FLOATABLE STRUCTURE AND METHOD OF MAKING SAME

Abstract

A floatable structure in particular a floatable platform including at least two separate hulls each having a longitudinal axis. Each hull having along the longitudinal axis a succession of hollow concrete segments.

Claims

1. A floatable structure, comprising: at least two separate hulls each having a longitudinal axis, each hull comprising along the longitudinal axis a succession of hollow concrete segments, each hollow segment comprising two preformed elements that are connected.

2. The structure of claim 1, further comprising a plurality of junction elements spaced along the longitudinal axis, each junction element connecting the two hulls together.

3. The structure of claim 1, wherein the or each cross-beam element comprising top and lower horizontal beams and diagonal beams connecting the top and lower horizontal beams.

4. The structure of claim 1, wherein the two preformed elements being half ring elements.

5. The structure of claim 1, wherein each hull comprises at least one cast in situ longitudinal beam.

6. The structure of claim 5, wherein each hollow segment comprising at least one pre-slab for casting the at least one cast in situ longitudinal beam.

7. The structure of claim 1, wherein each hull comprises post-tensioned tendons extending from one longitudinal end of the hull to the opposite longitudinal end.

8. The structure of claim 1, wherein each hull is closed by bulkheads at opposite longitudinal ends of the hull.

9. The structure of claim 1, wherein each hollow segment is connected to a respective cradle.

10. The structure of 1, wherein each hollow segment comprises at least one stiffening rib.

11. The structure of claim 1, wherein each hull comprises at least one internal reinforcement member.

12. A method for the construction of a floatable structure, the floatable structure comprising at least two separate hulls, the method comprising: a) assembling pre-formed concrete elements on respective cradles to form at least two adjacent segments successions, b) installing junction elements between the at least two adjacent segments successions, c) casting in situ at least one longitudinal beam along each succession of segments.

13. The method of claim 12, comprising installing pre-slabs on the segments before pouring concrete to form the top longitudinal beam.

14. The method of claim 12, further comprising pouring in situ joint between the junction element and the adjacent elements and prestressing the junction element once the joint has hardened.

15. The method of claim 12, wherein each pre-formed concrete element is cast horizontally in a U configuration with the concavity of the U oriented upwards, then pivoted vertically by a quarter of turn ready for installing on the cradle.

16. The structure of claim 2, wherein the junction element(s) being cross-beam element(s).

17. The structure of claim 3, wherein the beams comprise a pre-stressing layout.

18. The structure of claim 9, wherein each hollow segment being connected to a respective cradle by bolting.

19. The structure of claim 9, wherein each cradle comprises a shoulder against which an end of the element abuts.

20. The structure of claim 11, wherein the internal reinforcement member bears on the at least one stiffening rib.

Description

[0046] FIG. 1 is perspective schematic view of a floatable platform according to the invention,

[0047] FIGS. 2A to 2K illustrate various steps of making of the platform of FIG. 1,

[0048] FIG. 3 shows detail A of FIG. 2D,

[0049] FIG. 4 shows detail B of FIG. 2E,

[0050] FIG. 5 shows detail C of FIG. 2H,

[0051] FIG. 6 shows detail D of FIG. 2J,

[0052] FIG. 7 is a front view of the floatable body,

[0053] FIG. 8 is a front view of a half ring element,

[0054] FIG. 9 is a front view of the half ring element assembled to the cradle,

[0055] FIG. 10 shows detail E of FIG. 9,

[0056] FIG. 11 shows detail F of FIG. 9,

[0057] FIG. 12 is a front view of a cross beam element,

[0058] FIG. 13 is a front view of an internal brace,

[0059] FIG. 14 is a partial perspective view of a hull of the floatable body,

[0060] FIG. 15 is a perspective view in isolation of a half ring element,

[0061] FIG. 16 is a perspective view in isolation of a cradle,

[0062] FIG. 17 is a perspective view in isolation of a cross-beam element,

[0063] FIG. 18 is a perspective view in isolation of a slab element,

[0064] FIG. 19 is a perspective view in isolation of a bulkhead,

[0065] FIG. 20 is a view analogous to FIG. 1 of a variant embodiment of the platform, and

[0066] FIG. 21 illustrates in a partial and schematic manner the interlocking of shear keys at the interface of two consecutive half ring elements.

[0067] The floatable structure 1 shown in FIG. 1 is a platform comprising a top structure such as a top slab 2 and a floatable body 3 supporting the top slab 2.

[0068] The floatable body 3 comprises two hulls 10 each extending along a longitudinal axis X, the longitudinal axes of the hulls 10 being parallel in the example shown.

[0069] Each hull 10 comprises a succession of hollow segments 20 extending along the longitudinal axis X, and each hull is closed by bulkheads 70 at its longitudinal ends.

[0070] Each hollow segment 20 is in the example shown a ring segment of substantially circular outline, attached to a respective cradle 23.

[0071] Further structural details of the floatable platform 1 will become apparent when reading the description below of a method of making the platform 1, with reference to FIGS. 2A to 2K.

[0072] To manufacture a hull 10, one starts to position a few cradles 23 in line on a construction slab (not apparent) as shown in FIG. 2A. The cradles 23 are laid on a supporting structure lying above ground level at the assembly zone, as the completed platform will need to be transported to a launch site by any appropriate transportation equipment such as a tracked trolley or Self-Propelled Modular Transporter (SPMT) or similar equipment.

[0073] The cradles 23 are laid one next to the other with some axial spacing to allow the necessary movement of the adjacent ring segments 20 when they are assembled longitudinally. Any remaining gap between adjacent cradles 23 after assembly of the ring segments 20 is completed may be filled with any appropriate filler such as concrete.

[0074] The half ring elements 24 are fixed on the cradles 23 using bolts (not shown), introduced into openings 25 of the cradles 23 as shown in FIGS. 9 and 11.

[0075] Each cradle 23 comprises a top concave surface of shape complementary to the elements 24, with a central boss 26 as shown in FIG. 10. The boss 26 defines opposite shoulders 27 against which respective lower ends of corresponding half ring elements 24 abuts, thus blocking these in rotation.

[0076] Each half ring element 24 may be hoisted down onto the corresponding cradle 23, and the bolting of the element on this cradle preferably takes place before the element is detached from the hoist. The cooperation between the element 24 and the cradle 23 ensures the element 24 remains stable and withstands any transverse wind load that may occur on the construction site (if the assembly takes place outdoors).

[0077] FIG. 2B shows left and right half ring elements 24 lying on a respective cradle 23.

[0078] Since the floatable body 3 comprises two hulls 10, two successions of segments 23 are assembled, as shown in FIG. 2C, side by side.

[0079] Adjacent half ring elements 24 are preferably match cast and comprise on their axial end surfaces (i.e. faces transverse to longitudinal axis X) complementary male 24a and female 24b shear keys as shown in FIG. 21.

[0080] The elements 24 may be cast in a U configuration as shown in FIG. 8, with the concavity of the U facing upwards. The elements 24 may be cast along a long bench. During manufacture of the elements 24, the end of the formwork used to cast an element 24 may be vertical and be constituted by the end face of another element 24 previously cast. In this way the elements 24 are match cast, which allows to easily obtain interlocking shapes at the interface of adjacent elements.

[0081] After casting, the formwork is removed, and the elements may be pivoted about a quarter of a turn to reach a vertical configuration ready for installation on a respective cradle. This facilitates the handling of the elements and their installation on the cradles, as the elements may be heavy and bulky.

[0082] The contact surfaces of adjacent half ring elements 24 are coated with a binder 100 such as a polymer resin, e.g. an epoxy-based resin, before the elements 24 are brought together. Provisional longitudinal pre-stressing is advantageously applied to the elements 24 under assembly to ensure a good repartition of the binder at the interface of the elements 24 during polymerization of the binder and avoid any undesirable relative move of the elements 24.

[0083] Junction elements 30 are installed between the adjacent successions of ring segments 20 as shown in FIG. 2D.

[0084] Each junction element 30 is preferably a cross beam element 30 comprising, as shown in FIG. 12, a top beam 31 and a lower beam 32 connected by two diagonal beams 33 that cross in their middle. The beams 33 may be perpendicular to each other as in the shown example.

[0085] Top and lower beams 31 have ends 34 of a concave shape configured to substantially match the outer surface of the adjacent half ring elements 24.

[0086] The junction element 30 also comprises sheaths or ducts 36 extending internally along each beam 31, 32 or 33 for the introduction of tensioning tendons (not shown).

[0087] The junction elements 30 are preformed reinforced concrete elements that are installed using temporary stability components.

[0088] If the junction elements 30 are one-piece elements, they may be inserted horizontally between the hulls 10 with a corresponding trolley moving longitudinally between the hulls and erected once they reach their destination.

[0089] If the junction elements are made of multiple parts, some parts may be installed before the others. For example, if the junction element comprises a lower part and an upper part, the lower part is preferably installed before the corresponding half ring elements 24 are installed on their respective cradles 23.

[0090] The ends of the junction element 30 that are close to the half ring elements 24 may be provided with inflatable seals (not shown) that are inflated to fill the gap between the junction element and the adjacent half ring elements to define a cavity for pouring or injecting a joint such as grout. The use of inflatable seals avoids the need to access from above to the interface of the junction element with the half ring element. The presence of the inflatable seals may thus render the making of the joint easier.

[0091] The sheaths of the junction element may be extended into the segments. This operation may be achieved from the inside of the hull.

[0092] Once the joint has hardened at the interface of the junction element 30 with the adjacent half ring elements 24, the junction element 30 is ready for pre-stressing by post-tensioning corresponding tendons introduced in the sheaths or ducts.

[0093] The steps described above relating to the installation of the half ring elements 24 and junction elements 30 are repeated until the segment erection is complete for each hull 10, as shown in FIGS. 2E and 2F.

[0094] During the erection of segments 20, concrete pre-slabs 50 are inserted between the upper ends of the half ring elements 24, as shown in FIG. 4.

[0095] Each half ring element 24 comprises for this purpose at its upper end a fallen edge 52, provided with a pre-slab bearing 53, as shown in FIG. 8.

[0096] The pre-slabs 50 define, together with the fallen edges 52, a longitudinal channel 55 that acts as a formwork. The pre-slabs avoid the need to use other formwork tools.

[0097] The segment rings 20 define a longitudinal channel 40 at their base. The bottom of the channel 40 is defined by the cradles 23. The bottom end of each half ring element 24 comprises a raised edge 42. The channel 40 extends between these raised edges 42 and acts as a formwork.

[0098] The elements 24 preferably have rebar (not shown) extending in the channels 40 and 55 to improve the connection with the corresponding longitudinal beams that are cast in these channels.

[0099] Appropriate rebar is installed in the channels 40 and 55, together with longitudinal sheaths for tendons intended to provide pre-stressing.

[0100] A longitudinal lower beam 45 is cast in situ in the channel 40, as shown in FIGS. 2H and 5. A longitudinal top beam 56 is cast in situ in the channel 55, as shown in FIG. 2I.

[0101] Each half ring element 24 comprises a stiffening rib 60 extending along its inner surface along a median plane, between the raised edge 42 and the fallen edge 55, as can be seen in FIG. 6.

[0102] This rib 60 may be provided with openings 61 for the installation of longitudinal sheaths along the internal surface of each hull 10, for the introduction of external post-tensioning tendons.

[0103] For these external post-tensioning tendons, the sheaths that are installed are preferably HDPE sheaths with electro-weldable sleeves at their ends to ensure good sealing of the sheaths.

[0104] Once the hulls are ready to be closed at their longitudinal ends, reinforced concrete bulkheads 70 are installed into the end ring segments 20, as shown in FIG. 6.

[0105] The prestressing of the junction elements 30, typically made with internal post-tensioning tendons, occurs before the bulkheads 70 are installed. The tendons extending within the various beams of the junction elements 30 are tensioned. The tensioning of these tendons will cause the hulls 10 to behave like a monolithic structure.

[0106] The bulkheads 70 may be one-piece elements, as shown, or may be made of multiple parts if the weight of the bulkhead exceeds the capacity of the available hoisting equipment.

[0107] As for the interface of adjacent ring segments, the contact faces between the bulkhead and the adjacent ring segment are coated with a binder such as epoxy-based resin, after the continuity into the bulkheads 70 of the tendon sheaths extending within the longitudinal beams and through the ring segments stiffening ribs has been completed.

[0108] After bulkheads 70 are installed, the tendons are threaded in the corresponding longitudinal sheaths from outside the hull 10.

[0109] The top slab 2 is preferably assembled to the ring segments 20 after completion of the hulls 10 as shown in FIG. 2K.

[0110] The top slab 2 may be made of pre-slabs and other preformed elements. The components of the top slab 2 are connected to the hulls by reinforced concrete connections.

[0111] The top slab 2 is intended to carry various equipment (for example hoisting equipment, accommodations, storage tanks, plant processing equipment . . . ) depending the intended use.

[0112] Each hull 10 may comprise rebar (not shown) that extends within concrete parts of the top slab 2 that are cast in situ. This rebar may extend also into the concrete of the top longitudinal beam 56 of the hull.

[0113] The tendons extending within sheaths 62 and those (not shown) extending within the longitudinal beams 45 and 56 are tensioned to induce an axial load and corresponding pre-stressing into the succession of ring segments 20 and longitudinal beams 45 and 56.

[0114] The tensioning of the tendons is preferably coordinated with the making of the top slab 2 so that the tensioning of the tendons induces also some pre-stressing into the top slab 2.

[0115] After the tensioning of the tendons is completed, grout or other filler may be injected into the corresponding sheaths. In a variant, the filler is introduced before post-tensioning, by using unbounded prestressing tendons such as individually HDPE coated and greased strands.

[0116] If needed, one or more internal braces 80 or any other reinforcement member such as diaphragms or ties, are inserted in one or more ring segments 20 before bulkheads 70 are installed, as shown in FIG. 14, to prevent ovalization due to localized loads on the top slab 2. The one or more internal reinforcement members 80 are fixed inside the hull at one or more axial positions where the external load is expected or at the location(s) of the junction element(s).

[0117] Each reinforcement member 80 may exhibit a star configuration, with radial beams 82 as shown in FIG. 13. The beams 82 may be provided at their outer ends with flanges 84 for their fixation on corresponding ribs 60 by bolting or otherwise.

[0118] Once the structure 1 is fully equipped, it may be transferred to the launch site where it is put in water and the construction site may be re-used to make the next structure 1.

[0119] The invention is not limited to the example described above.

[0120] Various modifications may be brought to the structure 1.

[0121] The platform 1 is not limited to a given number of hulls 10 and may comprise three or more parallel hulls as shown in FIG. 20.

[0122] At least two separate hulls may be positioned in succession in the longitudinal direction of the platform 1. The longitudinal axes of the hulls may not be parallel. For example, the platform comprises four or more hulls having longitudinal axes oriented in a diamond or star configuration. This may involve the use of junction elements of different shapes and sizes.

[0123] Each hull may be provided with extra components. For example, an inspection door may be provided in the upper part of each hull.

[0124] Each hull may be provided with a liner to help prevent ingress of water.

[0125] Each hull may be provided with at least one internal wall to define at least two sealed compartments in the hull and help render the latter unsinkable in case of damage.

[0126] Upright reinforced concrete beams may connect the top longitudinal beam to the lower longitudinal beam to improve mechanical resistance and withstanding of vertical loads. These upright beams may be preformed and installed in the segments before the longitudinal beams are cast. These upright beams may comprise rebar extending within the concrete of the longitudinal beams. The upright beams may comprise rebar that extends within the concrete of the top slab. The upright beams may be pre-stressed thanks to post-tensioned tendons extending therethrough and possibly also through the top slab 2.

[0127] Ends of the post-tensioned tendons may be anchored against surfaces of the hulls in various manners, with the use of anchoring plates or other anchoring components such as embedded anchor heads with trumpet shape if needed.

[0128] The tendons used in the construction of the hulls are preferably high tensile strength steel cables made of individual units called strands. The tendons used for prestressing the hulls 10 may be of the type T15.7 strands with fGUTS=1860 MPa, with a 150 mm.sup.2 section area that is a 279 kN FGUTS (guaranteed ultimate tensile strength).

[0129] In case of unbounded tendons, when injecting cement grout or other filler in the cable sheath or duct before tensioning, the tendons are preferably individually sheathed with plastic material such as HDPE and lubricated (greased) within each individual sheath to insure unbounding with a low friction coefficient.

[0130] When required, the above-mentioned provisional tensioning may be achieved using bars (not shown) introduced into corresponding passages. These bars may have threaded ends to enable to couple bars one in line with the others to accommodate for the increase of length when the number of assembled segments become higher.

[0131] The left and right elements 24 and/or other concrete components of the hulls are preferably made of High-Performance Concrete (HPC). The concrete used for making these elements or components has a compressive strength of better than 30 MPa, preferably better than 60 MPa, and more preferably of 90 MPa or better.

[0132] Pre-stressing of the hull may also be achieved through internal tendons, extending within the thickness of the wall of the segments. In such case, left and right elements may be cast with corresponding sheaths, typically made of corrugated metallic ducts, and these ducts are connected in waterproof manner when the elements are assembled.

[0133] The left and right elements of the segments may be replaced by top and bottom elements or by any other elements dividing the segments in sectors, with same features as described above.