GB1593290A

GB1593290A - Vessel with a doublebottom

Info

Publication number: GB1593290A
Application number: GB41891/77A
Authority: GB
Original assignee: dba PARGA
Current assignee: dba PARGA
Priority date: 1976-10-16
Filing date: 1977-10-07
Publication date: 1981-07-15
Also published as: ES452472A1; BR7706880A; JPS5387484A; JPS57114780A

Description

(54) VESSEL WITH A DOUBLE BOTTOM (71) We, D.B.A. PARGA S.L., a Spanish Body Corporate of Orfila 3, 1"., Madrid - 4, Spain, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement.

This invention relates to a vessel having a double bottom.

A known form of double bottom for a vessel is a frame-type structure consisting of two flat and parallel steel plate surfaces, these being the bottom plating and the ceiling plating of the double bottom, and an internal reinforcement formed by primary and secondary members. The primary members are (a) the floor frames, arranged transversely of the vessel and between the bottom and ceiling plating over the full height of the double bottom, and (b) the keelsons, also over the full height of the double bottom but extending longitudinally of the vessel. Both the floor frames and the keelsons are of flat plate.The secondary members are (a) bottom longitudinal members adjacent the bottom plating and (b) double bottom longitudinal members adjacent the ceiling plating, these being arranged longitudinally and connected to the transverse floor frames, and being rolled or fabricated sections (angle, bulb flat, fabricated T, for instance). In addition, there are many couplings or brackets between the aforementioned members, and stiffeners; which are generally of flat or angular section, and are welded to the primary members and are designed to prevent buckling of the said primary members.

Such a structure is schematically illustrated in Figures la, Ib, 1c and ld, of the accompanying drawings, which respectively show a transverse cross-section on one floor frame, a transverse cross-section between floor frames, a plan view, and a longitudinal section showing half a cargo hold of a bulk carrier. These Figures show the bottom plating 1; the ceiling plating of the double bottom 2; the floor frames 3; the keelsons 4; the bottom longitudinal members 5; and the double bottom longitudinal members 6. The transverse primary members (the floor frames 3) are connected to the structure of the vessel's side when the double bottom is horizontal as far as the side, or to the structure of the hopper, indicated at 7, in the case of a double bottom with side hoppers, which is the case shown in these Figures and is common in medium and large size vessels.The longitudinal primary members (the keelsons 4) are connected to transverse bulkheads or to the seatings 8 of transverse bulkheads when these are provided, as in the case shown in the Figures, which again is common in medium and large size vessels.

The scantlings and the arrangement of the aforementioned members are regulated by the Rules of the Classification Societies and, in the case of vessels for transporting dry bulk materials and heavy loads, these Rules prescribes the arrangement of one floor frame for every two or three frame spaces, and of one keelson for every three or four longitudinal member spaces, giving in each case a maximum separation between floor frames and a maximum separation between keelsons. For vessels of and above a given length, the Rules also prescribe the use of a structure such as above described for the double bottom. It is a structure which is relatively complicated to construct, with many members to be assembled, and is quite heavy.

Recent development in, and increases in the size of, vessels has not been reflected in the dimensions of the holds, and in fact the ratio of the length to the width of holds has dropped as the size of the vessel increased, passing from ratio values above unity to values substantially below unity. The ratio between the span of the keelsons between bulkheads and the span of the floor frames between side hoppers has undergone the same transformation and, in bulk carriers exceeding about 45,000 TG (tons gross) that ratio is now around 0.5.

According to a first aspect of the present invention there is provided a vessel having a plurality of transverse bulkheads extending between the sides of the vessel; and a double bottom including: bottom plating and ceiling plating, longitudinal primary members extending over the full height of the double bottom between the platings, transverse primary members extending over the full height of the double bottom between the platings but only directly beneath the lines of securing of the transverse bulkheads to the ceiling plating, an array of transverse secondary members of a lesser height arranged along the entire length of the double bottom beneath and between the transverse bulkheads and connected to the longitudinal primary members adjacent the ceiling plating, and bottom secondary members of a lesser height adjacent the bottom plating.

A second aspect of the invention provides a vessel having a plurality of transverse bulkheads extending between the sides of the vessel; and a double bottom including: bottom plating and ceiling plating, longitudinal primary members extending over the full height of the double bottom between the platings, first transverse primary members extending over the full height of the double bottom between the platings but only directly beneath the lines of securing of the transverse bulkheads to the ceiling plating, second transverse primary members extending over the full height of the double bottom between the platings and disposed such that there are no more than two such transverse primary members between the adjacent lines of securing of two successive transverse bulkheads along the vessel, to the ceiling plating, an array of transverse secondary members of a lesser height arranged along the entire length of the double bottom beneath and between the transverse bulkheads and connected to the longitudinal primary members adjacent the ceiling plating, and longitudinal bottom secondary members of a lesser height adjacent the bottom plating.

The invention takes into account the aforesaid transformation in the span ratio, and provides a new double bottom structure in which the cargo weight and opposing water pressure forces are borne by the longitudinal primary members and in which because many of the transverse primary members have thus become unnecessary they are eliminated. Thus in the first embodiment all the primary floor frames other than those directly beneath the lines of securing of the bulkheads to the ceiling plating are eliminated, leaving as primary members only the various keelsons and just the pair of floor frames below the bulkhead hoppers.At the same time, the ceiling longitudinal secondary members are eliminated and instead, as secondary members, there may be solely bottom and ceiling transverse stiffness, which may generally be rolled sections, connected by welding to the keelsons and ending at the vessel side structure or at the side hopper structure.

In the second aspect of the invention, the ceiling longitudinal secondary members are again eliminated, but the bottom longitudinal secondary members are retained and are supported by the absolute minimum of transverse primary members (floor frames).

In both aspects of the invention the weight of the cargo is transmitted to the transverse bulkheads by the keelsons, and the cargo hold floor the ceiling of the double bottom is supported by way of both the keelsons and the ceiling transverse secondary members.

This new structure is lighter and much simpler per se because of the elimination of many transverse primary members, and it also has the effect of reducing the necessarv deck cross-section. This is because raising the neutral axis of the main section of the vessel as a result of the elimination of many at least of the longitudinal secondary members, increases the section modulus to deck as the moment arm to deck reduces. Since the required section modulus to deck is constant the necessary deck area crosssection can be less. As the section modulus to deck is always less than the section modulus in the bottom, this will be the critical one as regards not falling below the prescribed minimum value for either modulus, and the permissible reduction in the deck area cross-section this causes a further reduction in the total weight of the structure of the vessel.

The invention will be more clearly understood from the following description which is given by way of example only with reference to Figures 2a, 2b, 2c and 2d and Figures 3a, 3b, 3c and 3d of the accompanying drawings.

Figures 2a, 2b, 2c and 2d of the drawings show, respectively, a first embodiment in: a transverse section showing one of two floor frames located below the bulkhead seatings, a typical transverse section between floor frames, a plan view, and a longitudinal section of the double bottom of half a cargo hold of a bulk carrier, respectively. The drawings show bottom plating l; ceiling plating of the double bottom at 2; floor frames 3, these being the primary transverse members; keelsons 4, these being the primary longitudinal members; bottom transverse members 5; ceiling transverse members 6 adjacent plating 2; a side hopper 7; and the seating of a transverse bulkhead 8.

In this form of the invention the weight of the cargo is transmitted to the transverse bulkheads by way of the longitudinal primary members 4, the transverse primary members 3 serving mainly to give continuity to the bulkhead hoppers.

As a variation, the secondary bottom transverse members 5 can be replaced by larger section secondary bottom longitudinal members, disposed such that there are one or two of these secondary bottom longitudinal members between every two adjacent keelsons. At the same time, to support these secondary longitudinal members and to provide the structure with deformation resistance, one or possibly two further primary transverse members, arranged between the seatings of the bulkheads. The arrangement of the bottom longitudinal members 5 is advantageous, as it is possible to subtract their section, or a large part of their section, from the section corresponding to the bottom plating, thus attaining a further saving of weight in certain cases.

Such an embodiment is schematically illustrated in Figures 3a, 3b, 3c and 3d, which are views similar to those of the preceding Figures but showing this variation. The drawings again show the bottom plating 1; the ceiling plating of the double bottom at 2; the floor frames, that is the primary transverse members at 3; the primary longitudinal members or keelsons at 4; bottom longitudinal members at 5; the double bottom transverse members 6 adjacent the ceiling plating; a side hopper 7; and the seating 8 of the transverse bulkhead.

The structures of the two embodiments described above and illustrated in Figures 2a, 2b, 2c, 2d and 3a, 3b, 3c, 3d, represent a saving in weight which is a function of the above mentioned ratio between the spans of the primary members. In both cases, it represents a notable simplification in the construction of the double bottom; simpler assembly of services in the double bottom and likewise simpler maintenance thereof; it is more suitable for the modern methods of construction with prefabricated flat blocks.

Finally, in supporting the weight of the cargo by the transverse bulkheads, with the aid of the keelsons, it increases the contribution of the keelsons to the shear strength of the structure, eliminating critical situations which could otherwise appear.

The use of each of the two described embodiments will be accommodated to the specific conditions, type and size of the vessel, hold width, hold length, of each particular case, using the most suitable one in each case.

WHAT WE CLAIM IS: 1. A vessel having a plurality of transverse bulkheads extending between the sides of the vessel; and a double bottom including: bottom plating and ceiling plating, longitudinal primary members extending over the full height of the double bottom between the platings, transverse primary members extending over the full height of the double bottom between the platings but only directly beneath the lines of securing of the transverse bulkheads to the ceiling plating, an array of transverse secondary members of a lesser height arranged along the entire length of the double bottom beneath and between the transverse bulkheads and connected to the longitudinal primary members adjacent the ceiling plating, and bottom secondary members of a lesser height adjacent the bottom plating.

2. A vessel according to claim 1, wherein said bottom secondary members are transverse secondary members.

3. A vessel according to claim 1 wherein the bottom secondary members extend longitudinally.

4. A vessel according to claim 3, wherein there are one or two longitudinal bottom secondary members between adjacent primary longitudinal members.

5. A vessel having a plurality of transverse bulkheads extending between the sides of the vessel; and a double bottom including; bottom plating and ceiling plating, longitudinal primary members extending over the full height of the double bottom between the platings, first transverse primary members extending over the full height of the double bottom between the platings but only directly beneath the lines of securing of the transverse bulkheads to the ceiling plating, second transverse primary members extending over the full height of the double bottom between the platings and disposed such that there are no more than two such transverse primary members between the adjacent lines of securing of two successive transverse bulkheads along the vessel, to the ceiling plating, an array of transverse secondary members of a lesser height arranged along the entire length of the double bottom beneath and between the transverse bulkheads and connected to the longitudinal primary members adjacent the ceiling plating, and longitudinal bottom secondary members of a lesser height adjacent the bottom plating.

6. A vessel having a double bottom constructed and arranged substantially as hereinbefore described with reference to and as illustrated in Figures 3a, 3b, 3c and 3d of the accompanying drawings.

7. A vessel having a double bottom

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. members; keelsons 4, these being the primary longitudinal members; bottom transverse members 5; ceiling transverse members 6 adjacent plating 2; a side hopper 7; and the seating of a transverse bulkhead 8. In this form of the invention the weight of the cargo is transmitted to the transverse bulkheads by way of the longitudinal primary members 4, the transverse primary members 3 serving mainly to give continuity to the bulkhead hoppers. As a variation, the secondary bottom transverse members 5 can be replaced by larger section secondary bottom longitudinal members, disposed such that there are one or two of these secondary bottom longitudinal members between every two adjacent keelsons. At the same time, to support these secondary longitudinal members and to provide the structure with deformation resistance, one or possibly two further primary transverse members, arranged between the seatings of the bulkheads. The arrangement of the bottom longitudinal members 5 is advantageous, as it is possible to subtract their section, or a large part of their section, from the section corresponding to the bottom plating, thus attaining a further saving of weight in certain cases. Such an embodiment is schematically illustrated in Figures 3a, 3b, 3c and 3d, which are views similar to those of the preceding Figures but showing this variation. The drawings again show the bottom plating 1; the ceiling plating of the double bottom at 2; the floor frames, that is the primary transverse members at 3; the primary longitudinal members or keelsons at 4; bottom longitudinal members at 5; the double bottom transverse members 6 adjacent the ceiling plating; a side hopper 7; and the seating 8 of the transverse bulkhead. The structures of the two embodiments described above and illustrated in Figures 2a, 2b, 2c, 2d and 3a, 3b, 3c, 3d, represent a saving in weight which is a function of the above mentioned ratio between the spans of the primary members. In both cases, it represents a notable simplification in the construction of the double bottom; simpler assembly of services in the double bottom and likewise simpler maintenance thereof; it is more suitable for the modern methods of construction with prefabricated flat blocks. Finally, in supporting the weight of the cargo by the transverse bulkheads, with the aid of the keelsons, it increases the contribution of the keelsons to the shear strength of the structure, eliminating critical situations which could otherwise appear. The use of each of the two described embodiments will be accommodated to the specific conditions, type and size of the vessel, hold width, hold length, of each particular case, using the most suitable one in each case. WHAT WE CLAIM IS:

1. A vessel having a plurality of transverse bulkheads extending between the sides of the vessel; and a double bottom including: bottom plating and ceiling plating, longitudinal primary members extending over the full height of the double bottom between the platings, transverse primary members extending over the full height of the double bottom between the platings but only directly beneath the lines of securing of the transverse bulkheads to the ceiling plating, an array of transverse secondary members of a lesser height arranged along the entire length of the double bottom beneath and between the transverse bulkheads and connected to the longitudinal primary members adjacent the ceiling plating, and bottom secondary members of a lesser height adjacent the bottom plating.

7. A vessel having a double bottom

constructed and arranged substantially as hereinbefore described with reference to and as illustrated in Figures 2a, 2b, 2c and 2d of the accompanying drawings.