preceding claims, in which the firm load bearing surfaces are pile caps formed on the top of new piles which are put down adjacent to the external wall to provide newfoundationsforthe building.

5. A method according to claim 1, substantially as described with reference to the accompanying drawings.

6. A building which has been raised bodily by a method according to any one of the preceding claims.