Structural element, structure comprising a structural element and use of said structural element

Abstract

The invention relates to a structural element. In an embodiment, the structural element includes a stiff, elongate tubular member, wherein an inner surface of the tubular member and side faces enclose a core extending along at least a length of the tubular member, wherein the core is provided with a fluid under pressure. The invention furthermore relates to a method for hoisting a stiff, elongate tubular member.

Claims

1. A structure comprising: a supply line; a plurality of valves; and at least two stiff, interconnected elongated tubular members, individual ones of said at least two stiff, interconnected elongated tubular members comprising an inner surface and a plurality of side faces that enclose a core extending along at least a length of said tubular member, wherein said core is coupled to said supply line through a corresponding one of said plurality of valves and said core is supplied with fluid under pressure, wherein the valve to which said core is coupled is dedicated solely to said core, and said plurality of valves share said supply line, further comprising a controller arranged to control said plurality of valves, wherein said controller is configured to provide independent pressure adaptation to said cores of said at least two elongated tubular members.

2. The structure according to claim 1, wherein said core extends substantially along an entire length of said individual ones of said at least two elongated tubular members.

3. The structure according to claim 1, wherein said fluid under pressure extends substantially along an entire length of said inner surface.

4. The structure according to claim 1, wherein said controller is arranged to adjust pressure of fluid in said core based on pressure measurements.

5. The structure according to claim 1, wherein the controller is configured to individually control each valve coupled to each core.

6. The structure according to claim 1, wherein said structure is configured for a liquid fluid.

7. The structure according to claim 1, wherein said side faces are positioned at opposed ends of the elongated tubular member.

8. The structure according to claim 1, wherein said fluid under pressure within said core has a pressure in a range from 0 Pa up to a maximum allowable circumferential stress of said at least two elongated tubular members.

9. The structure according to claim 8, wherein said fluid under pressure within said core is approximately half of said maximum allowable circumferential stress.

10. The structure according to claim 1, wherein said core is provided with a plurality of compartments.

11. The structure according to claim 10, wherein said plurality of compartments extends along substantially an entire length of said core.

12. The structure according to claim 1, wherein said core is provided with at least one compartment.

13. The structure according to claim 12, wherein said at least one compartment is substantially spherical in shape.

14. The structure according to claim 12, wherein said at least one compartment extends substantially along an entire length of said core.

15. The structure according to claim 12, wherein said at least one compartment is substantially tubular in shape.

16. A structure comprising: a supply line; a plurality of valves; and at least two stiff, interconnected elongated tubular members, individual ones of said at least two stiff, interconnected elongated tubular members comprising an inner surface and a plurality of side faces that enclose a core extending along at least a length of said tubular member, wherein said core is coupled to said supply line through a corresponding one of said plurality of valves and said core is supplied with fluid under pressure, wherein the valve to which said core is coupled is dedicated solely to said core, and said plurality of valves share said supply line, further comprising a controller arranged to control said plurality of valves, wherein said controller is arranged to adjust pressure of fluid in said core based on pressure measurements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is further illustrated by the following Figures, which show a preferred embodiment of the device according to the invention, and are not intended to limit the scope of the invention in any way, wherein:

(2) FIGS. 1a-d schematically show a first embodiment of the structural element according to the invention in cross-section;

(3) FIG. 2 schematically shows a spreader bar according to the invention in cross-section;

(4) FIG. 3 schematically shows the structural element provided with a pressure vessel in cross-section;

(5) FIGS. 4-9 schematically show different embodiments of the spreader bar with compartments in cross-section, and;

(6) FIG. 10 schematically shows a structure according to the invention in cross-section.

DETAILED DESCRIPTION

(7) In FIG. 1 a structural element 1 according to the invention is shown. The structural member comprises a tubular member in the form of a tube 2 manufactured from stainless steel with a wall thickness of 12.5 mm. The tube 2 has a diameter of 0.5 meter and is 30 meters in length. In order to increase the overall stiffness and the stability of the tube 2, the hollow core 3 of the tube 2 is filled with a fluid, in this case pressurized gas. The gas in the core 3 has a pressure of 7 MPa. The core 3 is enclosed by the inner surface or wall 2a of the tube 2 and the end faces 4a and 4b of the tube 2.

(8) The core 3 shown in FIG. 1 extends along the whole length, in the direction indicated with I, of the tube 2. The gas under pressure in the core 3 therefore exerts pressure on the whole inner surface 2a of the tube 2 and the end faces 4a and 4b, increasing the stiffness and the stability of said tube 2.

(9) In FIG. 1b an alternative of the tube 2 is shown, wherein the tube 2 comprises two cores 3a, 3b. The first core 3a is enclosed by a first face in the form of an end face 4a and a second face in the form of an intermediate face 5a. The second core 3b is formed accordingly with side faces 4b and 5b. The space 6 between the cores 3a and 3b does not contain fluid under pressure.

(10) Although the cores do not extend along the whole length of the tube 2, the gas in the cores 3a and 3b do exert pressure on the whole inner surface 2a along the lengths of said cores 3a and 3b. In the radial plane perpendicular to the axis of the tube 2, the gas exerts a pressure directed radially outwardly on the whole inner diameter of surface 2a. An axial pressure is furthermore exerted on side faces 4a, 5a and 4b, 5b. The stiffness and stability of the tube 2 is hereby improved with respect to conventional tubes for use in for instance construction.

(11) For hoisting a tube 2 it is advantageously to provide at least a length of the tube in the middle region of the tube 2 with a core 3 as shown in FIG. 1c. When hoisting, the highest stresses occur in said middle region. The tube 2 can hereto be provided with hoisting means in the form of slings 7 as for instance shown in FIG. 2.

(12) Prior to hoisting, the core 3 is provided using side faces 5a and 5b. In this example, the side faces 5a and 5b are in the form of plugs. The plugs comprise a body 51 and inflatable tubular members 52. For placement of the plugs, the tubular members 52 are deflated, allowing easy placement of said plugs in the tube 2. When the plugs are in place, the members 52 are inflated, sealing the core 3. The core 3 can then be provided with a fluid under pressure. In this example also end faces 4a and 4b are provided. The regions indicated with 3a and 3b are however not filled with a fluid under pressure.

(13) After correct placement of the tube 2 by hoisting, the plugs 5a and 5b can be removed using lines 53 and the tube 2 can for instance be incorporated in a pipe-line after removal of faces 4a and 4b. It is for instance also possible to provide a core 3 prior to hoisting which extends along the whole length of the tube 2 as shown in FIG. 2.

(14) FIG. 1d shows an alternative embodiment of the tube 2 as shown in FIG. 1c. Instead of a straight tube 2 as shown in FIG. 1c, the tube 2 may have tube ends with end faces 4a, 4b which are single bended or curved in multiple directions. The tube 2 has hollow tube ends which are curved.

(15) A middle region of the tube 2 extends in a lateral direction. Here, the lateral direction is a horizontal direction. The tube ends extend in an upwards direction. At least a length of the tube 2 in the middle region of the tube 2 has a core 3. The core is provided with a plurality of compartments in the form of inner tubes 12 which extend in the core 3. The core 3 is enclosed in between a first intermediate face 5a and a second intermediate face 5b. When hoisting, the highest stresses occur in said middle region. In particular, the middle region is vulnerable to deformations. For that reason the tube 2 is reinforced in the middle region.

(16) At least one sling 7 is provided for hoisting the tube 2. As illustrated, four slings 7 are connected to the tube 2 and at a central point connected to each other. Two slings 7 are connected at the outer tube ends and two slings are connected at the intermediate faces 5a, 5b of the structural element. Herewith, the structural element can be hoisted in a stable manner and a risk on unallowable bending may be prevented.

(17) In FIG. 2 the structural element comprising the tube 2 is used as a spreader beam. The tube 2 is hereto provided with hoisting means in the form of slings 7 for connection to a crane (not shown). Slings 8 are furthermore provided to be attached to the device or structure to be hoisted. The spreader beam according to the invention is cheap to manufacture and light, allowing heavier loads to be lifted with relative small cranes.

(18) As an example, a conventional spreader bar a diameter of 508 mm and a wall thickness of 12.5 mm manufactured from steel is capable of lifting a structure of 16 tons with a length of 18 meters. In contrast, the spreader bar according to the invention is capable of lifting a structure weighing 16 tons of at least 30 meters in length. Although a conventional spreader frame is capable of lifting the same structure as the spreader bar according to the invention, the spreader frame has a weight at least four times higher than the spreader bar according to the invention and is six times more expensive.

(19) In FIG. 3 a structural element in the form of a spreader beam 1 provided with a pressure vessel 9 is shown. The tube 2 is provided with a valve 11 extending into the core 3 of said tube 2. The valve 11 is connected to the vessel 9 by a supply line. In case the pressure in the core 3 drops, which can for instance be measured using pressure sensor provided in the core or in the valve 11, an additional amount of gas and/or liquid can be supplied to the core 3. Even if the core 3 has a leak, the strength of the tube 2 can be guaranteed long enough to be able to lower the structure being hoisted. This provides a fail-safe spreader bar. To further improve the safety, a pump 10 is provided to increase the pressure in the vessel 9 or for instance directly in the core 3 (not shown).

(20) In FIG. 4 the structural element is provided with a plurality of compartments in the form of inner tubes 12 which extend in the core 3. The tubes 12 extend at a distance from the inner surface 2a as can be seen in the cross-sections of FIGS. 5a and 5b taken perpendicular to FIG. 4. This allows the fluid in the core 3 to exert a pressure on the inner surface 2a and side faces 4a and 4b of the tube 2. In FIG. 5a the core 3 is filled with a liquid under pressure, while the tubes 12 are filled with a gas under pressure. The tubes 12 are in this embodiment manufactured from airtight cloth. It is however also possible to manufacture the tubes 12 from a stiff material.

(21) In the embodiment shown in FIG. 5b both the core 3 and the tubes 12 are filled with gas, the gas in the tubes not being pressurized. In this embodiment the tubes 12 are manufactured from a stiff material, in this case plastic.

(22) In FIG. 6 another embodiment is shown wherein the core 3 of the tube 2 comprises compartments in the form of a plurality of spheres 13. The spheres 13 extend along the longitudinal axis of the tube 2 and have a diameter corresponding to the diameter II of the tube 2 in order to achieve a proper fit of said spheres 3. A modification is shown in FIG. 7, wherein the compartments have varying sizes and shapes.

(23) In FIG. 8 a spreader bar is shown having a single compartment in the form of a tube 12. The tube 12 extends coaxial to the tube 2 and has a diameter smaller than the diameter of the tube 2. This allows the gas in the core 3 to exert pressure on the whole inner surface of the inner wall 2a and side faces of the tube 2.

(24) In FIG. 9 the spreader bar shown in FIG. 8 is provided with a pressure vessel 9 and a pump 10. The vessel 9 is arranged to supply additional pressure to the core 3. It is also possible to supply additional pressure to the tube 12 if needed.

(25) In FIG. 10 a structure according to the invention is shown. The structure is manufactured from a plurality of structural elements 1a-d in the form of tubes. Each of the tubes is provided with a core 3a-d. The cores 3a-d are filled with a liquid under pressure. The cores 3a-d of each of the elements 1a-d are connected by valves 11a-d to a common supply line 14 for connection to a pressure vessel 9 provided with a pump 10. The structure is furthermore provided with a controller (not shown) for controlling the valves 11a-d.

(26) If for instance one of the elements 1a-d is stressed, for instance due to a change in load, a deformation of the structure by for instance an earthquake or a collision with for instance a vehicle or a wave, the pressure in the core of said element can be adjusted to compensate for the change in stress. The pressure in a particular core can be increased up to the ultimate loading limit of said element, allowing the element to reach its maximum strength. In case one of the elements 1a-d is deformed or collapsed, the surrounding elements can be adjusted to compensate for the loss of one of the elements by increasing the pressure in the remaining cores 3a-d.

(27) By changing the pressures in the cores, the natural frequencies and the damping of the structural elements, in particular the elements forming the structure, are changed. Next to changing the he static characteristics of the structure, this also allows changing the dynamic response of said structure. Resonance of the structure can hereby effectively be prevented, resulting in lower stresses and vibrations. The resulting fatigue damage is hereby significantly reduced.

(28) In the structure of FIG. 10 the pressures in the cores 3a-d are adjusted actively. That is, a controller is arranged to adjust the pressures in said cores 3a-d bases on pressure measurements. Additional pressure can be supplied using the pump 10 or other suitable means.

(29) It is also possible that a structure without pressure vessel 9 and pump 10 is used. The cores 3a-d are then interconnected using suitable lines. These lines can be provided with valves 11a-d. When one element, for instance element 1a, is stressed, the pressure in core 3a will rise. Due to the pressure difference between the cores, the overpressure in core 3a will be distributed to the other cores 3b-d, dependent on the switching of the lines. The pressures in the other cores 3b-d will therefore also rise, compensating for the load experienced by element 1a. The same applies in case the pressure drops in one of the cores 3a-d.

(30) The present invention is not limited to the embodiment shown, but extends also to other embodiments falling within the scope of the appended claims. It should be noted that the features described for instance the structural element can also be applied to the structure according to the invention and vice versa. It is for instance possible to provide the cores of the structure with compartments.