US3396944A

US3396944A - Jacking systems for use in the construction of buildings

Info

Publication number: US3396944A
Application number: US537975A
Authority: US
Inventors: Jansz Joost Werner
Original assignee: Richard Costain Ltd
Current assignee: Richard Costain Ltd
Priority date: 1964-05-08
Filing date: 1966-03-28
Publication date: 1968-08-13
Anticipated expiration: 1985-08-13
Also published as: NO118871B; US3309062A; ES312682A1; GB1102274A; FI46053C; AT286551B; DK111636C; NL6405158A; FI46053B; DK111636B; CH444423A

Description

Attorney 5 Sheets-Sheet 1 J. W. JANSZ Fig.1

JACKING SYSTEMS FOR USE IN THE CONSTRUCTION OF BUILDINGS H CH0 Inventor d. W Ja nsz Wm w m 1 /w 9 fl O oooooh oMvooo 40.] A||\|/O o Q m M m m I 4 mm I m 0 0 Z 1 W J W F 0 I w m m 0 o :I 1% t? m 1. O O0 000 OO 0 2 o m ll 4 MMN i w Aug. 13, 1968 Filed March 28, 1966 3, 1968 J. W. JANSZ I 3,396,944

JACKING SYSTEMS FOR USE IN THE CONSTRUCTION OF BUILDINGS Filed March 28, 1966 5 Sheets-Sheet 2 E 12 E12 Fig.3

29 NV 29 W m [32 1H J T 30 T 35 l W 52 Inventor JNJansz A Home y 3, 1968 J. w. JANS-z 3,396,944

JACKING SYSTEMS FOR USE] IN THE CONSTRUCTION OF BUILDINGS Filed March 28, 1966 Y 5 SheetsSheet 5 W 1T1'\ 3o r- --rmm1m-, 3 351 3 8 l I s s a; g l 52 54 i I 59 I EEE Z 5'5 l I w 62 G3 64 65 ea 67 61 49 Inventor JIM. Jmsz By :M

/& Wtome y Aug. 13, 1968 J. w. JANSZ 3,396,944

JACKING SYSTEMS FOR USE IN THE CONSTRUCTION OF BUILDINGS Filed March 28. 1966 5 Sheets-Sheet 4 y7/// //(cy Inventor 16M Attorney 7 J. W. JANSZ Aug. 13; 1968;

JACKING SYSTEMS FOR USE IN THE CONSTRUCTION OF BUILDINGS y 2 m .1 r5 LID. e 0 I. e m A h e2 S J m m N o h 6 S H J 5 B 9 .U

Filed March 28, 1966 United States Patent 3,396,944 JACKING SYSTEMS FOR USE IN THE CONSTRUCTION OF BUILDINGS Joost Werner Jansz, The Hague, Netherlands, assiguor to Richard Costain Limited, London, England, a British company Continuation-impart of application Ser. No. 454,367, 'May 10, 1965. This application Mar. 28, 1966, Ser. No. 537,975 Claims priority, application Netherlands, May 8, 1964, 6405158; Great Britain, Mar. 31, 1965, 13,738/65 11 Claims. (Cl. 25489) ABSTRACT OF THE DISCLOSURE The present invention relates to a jacking system for use in the construction of buildings in which the vertical and horizontal structures of each successive storey, starting from the top storey downwards, are constructed at or near ground level and subsequently raised by a plurality of jacking devices (together with all the completed storeys thereabove) to permit the construction of the vertical and horizontal structures of a further storey therebeneath. The jacking system includes horizontal level control means for maintaining the floors at all times in a near-perfect horizontal plane during the jacking operation. This is achieved by controlling the jacking devices so that when a jacking device rises through only a small predetermined substep of the order of /2 mm. it is stopped from rising further until all the jacking devices have been raised through the predetermined small substep.

The present invention relates to the construction of buildings, particularly to high buildings of ten or more storeys, although the invention is applicable to the construction of buildings of lesser height.

The present invention is a continuation-in-part of my application Ser. No. 454,367, filed May 10, 1965, which is assigned to the same assignee as the present application and has now issued under Patent No. 3,309,062.

A method of constructing tall buildings is known (see our prior British Patent No. 956,134) in which the vertical and horizontal structures of each successive storey, starting from the top storey downwards, are constructed at or near ground level, and subsequently raised by one storey height (together with all the completed storeys thereabove) to permit the construction of a further storey therebeneath. By this method the necessity for tall cranes and high hoists is avoided and the building workers only have to work at low heights.

The raising of the successive storeys is effected by jacking devices on which the full weight of the building rests until the building has reached its full height, when the jacks are removed and the building anchored to its foundations.

In the prior practical application of this method, as described in the aforesaid patent specification, the building is supported on a central core from which all the floors are supported in cantilever fashion. The jacking devices act directly on the central core structure which, together with the projecting floors, provides a substantially rigid structure.

In applying the method to buildings of which the floors are not rigid and capable of being raised as an integral unit, the difficulty arises of raising all parts of the floor by substantially equal amounts so that all parts of the floor will at all times be in a near-perfect horizontal plane and the introduction of excessive stresses in the structure, due to differential deflections, which can give rise tocracking or other damage to the structure, will be avoided.

The present invention has for its object to provide a "ice method of and apparatus for raising a building structure by means of jacking devices which overcomes the above diificulty.

To this end the invention consists in raising the building by means of a plurality of jacking devices which are auto matically controlled so that, at each actuation, each jacking device can rise by only a small predetermined substep, preferably of the order of /2 mm, such raising movements of the jacking devices being registered in a control device which prevents the jacking devices from again being actuated to execute another substep until the control device registers that all the jacking devices have correctly completed the previous substep.

In order that the invention may be more clearly understood, the application thereof will now be particularly described by way of example in connection with a building comprising a central core structure from which the floors project and of which the perimeters of the floors are supported by columns, reference being made to the accompanying drawings, in which:

FIGURE 1 is a diagrammatic plan view of the building.

FIGURE 2 is a diagrammatic vertical section of the building, during erection.

FIGURE 3 is a hydraulic circuit of the jacking system and details of one form of jack construction.

FIGURE 4 is a schematic diagram of the electric control circuit of the jacking system.

FIGURE 5 is a modification of the hydraulic circuit of FIGURE 3.

FIGURE 6 is a view explaining the construction of the wall of the central core structure.

FIGURES 7, 8, 9 and 10 are diagrams explaining alternative methods of erecting the supporting columns.

FIGURE 11 shows in more detail a side view of the apparatus for carrying out the method illustrated in FIG: URE 10.

FIGURE 12 is an end view of FIGURE 11.

FIGURE 13 is a plan view on the line A--A of FIG- URE 11.

Referring to FIGURES 1 and 2, the building generally comprises a central core structure comprising a supporting wall 101 around which the floors 102 project, their perimeters being supported on supporting columns 103. The floors can also project inside the central core walls which may also accommodate the staircase, lifts and other services.

The method of construction consists in first constructing, at or near ground elvel, a base slab 104 beneath which is a jacking chamber 105 of which the base is carried on very strong foundations 106. The slab 104 may be supported from the base of the jacking chamber by perm-anent or temporary piers 107. Disposed in the jacking chamber are a plurality of jacking devices 1 located at positions for raising the core wall 101 and the supporting columns 103, the slab being provided with

openings

108, 109 through which the wall structure and supporting columns can respectively pass as they are raised by the jacking devices.

The roof structure 110 is first constructed on the slab 104 and lifted by the jacking devices in steps to the full height of the storey below it, during which a section of the supporting wall strupcture 101 and column sections 103 therebeneath are constructed or erected and supported from the jacking devices or temporary supports as will be hereinafter explained. The next floor structure is constructed on the slab 104 either before, after or during the erection of the wall structure and column sections which have to support it, and is then raised in steps by the jacking devices with the already erected structure there-above, the operation being repeated for each floor until the Whole building is erected. The jacking devices are operated in a manner such that the floors will be raised, with the central core and supporting columns, so as to be at all times in a near-perfect horizontal plane whereby to avoid the introduction of excessive stresses in the structure due to differential deflections which could cause cracking or other damage to the floor structures and the joints between the fioors and the central core or supporting columns. To achieve this the jacks are 'so constructed and so automatically controlled that, at each actuation, each jack can rise through only a predetermined small distance or substep, for example /2 mm., all the jacks having to complete this small substep before any of the jacks can again be actuated to raise the structure through a similar small substep.

One form of construction of stroke-controlled jack suitable for use in carrying out the method of this invention, and the mode of controlling the jacks for achieving the level control of the structure will be described with reference to FIGURES 3 and 4. FIGURE 3 shows the hydraulic circuit for the jacks, two groups I and II of which are shown at the top of the figure, the left-hand jack of group I being sectioned to show the construction of the jacks, the remaining jacks only being shown in outline. FIGURE 4 shows the electrical circuit of the jacking system and includes a fragmentary plan, on an enlarged scale, of the ratchet teeth on the jack and the associated electric switches.

Dealing first with the construction of the hydraulic jack 1 itself, this, as shown, comprises a cylinder 2 in which slides a piston 3 secured to a piston rod 4. The jack 1 is of the single-acting type, liquid under pressure for lifting the load being supplied to one side 5 of the piston 3 through

pipes

7, 8 from a pump 23 driven by a motor 24.

The piston rod 4 is provided with a screw thread on which is threaded a nut 9. The nut 9 is movable by auxiliary mechanism which controls the jack stroke, consisting of ratchet teeth 10 (see also FIG. 4) provided around the nut 9 and cooperating with a pawl 11, which is actuated by an auxiliary single-acting hydraulic cylinder 12 provided with a piston 13. To rotate the nut 9 by means of pawl 11 and ratchet teeth 10, liquid under pressure from pump 23 is supplied to the side 14 of the piston 13 through

pipes

7 and 15. A common solenoidoperated control valve 26 provides for simultaneous supply of pressure liquid from pump 23 through

pipes

7 and 8 to the jack cylinder 2, and through

pipes

7 and 15 to the auxiliary cylinder 12 of the jacks of each group. Each control valve 26 is actuated by a solenoid 29, and when in its right-hand position (as shown in FIGURE 3) connects oil pressure from pump 23 and pipe 25 to pipe 7 and hence to

pipes

8 and 15. When the solenoid 29 is energised, the valve 26 is moved to its left-hand position where the supply of oil from the pump to the pipe 7 is cut OE, and the pipe 7 is connected via the passage 30 in the valve 26 to the pipe 32 leading back to the oil reservoir 31. Upon release of the oil pressure in the cylinder 12, the pawl 11 and piston 13 are returned to their initial positions by a compression spring 19 which may, for example, be incorporated in the cylinder 12. The jack cylinder 2 is connected via a nonreturn valve 21 with the pipe 7 so that, upon release of the pressure in pipe 7, the pressure in the jack cylinder 2 will be maintained. A manually operated valve 27 is provided for releasing the oil pressure from the jack cylinder 2 when the jack is to be individually lowered for the insertion of a spacer block or the like to start another jacking step. For lowering a jack a worm wheel may be provided on a zone of the periphery of the nut 9 whereby the nut 9 may be turned backwards, for example by means of a worm fixed in a hand drilling machine or the like, to allow the piston rod 4 to move downwards.

The nut 9 effects a follow-up movement during the jack stroke, continuously applying itself against the jack cylinder 2 so that the nut also serves as a locking device which safeguards the jack against untimely lowering in the event of failure of the hydraulic pressure.

The pitch of the screw thread on the piston rod 4 and the number of ratchet teeth 10 around the nut 9 are so related that each advance of the nut by a distance of one ratchet tooth corresponds to the jack piston being raised through a height of /2 mm. Associated with the ratchet teeth 10 is a switch 20 which produces a signal each time it moves over a tooth to actuate the solenoid 29 of its associated valve 26 which moves to cut off the supply of oil to the jack or jack group concerned and at the same time to connect the pipe 7 to the pipe 32. Associated with the pawl 11 are two

switches

17, 18, the switch 18 actuating each time the pawl commences a forward movement and each time it completes a return movement. The switch 17 is a safety switch which is only actuated by the pawl 11 if the latter moves through a distance corresponding to more than one tooth of the ratchet 10 (preferably corresponding to a distance of two teeth), thus indicating improper operation of the jack stroke control mechanism and stopping further actuation of the entire system as will be hereinafter described.

The jack is provided with a further safety switch 22 which cooperates with the nut 9 and actuates in the event that the nut for some reason, fails to remain in contact with the jack cylinder 2 which can only occur if the nut has not been able to follow up sufiiciently quickly to control the rise in the piston. Preferably the switch 22 is arranged to operate if the nut 9 separates from the jack cylinder by a distance of 1 mm.

The hydraulic circuit also includes a solenoid operated bypass control valve 28 which is switched to its left-hand position by the solenoid 33 when all the valves 26 are in their left-hand positions and cutting off the supply of oil to the jacks, so that the oil from the pump 23 is then bypassed through the passage 35 in the valve 28 and pipe 36 back to the oil reservoir 31. 34 is a high-pressure relief valve which normally regulates the maximum oil pressure which can be applied to the jacks but can also be moved to an open position to leave a free passage therethrough. The system also includes a low-pressure relief valve 37 since it is sometimes necessary, for example when raising a jack after it has been lowered, to apply to the jack a lower working pressure, the corresponding control valve 26 then being selectively actuated to feed oil to the jack in question. In this case, the operation of the appropriate manual control to open the selected valve 26 also closes the bypass valve 28 and locks the high pressure relief valve 34 in its open position leaving a free passage to the low-pressure relief valve 34 so that the oil pressure applied to the jack cannot exceed the preset value of the low-pressure relief valve 37. Oil filter 38 cleans the oil which flows through the relief valves.

The multiplicity of jacks required to raise the entire building structure is generally divided into groups each consisting of two .or more jacks supervised by a master jack equipped with a master contact 20. The other jacks in a group are hydraulically interconnected as shown in FIGURE 3 and act as slave jacks. The safety contacts 17 act as limit contacts for both slave and master jacks. If the master contact 20 of a master jack fails to work, the system will be automatically stopped by contact 17. If a slave jack in a group runs faster than the master jack for some reason or another its contact 17 operates the

control valves

26, 28, thus stopping the system. While FIGURE 3 shows an arrangement in which the pump 23 is common to several groups .of jacks, it will be understood that each jacking group could have its own individual pumping unit.

Electrically the system is built up in series fashion so that a following /2 mm. substep can only be initiated when all the contacts 18, which are connected in series, have delivered their signals, first indicating that all the pistons 13 have actually started a forward stroke and secondly indicating that they have all properly retracted. All the master contacts 20 must also have indicated that the nuts have moved by one tooth before a subsequent substep can be initiated. When a

contact

17 or 22 actuates, this specific group stops immediately while the other groups finish their substep normally. It is then impossible to start the next substep automatically and the fault has to be rectified before further raising substeps can be performed.

FIGURE 4 diagrammatically shows the electric circuit of the system. One jack group and pumping unit are shown. From the

contacts

17, 18, 20 and 22 on a jack 1 wires lead to a connection box 45 on the pumping unit indicated by the block 46 in which are indicated the

valves

26 and 28, the pump motor 24, and a relay 47 for selecting whether the pumping unit operates under high pressure or low pressure. The equipment in the pumping unit 46 is connected by wires to its corresponding connection box 48 on the central control desk 49 which includes the memory control unit 50 and a plurality of sets of indicator lamps 51 corresponding to the

contacts

17, 18, 20, 22 of each hydraulic group. In the memory device 50 of the response of the contacts is registered and the series control effect is supervised. 52, 53 and 54 are three counters, respectively the substep counter, the block height counter and the total counter. The mains supply is indicated at 55, the starters being indicated at 60 With their fuses at 61. Associated with the unit 50 are various switches, namely the start-stop switch 62, group-separating switch 63 which serves to cut out one or more hydraulic groups for a number of substeps if required, selector switch 64 for selecting high or low pressure operation, switch 65 by means of which one or more contacts 22 can be cut out of operation, deblocking switch 66 for deblocking a contact 17 which has been actuated, and deblocking switch 67 for deblocking a contact 22 which has been actuated.

So long as the pulses from

contacts

20 and 18 are received in the unit 50 from each jacking group at each substep, and no pulses are received from

contacts

17 or 22, the memory unit will reset at the completion of each substep and the substeps will automatically repeat so long as the start-stop switch 62 is operated. The structure is therefore raised with the floors always in a near-perfect horizontal plane. In the event of a fault occurring as indicated by improper operation of a

contact

18 or 20, or by operation of a

contact

17 or 22, the jacking system stops operating. At no time during jacking can one part of a floor he raised above another part of the floor by more than 1 mm., nor fail to be raised as high as another part of the floor by more than 1 mm., without the Whole jacking system coming to a halt. Therefore, by ensuring that all floors are raised with great precision in the horizontal plane, the introduction of parasitic stresses in the structure is avoided during jacking operations.

FIGURE shows a modification of the hydraulic circuit of FIGURE 3 which can improve the smooth working of the system. Only those parts of the circuit are shown which are necessary for understanding this modification. The

pipes

8 and 15 are not connected together as in FIG- URE 3 but are connected to the pipe 7 through individual devices. Between the pipe 7 and the pipe 15 is a reducing valve 39 capable of being preset to a desired pressure value. Valve 39 is shunted by a nonreturn valve 40 which permits oil flow to bypass the valve 39 when oil pressure is released when the control valve 26 moves to its lefthand position. The manual valves 27 connect with the pipe 15. Between the pipe 7 and the pipe 8 is a springloaded nonreturn valve 41 which opens to allow oil pressure to be applied to the jack cylinders. The operation is as follows. When the control valve 26 is in its right-hand position as shown, the oil flow is initially-resisted by the spring-loading on valve 41 but passes through the reducing valve 39 to apply pressure to the cylinder 12. The valve 41 opens and oil pressure is applied to the jack cylinder, but the pressure applied to the nut-actuating cylinder 12 does not at any time exceed the pressure set by the reducing valve, irrespective of the value of the pressure applied to raise the jack which depends on the load to be raised and thus increases as the building work proceeds.

When the valve 26 moves to its left-hand position, the

oil pressure in the cylinder 12 is released and .oil flows back to the oil reservoir through the pipe 15, nonreturn valve 40, passage 30 and pipe 32. When a jack is to be lowered and its manual valve 27 is opened, oil flows back to the reservoir through the same path. The nonreturn valves 21 and 41 both stop oil flow in the same direction and provide double security against leakage of oil from the jack cylinders.

' FIGURE 6 illustrates a method of constructing the supporting walls 101 which, in the embodiment shown, is constructed of blocks 111 which may be made of concrete, steel or other suitable material and which may be bonded together to form the bearing walls or sections of the bearing walls by means of in situ reinforced or prestressed concrete jambs or lintels, and/or in situ reinforced or prestressed in-filling or casing, and/or horizontal posttensioning.

As shown, the blocks 111 are raised simultaneously in substeps by all the jacks 1 as above described, and when raised through the predetermined jacking step, equivalent to the height of a block, as indicated by the substep counter 52 at the controldesk, each jack is lowered in turn to allow the insertion of another block, such as 111a, the jack then-being raised under reduced pressure until it takes the-load through the inserted block. This reduced pressure on the jack allows the inserted block to be moved into correct relation with the other blocks in the same horizontal row, for example by a sideways force. When all the blocks of a horizontal row have been inserted, and preferably bonded together, for example by horizontal post-tensioning, the whole wall structure can then again be raised in substeps through the height of a row of blocks, the raising of the blocks simultaneously raising the floor structures thereabove which are joined to the bearing wall.

Instead of using the blocks as a permanent part of the wall structure, they may simply serve as spacers and after the structure has been raised through a desired height, for example the height of a storey, the spacers may be removed and replaced by either in situ construction or prefabricated bearing wall sections. During this operation the load on each jacking device is either transferred selectively to adjacent jacking devices or to some form of temporary support. During raising the spacers may be temporarily held together, for example by horizontal posttensioning.

The permanent bearing walls may increase in thickness, width or number from top to bottom of the building in accordance with the loads they have to carry.

FIGURES 7 to 10 are diagrams explaining various methods of erecting supporting columns. In the various figures successive stages of the erection are indicated by the references (a) to (c) or (a) to (d).

As shown in FIGURE 7 the columns 103 are raised by jacks 1 positioned directly therebeneath (as shown at stage a) and after each column has been raised in substeps through a jacking step, which may correspond to the stroke of the jacks or some selected lesser distance, each column is supported (as shown at stage 12) on temporary supports comprising a yoke 112 and temporary support members 113, the columns having brackets 114 which rest on the yoke. The jack is then lowered to allow the insertion of a spacer block 115 and the raising operation is repeated until suflicient spacer blocks have been inserted corresponding to the height of a column section 103. Then (as shown at stage 0), while the previously erected part of the column is supported on the yoke 112 and temporary supports 113 at that level, the spacer blocks 115 are removed and replaced by a column section 103. The temporary support members preferably support the load from the base of the jacking chamber and may also comprise spacer blocks.

In the modification shown in FIGURE 8, the column is raised in similar steps by successively inserting spacer blocks 115 while the column is supported on temporary supports, but in this case each column is provided with a plurality of brackets 114 so that the yoke 112 can always be supported by temporary support members 113 at the same height, either above the base slab 104 (as shown) or therebeneath. In FIGURE 8, stages (a) (b) and correspond to stages (a) (b) and (c) in FIGURE 7.

In the modification shown in FIGURE 9, the columns are raised by jacking devices comprising pairs of jacks 1 acting respectively on opposite ends of yoke member 112 which supports the column (as shown at stage a). At stage b the column is supported by a temporary support member 113 (e.g., spacer blocks) disposed directly beneath the columns, while the jacks are retracted to allow the insertion of spacer blocks 115 between the jacks and the ends of the yoke 112. When a column has been raised through the required height, a further column section 103 is inserted therebeneath (see stage 0) and is supported on a temporary support 113 (see stage d) while the yoke is separated from the column section with which it was engaged and is engaged with the newly inserted column section before repeating the raising operation.

FIGURE shows a further modification in which a column is again raised by jacking devices comprising a pair of jacks 1 and a yoke 112, but instead of inserting spacer blocks between the jacks and the yoke ends, the spacers are constituted by spacer members 116 secured to the column section 103 above the yoke. After a column has been raised by the jacks (see stage a) it is supported by a temporary support 113 (see stage b) while the jacks and yoke are lowered and further spacer members 116 are secured to the column. The spacer members 116 conveniently comprise metal plates applied to opposite sides of a column and bolted together. The upper edges of the plates bear against the bottom edges of the plates thereabove. The upper edges of the upper pair of plates 116 on a column section bear against a head plate 117 on the column section, which head plate is secured to and bears against a foot plate 118 at the foot of the column section 103 thereabove. After a column section has 'been raised through the height of a column section, another column section is inserted therebeneath (see stage 0) and is supported by a temporary support 113 (see stage d) while the jacks and yoke are lowered to engage the yoke beneath the head plate 117 of the newly inserted colurrm section 103.

FIGURES 11 to 13 show respectively a side view, end view and a plan of a practical construction of the yoke and spacer plates for carrying out the column lifting method described with reference to FIGURE 10'.

Referring to FIGURES 11 to 13, the yoke comprises two

side beams

112, 112a which are adapted to be urged together and clamped against opposite sides of the supporting column 103, shown as an H-section steel column, by means of the handwheels 119 coacting with screw bars 120 extending between the side beams of the yoke. Opposite ends of the yoke beams rest on the plungers of the pair of jacks 1. By loosening the handwheels 119 the yoke beams can be released and moved down the column, when the jacks are lowered, while the column is being supported on a temporary support. The spacer plates 116 are bolted together across opposite faces of the column by bolts 121 so that the upper and lower edges of adjacent plates abut each other to support the load, the upper edge of the upper plate bearing against the underside of the head plate 117 of a column section which is secured to the foot plate 118 of the column section thereabove by bolts 122. After a pair of spacer plates 116 have been fixed, and the jacks are raised with low pressure so that the yoke beams bear against the bottom edges of the spacer plates, the handwheels 119 are tightened to clamp the yoke beams to the column section.

The floor structures may be constructed of steel, concrete or a combination of these or any other suitable material, and may be wholly or partly prefabricated or constructed in situ. They may be prestressed either by pre-tensioning or post-tensioning.

The jacking devices may comprise individual hydraulic or screw jacks, or combinations of two or more such jacks with a yoke or other bridging structure. The tem porary supports which take the load oil the jacking devices while the jacking device is being retracted prior to carrying out another jacking step may comprise adjacent jacking devices, specially provided screw or hydraulic jacks, blocks and shims of various heights or adjustable wedges, blocks and short stroke screw or hydraulic jacks, yokes or bridging structures supported on pedestals or blocks, or other convenient supports. The spacers used may comprise blocks, plates, beams or column pieces and may be made of concrete, steel or other suitable material.

Column sections may be prefabricated or made in situ and may be of steel, concrete or other suitable material. The column sections are conveniently of storey or halfstorey height.

While particular embodiments have been described, it will be understood that various modifications may be made without departing from the scope of the invention, and that the method according to this invenion of raising the structure so that the floors remain in a near-perfect horizontal plane during jacking, may be applied to building structures in which the floors are suported partly on columns and partly on walls, or wholly on columns or walls, the walls being either core, perimter or transverse walls or combinations of these. Further, instead of constructing the floor structures at ground level, they may be constructed at the level of one of the lower floors of the building.

I claim:

1. A jacking system for use in the construction of buildings in which the vertical and horizontal structures of each successive storey, starting from the top storey downwards, are constructed near ground level and subsequently raised by a plurality of jacking devices, together with all the completed storeys thereabove, to permit the construction of the vertical and horizontal structures of a further storey therebeneath, said system including a plurality of jacking devices, at least one source of power for actuating said jacking devices, screw means associated with the jacking devices, drive means rotating said screw means through an angle corresponding to the amount by which its associated jacking device rises, switch means producing a signal each time said screw means turns through a small angle corresponding to the jack being raised through a predetermined small substep, means responsive to a Signal from a jacking device to stop the associated jacking device from actuating, a control device in which the signals from all the jacking devices are registered, and means for preventing subsequent actuation of a jacking device to execute a subsequent substep unless the control device registers Signals, corresponding to the same previous substep, from all the jacking devices.

2. A jacking system as claimed in claim 1, wherein each jacking device has associated therewith means for producing at least one further signal in the event of improper operation of the jacking device by over-running the predetermined substep, and means responsive to the production of any said further signal for preventing the jacking devices of the system from executing a subsequent substep.

3. A jacking system as claimed in claim 1, wherein each jacking device includes a hydraulic jack having a piston movable in a cylinder, the piston having a piston rod provided with a screw thread, a nut rotatably mounted on said screw thread and having ratchet teeth, a pawl associated with said ratchet teeth and driven by an auxiliary hydraulic device to turn the nut in a direction to screw down the piston rod and bear against a part which is fixed relative to the jack cylinder, pipes for supplying hydraulic fluid to said jack cylinder and auxiliary hydraulic device from a source of hydraulic fluid under pressure whereby said pawl turns the nut to perform a follow-up movement when the jack piston is raised by applying thereto hydraulic fluid under pressure, a control valve for interrupting the supply of hydraulic fluid to said pipes, an electric switch cooperating with said pawl and ratchet mechanism to produce a signal when said ratchet has turned by an amount corresponding to a substep, means actuated by said signal to operate the control valve to stop the supply of hydraulic fluid to the jack and releasing hydraulic pressure from said auxiliary hydraulic device, means returning said pawl upon said release of hydraulic pressure from said auxiliary hydraulic device, and means feeding said signal to the control device to be registered thereby.

4. A jacking system as claimed in claim 3, wherein said signal is produced by a switch actuated by the ratchet teeth and wherein a second electric switch is associated with the pawl and is actuated thereby to produce a signal at the beginning of a pawl stroke and at the end of the return stroke of the pawl, means feeding the signals produced by said second switch to the control device, means insaid control device for registering the signals received from the second switches associated with the respective jacking devices of the system, and means responsive to the means for registering the signals from said second switches for preventing the jacking system from executing a further substep unless the control device registers signals indicating that each pawl has started a stroke and has completed its return stroke.

5. A jacking system as claimed in claim 4, wherein each jacking device includes a third switch associated with its pawl and arranged to operate only if the pawl executes a movement exceeding that corresponding to the predetermined substep, and means responsive to the operation of any of the third switches associated with the respective jacking devices for preventing the system from executing a subsequent substep.

6. A jacking system as claimed in claim 5, wherein each jacking device includes a fourth switch arranged to operate if the nut separates from the fixed part against which it bears on follow-up by a distance of the order of twice a substep, and means responsive to the operation of any of the fourth switches associated with the respective jacking devices for preventing the system from executing a subsequent substep.

7. A jacking system as claimed in claim 3, including a pressure reducing valve in the pipe leading to the auxiliary hydraulic device, whereby the auxiliary hydraulic device always operates at the hydraulic pressure set by the reducing valve irrespective of the hydraulic pressure necessary to raise the jacking devices, and a non-return valve shunts the pressure reducing valve to allow free flow of hydraulic fluid from the auxiliary hydraulic device when the fluid pressure therein is released.

8. A jacking system as claimed in claim 3, wherein a jacking device comprises two jack cylinders arranged side-by-side and spaced apart and with their pistons projecting upwardly and bridged by a yoke comprising two beams between which can be located a column section to be raised, means being provided for forcing said beams together to clamp on to a column section therebetween.

9. A jacking system as claimed in claim 3, including means for lowering a jacking device after it has been raised through a desired number of substeps without lowering other jacking devices, and means for reducing the hydraulic pressure applied to said jacking device to raise it after it has been lowered.

10. A jacking system as claimed in claim 3, in the construction of a building of which the floors are supported at least in part on supporting columns, including temporary support means for temporarily supporting a raised column in its raised posit-ion while the associated jacking device is lowered preparatory to another jacking step.

11. A jacking system as claimed in claim 8, including spacer plates adapted to be secured to a column above the yoke to be raised thereby, temporary support means being provided for supporting the column at its raised height while the yoke is lowered to enable spacer plates to be secured to the column preparatory to another jacking step.

References Cited UNITED STATES PATENTS 2,975,560 3/1961 Leonard 25489 3,036,816 5/1962 Stubbs et a1. 254- X 3,201,088 8/1965 Long 254-89 3,327,997 6/1967 Zenke 254-89 OTHELL M. SIMPSON, Primary Examiner.