Trans RINA, Vol 161, Part A4, Intl J Maritime Eng, Oct-Dec 2019


Figure 12: Maximum normal stress due to torsion (Sagging condition)


From Figure 12, it is seen that normal stress due to torsion is maximum at near cargo hold bulkheads. From Figure 10, it is also observed that maximum normal stress due to torsion occurs at the hatch coaming top.


4.10


INFLUENCE OF DIFFERENT LOADING CONDITIONS


Full load and lightweight conditions for the investigated double hull-open deck river-sea container vessel is considered for combined bending and torsional structural response analysis.


The influence of different loading conditions is shown in Figures 13 and 14.


From Figures 13 and 14, it is observed that in both conditions normal stress due to torsion is maximum at near the aft and forward cargo hold bulkheads. In full load condition, the effect of torsion is much predominant at aft and forward cargo hold bulkhead ends. Still in both conditions, the maximum normal stress value is less than the allowable value. It is also seen that in both cases normal stress due to horizontal bending moment does not have significant impact. So, for further combined bending and torsional strength analysis for different hull configurations full load condition is considered.


Figure 14: Combined bending and torsional structural response of full load condition


4.11


INFLUENCE OF DIFFERENT HULL CONFIGURATIONS ON COMBINED BENDING AND TORSION EFFECTS


In this section, the difference between different hull configurations on combined bending and torsional structural strength is presented. Change of hull configuration induces change of hull girder transverse section geometric properties. Hull strength check should be performed for each configuration.


For this purpose, 3D FE model for different hull configurations are prepared using FEMAP. Comparison of stress distribution is shown in Figures 15 to 19 along the length and depth of the vessel for various hull configurations. In this analysis, incline load case has been considered to investigate the combined effect of vertical bending, horizontal bending and torsion upon different hull configurations. For the combined bending and torsion stress distribution along the length, hatch coaming top has been selected because maximum stress occurs at hatch coaming top.


Figure 15: Combined bending and torsion stress along the length for different hull configurations


Figure 13: Combined bending and torsional structural response of lightweight condition


©2019: The Royal Institution of Naval Architects


From Figure 15, it is observed that among the different hull configurations the highest combined bending and torsion stress value is found for single hull vessel which is 199.1 MPa at X=25.744m near the aft cargo hold bulkhead but still it is under the allowable stress limit


A-455


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