Challenges and Constraints in the Application of Rule-Based Hull Girder Load Adjustments: Insights with Future Directions

The International Association of Classification Societies (IACS) has introduced the concept of the Equivalent Design Wave (EDW) for the calculation of dynamic loads for structural analysis in the Common Structural Rule (CSR) for the design of bulk carriers and oil tankers. An EDW is a set of loads representing a design wave whose response is equivalent to the required design value at a given probability level. Classification societies are applying the EDW concept by implementing design loading equations for LNG carriers, bulk carriers, and oil tankers. According to the EDW loads, dozens of load cases are generated using the design load formula, and the hull girder loads calculated from them are adjusted to the target values. In this short communication, the hull girder load is adjusted according to the method described in the DNV rule for a cargo hold model of an LNG carrier. The adjusted load is distributed as a nodal force by shear flow and simple beam theory. An alternative method is introduced by comparing existing methods with regard to adjustment methods and load distribution. After discussing existing methods, a method for adjusting all hull girder load components in three steps and a load distribution method using the stress field were derived. The limitation of the current technique and insights summarised in this short communication may support readers in understanding the rule-based hull girder load adjustment technique. In addition, this limitation may clearly motivate the demand for alternative technology development for hull girder load adjustment.