CA1305869C - Wall casting system - Google Patents

Abstract

Abstract A wall casting system for progressively forming a plurality of vertically superimposed wall segments, and comprising a framework 10 from which formworks 11 are suspended and capable of being positioned to define a space within which concrete is to be poured to form said progressive wall segments. The system further comprises a jack support 19 adapted, in use, to engage within pockets 24 in a lower wall segment preceding a previously cast wall segment, with a jack 21 between said jack support 19 and said framework 10 to elevate the framework to an upper position for the casting of a further wall segment. The system further comprises a main support 20 adapted, in use, to engage with pockets 24 in the previously cast wall segment while the jack support 19 is subsequently disengaged from its associated pockets and raised by the jack to the position of said main support 20 to engage the same pockets 24 as the main support whilst pouring of concrete for said further wall segment is carried out.

Description

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WALL CASTING SYSTEM
This invention relates -to an improved method and apparatus, for -the incrernental constructLon oE walls, ln particular, for constructing vertical walls oE concrete in the building and construction industry.
Currently, incremental, self-climbing systems are 10 limited;
a. in -the amount and extent of adjustment to much of the cast surface, b. in the control available to the overall direction of the forming system in its climbing operation, 15 and ~3~586~

c. in the speed and utility of the system, especially if it depends on the support of the just cast, incremental lift in the height of the wall.
One such known system is disclosed in the 5 specification of Australian Patent No. 490,759.
The object of this invention is to overcome the above difficulties, by increasing the control and speed of the operation, and so improve accuracy and economy in the construction According to the invention there is envisaged a wall casting system for progressively forming a plurality of vertically superimposed wall segments, said system comprising a framework from which formworks are suspended and capable of being positioned to define a space wi-thin which concrete is to 15 be poured to form said prOCJreSSiVe wall segments, said system comprising a jack support adapted, in use, to engage within support means in, or on, a lower wall segment preceding a previously cast wall segment, jack means between said jack support and said framework to elevate the said framework to an 20 upper position for the casting of a further wall segment, a main support adapted, in use, to engage with means in, or on, the prev.iously cast wall segment whilst said jack support is subsequently disengaged from its associated support means and raised by said jack means to the position of said main support 25 to engage the same support rneans as sald main support wh.ilst pouring of concrete for said furthe~r wall ~egment 1.~ carried out.
One preferred embodiment of the invention will be described with reference to the accompanying drawings, in 30 which:
Figure 1 is a plan view of the system of this preferred embodiment of the present invention with the overlying working platforms for the system omitted for the simplicity of description;
Figure 2 is a vertical cross-sectional view taken along line 2-2 of Figure l;

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Figure 3 is an enlarged vertical cross-sectional view of the left hand end of the view of Figure 2;
Figure 4 is an enlarged plan view of the arrangement of the formworks at two wall sections to be cast to form a 5 corner of the wall structure being cast by the system of Figures 1 to 3;
Figure 5 is an enlarged view of the devices which are utilized to lock an outer sheath fixed to the cylinder of the ram assemblies used in the system to the associated main 10 supports used in the system;
Figure 6 is an enlarged cross-sectional view of the manner in which the formworks are suspended and otherwise supported during casting of wall segments; and Figures 7~, 7B, 7C and 7D are a series of views of 15 part of the system showing relative movements of the various integers during progressive steps in the casting of superimposed wall segments.
The system of this preferred embodiment of the invention is primarily used to cast a group of four hollow 20 towers forming a central core of a multi-storey building and which may form lift shafts and stair well shafts for the building.
In this embodiment, the four towers to be cast from concrete, comprise two substantially rectangular 25 cross-sections towers L forming lift shafts, ancl two substantially square cross-section -towers S forming shafts for stair wells, each at which are to be formed from progressively cast wall segments by the system of the preferred embodiment.
The wall casting system comprises an overhead 30 framework generally indicated as 10 from which formworks 11 for wall forming purposes are suspended. The framework 10 is composed of main beams 12 extending longitudinally of the system, and each consisting of a pair of spaced apart steel channel sections 12a, upon which are superimposed and fixed a 35 plurality of laterally extending secondary beams 13, also each consisting of a pair of spaced apart steel channel sections 13a. Some of the formworks 11 which are required to be :~3~8~i~

shifted relatively large distances away from cast wall segments to allow access for personnel to clean their wall casting surfaces, namely those adjacent ~he exterior surfaces of the towers, are carried by the framework 10 by roller 5 assemblies 14 from which the respective formworks are suspended and which, in the case of the formworks which are to move longitudinally of the structure, run along the main beams 12 and which, in the case of formworks which are to move laterally of the structure, run along the secondary beams 13.
Those formworks within the interior of the towers and to which access for cleaning can be achieved at a different level without the necessity to be rolled away from the respective towers, are suspended from the framework 10 by cables 15 extending over a pair of pulleys 16 to a hand 15 operated winch 17, or an electric winch, carried by vertical support columns 18 the functions of which are to be later described.
Extending downwardly within each of the rectangular towers S is a pair of spaced apart jacking/support assemblies, 20 each comprising a jacking beam 19, a shear key beam 20, a pair of jacking rams 21, a connector 2la for connecting the tops of each of the rams to each of the main beams 12 extending across the tops of each of the towers S. The framework 10 also suspends the shear key beams 20 by the vertical support 25 columns 18 which, in turn, are connected, via connectors 18a, to the framework 10 at their tops. In the towers ~ where jacking/support assemblies are not used, tie beams 22 are used to connect the support columns 18 together in place of the shear key beams 20, whilst in the case of the support columns 30 18 in all towers, transverse bracing ties 23 are used.
With the system of this preferred embodiment alternative means of support are necessary for the self-climbing operation. The self-climbing jacking/support assemblies for instance, have two alternative means of 35 support, (but on the one member) in climbing from one support point to another. Slip form systems employ self climbing jacks on rods which are generally cast into the wall. Many of the problems of continuously cast, slip form systems, as outlined in the introductory section of the specification of Australian Patent 490,579, have been overcome in incremental casting systems described in that Aus-tralian patent 5 specification and in which alternative means of support are used from quite separated support points, one cast segment apart. The aforesaid system employed self-climbing movable jacks on climbing posts for instance, which were cast into the top of the freshly poured wall segment as one complete means 10 of support. The other means of support were pockets in the wall in the last previously poured segment, into which retractable shear keys engaged from the bottom of the formworks. These pockets supported the system whilst it was set up, and during the pouring of the next to be cast segment.
15 Thus, the incrementally cast system had two, alternative, internal, support systems.
In the new incrementally cast system of the present invention, unlike any of the above systems, the alternative means of support originate from the same support points in the 20 previously cast segment, and in that respect reference should be made to Figures 2, 3 and 7A to 7D of the drawings.
Pockets 24 cast as shown in the concrete for previously cast wall segments, using blockouts 25 on the relevant formworks 11, support pivoted feet 26 on the opposite 25 ends of the shear key beams 20 and spring loaded feed 27 on the ends of the jacking beams 19. These feet 26 and 27 on the shear key and jacking beams form two alternative support means within the system, and nest within each other as shown in Figures 2, 3 and 7A so that they use the same cast-in pockets 30 24 as means of support. The two different types of feet may alternatively and independently support the entire system on bearing surfaces at the bottom of the same cast-in pockets 24.
The advantages of this new approach to support are as follows:

a. Only a single set of support points are provided on the cast wall segments. This is both simplifying and economical as only one set of blockouts 25 need to be provided for the formworks 11 used in the system.
b. The cast-in pockets 24 are formed in the previously poured but one wall segment, so that all jacking opera-tions to be later described are supported on concrete for wall segments that is at least one climbing cyc~e older than that previously employed in Australian Patent No. 490,759 for example. As can be seen in Figure 7C in particular; the entire system can be supported on a lower cast wall segment, until after the casting of the concrete two segments in advance of that wa]1 segment. Concrete at the lower wall segment is older, and has aged to a higher strength and durability. Hence, a greater factor of safety in support strength of the concrete is available, or alternatively, if safety is sufficient, cycle times can be reduced as this system can be supported from wall segment at least one climbing cycle older than any other known system.

The following describes a typical activity cycle for 25 casting vertical walls of concrete in the form of a plurality of vertically superimposed waLL segrnents, and with reference to Figures 7A to 7D of the drawings.
i. Strip and disengage the formworks 11 from the previously cast wall segments as shown in Figure 7A.
ii. Lift the system to the next level for casting a wall segment by extending the jacking rams 21, as shown progressively through Figure 7B
to Figure 7C, and then laterally restrain and contain the system as necessary wi-th the system being supported primarily via the foot of the jacking beams 19 engaged within the pockets 24 in the previous but one cast wall segment and wi-th the feet of the shear key beams providing additional support within the pockets 2~ in -the previous cast wall segment.
iii. Retract the jacking rams 21 as shown in Figure 7D.
iv. Plumb and locate the system.
v. Clean the formworks and place reinforcement, block-outs for openings, sleeves, etc.
vi. Close forms.
vii. Pour/cast concrete at the level of the new wall segments.
In the lif-ting or jacking part of the operation, the 15 upper apparatus as a whole, inc]uding the overhead framework 10 comprising the main beams 12 and the secondary beams 13, support columns 18, and the suspended formworks 11, are thrust upward by the hydraulic rams 21 in a single stroke. The hydraulic rams 21 are supported on the jacking beams 19 which 20 are set in the shear key pockets 24 in the lower but one wall segment as shown in Figures 7B and 7C.
The rams 21 are supported on the jacking beams 19 in a 'limited pin' fashion, and may be laterally restrained in passing through, and also at, the level at the shear key beams 25 20. The 'limited pin' relationship allows sufficient rotational freedom between the rams 21 and thelr resp~ctive jacking beams 19 to prevent interference with other rams in the system and so preventing a possible 'binding up' in the jacking operation. This freedom however, is limited so that, 30 in retraction of the rarns 21, their beams 19 are drawn up with it in a sufficiently correct orientation for eventually engaging in pockets 24 higher up the wall.
The system is restrained laterally during the jacking operation by the last cast segment of the wall, either 35 by sliding the pivoted feet 26 of the shear key beams 20 over 13~S869 _ 9 _ the surface of the walls or by guides or rollers ~see rollers 28 on working platforms supported above the shear key beams 20).
The jacking component of the climbing operation is 5 terminated when the pivoted feet 26 on the ends of the shear key beams 20 pass the next cast-in pockets 24 higher up the wall. Due to eccentric gravitational forces, the feet 26 may automatically rotate and engage the pockets 24. Some reversal of the jacking operation will then settle or land the feet 26 10 and therefor the system in the pockets 24 at the higher level.
The climbing operation is completed by the retraction upward of the rams 21 and the structure supported thereby and this is done by the continued reversal of the hydraulics for the rams 21. The feet 27 on the ends of the 15 jacking beams 19 pass over the surface of the wall until, at the higher pocket level, upon engagement between the two beams 19 and 20 and feet 26 and 27 in the system, the feet 27 spring out into the same pockets 24, and adjacent to the pivoted feet 26. Reversal again of the jacking operation, will settle the 20 jacking beam feet 27 in the bottoms of the wall pockets 24 and the system is ready for the next self-climbing operation.
The above however, although preferred, is not a rigid sequence and may involve, as examples,the following variations:
Items v. to vii. inclusive may be done progressively, in a lar~e or multi-celled core wall system for instance. And, as has been described earlier above, the retraction of the rams 21, item iii. may be delayed in this sequence for almost a complete cycle, until just before the 30 next lift, between items i. and ii. In this latter case the jacking operation, item ii., remains incomplete as the system is not 'landed' in pockets 24 at the higher level, but remains supported at the pockets in the level of the jacking beams 19.
A still further variation to the jacking operation is, that if 35 required at any stage during the construction of a wall, any ~o~

fraction of a full lift or stroke of the rams 21, may be used to cast a wall segment without having to settle or land the system at the level of the shear key beams.
The advantage of this self climbing system are as 5 follows:
a. Delay in the self-climbing transfer of load from via the jacking beams to the shear key beams allows for the system to be supported at lower segments of the cast wall. The consequence is the improvements in the factor of safety in support strength, or reduced pour cycle times for the same factor of safety, as described earlier.
b. Any fraction of a full climbing increment can be poured without transfer load from the jacking to the shear key beams. The jacking system does not occupy wall space and need not be removed or shifted before the next segment is cast or poured.
c. The location of the rams 21 is more flexible. Ram locations are not limited to being at the top of a wall, but may be placed anywhere in the plan consistent with adequate strength and stability.
d. The capac:ity of the two alternative means of support via the jacking or shear key beams allows larger spans, and larger spaces between structural mc-~mbers in the overhead framework 10, than has been experienced in previous waL1-formincJ systems. A
greater variety of wall constructions can consequently be accommodated with the system. The spaces in the overhead frarnework 10 are also now sufficient Eor the passage of full width sheets of reinforcing fabric in the steel reinforcement for the wall.
e. All jacking elements are concealed below the framework 10 or any upper decking carried thereby, and as such there are no protruding elements above the framework or upper deck which offer the ~3V58~

possibility of collision with crane lifted loads during reinforcement supply and concreting operations, for instance.
Thus, the jacking and alternative support system of 5 the present invention has the advantage of versatility and flexibility in the pouring of a wall construction that aids safety, speed of construction and economy.
It will be noted that the jaclcing beams 19 are each associated with shear key beams 20, to complete the 10 self-climbing combination. On the other hand, extra shear key beams 20 may be provided as additional support for the system.
In either case, the complete system is supported either on the jacking beams 19, or the shear key beams 20, or both, via their respective feet in the poc!cets of lower previously cast 15 wall segments.
The shear key beams 20 support all the overhead framework 10 and a series of working platforms 29 throughout the system. From the overhead framework then, can be suspended typically, a multiplicity of formworks 11 and 20 working platforms 29 for their access, limited only by the capacities of the lifting rams 21 and the interconnecting structure of columns 18 and beams 12, 13 and 22.
Bracing between the shear key beams 20 and the overhead framework 10 can be used to provide structural 25 integrity and resists lateral forces such as wind loads.
Any particular wall construction, cellular in plan to form a series of towers L and S, can be constructed using the system together with an overhead framework 10 tha-t suits both the plan layout and the components of the system. Every 30 cell in a construction need not necessarily contain wall pockets and jacking/support assemblies. Sufficient wall pockets and assemblies need be provided only to ensure stability and safety in the construction of a particular wall layout.
Some working platforms 29 are supported off the upper framework 10 at locations generally in accordance with previous incrementally cast formwork systems.

i. The common, upper working platforms 29 on the overhead framework 10 is a heavy duty working platfor~ which could support mansheds, toilets and the like, and upon which reinforcement and other construction components could be stored awaiting inclusion in the cast walls. It is also the level from which concrete is poured, into pouring chute assemblies 30, after pouring chute covers 31 are removed, as it has access to the top of the walls and from which jacking might also be controlled, as it has ready access to the extremities of the entire system.
ii. Each tower in plan, in the wall construction, has lower and intermediate levels of platforms 29 for personnel access to the wall casting region for the placement of reinforcement, opening block~outs, sleeves, etc., and the stripping and cleaning of forms. Each lower platform is supported by an arrangement of ties 32.
20 iii. The external perimeter of the system has-a lower level of platforms 29, for similar personnel access, and is suspended from the overhead framework by external scaffold hangers 33, with external cladding 34, with connecting and supporting structureæ of beams 35 and 36 and strapping for th~ platforms 29.
A wire mesh and timber panel barrier 38 is also connected to the hangers 33.
iv. Trailing platforms, may be added to make good tie-bolt holes and imperfect surfaces and are also supported by arrangement of beams and ties, which in turn are suspended from the lower platforms 29.
Rubber seals 37 may also be provided along the edges of the lower platforms.
v. Removable platforms formed from hangers with planks 34 and hooked onto the top edges of the formworks 11 may also be provided where necessary for cleaning of the formworks.

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Each cell containing jacking/support assemblies may also contain a platform for inspection of feet engagement with the pockets 24.
As is common practice, access to each of these 5 levels, to and from the common overhead framework 10, is via hinged hatchway and ladder access. Access to the system as a whole, is by a scaffold tower within the completed walls, and from lower levels of the construction.
The formworks 11 are supported off the upper 10 structure, and unlilce the system of Australian Patent No.
490,759, all are completely independent of the structural support to the system in either of its support modes. In Australian Patent No. 490,759, the formworks were the structural element between the 'retractable support means' or 15 shear keys, in the concrete wall pockets, and -the overhead structural framework which was also attached to the jacks. In the system of the present invention any formworks may be independently adjustable relative to the upper structure.
Typically, each formwork 11, internal to the wall 20 construction, is located at the top, with reference to Figures 3 and 6, by two sets of brackets. Each set consists of a support arm 41, which may move the form up and down relative to the structure and a horizontal adjustment bracket 42, which can move the formwork in two directions relative to the 25 structure. The support arm has two alternative pivot locations 41a which enable the associated ~ormwork to move inwardly and outwar~ly for two diferent wall thlcknesses, particularly in situations where the wall thickness at higher levels in a building do not have to be as great. More than 30 two alternative locations 41a may be provided if necessary.
The lower end of the formwork 11 is simply pushed against the side of the top of the previous segment to execute a seal with the existing structure. Typically, a push-pull prop (not shown) is used against the corresponding formwork 11 35 on the other side of the cell or tower and/or bottom wall ties 43 to draw the formworks 11 on each side of the wall to the top of the last segment.

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Alternatively, in a typical rectangular cell or tower bounded by four walls, the short internal formworks 11 at each end of the cell may be supported, by brackets and swing arm assemblies, from the ends of the internal, long, 5 formworks 11, instead of independently off the main framework 10. This is done to facilitate the adjustment of all four internal formworks 11 from just four points on the structure.
The correct vertical and horizontal adjustments of the long side formworks 11 will then carry with them the end formworks 10 11 which will be automatically in adjustment. Figure 4 of the drawings, shows an arrangement of corner stripping turnbuckles 45 and 46, and an end formwork support bracket 44, which places internal, cell formwork adjustments readily at hand at each of the four, near corner locations. In addition, an 15 internal overlap corner panel 48 is provided at each internal corner, and is drawn in-to tigh-t engagement with all edges of the adjacent panels by a clamping arrangement 49 between it and the internal structures of each of the formworks 11 at the corner.
The advantages of this feature of independence and adjustment between the formworks and the remaining structure of the system are as follows:
i. Ready and early correction of errors in the upward direction of travel of the formworking system. As soon as the upper shear key beams 20 are landed in upper poc};ets 24, or laterally restrained a~Jainst the top of -the previously cast wal~ segment, there exists a ~;tatic base (the upper platform 29 for instance) upon which measurements can be ma~e for deviations from design location and plumbness. This may, and desirably, should be done before any formworks are located for the next segment to be cast. Such correction of the system as a whole remains unaffected by the subsequent movement of any individual and independent formworks.

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ii. To facilitate adjustment to changes in a wall section, a formwork 11 may be adjusted to a new position, or modified, or replaced altogether with a new formwork without affecting the system.
5 iii. General ease and speed of adjustment of the mass of the formworks 1] alone, in contrast to the need to move the entire mass of the system to accomplish adjustments in previous systems, (such as in Australian Patent No. 490, 759).
10 iv. Greater accuracy, because of the independence between the formworks 11 and the system as a whole, and because of the ease with which adjustments are made~
In addition, with reference to Figure 1, an external 15 corner bracing arrangements 50 is illustrated and comprises cables 51 shackled between the vertical 35 and the member 52 of the associated upper framework 10, and diagonal wires (not shown) shackled between the same member 52 and the top of the vertical 35 of the adjacent platform at the corner.
With reference to Figure 5 of the drawings, in order to lock the jacking rams 21 relative to the shear key beams 20 and allow adjustment of the locking position, the cylinder of each ram has a pair of sheaths 53 partially surrounding and affixed to opposite sides thereof and including a plurality of 25 vertically spaced apart apertures 54 therein. The shear Icey beams carry a pair of ups-tanding adjustmcnt bolts 55 on either side of the rams 21 up and down which housings 56 for respective locking bolts 57 are adjustable. Each locking bolt 57 is retractable from respective apertures in the sheaths 53 30 by pins 58 attached to the locking bolts and extending out of the respective housings to pivoted connections 59 to operating handles 60 via eccentrics, to allow the pins 58 and the locking belts 57 to be retracted against the action of compression springs 61 to enable relocation of the locking 35 bolts in alternative apertures 54 when the relative locked positions of the respective shear key beam and the ram cylinder, via the sheaths 53, is required to be altered during operation of the system. The locking arrangement described above also enables the system -to be locked at any position during a lift, such as may become necessary for safety purposes, for example, high wind conditions.
As access to at least one side of each wall cavity is necessary for the placement of reinforcement, block-outs for openings, the cleaning of formworks, etc., when a wall is a partition between two cells, and not an external wall in a construction, rolling away of the relevant formwork 11, 10 internally, is difficult. It is also difficult to provide the space internally for the formworks to roll away from the construction and the retraction of the formworks at the internal corners is a special situation and is especially difficult to achieve satisfactorily.
~y utilising shear key beams 20 with sliding, pivoting feet 26, the feet can be withdrawn from the wall sufficiently to lower a detached formwork 11, by the winch 17, below the general level of wall cavity access. This then allows easy, unimpeded access, to one side of any internal 20 partition wall cavity.
The lowering of formworks 11 is not limited to only those panels above shear key beams 20, but the sliding feet 26 make it possible to lower even these panels if the geometry of the wall construction so dictates. The limitation placed on 25 the system however in the latter case, is that the system iEi not supported on shear key beams 20 when tlle panel~i are lowered and returned past the Eee-t 2~, but is supported on the lower jacking beams 19.
When the system is used in a wall construction that 30 consists of a single cell that contains not more than two jacking/support assemblies, the upper framework 10 may require additional stability during the lifting operation. A trailing set of wheels, rollers or guides may be fitted, which are rigidly connected to the upper structure via rigid bracing and 35 bear against the inside surfaces of the walls and of the shear key beams 20. The vertical distance between the level of ~3~

contact of the shear key beam 20 with the walls and the contact of the trailing guides' with the walls gives directional stability to the upper framework.
The top connection of the hydraulic rams 21 to the 5 overhead framework 10 may allow lateral movement. This feature allows the entire system to be moved laterally from the cast construction if necessary, and adjusted in location.
It will be appreciated frorn the above description that a single set of wall pockets 24 provides more than one 10 form of support in the self-climbing operation, and in order to allow different portions of the bearing area of the bottoms of the pockets to support the alternative bearing feet 26 and 27, at least one of the feet must be split or divided in its bearing area if the centre of bearing of the alternative beams 15 is to be central in the pocket.
It will also be appreciated from the preceding description of the preferred embodiment that the self-climbing system allows for any fraction of an incrementally cast wall segment to be poured without settling the system into the wall 20 pockets.
The alternative means of support in the self-climbing operation need not be employed short of the full stroke of the rams 21 as there is no jacking or support equipment above the previously cast segment that might occupy 25 the space for the next segment, -that is, no support must be removed before the next segment is cast. Transfer from support means on the jacking beams lg to the shear key beasns 20 and vice versa is consequently not necessary for this reason, but only to execute self-climbing. Such a feature is 30 useful for pouring a 'short lift' in the incremental casting of a wall, or, as has been described earlier, it may be used to support the Æormwork system at the level of a lower pocket 24 where concrete is one climbing cycle older in curing time.
This increases the factor of safety in support 35 strength of the concrete, or alternatively, for the same factor of safety, the possible pour cycle time between one cast increment and the next above, may be reduced.

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It will also be noted that the supporting structure for -the system and the formworks 11 are effectively independent, which is not the case with known self-climbing formwork systems where the surfaces that form the concrete 5 cast wall also form part of the structure that supports the system.
This feature of the present invention provides the ability to differentiate between adjustment in relation to direction-location and plumbness of the climbing system as a 10 whole, from that of individual formworks. The freedom, accuracy and ease of adjustment that it offers and the consequent advantages have been outlined above.
Consequently, the 3-way adjustment of the formworks 11 relative to the structure of the system, via the adjustment 15 support arms 41 and bracket assemblies 42, is possible with the present invention as discussed previously.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:-

1. A wall casting system for progressively forming a plurality of vertically superimposed wall segments, said system comprising a framework from which formworks are suspended and capable of being positioned to define a space within which concrete is to be poured to form said progressive wall segments, said system comprising a jack support adapted, in use, to engage within support means in, or on, a lower wall segment preceding a previously cast wall segment, jack means between said jack support and said framework to elevate said framework to an upper position for the casting of a further wall segment, a main support adapted, in use, to engage with means in, or on, the previously cast wall segment while said jack support is subsequently disengaged from its associated support means and raised by said jack means to the position of said main support to engage the same support means as said main support whilst pouring of concrete for said further wall segment is carried out.