Consequences of CSR BC & OT on bulk carriers
- The side shell plating both in the mid-ship area and in way of engine room and aft peak may need reinforcement or increase in thickness due to buckling check and higher minimum thickness requirements.
- The GRAB notation requirement has been modified. The minimum mass of unladen grab has been increased to 35 ton for Capesize vessels and 30ton for Panamax vessels, in order to reflect the weights of the grabs currently used in some dry cargo terminals. Larger grab weight will give thicker inner bottom plating for vessels with length equal or greater than 200 m.
- Bottom plates and stiffeners in cargo hold 2 (and cargo hold 3 for large vessels) may need to be reinforced due to extended slamming reinforcement area.
- The increased scope for FE analysis has a significant scantling impact in the way of the foremost and aftermost cargo holds, and also primary members connected to collision bulkhead inside fore peak tank and structures attached to engine room bulkhead inside engine room. Typical areas of concern are shown in the figure.
- Some stiffeners in way of bottom, side shell and deck plate have fatigue life less than the required 25 years. Fatigue life can be increased by improving end connection details. CSR BC & OT requires standard structural details for fatigue concerned locations and alternative design is not acceptable unless direct analysis proves equivalent fatigue capacity to the standard details.
- It is further seen that hatch corner design and /or scantling in way of outside mid-ship region may need to be improved. Particularly for Handymax vessels, the size of hatch opening is relatively larger than for the bigger Bulk Carriers. This will lead to higher warping stresses due to hull girder torsion, so special attention is needed. In addition, oblique equivalent design wave (EDW) is added in CSR BC & OT to take into account warping stress correctly. It means more reliable results with respect to torsional deformation are now available.
- The hull girder ultimate strength (Intact condition) results are reviewed and in general this is expected to give some scantling increases. This is due to the double bottom effect which is added. Hull girder ultimate residual strength (damaged condition) does in general not show any scantling impact.
- The screening criteria for fine mesh local analysis in CSR BC & OT is more demanding than CSR-BC, which may lead to local reinforcements.