2 Local Areas to be Assessed by Fine Mesh Analysis

2.1 List of mandatory structural details

2.1.1 List of structural details

In the midship cargo hold region, the following structural details are to be assessed according to the fine mesh analysis procedure defined in [1.1.3]:

a) Hopper knuckles for ship with double side as given in [2.1.2],
b) Side frame end brackets and lower hopper knuckle for single side bulk carrier as given in [2.1.3],
c) Large openings as given in [2.1.4],
d) Connections of deck and double bottom longitudinal stiffeners to transverse bulkhead as given in [2.1.5],
e) Connections of corrugated bulkhead to adjoining structure as given in [2.1.6].
f) Bracket at the heel of horizontal stringer as given in [2.1.7],

For each above mentioned structural detail, one fine mesh model is required within all the cargo hold models covering the midship cargo hold region. The selection of the location of this fine mesh model is to be based on requirements given from [2.1.2] to [2.1.7] from all cargo hold analyses in the midship cargo hold region.

2.1.2 Hopper knuckles for ship with double side

Fine mesh analysis is to be carried out for the lower and upper hopper knuckles of either welded or bent type, in way of a typical transverse web frame, as indicated in Figure 1.

For double side arrangements without the hopper plating, i.e. where the inner hull longitudinal bulkhead is fitted directly to the inner bottom, fine mesh analysis is to be carried out for the heel of the transverse web frame.

The transverse web frame which, in the cargo hold analysis, has the maximum yield utilisation factor, λ_y, in knuckle is to be selected for the fine mesh analysis.

2.1.3 Side frame end brackets and lower hopper knuckle for single side bulk carrier

Fine mesh analysis is to be carried out for the lower hopper knuckle of either welded or bent type, lower and upper end bracket of side frame, as indicated in Figure 2.

The side frame which in the cargo hold analysis has the maximum yield utilisation factor, λ_y, in end bracket joints is to be selected for the fine mesh analysis.

Figure 1 : Mandatory areas at hopper knuckles for ships with double side

Figure 2 : Mandatory areas at lower upper knuckle and side frame end brackets for single side bulk carrier

2.1.4 Large openings

Large openings in way of primary supporting members, for which their geometry is required to be represented in the cargo hold model in accordance with Ch 7, Sec 2, [2.4.9], are to be assessed by fine mesh analysis.

The structural member in way of the large openings having the maximum yield utilisation factor, λ_y, in the cargo hold analysis is to be selected for the fine mesh analysis.

2.1.5 Connections between deck and double bottom longitudinal stiffeners and adjoining structures of transverse bulkhead

Fine mesh analysis is to be carried out for the connections of deck and double bottom longitudinal stiffeners and adjoining structures of transverse bulkhead, either plane or corrugated bulkhead. The adjoining structures of transverse bulkhead include the structural members in way of the bulkhead, the partial deck girders and partial double bottom girders, if any.

For example, the following structural members are to be assessed, some of them being shown in Figure 3:

At least one pair of connections between inner and outer bottom longitudinal stiffeners and adjoining structures of transverse bulkhead.
At least one pair of connections between inner and outer bottom longitudinal stiffeners and adjoining structures of adjacent floor to the transverse bulkhead.
At least one connection between deck longitudinal stiffener (fitted above or below deck) and adjoining vertical structure of transverse oil tight bulkhead.
Connection between deck longitudinal partial girder on top of transverse oil tight bulkheads when fitted and adjoining vertical structure of transverse oil tight bulkhead.
Connection between bottom longitudinal partial girder in way of transverse oil tight bulkheads when fitted and adjoining vertical structure of transverse oil tight bulkhead.

The selection of the connections between longitudinal and vertical stiffeners to be analysed is to be based on the maximum relative deflection between supports, i.e. between floor and transverse bulkhead or between deck transverse and transverse bulkhead. Where there is a significant variation in end connection arrangement between stiffeners or scantlings, analyses of additional connections may be required by the Society.

Outside the midship cargo hold region, the scantlings of the connections as given above are not to be less than the required scantlings obtained for the midship cargo hold region unless an equivalent strength is demonstrated by fine mesh analysis.

2.1.6 Connections between corrugation and adjoining lower structure

Fine mesh analysis is to be carried out for connections between corrugation and adjoining lower supporting structures. For example, the following structural members, as shown in Figure 4, are to be assessed:

Connection of the corrugation and supporting structure in way of lower stool shelf plate.
Connection of the corrugation and lower supporting structure to inner bottom if no lower stool is fitted.
Connection of the corrugation and the upper corner of the gusset plate if shedder plate with a gusset plate is fitted at top of the lower stool.

The corrugation unit as defined in Ch 8, Sec 4, [3.3.2] which, in the cargo hold analysis, has the maximum yield utilisation factor, λ_y, in way of the corrugation connection, is to be selected for the fine mesh analysis.

Where there is a significant variation in the arrangement of supporting structure of the corrugation, analysis of additional locations may be required by the Society.

For ships with both longitudinal and transverse corrugated bulkheads, fine mesh analysis is required for the connection between corrugations and supporting structure in way of the lower stool shelf plate or inner bottom, if no lower stool is fitted, at the intersection between longitudinal and transverse corrugated bulkheads.

Figure 3 : Examples of mandatory areas at connections between double bottom and deck longitudinals and adjoining structure of transverse bulkhead

Figure 4 : Mandatory areas at connections between corrugations and adjoining lower stool

2.1.7 Bracket at the heel of horizontal stringer

Fine mesh analysis is to be carried out for the bracket at the heel of horizontal stringers. All structural elements adjacent to the heel including the inner hull, longitudinal and transverse bulkhead are to satisfy the stress acceptance criteria. The heel of horizontal stringer which, in the cargo hold analysis, has the maximum yield utilization factor, λ_y, is to be selected for the fine mesh analysis. Where there is a significant variation in the arrangement of the bracket at the heel and the horizontal stringer, analysis of additional locations may be required by the Society.