船舶及海洋結構物的疲勞是一個受到大量隨機變數與不確定因子所影響的問題，在設計過程中相關的參數量需考慮其模糊性的存在，假如都是以一些確定的數值來設計，則可能會造成不經濟或不安全之顧慮，亦即結構強度的判斷準則與外力負荷是具有模糊性的。故本研究之主要目的是引用模糊集合觀念於二階可靠度中。採用經驗二階可靠度方法結合模糊理論來進行船舶結構可靠度分析時，對於船殼極限狀態函數中之各個隨機變數以及不確定因子，本文取三角形隸屬函數來將其隸屬程度予以量化，並以截集的方法來控制其容差大小，進而求得各種破壞模式不同 -截集下之破壞機率的置信區間。
本研究針對兩艘實船，175700噸之雙殼散裝貨輪與26萬噸之單殼油輪，分別進行模糊一階可靠度和模糊二階可靠度分析。目的是希望藉由模糊集合觀念，提供船體結構設計者更多的設計參考資訊與更寬廣的設計空間。

Basically, the failure problem of marine structures is affected by several factors, which are random in natural. If deterministic values alone are used as design parameters to describe those random factors while ignoring fuzzy characteristics in design, this may cause some economical or safe concerns for marine structures. In another word, the fuzziness lies in both strengths and loads. The purpose of this study is to employ the fuzzy set concept into the SORM. While utilizing an empirical SORM combined with the fuzzy theory to analyze a ship structure, a triangular membership function is applied to get intervals.
Two boats, a double-hull bulk carrier and an oil tanker are select as examples to analyze the fuzzy reliabilities based on both FORM and SORM. It is believed that this algorithm may provide more design information for ship structure designer.

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