The present invention relates to a method of raising a building.
In the building industry, it is often necessary to raise a building, e.g. to raise a riverside or seafront building above flood or high-tide level. A typical example of this is the city of Venice, where the ground floors of buildings are regularly flooded by so-called “high-water phenomena”.
Alternatively, a building may be raised to build a basement underneath, in situations in which excavating underneath the building is undesirable or impossible, or to increase the height, to make full use, of a floor.
Patent IT1303956B proposes a method of raising a building, whereby a new foundation is built comprising a number of through holes; and, for each through hole, a connecting member fixed to the foundation, adjacent to the hole, and projecting at least partly upwards; a pile is then inserted through each hole, and a first thrust is applied statically to the pile to drive it into the ground (the first thrust is applied by a thrust device located over the pile, cooperating with the top end of the pile, and connected to the projecting part of the connecting member, which, when driving the pile, acts as a reaction member for the thrust device). Once all the piles are driven into the ground, a second thrust is applied statically between each pile and the foundation to raise the building with respect to the ground; and, once the building is raised, each pile if fixed axially to the foundation.
Patent Application WO2006016277A1 proposes a method of raising a building resting on a supporting body in turn resting on the ground, whereby a new foundation is built comprising a number of through holes; and a number of connecting members, each fixed to the foundation, close to a hole. A pile is then inserted through each hole, with its bottom end resting on the supporting body, and its top end projecting from the hole; each pile is then fitted with a thrust device, which rests on the top end of the pile on one side, and is connected to the corresponding connecting member on the other side; and, finally, thrust is applied statically to each pile by the thrust device to raise the building with respect to the supporting body. Once the building is raised, each pile is fixed axially to the foundation. The difference between the lifting methods proposed in Patent IT1303956B and Patent Application WO2006016277A1 substantially lies in the fact that, in Patent IT1303956B, each pile is driven individually into the ground before commencing the lifting operation, whereas, in Patent Application WO2006016277A1, a supporting body already exists between the building and the ground, so the building is raised without driving the piles into the ground first.
In the case of a very large building and/or unusual structural situations, the above known methods leave room for improvement, in that, at the actual lifting stage, the building structure has been found to potentially undergo severe stress requiring major consolidation work.
It is an object of the present invention to provide a method of raising a building, which is cheap and easy to implement and an improvement over the above known methods.
According to the present invention, there is provided a method of raising a building, as claimed in the accompanying Claims.
A number of non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which:
Number 1 in
First, a survey of building 1 is conducted to determine the value and distribution of the masses constituting building 1, and which comprises floor plans of the various floors, and drawings of all the walls, showing door and window openings and any damage to the walls. Given the thickness and density of the walls, it is possible to determine their weight and weight distribution.
A static analysis of building 1 is also made to ensure it is capable of safely withstanding lifting-induced stress; and, if necessary, building 1 may be consolidated and strengthened before it is raised.
A survey of ground 2 beneath building 1 is then conducted to obtain detailed information of what is to be found beneath zero level and down to a depth of at least 5 m. Knowing the nature of ground 2 beneath building 1 is essential to select the type of foundation to be constructed (e.g. long piles, short piles or even footings).
As shown in
Mat 7 is typically constructed in portions extending between the walls. To achieve structural continuity between the various portions of mat 7 and supporting walls 4, mat 7 is posttensioned by means of a number of metal posttensioning cables 8 (shown by dash lines in
If supporting walls 4 are not very coherent, cohesion may be improved by resin injection or bolting.
When constructing mat 7, some areas of mat 7 are prepared for subsequently driving foundation piles 9 (shown in
As shown in
Each hole 12 is surrounded with a number of threaded anchoring ties 16, each of which is connected to fastening ring 14, extends through mat 7, and projects vertically outwards of mat 7. A connector 17 (
As shown in
Each shaft 18 is tubular, has a through inner conduit 20, and is smaller crosswise than relative hole 12 to fit relatively easily through hole 12. Each foot 19 is defined by a flat, substantially circular plate 21 with a jagged outer edge, but may obviously be defined by a flat plate 21 of a different shape, e.g. oval, square or rectangular, with a jagged or smooth edge. Each foot 19 is larger than or the same size crosswise as relative hole 12, is initially separate from shaft 18, and, when constructing mat 7, is placed substantially contacting ground 2 beneath mat 7 and coaxial with hole 12. Each shaft 18 therefore only engages foot 19 to form foundation pile 9 when shaft 18 is inserted through hole 12.
To ensure sufficiently firm mechanical connection of each shaft 18 to foot 19, foot 19 has a connecting member 22, which engages shaft 18 to fix shaft 18 transversely to foot 19. For example, in the embodiments shown, each connecting member 22 is defined by a cylindrical tubular member, which extends perpendicularly upwards from plate 21, and is sized to relatively loosely engage a bottom portion of inner conduit 20 of shaft 18. Obviously, connecting member 22 may be formed differently.
A bottom end portion of each guide tube 13 is fitted with at least one sealing ring 23 made of elastomeric material, and which engages the outer cylindrical surface of shaft 18 of foundation pile 9, when foundation pile 9 is fitted through corresponding hole 12.
When constructing mat 7, at least one injection conduit 24 is formed at each hole 12, is defined by a metal tube extending through mat 7, and has a top end projecting from mat 7, and a bottom end terminating adjacent to hole 12 and contacting a top surface of plate 21 of foot 19.
As shown in
Depending on the structural characteristics of mat 7, the characteristics of ground 2, and the characteristics of building 1, each foundation pile 9 is assigned a rated load, i.e. a weight that must be supported by foundation pile 9 without yielding, i.e. without breaking and/or sinking further into ground 2. To ensure the respective rated load is complied with, each foundation pile 9 is normally driven until it is unable to withstand thrust by pile-driving device 10 greater than the rated load without sinking further into ground 2. This operating mode is made possible by driving one foundation pile 9 at a time into ground 2, so that, when driving in foundation pile 9, practically the whole weight of mat 7 and building 1 can be used as a reaction force to the thrust of pile-driving device 10. More specifically, each foundation pile 9 is driven with a force equal to 1.5-3 times the rated load of foundation pile 9, thus ensuring maximum safety of building 1 both during and at the end of the lifting operation.
The way in which each foundation pile 9 is driven into ground 2 will now be described with particular reference to
To drive foundation pile 9 into ground 2, shaft 18 is first inserted through hole 12 to engage (as described above) foot 19 located beneath mat 7, in contact with ground 2 and coaxial with hole 12. Once shaft 18 engages foot 19 to define foundation pile 9, a pile-driving device 10 is set up over foundation pile 9, cooperates with the top end of foundation pile 9, and is connected to ties 16. In a different embodiment not shown, pile-driving device 10 may be connected to guide tube 13.
In one possible embodiment shown in
Once connected to respective foundation pile 9 as described above, pile-driving device 10 is operated to expand and exert static thrust on foundation pile 9 to drive foundation pile 9 into ground 2. The reaction force to the thrust exerted by pile-driving device 10 is provided by the weight of mat 7 and building 1, and is transmitted by ties 16, which act as reaction members by maintaining a fixed distance between top plate 26 and mat 7 as hydraulic jack 25 expands, thus driving in foundation pile 9.
Obviously, pile-driving device 10 may be formed differently, providing it exerts static thrust on foundation pile 9 to drive foundation pile 9 into ground 2. For example, pile-driving device 10 may be of the type described in Patent Application IT2004BO00792, which is included herein by way of reference.
As foundation pile 9 is driven into ground 2, foot 19 forms in ground 2 a channel 29 of substantially the same transverse shape and size as foot 19, and which comprises an inner cylindrical portion engaged by shaft 18, and a substantially clear outer tubular portion. Simultaneously with the sinking of foundation pile 9 into ground 2, substantially plastic cement material 30 is pressure-injected along injection conduit 24 into the outer tubular portion of channel 29. More specifically, cement material 30 is substantially defined by microconcrete for fluidity and smooth pressure-injection along injection conduit 24. Sealing ring 23 prevents the pressure-injected cement material 30 from leaking upwards through the gap between the outer surface of shaft 18 and the inner surface of guide tube 13.
If ground 2 has a tendency to shrink (as in the case of peat layers), substances (e.g. bentonite) may be added to cement material 30 to reduce friction (and therefore adhesion) of ground 2 with respect to cement material 30 as it dries, and so allow ground 2 to shrink freely and naturally with time. Waterproofing substances may also be added to cement material 30 to make it substantially waterproof even prior to curing. This is necessary when foundation pile 9 is sunk through groundwater, particularly high-pressure and/or relatively fast-flowing groundwater, and prevents cement material 30 from being washed away and so degraded. Tests also show that, when working through groundwater, it is important to inject cement material 30 at higher than the water pressure, to avoid the formation of breaks in cement material 30.
As stated, each shaft 18 is divided into segments, which are driven successively, as described above, through hole 12 and welded to one another. More specifically, once a first segment of shaft 18 is driven, pile-driving device 10 is detached from the top end of the first segment to insert a second segment, which is butt welded to the first (possibly with a connecting piece in between); and pile-driving device 10 is then connected to the top end of the second segment to continue the driving cycle. The segments forming each shaft 18 are normally identical, but, in certain situations, may differ in length, shape or thickness.
As shown in
To do this, each foundation pile 9 is fitted with a lifting device 11 resting on the top end of foundation pile 9 on one side, and connected to ties 16 on the other side. In actual use, each lifting device 11 is operated to produce, between foundation pile 9 and mat 7, static thrust which is transmitted to mat 7 by ties 16.
As shown in
In actual use, each hydraulic jack 31, 32 is operated to expand and so exert thrust, between foundation pile 9 and mat 7, which is transmitted to mat 7 by ties 16, which act as reaction members by maintaining a fixed distance between top plate 26 and mat 7 as hydraulic jack 31, 32 expands.
In a preferred embodiment, ties 16 are fitted with safety bolts 37 located on top of and kept close to bottom plate 35 to limit downward travel of mat 7 in the event of a breakdown (hydraulic failure, resulting in loss of pressure, or mechanical failure) of hydraulic jack 31, 32.
As shown in
In a preferred embodiment shown in
Lifting devices 11 of each work group are connected to a respective main hydraulic central control unit 38 supplying all the main hydraulic jacks 31, and to a respective secondary hydraulic central control unit 39 supplying all the secondary hydraulic jacks 32. It is important to note that hydraulic central control units 38 and 39 of one work group are independent of hydraulic central control units 38 and 39 of the other work groups.
At the start of the lifting operation, the hydraulic circuits of secondary hydraulic jacks 32 of each work group are connected in parallel to a pump (not shown) by secondary hydraulic central control unit 39, so that all the secondary hydraulic jacks 32 of all three work groups are expanded simultaneously a very short distance (roughly a centimetre) and so pressurized. Next, the hydraulic circuits of secondary hydraulic jacks 32 of each work group are disconnected from the pump and connected in parallel to one another, so that the hydraulic pressure of all the secondary hydraulic jacks 32 in the same work group is maintained constant by virtue of the communicating vessel principle.
At this point, actual lifting of building 1 is commenced. The hydraulic circuits of main hydraulic jacks 31 of each work group are connected in parallel to a pump (not shown) by main hydraulic central control unit 38; and actual lifting of building 1 is performed by simultaneously expanding the main hydraulic jacks 31 of one work group at a time, while the main hydraulic jacks 31 of the other two work groups are left idle. In other words, the actual lifting of building 1 comprises simultaneously expanding the main hydraulic jacks 31 of one work group at a time to raise the building 2-3 cm per step. As a result, building 1 rotates slightly with respect to the horizontal, which is permitted by the compensating effect of secondary hydraulic jacks 32. In other words, each rotation of building 1 is induced by lifting devices 11 of one work group, and some of the secondary hydraulic jacks 32 of the other two work groups not involved in the lifting operation expand or contract slightly to accompany the different lift levels of the various parts of building 1.
Statically speaking, building 1, reinforced with mat 7, must be thought of as resting on three points (thrust barycentres A) having a spherical hinge (simulated by the hydraulic parallel connection of secondary hydraulic jacks 32), so that lifting can be performed by activating one work group at a time, and the whole building 1 rotates about the axis through thrust barycentres A of the other two idle work groups, without producing any hyperstatic constraints.
Building 1 is normally raised at a very slow speed (calculated at thrust barycentres A of the three work groups) to maintain isostatic conditions. Working at slow speed ensures a wide margin of safety during the lifting operation, in that, by totally eliminating dynamic forces, reference can be made to static-condition standards. Moreover, lifting can be interrupted at any time to monitor, calibrate or make changes to the electric control system or hydraulic system.
At each lift step, building 1 normally tilts by fractions of a degree with respect to the vertical. The building 1 weight force component along the tilt plane is very small, and can easily be balanced (if necessary) by means of ties activated by hydraulic compensating jacks.
As it is being raised, building 1 is monitored constantly by a control unit 40 connected to pressure sensors 41 for measuring the actual pressure of hydraulic central control units 38 and 39, and to a number of wide-base strain gauges 42 fitted to supporting walls 4 of building 1 to measure stress induced by the lifting operation on building 1.
During the lifting operation, mat 7 is also monitored constantly by control unit 40, which is connected to a network of inclinometers (not shown) connected to mat 7 to real-time calculate a graph of deformation of mat 7, and is connected to a precision optical device (not shown) which monitors a number of topographical reference points to occasionally check the inclinometer data. In other words, control unit 40 monitors flexural deformation of mat 7 by means of a main system defined by the inclinometers, and by means of a redundant secondary system defined by the precision optical device.
It is important to note that flexural deformation of mat 7 must be maintained within a very small range and, above all, absolutely stable throughout the lifting operation, on account of it depending substantially on the inevitable distances (which remain constant at all times) between the weight distribution of building 1 and the thrust of lifting devices 11. If a predetermined maximum flexural deformation of mat 7 is exceeded during the lifting operation, the thrust of lifting devices 11 must be balanced better.
Further trimming of mat 7 may be achieved by adjusting opposite posttensioning cables 8 capable of producing predetermined reactions.
As shown in
In a different embodiment not shown, a body of elastic material (e.g. neoprene) is interposed, inside guide tube 13, between the top end of foundation pile 9 and fastening plate 44, normally to enhance the antiseismic characteristics of mat 7.
Preferably, each foundation pile 9 is driven so that the top end is below the top surface of mat 7; the projecting portion of guide tube 13 is then cut; and, finally, fastening plate 44 is fixed to the rest of guide tube 13, so it is substantially coplanar with the top surface of mat 7, and the whole top surface of mat 7 can be walked on.
Before being fixed axially to mat 7, foundation pile 9 can be preloaded with a downward thrust of given force for as long as it takes to weld fastening plate 44 to guide tube 13. In other words, downward thrust of given force is exerted on foundation pile 9 when welding fastening plate 44 to guide tube 13. Preloading foundation pile 9 when fixing it to mat 7 allows any yielding of foundation pile 9 to develop rapidly, as opposed to over a long period of time. The advantage of this obviously being that rectifying yield of one or more foundation piles 9 while work is under way is relatively cheap and straightforward, but is much more complicated and expensive once the work is completed.
It should be pointed out that raising the building forms a space underneath mat 7, which may be used to build a basement (obviously, provided there are only a small number of foundation piles 9). Alternatively, the space formed between the underside of mat 7 and ground 2 may be filled with conventional cement materials or nonconventional materials (e.g. polyurethane foam). If the building is raised to a considerable height (about a metre), only the projecting part of foundation piles 9 may be covered to form actual supporting pillars, and filling limited to the areas beneath supporting walls 4; in which case, building 1 would be structurally similar to one built on piles.
In a different embodiment shown in
As shown in
In the above embodiment, mat 7 is constructed entirely just before the lifting operation. In an alternative embodiment, at least part of mat 7 may already be built, in which case, holes 12 are core-drilled.
In the embodiments shown in the drawings, building 1 has only supporting walls 4. In a different embodiment not shown, building 1 may also have other supporting members (typically, supporting pillars) combined with or instead of supporting walls 4.
If building 1 shares one or more supporting walls 4 with adjoining buildings, all the floors 6 connected to the shared supporting wall 4 must be detached, to lift floors 6 with respect to the shared supporting wall 4, and then reconnected to the shared supporting wall 4. Before being detached from a shared supporting wall 4, floor 6 must obviously be adequately supported by a temporary metal frame adjacent to but not contacting the shared supporting wall 4. The above method may also be applied to particularly large buildings (e.g. with a base of over 1000 sq.m) which are divided into a number of parts raised separately.
The lifting method described above may obviously be used to advantage to raise any type of construction, e.g. a bridge.
Number | Date | Country | Kind |
---|---|---|---|
B02006A000414 | May 2006 | IT | national |
PCT/IB2007/001362 | May 2007 | IB | international |