EP0146332A2

EP0146332A2 - Barges and methods of increasing barge capacity

Info

Publication number: EP0146332A2
Application number: EP84308601A
Authority: EP
Inventors: Nico Deboer; Stafford J. Menard
Original assignee: McDermott International Inc
Current assignee: McDermott International Inc
Priority date: 1983-12-19
Filing date: 1984-12-11
Publication date: 1985-06-26
Also published as: AU3657884A; ES8609105A1; JPS6175091A; ES8609104A1; ES548063A0; ES548064A0; BR8406492A; ES8604458A1; KR850004433A; ES538725A0

Abstract

A variable capacity floating structure includes two barges (11, 12) which are connected by two or more hinge assemblies (30) at mating ends of the barges. Each hinge assembly (30) in- dudes one or more bracket plates (33) attached to the mating end of each barge (11, 12) and having apertures (46) therethrough for alignment of the apertures with each other, and a pin (43) insertable into and removable from the apertures (46) to respectively connect and disconnect the barges (11, 12) whereby each barge is rotatable about the pin (43) relative to the other when the barges are connected.

Description

This invention relates to barges (e.g. barges for the transportation and/or launching of heavy structures such as prefabricated structural components of an offshore oil drilling platform such as a drill jacket) and to methods of increasing the capacity of barges.
The jacket of an offshore drilling platform is an elongate tubular lattice that extends from a base to a deck of the platform, encloses conductor pipes, and to which deck modules are fitted. The jacket is prefabricated onshore and loaded aboard a launch barge on its side by sliding it along skid rails onshore and then onto skid rails on the deck of the barge.
The launch barge is typically a flat-bottomed and flat-decked barge having a large clear deck space for receiving the jacket. The jacket is temporarily welded to the barge with bracing material and then transported to the installation site. The launch barge is fitted with a tilting mechanism by means of which the jacket can be caused to slide into the water. At the installation site, the bracing is cut, jacks are employed to slide the jacket along the skid rails until its centre of gravity is properly located relative to the tilting mechanism, and the jacket is then slid off the tilting mechanism into the water.
Launch barges must be skillfully designed to accomodate the significant loads imposed by the weight of the jacket, the launch stresses, and the normal forces encountered while the barge is underway. In order to increase the capacity of the launch barge so that it can carry greater structural weight, permanent alterations have had to be made to the barge. Such alterations include the permanent addition of sponsons, deck strapping, and additional barge length. The addition and removal of such additions is labour intensive, time consuming, and quite expensive.
According to a first aspect of the invention, the capacity of a barge may be readily and adjustably increased by the provision of means for releasably connecting a first barge and a second barge serially with bow end to stem end. Two or more hinge assemblies, mounted at laterally spaced intervals along mating ends of the first and second barges and substantially perpendicular to the longitudinal axes of the barges, interconnect the barges.
Each hinge assembly, according to a preferred feature of the invention, includes bracket plates, at least one being attached to one of the first and second barges and at least two being attached to the other barge and which longitudinally and vertically extend in an interleaved arrangement. Each of the plates of the assembly includes an aperture extending laterally therethrough which is alignable with like apertures in the other plates of the assembly. Means are provided for axially reciprocating a hinge pin into and out of the apertures of each hinge assembly to respectively connect and disconnect the first and second barges. When the barges are so connected, each is rotatable about the hinge pins relative to the other.
According to a further preferred feature of the invention, each hinge assembly includes three groups of laterally adjacent bracket plates, the bracket plates of each group being interconnected by a heavy walled pipe sleeve which extends through the apertures and through which the hinge pin is slidably received. Two of the groups of brackets are connected to a first one of the barges and the third group is connected to the second one of the barges and extends into a space between the other two groups.
According to a second aspect of the invention there is provided a floatable load carrying structure comprising a first barge, a second barge, and means for connecting the first barge and the second barge in end to end relation, the connecting means including at least two hinge assemblies mounted at spaced intervals along the mating ends of the first and second barges, each hinge assembly including: a plurality of longitudinally and vertically extending bracket plates, at least one of the bracket plates being attached to the first barge and others of the bracket plates being attached to the second barge, each of the bracket plates having an aperture therethrough which is alignable with the apertures of the other bracket plates; and an elongate pin insertable into and removable from the apertures to respectively connect and disconnect the first and second barges to allow rotation of the barges about the pin relative to each other when the barges are connected.
According to a third aspect of the invention there is provided an extension for a first barge to increase the capacity thereof, the extension comprising a second barge and means for connecting the second barge to the first barge in end to end relation, the connecting means including at least two hinge assembly portions attached at spaced intervals along the mating end of the second barge, each hinge assembly portion including: at least one longitudinally and vertically extending bracket plate attached to the mating end of the second barge and having an aperture therethrough for aligning with like apertures in at least two bracket plates attached to the mating end of the first barge, and an elongate pin insertable into and removable from the apertures to respectively connect and disconnect the first and second barges to allow rotation of the barges about the pin relative to each other when the barges are connected.
According to a fourth aspect of the invention there is provided a method of increasing the capacity of a first barge, the method comprising attaching a plurality of bracket plates to ends of the first barge and a second barge, including attaching at least one bracket plate to an end of the first barge and other bracket plates to an end of the second barge, each bracket plate having an aperture therethrough which is alignable with the apertures of the other bracket plates, positioning the first and second barges in end to end relation and aligning the bracket plate apertures, and inserting an elongate pin into the apertures to connect the first and second barges whereby each barge is rotatable about the pin relative to the other.
A preferred embodiment of the invention described hereinbelow provides a variable capacity barge by the quick and inexpensive connection and disconnection of one or more barge extensions.
The invention will now be further described, by way of illustrative and non-limiting example, with reference to the accompanying drawings, in which like references designate like or corresponding parts throughout, and in which:

Figure 1 is a partly broken-away, schematic plan view of a launch barge or floatable load carrying structure embodying the invention;
Figure 2 is a side elevational view of the launch barge of Figure 1;
Figure 3 is a partial elevational view showing the interconnection of primary and secondary barges to form the launch barge;
Figure 4 is an enlarged elevational view showing hinge assemblies of the launch barge; and
Figure 5 is a view taken along a line 5-5 of Figure 4.

Figure 1 shows a launch barge 10 for transporting and launching a prefabricated offshore structure such as a drill jacket (not shown). The launch barge 10 is composed of two serially connected units, i.e. a secondary extension barge 12 which is releasably connected at its bow to a primary barge 11 at its stern in a manner described hereinafter.
The primary barge 11 is a conventional flat-bottomed and flat-decked barge modified by removal of a tilting mechanism, the so-called rocker arms, which generally are installed at one end of the barge for tilting and sliding the jacket from the deck 13 into the water. A launchway extension 14 is fixed to the end of the primary barge 11 in a stationary manner in lieu of the conventional rocker arms.
The secondary extension barge 12 is outfitted with a pair of rocker arms 15 and 16 mounted at the end of the deck 17 of the barge 12 which is remote from the primary barge 11, that is, at the stern of the barge 12.
The launch barge 10 includes a pair of skid rails 18 and 19 mounted on and longitudinally extending along the length of each of the decks 13 and 17. The skid rails 18 and 19 provide means for sliding the jacket onto and off of the barge. The rocker arms 15 and 16 are longitudinally aligned with the skid rails 18 and 19 respectively.
As best shown in Figure 3, the upper portion of the bow of the secondary barge 12 overlies a lower portion of the stem of the primary barge 11. The length of the launchway extension 14 is truncated relative to the length of the rocker arm which it replaces so that it does not extend to, or beyond, the stern of the primary barge 11 and allows the bow of the secondary barge 12 freely to rotate through an arc on either side of the horizontal plane in which the decks normally extend without contacting the primary barge.
The primary barge 11 and the secondary barge 12 are releasably connected to each other at their mating ends by a series of integrally attached hinge assemblies 30 located at laterally spaced intervals along the mating ends.
Each hinge assembly 30 includes groups of brackets designated herein as padeye assemblies 31 and 32. The radeye assembly 31 is connected to the mating end of the primary barge 11 and interleaved intermediate two laterally adjacent padeye assemblies 32 connected to the mating end of the secondary barge 12. Each of the padeye assemblies 31 and 32, as best shown in Figures 4 and 5, is composed of three vertically and longitudinally extending brackets 33 which are laterally spaced and interconnected by a heavy-walled pipe sleeve 34 extending through laterally aligned apertures 46 in each of the brackets 33. The pipe sleeve 34 is weldably fixed to each of the brackets 33 that comprises a respective one of the padeye assemblies 31 or 32. The three sleeves 34 of each hinge assembly 30 are axially alignable in an end to end mounting arrangement. The brackets 33 are preferably connected to and extend vertically from the bottoms 36 and 37 of the respective barges 11 and 12 and are continuously vertically welded, at each side of one edge, along their length, and are spaced, at the opposite end, from the other barge when the barges are connected. An arcuate facing plate 38 and 39 overlies and interconnects an extreme edge of each of the brackets 33 of each respective padeye assembly 31 and 32. The laterally outermost brackets 33 of each assembly 31 and 32 are preferably aligned with bulkhead plates 35 of the respective barge to which the bracket is weld-united in order to strengthen the connection with the respective barges 11 and 12.
The barges 11 and 12 are interconnected by hinge pins 43 inserted in the apertures 46 to permit relative rotational movement between these units in response to water undulations which may be attenuated by well known means of buoyancy control. It is envisaged that the provision of such rotational movement between the barges 11 and 12 may allow a substantial reduction in the size of the rocker arms 15 and 16, although it may not be possible to eliminate the rocker arms altogether.
Each hinge assembly 30 includes a hydraulic actuator 40 comprising a cylinder 41 and a piston rod 42 integral with a piston (not shown) mounted slidably within the cylinder. The piston rod 42 is longitudinally connected to a hinge pin 43 which may be retractably extended through a tubular housing 44 connected in end to end relation to an adjacent one of the pipe sleeves 34. The piston rod 42 is designed for reciprocation of the hinge pin 43 axially into and out of the respective sleeves 34 of the padeye assemblies 31 and 32 of the respective hinge assembly 30. The hydraulic actuator 40 may be energised by well-known means. Thus, the actuator 40 is operable to connect and disconnect the barges 11 and 12 to and from each other by the respective insertion or extraction of the hinge pin 43 into or out of all of the sleeves 34 of a group of padeye assemblies 31, 32. The activator 40 is fixedly connected to the barge 12 by attachment with a mounting plate 45. However, it may alternatively be connected to the barge 11.
A launch barge 10 embodying the present invention may comprise a primary barge 11 of about 198 m (650 feet) in length, with a beam of about 52 m (170 feet), connected to a secondary barge 12 of about 107 m (350 feet) in length, with a launch end width of about 76 m (250 feet), the depth of each barge 11 and 12 being about 12 m (40 feet). The combined unit includes eight laterally spaced hinge assemblies 30 each including 51 mm (2 inch) thick brackets having lengths of about 3.66 m (12 feet), sleeves each with a 457 mm (18 inch) outer diameter, a 311 mm (12.25 inch) inner diameter, and a length of 635 mm (25 inches) for accomodating a 305 mm (12 inch) outer diameter pin. Static calculations have indicated that such a combined flexible structure can accomodate a shear stress of about 158.8 MN (35.7 Mlbf) which is more than double the highest calculated shear load of about 76 MN (17 Mlbf) for a 488 m (1,600 foot) long, 76,200 tonne (75,000 ton) jacket. A jacket of such size has not been built to date. 76,200 tonne (75,000 tons) can be accomodated at a maximum draft of 5.8 m (19 feet). If the connection between the barges 11 and 12 were rigid, static calculations indicate that the moment at the connection would be 12,880 MN-m (9,500 Mlbf-ft), which is approximately twice the moment that such a conventional barge would be capable of handling. However, with the provision of the hinge assemblies 30, the extension barge 11 may rotate about the hinge pins 43 with the result that the moment at the hinges is, therefore, zero. Thus, the arrangement embodying the invention is provided to increase the capacity of existing barges to allow launching of jackets larger than the original design capacity of the barge without extensive rebuilding and reinforcement of the barge. The arrangement embodying the invention is provided to permit fast attachment and disengagement while allowing each barge of the dual unit to be separated and used as separate launch barges when not being used in combination for transporting and launching very large jackets.
The components of the hinge assemblies may be mounted to barges having various lengths so that different barges can be readily combined to obtain relatively larger or smaller overall lengths.

Claims

1. A floatable load carrying structure comprising a first barge (11/12), a second barge (12/11), and means for connecting the first barge and the second barge in end to end relation, the connecting means including at least two hinge assemblies (30) mounted at spaced intervals along the mating ends of the first and second barges, each hinge assembly (30) including: a plurality of longitudinally and vertically extending bracket plates (33), at least one of the bracket plates being attached to the first barge (11/12) and others of the bracket plates being attached to the second barge (12/11), each of the bracket plates (33) having an aperture (46) therethrough which is alignable with the apertures of the other bracket plates (33); and an elongate pin (43) insertable into and removable from the apertures (46) to respectively connect and disconnect the first and second barges (11, 12) to allow rotation of the barges (11, 12) about the pin (43) relative to each other when the barges are connected.

2. A floatable structure according to claim 1, wherein each hinge assembly (30) includes a group (31) of the bracket plates (33) attached to the first barge (11/12) and interleaved between a pair of groups (32) of the bracket plates (33) attached to the second barge (12/11).

3.. A floatable structure according to claim 1, wherein each hinge assembly (30) comprises a group (31) of three laterally adjacent bracket plates (33) attached to the first barge (11/12) and interleaved between a pair of groups (32) of three laterally adjacent bracket plates (33) attached to the second barge (12/11), and a pipe sleeve (34) inserted into the apertures (46) of each group (31, 32) of bracket plates (33) and weldably connected to and uniting the three laterally adjacent bracket plates of each group of bracket plates.

4. A floatable structure according to claim 3, wherein the connecting means includes facing plates (38, 39) connected to the three laterally adjacent bracket plates (33) of each group (31, 32) at edges of the plates longitudinally remote from the end connected to the respective barge.

5. A floatable structure according to any one of the preceding claims, wherein each of the bracket plates (33) extends vertically from the bottom (36, 37) of the respective one of the first and second barges (11, 12).

6. A floatable structure according to any one of the preceding claims, wherein the connecting means comprises means for reciprocating the pin (43) into and out of the apertures (46).

7. A floatable structure according to claim 6, wherein the reciprocating means includes a piston connected to the pin (43) and a hydraulic actuator (40) mounted to one of the first and second barges (11, 12) and connected to the piston for reciprocating the pin (43) into and out of the apertures (46) of the bracket plates (33).

8. An extension for a first barge (11/12) to increase the capacity thereof, the extension comprising a second barge (12/11) and means for connecting the second barge (12/11) to the first barge (11/12) in end to end relation, the connecting means including at least two hinge assembly portions (30) attached at spaced intervals along the mating end of the second barge (12), each hinge assembly portion (30) including: at least one longitudinally and vertically extending bracket plate (33) attached to the mating end of the second barge (12/11) and having an aperture (46) therethrough for aligning with like apertures in at least two bracket plates (33) attached to the mating end of the first barge (11/12), and an elongate pin (43) insertable into and removable from the apertures (46) to respectively connect and disconnect the first and second barges (11, 12) to allow rotation of the barges (11, 12) about the pin (43) relative to each other when the barges are connected.

9. An extension according to claim 8, wherein the connecting means comprises means for reciprocating the pin (43) into and out of the apertures (46).

10. An extension according to claim 9, wherein the reciprocating means includes a piston connected to the pin (43) and a hydraulic actuator (46) mounted to the second barge (12/11) and connected to the piston for reciprocating the pin (43) into and out of the apertures (46) of the bracket plates (33).

11. A method of increasing the capacity of a first barge (11/12), the method comprising attaching a plurality of bracket plates (33) to ends of the first barge (11/12) and a second barge (12/11), including attaching at least one bracket plate (33) to an end of the first barge (11/12) and other bracket plates (33) to an end of the second barge (12/11), each bracket plate (33) having an aperture (46) therethrough which is alignable with the apertures (46) of the other bracket plates (33), positioning the first and second barges (11, 12) in end to end relation and aligning the bracket plate apertures (46), and inserting an elongate pin (43) into the apertures (46) to connect the first and second barges (11, 12) whereby each barge is rotatable about the pin (43) relative to the other.

12. A method according to claim 11, comprising applying hydraulic pressure to a hydraulically actuated piston connected to the pin (43) to insert the pin (43) into the apertures (46).