Trans RINA, Vol 153, Part A4, Intl J Maritime Eng, Oct-Dec 2011 demonstrated in [6] or in this linear FE analysis.


Certainly the welds are stressed well over their capacity and cracks will form first on coatings [10] and then on the welds, and eventually propagate along the weakest path of the plate materials involved. This effect may well appear within the first few years of the vessel’s life as described in [12].


In order to satisfy the allowable stress of the applicable rule, a further reduction of the nominal stress is required. This can be achieved with the increase of the double bottom height, the drastic increase of the thickness of floors and girders, the introduction of additional floors and girders, or a combination of all these. Obviously the most drastic solution would be the addition of girders / floors, since this would reduce the load carried by each member. The stresses calculated are at about 22% higher than the allowable. In this paper we investigated the effect that the increase of the double bottom height would have on the reduction of the stresses, as shown in Table 4. The companion paper to be issued shortly, investigates the optimum combination of the three alternatives in order to determine the most efficient solution.


Table 4 Ratio of Maximum / Allowable Stress Intensity at Double Bottom Girders


Double Bottom Girders Max. Nominal Stresses intensity with various Double Bottom Heights at LC 9 Cargo Hold No 4


D.B. Height 1610 1680 1800 1900 2000


C.L Side DB Girder


1.21 1.18 1.14 1.11 1.08


No4 DB Girder 1.25 1.22 1.18 1.15 1.12


Figure 7 Hot Spot Stress Calculation [as defined in Fig. 6]


©2011: The Royal Institution of Naval Architects


A-257


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64