Abstract:
A plurality of floatable constructions are provided, the constructions including a floating base for a building, the base having at least one buoyant basement unit defining a basement level, and a reinforced concrete transfer platform atop the basement unit. The basement level can provide habitable or functional space for the building, and the transfer platform has at least one access opening giving access to the basement level which is enhanced by windows for light and ventilation. Methods and means of tying modular components of the structures together, and materials suitable for manufacturing such ties, are also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Pursuant to 35 U.S.C. 119(a), the instant application claims priority to prior United Kingdom application number GB 1201877.6, filed Feb. 2, 2012. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to constructions that are normally at rest on the ground or some form of solid support, but can float during periods of flooding. In particular, but not exclusively, the invention relates to constructions having a buoyant basement structure which support conventional buildings. 
       BACKGROUND OF THE INVENTION 
       [0003]    In modern urban environments, the development and construction of large buildings for residential, commercial, leisure or industrial use can often be beset with problems. 
         [0004]    For example, a site in UK may have been previously developed, but with a change of legislation the land may now be classified as within a flood zone, e.g. Planning Policy Statement 25 (PPS 25) &amp; the Development and Flood Risk Practice Guide dated June 2008. PPS25 is part of the holistic approach to managing risk set out in the Government&#39;s strategy for flood and coastal erosion management, Making Space for Water (Defra, 2005). 
         [0005]    Flooding can cause substantial damage to property and threaten human life, as the floods of 2007 in the UK showed. Such damage is a consequence of previous decisions about location and nature of settlement and land use. 
         [0006]    Floating or floatable buildings, which are not based on vessels, are known. For example, U.S. Pat. No. 6,199,502 describes the use of connectable concrete flotation modules with polystyrene cores to create a floating pontoon on which structures can be supported. The flotation modules are designed to be transportable by land vehicles, so that a large number of modules are required to create a floating platform of modest size, and the weight that can be supported by the platform is limited. 
         [0007]    U.S. Pat. No. 5,647,693 describes a floatable building having a watertight concrete basement of unitary construction which provides buoyancy in the event that the site of the building is flooded. As in a conventional building with a basement, the walls of the basement structure support the floor joists and walls of the building above. This limits design freedom and compromises access to the basement. The basement is constructed at the site of the building, and remains in place after construction until floodwater raises the building. 
       SUMMARY OF THE INVENTION 
       [0008]    According to a first aspect of the invention, there is provided a construction defined by claim  1 . 
         [0009]    According to a second aspect of the invention, there is provided a method of constructing a structure that can float defined by claim  26 . 
         [0010]    According to a third aspect of the invention, there is provided a construction defined by claim  51 . 
         [0011]    Such a construction preferably comprises a floating base for a building, the base having at least one buoyant basement unit defining a basement level, and a reinforced concrete transfer platform atop the basement unit. The basement level can provide habitable or functional space for the building, and the transfer platform has at least one access opening giving access to the basement level which is enhanced by windows for light and ventilation. 
         [0012]    The basement unit may be manufactured from 300 mm micro fibre reinforced concrete. On the top of the wall sections ties may be cast in to connect the walls to the transfer platform. In embodiments in which the transfer platform is made of concrete, the walls may comprise a plurality of ties, each tie extending partly within the transfer platform. In such an embodiment, the ties may be connected to the reinforcement of the transfer platform. 
         [0013]    Preferably, the ties extend from the basement unit into the transfer platform, so as to securely connect the transfer platform to the basement unit. The ties may, for example, be cast into the basement unit during construction of said unit, or may be bolted or otherwise affixed to the basement unit. 
         [0014]    Optionally, the ties may extend from the transfer platform into the basement unit. In this case, the ties may be inserted into holes drilled in one or more basement units, and the ties may be retained in the holes by adhesive filler, such as a resin grout or mortar. 
         [0015]    Preferably, where a part of a tie extends within a basement unit, that part of the tie is approximately 400 mm to 750 mm in length. Preferably, the ties comprise reinforcing bars. 
         [0016]    Preferably, additional starter bar ties may be cast into the concrete wall sections to provide a means of attachment to a walkway discussed in detail below. 
         [0017]    The ties may, for example, be cast into the basement unit during construction of said unit, or may be bolted or otherwise affixed to the basement unit. 
         [0018]    Preferably, the starter bar ties comprise reinforcing bars. 
         [0019]    The transfer platform preferably comprises a lightweight reinforced concrete slab. For example, the transfer slab may include an array of voids, optionally formed by an array of void formers. Alternatively, the transfer platform may be formed of a plurality of wooden joists, which are preferably secured to the walls of the basement unit by galvanized straps. In this way, the mass of the floating basement unit can be kept to a minimum, and the centre of gravity can be low in the base so as to provide stability to the base. 
         [0020]    The upper surface of the transfer platform may include a layer of tiles or timber floorboards to form a finished floor. 
         [0021]    The construction comprises guide means for preventing horizontal movement of the basement unit. The guide means may comprise locating means which are fixed relative to the ground and engagement means arranged to engage with the locating means. The engagement means may, for example, comprise rollers arranged in rolling contact with the locating means, or sliders arranged in sliding contact with the locating means. 
         [0022]    The locating means may comprise either timber or steel piles set into the ground. Advantageously, steel hollow piles could house apparatus for extracting heat from the ground for supply to the building, such as ground source heating apparatus. 
         [0023]    The basement units are preferably micro-fibre reinforced concrete which, advantageously, is approximately 300 mm thick. However, it is conceivable that the basement units could be formed of other materials, such as steel. 
         [0024]    Sheet steel piling (preferably corrugated) may form the walls of the excavated pit. 
         [0025]    A depth of 500 mm of water in the pit is preferably sufficient to lift the basement unit through displacement pressure. 
         [0026]    Advantageously, the basement unit can provide a load-bearing platform to support the weight of a superstructure thereon. 
         [0027]    In preferred embodiments, the construction comprises a floating basement unit in accordance with the first aspect of the invention, and a superstructure upon the basement unit. A transfer platform provides a load-bearing surface to distribute the weight of the superstructure across the basement unit. 
         [0028]    The basement unit having the transfer platform provides a mechanically uniform platform upon which a superstructure of substantially any design and construction can be built. In some embodiments, the transfer platform may provide a driveway upon which vehicles may be parked. The weight of the superstructure is distributed across the base via the transfer platform, so there is no need for correspondence between the position of the load-bearing parts of the superstructure and the position of features within the basement structure. Thus, the present invention offers a flexible and adaptable way of constructing floating buildings. 
         [0029]    As well as providing support for the superstructure, the transfer platform can act as a fire barrier. Thus, if fire were to break out in the basement level, unlike an open-framed load bearing structure, the transfer platform would act to slow passage of fire up into the superstructure. Consequently, the basement level can be arranged to house plant for the building, such as equipment associated with electricity generation, metering or distribution, gas supply, water treatment, waste processing and so on. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0030]    The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
           [0031]      FIG. 1  shows a cross-sectional view of a construction forming a preferred embodiment of the present invention; 
           [0032]      FIG. 2  shows a plan view of the construction of  FIG. 1 ; 
           [0033]      FIG. 3  shows a cross-sectional view of a walkway of the construction of  FIG. 1 ; 
           [0034]      FIGS. 4   a  and  4   b  show the construction of  FIG. 1  in two positions; 
           [0035]      FIG. 5  shows a cross-sectional view of a construction forming a preferred embodiment of the invention in a first position; 
           [0036]      FIG. 6  shows a cross-sectional view of the construction of  FIG. 5  in a second position; 
           [0037]      FIG. 7  shows a footbridge extending from ground level to a superstructure in a preferred embodiment of a construction; 
           [0038]      FIG. 8  shows a plan view of the construction of  FIG. 7 ; 
           [0039]      FIG. 9  shows a plan view of a locating pile; and 
           [0040]      FIG. 10  shows a detailed cross-section of a transfer platform. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0041]      FIG. 1  shows a first embodiment of a construction comprising: a pit  100 ; a buoyant basement unit  22 ; and a superstructure  20  built upon the basement unit  22 . 
         [0042]    Preferably, the basement unit  22  comprises a floor and external walls and one or more internal walls to define rooms in the basement level. Optionally, the floor is generally rectangular in plan, so that the rooms may be generally cuboidal. 
         [0043]    Preferably, an external floor  33  extends from the basement unit  22 . Preferably, the external floor  33  is formed integrally with the basement unit  22 . The external floor  33  may be polystyrene encased concrete, and can therefore act as an additional float. Optionally, the external floor  33  substantially surrounds the top of the basement. Thus, the external floor  33  can provide a walkway to ensure that nobody can fall into the excavated pit in which the basement unit  22  is located. Preferably, there is a gap of no more than 75 mm between the edge of the external floor  33  and the pit  100  when the basement unit  22  is not floating. This can allow flood water to cascade down into the pit  100 . 
         [0044]    The pit  100  is formed by digging below ground level  23  to a depth sufficient to accommodate the majority of the buoyant basement unit  22 . The size of the pit  100  is greater than the size of the basement unit so that a recess  24  will surround the basement unit  22  when it is not floating. Preferably, the recess  24  will have a width (i.e. the distance between the basement unit  22  and the walls of the pit  100 ) of between 75 mm and 100 mm. 
         [0045]    The pit  100  is preferably formed by excavating below ground level  23 , for example, in a flood plain area  23 . 
         [0046]    The buoyant basement unit  22  comprises outer walls  26  and a floor. It can provide a floating base upon which the superstructure  20  is built or placed. 
         [0047]    The basement unit  22  may comprise a transfer platform  25  which spans the entire basement unit  22 . The transfer platform  25  may comprise a single unitary transfer slab, or a plurality of joists (e.g. timber joists). 
         [0048]    When a plurality of joists form the transfer platform  25 , these may abut each other to form a substantially continuous floor. Alternatively, the joists may be provided with an additional surface mounted thereon, such as a plurality of abutting floor boards, to form a substantially continuous floor. 
         [0049]    The bottom face of the transfer platform  25  rests upon and is attached to the tops of the outer walls  26  of the basement unit  22 . In this way, the transfer platform  25  may close the open top of the basement unit  22 . 
         [0050]    The basement unit  22  may be a habitable space comprising one or more rooms separated by internal walls. For the comfort of the user, one or more windows  27  may be provided to provide light and/or ventilation. Preferably, the depth of the pit  100  is chosen such that the lower extent of the window(s)  27  is at ground level when the basement unit  22  is not floating. In which case, the basement unit may extend above the external floor by between 0.8 m and 1 m. 
         [0051]    The basement unit  22  may be formed of concrete in which is cast reinforcing bars  44  (as can be seen in  FIG. 3 ). Preferably, the basement unit  22  is formed of fibre-reinforced concrete. 
         [0052]    When a single unitary transfer platform  25  is used, this is preferably formed as a lightweight reinforced concrete slab, for example of the type marketed as BubbleDeck®. The slab  25  contains a plurality of voids, preferably defined by void formers in the form of hollow plastic spheres, arrayed within a lattice of reinforcing bars. The reinforcing bars and voids are set within a concrete matrix. 
         [0053]    The transfer platform  25  is preferably permanently attached to the basement unit  22 . The connections between the basement unit  22  and the transfer platform  25  may consist of reinforcing bars  44  which extend upwardly from the outer walls  26  of the basement unit  22  and into the transfer platform  25  (as can be seen in  FIG. 3 ). 
         [0054]    Furthermore, the transfer platform  25  may be formed of concrete cast directly onto the top faces of the basement units  22  to form the connections. In this way, the transfer platform  25  and the basement units  22  can be considered as a continuous reinforced concrete basement structure. 
         [0055]    The basement structure  22 , and hence the building, may be constrained from lateral movement by a number of locating piles  28 . Preferably, each locating pile  28  consists of a 300 mm steel column pile, which is driven into the ground adjacent the basement structure  22 . At least one locating pile  28  is provided adjacent at least two of the outer sides  26  of the basement structure  22 . 
         [0056]    Pile guides are attached to the outer surface of the basement structure  22 , just above the water line. Each pile guide  28  may comprise one or more rubberised rollers (not shown) mounted on a galvanized steel frame. The frame of each pile guide extends around one of the locating piles  28 , and the rollers bear upon the outer surface of the associated pile  28 . In this way, the basement structure  22 , and the superstructure can rise or fall to accommodate changes in the water level. However, lateral or side-to-side motion of the basement structure  22  is prevented so that the building remains in the desired position above its normal resting place. 
         [0057]    Within the basement structure  22 , windows  27  can be position at the top of the walls above ground level  23 . 
         [0058]    The basement unit  22  may be located on one or more (preferably two) concrete spreader bars  31  which preferably have a rectangular cross-section (preferably 500 mm deep×300 mm wide) and a length sufficient to extend across the majority of the basement unit  22 . 
         [0059]    These may be located on top of vertically oriented 300 mm diameter piles  32 , which are driven into the ground in the conventional manner. The depth of these piles  32  may vary depending on the weight of the structure. 
         [0060]    Alternatively, a blinding layer of concrete  41  may be provided on the ground. 
         [0061]    In which case, the spreader bars  31  could be replaced small blocks cast into the binding layer  41 . 
         [0062]    The spreader bars  31  or blocks (preferably formed of concrete) can allow flood water to trickle underneath the basement unit  22  to prevent a vacuum forming between the floor of the basement unit  22  and the surface on which it rests. 
         [0063]    The side walls  102  of the excavation can be kept in the vertical position by the use of steel sheet piling  21  or by the use of other materials such as pre-cast concrete planks or engineering brickwork. 
         [0064]      FIG. 3  shows a section of the external floor  33  around the basement unit  22 . Preferably, the external floor  33  comprises fabric reinforcement  35  encased in concrete. The external floor  33  is preferably joined to the basement unit  22 . This may be achieved by the addition of splice reinforcing bars  34 , which are attached to the reinforcing bars  44  of the outer walls  26 . 
         [0065]    Most preferably, the external floor  33  encapsulates buoyant float material  36 , such as polystyrene, to thereby increase the buoyancy of the basement unit  22 . 
         [0066]    In cross-section, the external floor  33  may be tapered from its upper surface, which can provide a walkway. 
         [0067]    The external floor  33  is preferably attached to the basement unit  22  so that its upper surface is at ground level  23  to provide a cover over the pit  100 . The cover preferably does not necessarily entirely close the pit  100  and there may be a gap around its periphery to allow water to fill the pit  100 . Additionally a grill such as a metal grating can be placed over the remaining gaps between the pit  100  and the external floor  33  for safety. Preferably, the gap is not more than 75 mm. 
         [0068]    The external floor  33  may continuously surround the basement unit  22  or may be formed of one or more discrete sections separated by gaps. In either case, the external floor covers a portion of the recess  24  when the basement unit  22  is not floating. 
         [0069]    Preferably, the upper surface of the external floor  33  is flush with ground level  23 . 
         [0070]    The external floor  33  may be an integral part of the basement unit  22 . 
         [0071]    The superstructure  20  can be pre-fabricated or manufactured on the basement unit  22 . 
         [0072]    Renewable energy sources can be positioned on the roof of the superstructure  20 , such as solar photovoltaic panels and wind turbines. 
         [0073]    Whilst the description above has been directed to the use of a single buoyant basement unit  22 , the inventors have envisaged the use of multiple buoyant basement units  22 , connected together to form a single floating structure. Preferably, the multiple basement units  22  would have a single transfer platform  25  affixed thereon and may together be substantially surrounded by an external floor  33 . 
         [0074]    It will be appreciated that the access ramps and other connections between the ground and the basement unit  22 , external floor  33  and/or superstructure  20  are arranged to accommodate the rising and falling motion of the building. 
         [0075]    The superstructure is preferably a building having a plurality of rooms (for example a house). 
         [0076]    As can be seen from  FIGS. 4   a  and  4   b , when constructed as set out above, the buoyant basement unit  22  may be movable between a position in which it rests upon the floor of the pit (either directly, or via supports  31 ) to a position in which it floats upon a sufficient volume of water. The minimum volume of water suitable for initial displacement of the mass of the basement unit  22  and the superstructure  20  preferably corresponds to a depth in the range of 0.5 m to 1 m within the recess  24 . 
         [0077]    As shown in  FIG. 5 , a second embodiment of a construction may include access to the pit  100  via a manhole  40  (preferably, a 600 mm×600 mm manhole with a replaceable cover). A metal ladder  41  between the floor of the pit  100  and the manhole  40  may be provided. This allow for maintenance and the clearance of any silt or debris which may accumulate in the pit  100 . 
         [0078]    Optionally, in either embodiment, a fence or handrail  60  is attached around the walkway. 
         [0079]    Preferably, a barrier  61  extends down into the pit  100  from the basement unit  22  or, more preferably, from the outer edge of the external floor  33 . This may be secured in place by one or more brackets  62  attached to the sheet piles  21 . 
         [0080]    Optionally, the barrier  61  may extend past the external floor  33  to form the fence or hand rail  60 . 
         [0081]      FIG. 6  depicts the construction in a raised position when the water level  50  has risen above ground level  23 . In this position, the barrier  61  can prevent debris from entering the pit  100 . 
         [0082]    The barrier  61  may be arranged to prevent the passage of debris therethrough but allow the passage of water. The barrier  61  is preferably formed of a mesh or an apertured sheet. Preferably, reinforcement is provided to maintain the shape of the barrier  61 . 
         [0083]      FIG. 7  shows an optional footbridge  70  extending from ground level  23  around the pit  100  to the superstructure  20 . Alternatively, the footbridge  70  may span from ground level  23  to the basement structure  22 , or to the external floor  33 . 
         [0084]    Small metal ramps  73  may be provided at either end of the footbridge  73  ensure ease of access for wheelchairs. 
         [0085]    Optionally, a drive way may be provided to allow access for vehicles to the basement unit  22  when it is not floating. 
         [0086]    The footbridge  70  is free to pivot at either end to compensate for movement of the construction. Preferably, at least one end of the footbridge  70  is free to move laterally relative to the ground  23  and/or the construction, to compensate for large displacements of the construction. In preferred embodiments the end of the footbridge  70  at the construction is free to pivot while the other end of the footbridge  70  rests on rollers. 
         [0087]    Preferably, the pivot at the construction end of the footbridge  70  is mounted on the external floor  33 , the transfer platform  25 , or the basement unit  22 . 
         [0088]    As can be seen from the plan view of  FIG. 8 , a driveway  74  for a vehicle may also be provided to span the pit  100 . This would have the same general construction as that set out above for the footbridge  70 . 
         [0089]    A garage or porch  76  can be constructed adjacent to the superstructure  20  for sheltering a vehicle and/or providing an area for bin storage. 
         [0090]      FIG. 9  shows a plan view of a preferable arrangement of locating pile  28 . As shown in the figure, the locating pile  28  stands outside the basement unit  22  and passes through an opening in the external floor  33 . At least one roller  80  is provided to maintain the position of the locating pile  28  relative to the opening. Preferably, a pair of rollers  80  are provided to retain the locating pile  28  therebetween. 
         [0091]    As shown in  FIG. 9 , the locating pile  28  may be an I-beam, which provides channels in which rollers  80  may be provided. 
         [0092]    Preferably, the rollers  80  comprise Teflon. 
         [0093]    Optionally, the rollers  80  are attached to a metal bracket  83 , which is attached to the external floor  33  using bolts  81 . 
         [0094]      FIG. 10  shows a detailed cross-section of the transfer platform  25  to the wall of a preferred superstructure  20 . In this figure, the transfer platform  25  comprises a plurality of timber joists  87 , upon which a surface  86  (preferably formed of medium density fibreboard) is provided. Surface  86  provides a continuous surface on which a floor finish  85 , such as floor boards or carpeting, may be laid. 
         [0095]    The joists  87  may abut or be spaced apart. When the joists  87  are spaced apart, an insulating material is preferably provided therebetween. 
         [0096]    Preferably a layer is provided upon the transfer platform  25  of a breather membrane (such as Tyvek DuPont® Airguard® Control). Thus, an air and vapour tight base may be provided. 
         [0097]    In preferred embodiments, the breathable membrane may extend up a at least a portion of the walls of the superstructure  20 . 
         [0098]    The wall of the superstructure  20  may be formed of timber  83  on which a surface of acrylic render  86  is provided. A layer of vapour check barrier and a layer of fibre board may be provided on the inner surface.