Page 21: of Maritime Reporter Magazine (August 2015)

Shipyard Edition

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With the increase in the classi? cation requirements for oil tank barges comes the need for additional guidance on the use of advanced analysis tools to satisfy the ABS requirements.

eral years for chemical tank barges, the the empty ballast tanks and above the expansion of the requirement to include cargo level in full tanks. The ? nite ele- oil tank barges (which includes asphalt ment model is then used to solve for the barges) is expected to signi? cantly in- accurate thermal gradients between the crease the demand for advanced analysis project speci? c cargo core temperature, to evaluate the steady state temperature and the ABS required external air tem- distributions in integrated double hull perature of 5°C (41°F) and a sea temper- tank barge structures, and the thermal ature of 0°C (32°F).

stress resulting from the large thermal Hydrostatic and hydrodynamic seaway gradients generated between the heated loads are calculated with a full hydrody- cargos and signi? cantly cooler external namic analysis for the barge in a realistic sea water. extreme sea state and combined with the

With the increase in the classi? cation thermal loads for a series of critical load requirements for oil tank barges comes cases developed to maximum global and the need for additional guidance on the local design loads on the structure. The use of advanced analysis tools to satisfy ? nite element model is solved, and the the ABS requirements. While ABS does resulting stresses are evaluated against not currently have published guidance the appropriate acceptance criteria from on the use of Finite Element Analysis the classi? cation society. To optimize the (FEA) for the calculation of temperature design and veri? cation efforts, SAGA is distributions or thermal stresses, they are paired with other industry leading soft- currently working to develop a guidance ware and can account for various regu- note for thermal analysis. At a February lation standards throughout the industry 2015 FEA Seminar and Workshop pre- (ABS, DNV-GL, or BV for example). sentation in New Orleans, ABS present- For the majority of these projects in the ed their ongoing work to develop guid- US, the acceptance for both yielding and ance for the use of advanced analysis in buckling are evaluated in global FEA thermal stress assessment, and provided models with the ABS Dynamic Loading several examples of the successful work Approach (DLA) Guide and ABS Steel performed by naval architecture and ma- Vessel Rules (SVR), respectively. rine engineering ? rm, Viking Systems As these rules begin to develop, the

International, Inc. The examples pro- ? nite element analysis will be an inte- vided by ABS showcased the process de- gral part of solving the complex interac- veloped by Viking over the past 15 years tion between thermal loads and tradition to leverage existing advanced analysis barge hydrostatic and dynamic seaway tools along with in-house developed loads. Methods have shown the ability to

SAGA software to load and evaluate the accurately predict the thermal distribu- structure for the combined effects of the tion of real world operating barges. The thermal loads with traditional hydro- development of custom analysis tools static and seaway loads. (Image: steady put in place has ef? ciently streamlined state temperature distribution plot) this complex process to generate a more

Viking Systems International Inc has ef? cient approach while satisfying the worked with shipyards, designers, and increase class requirements, compared to owners of heated cargo barges and tank- previous traditional methods. ers over the past 15 years to develop a methodology for the prediction of the steady state temperature distribution through the double hull structure. Viking

The Author has worked with thermal measurements from several barges in service to corre-

Fritz Waldorf is Director of Sales and late with the numerical predictions, and

Marketing for Viking Systems Interna- tional, Inc. Viking Systems has been validate the methodology. The advanced assisting shipyards and ship designers analysis method incorporates solid ele- worldwide with the ef? cient implemen- ments into a global ? nite element model tation of advanced analysis tools in the to represent the boundary layer of the ? oating vessel design process. heated cargo and the external seawater e: and air, as well as the stagnant air within 21

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