Trans RINA, Vol 153, Part A4, Intl J Maritime Eng, Oct-Dec 2011
“postage stamp” type) at the upper end connection of the longitudinal girders to the inner bottom in way of the lower stool side plate, as shown in Figure 5. These inserts are commonly applied by the builders / designers to most of the latest designed Panamax and Handymax bulk carriers. However, the increased stiffness of the patch attracts more load thus affecting adversely the adjacent structures (floor, inner bottom, lower stool side and lower stool diaphragm plating). It therefore follows
that in order to ensure satisfactory stress levels at the end connections without the need of the small thick plate inserts, the double bottom height needs to be increased. The dominant loading conditions for the double bottom grillage to produce the maximum stress values presented in Table 3, is the oblique seas conditions. It is therefore unfortunate that CSR do not consider oblique seas yet, despite the insistence from the Greek shipping industry.
Figure 5: Typical Double Bottom Long. Girder and Floor connections in way of the Lower Stool - Showing quality of material & thickness of critical members [i.e. 25.0/30.0 AH36 girder “postage stamp” (insert) plate welded to 11.5 AH32 (floor)]
Table 2: Shear Load on Double Bottom Girders and Floors of Gargo Hold No4 for Loading Case 9 (Worst Case) Shear Capacity of D.B Grillage for DB Height Variations
DB
Height (mm)
1610 1680 1800 1900 2000
DB
Height (mm)
1610 1680 1800 1900 2000
S. Grd. No9 P (tons)
388.0 397.3 404.3 412.4 419.8
Fl. No 1 (tons)
217.0 218.6 222.6 225.6 228.8
Fl. No 2 (tons)
313.4 316.6 322.6 336.0 332.6
S. Grd. No4 P (tons)
602.0 607.3 616.0 621.4 628.2
Fl. No 3 (tons)
384.5 387.0 387.9 398.4 403.0
C.L Grd. (tons)
690.0 694.0 701.4 709.2 715.6
Fl. No 4 (tons)
434.0 437.4 443.0 448.7 453.5
Fl. No 5 (tons)
S. Grd. No4 SB (tons)
676.0 683.3 693.0 700.6 707.3
Fl. No 6 (tons)
441.7 392.1 445.0 395.5 451.2 402.0 456.1 406.6 461.0 411.4
S. Grd. No9 SB (tons)
489.0 497.8 510.9 521.7 531.9
Fl. No 7 (tons)
323.4 326.7 332.0 337.6 342.6
Fl. No 8 (tons)
211.0 213.8 218.5 222.5 215.2
Total shear Capacity (tons)
2,845.0 2,879.7 2,925.6 2,965.3 3,002.8
Total (tons)
2,717.1 2,740.6 2,779.8 2,834.1 2,847.3
A-254
©2011: The Royal Institution of Naval Architects
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