Determination of LRFD environmental load factor in the java sea for unbraced monopod structures using reliability analysis

Abstract

Case studies were carried out for unbraced monopod structures located in the Java Sea by reviewing the value of the reliability index. This sea has a depth of 33 meters and a 100-yr wave height of 6.29 meters. The structures are designed optimally with a unity check ratio of 1.00 using API RP 2A WSD and API RP 2A LRFD standards under storm condition, assumed to be unmanned. For LRFD criteria, the value of the environmental load factor is varied, namely 1.35, 1.20, 1.10, and 1.00. Collapse analysis using static pushover analysis of the model produces a minimum RSR value meeting the minimum criteria for un-manned structures of 1.6. The reliability analysis process uses the First Order Reliability Method II (FORM II). The structural reliability index value has met the minimum criteria issued by DNV of 3.71 for the structure that is designed using the environmental load factor of 1.35. It can be concluded for unbraced monopod structures designed in the Java Sea, the environmental load factor value of 1.35 is following the minimum reliability index value proposed by DNV.