Objective To address the applicability issues of traditional structural assessment methods for funnel areas under the combined action of local loads and hull girder loads, which arise from the strength evaluation of funnels arranged near midship, two new structural assessment methods for such funnels are proposed.
Methods Four methods were used to evaluate the structural strength of the funnel area: the traditional strength assessment method for funnels in aft-engine ships, the current strength assessment method for mid-ship funnels, and two new assessment methods. The new methods are the load case combination method considering local loads and hull girder loads, with one variant disregarding hull girder load correction and the other considering it. The results from each method were compared with those from a full-ship finite element analysis.
Results The results show that for funnels arranged near mid-ship, the traditional assessment method designed for aft-engine funnels is not applicable. Its calculation error can exceed 80%, and the results are on the unsafe side. The current assessment method for mid-ship funnels, while still usable, yields overly conservative results, potentially leading to material waste. In contrast, the calculation results of the two new methods are significantly closer to those of the full-ship finite element analysis, with errors within 12%. Among them, the load case combination method without hull girder load correction can reduce the calculation error to around 10% while keeping the results on the conservative side, better meeting the needs of practical engineering applications.
Conclusion Compared to traditional methods, the two newly proposed methods, both implemented within the framework of current regulations, are efficient approaches that consider the combined effect of local loads and global loads in the funnel area. They significantly improve the accuracy of the calculation results.
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