Four years after becoming the first class society to develop and release software to do the intensive calculations called for by IACS’ Common Structural Rules (CSR), ClassNK today has 90 clients for PrimeShip-HULL
Adopted by International Association of Classification Societies (IACS) in 2013, the CSRs were designed to enhance ship safety and reliability[ds_preview] by requiring a more comprehensive structural analysis at the design stage. The new rules encompassed the need for FEM analyses covering the entire range of cargo hold structures as well as new formulae for buckling, fatigue, and residual strength criteria.
The CSRs represented a self-evident step forward for the safety of bulk carriers and oil tankers, but they also brought practical challenges for shipyards and vessel designers as the calculations needed to perform these analyses and satisfy the requirements are both complicated and time-consuming. They add considerably to overall vessel design time. Indeed, before their introduction, there were fears that the rules would impose such an impossible burden that yards would be unable to cope. Today, a version for container ships, even though the vessel type is not subject to IACS CSRs, is offered, too.
Asked about major changes in ship design, the Japanese state that as recent structural rules implement the latest analysis techniques, strength evaluation methods have become more advanced and complex. Required man-hours for analysis are increasing, especially for CSR, with an increase in calculation requirements and an expansion in the scope of finite element analysis to include the fore and aft parts in addition to the midship in order to comply with the IMO GBS. »Due to the increasing complexity of recent regulations and analysis amounts, the industry is relying more and more on analysis software, making it more difficult for designers to examine calculation results on their own. ClassNK conducts its development with the belief in mind that is necessary to provide software which clearly reveals its calculation process so that designers can implement the designs with enough understanding on figures,« it is concluded.
600 licenses in use
ClassNK created PrimeShip-HULL to alleviate this burden. The solution is now used by around 90 shipbuilding and design companies, located mainly in Japan, South Korea, China and other countries in East Asia – reflecting where most of the world’s ships are now built. In fact, with more than 600 licenses in use, most shipyards constructing the ships subject to the CSR now utilize ClassNK’s software, the classification states.
Earlier this year, ClassNK released the fifth version of PrimeShip-HULL. As well as absorbing IACS’ latest round of amendments to CSR, the update is said to »include several refinements to existing functions and introduces some completely new ones aimed at sustaining its remarkable level of uptake«.
In addition to UI tweaks aimed at streamlined workflow, the report generator in the prescriptive calculation software now operates independently. This allows users to continue editing cross-section data or other tasks whilst a report is generated in the background.
The ability to transfer data between the CAD – and other design tools used by naval architects – and PrimeShip-HULL quickly and efficiently has been key to the software’s success, the classification society adds. In the latest round of development, the data linkage function for importing body plan data from 2D CAD software has been further enhanced making it possible to create sectional data from the body all at once, eliminating the need for repetitious data conversion.
Integrated with NAPA Steel
PrimeShip-HULL is tightly integrated with NAPA Steel, one of the programs most widely used by the world’s shipyards. For instance, in the case of oil tankers, data from 3D structures such as transverse webs, bulkheads and other non-longitudinal members can be effortlessly transferred between the two applications. The developers hope that this is particularly helpful when conducting structural evaluations in the initial design phase.
The direct strength assessment software now includes a parameter check and update function which can detect model-dependent parameters and update them automatically. This saves time by preventing parameter setting errors that would otherwise require the assessment to be redone. The yield assessment calculator has become more user-friendly and the buckling assessment calculator has been optimized to shorten the calculation times.
Overall, the enhancements and new functions are supposed to further reduce necessary man hours and shorten design lead times.
According to ClassNK, some yards have reported an over 50% reduction in the man-hours spent on structural evaluation for prescriptive requirements and for direct strength requirements through Finite Element Analysis (FEA), although results depend on vessel type, structure, and coarseness of the original CAD data.
In addition, ClassNK offers a version of PrimeShip-HULL for container ships, even though the vessel type is not subject to IACS CSRs. Its availability demonstrates that the rule calculation system’s ability to evaluate strength requirements such as hull girder strength, local strength, buckling strength, ultimate strength and fatigue strength has inherent value for designers and shipbuilders. The direct strength calculation is capable of conducting FEA and can be used to perform various yield, buckling and torsional strength analyses, for example.
