Although the original CSRs were developed separately for oil tankers and bulk carriers by two different working groups, it was soon recognised by IACS that there was a need to harmonise the two sets into a single version. That work was completed in 2013 and the new harmonised common structural rules adopted in December that year took effect in July 2015.
The rules are applicable to all IACS members and with the advent of the common rules, class societies developed software to check and compare newbuilding designs against the requirements of the rules. However, despite the concept of common rules having been devised to address the issue of individual classification societies competing on lowered standards, there were still many who did not believe that the rules would be applied equally.
Two class societies – ABS and LR – have tried to dispel this idea by jointly establishing Common Structural Rules Software LLC (CSRS) to provide industry with a validated and verified suite of software tools for CSR. It was the joint venture’s hope that other societies would recognise the value of the suite and consider adopting it, but so far that has not happened and ClassNK and DNV GL both operate using their own software.
Last May, at MSC 96, the IMO recognised that the harmonised CSR met the goals and functional requirements of the organisation’s own Goal-based Ship Construction Standards. Later in the year IACS made some changes to the CSR resulting in a new version that takes effect in July this year.
In response, both CSRS and ClassNK have updated their software to incorporate the changes. The joint venture’s version 2.5 of the CSR Prescriptive Analysis (PA) and CSR Finite Element Analysis (FEA) software allows assessment of whole vessel structures – including new bulk carrier and oil tanker designs using either the 2015 or the 2017 versions of the common rules.
Both applications PA and FEA are standalone desktop applications that can be downloaded from the company website. Upgrading to the new software is straightforward. A user uninstalls the previous version and then downloads the new version from the website. All existing projects work seamlessly with the new revised release. Detailed instructions on how to install the new version of the software are available on the CSRS website in the User Guide and Release Notes provided with the software. At the moment, the software does not interface with CAD programmes, but this feature is on the CSRS PA and FEA roadmaps, and there are plans to implement an interface in later releases.
The PA application is used to assess hull girder ultimate strength and hull local scantlings while the FEA app uses a Finite Element Analysis approach for strength and fatigue assessment on different tanker and bulk carrier structures. The current PA and FEA releases have multi-rule year capability, which allows users to evaluate ships for both 2017 and 2015 IACS rules. The 2015 IACS rules are in force today.
The updated CSR Prescriptive Analysis software requires only that the user input the appropriate data. All of the outputs are claimed as being clear, straightforward and easy to read. A summary report provides required and offered scantlings with graphic representation of any deficiencies.
An intermediate report summarises dominant criteria for each structure and a detailed report provides data for every parameter value. In conjunction with CSR FE Analysis, this complete tool makes verifying compliance with CSR possible with minimal effort.
ClassNK also released a new version of its software in February. PrimeShip-HULL (HCSR) Ver.4.0.0 incorporates the 2017 rule amendments and offers a new function to preview reports in the direct strength assessment software, improving overall performance and usability. In the prescriptive calculation software the calculation time has been reduced and the initial design function for quick sectional evaluation can now link with other sectional data in order to automatically extract longitudinal parameters, reducing the potential for inputting errors. There is also an enhanced data linkage function with 3D-CAD software NAPA Steel. This enhanced function now makes it possible for 3D model data of NAPA Steel to be imported into the initial design function and members’ data modified in the fullship design function to be imported back to NAPA Steel, a feature which is expected to significantly reduce the man hours required for structural evaluations in NAPA Steel.