• Journal of Ocean Engineering and Technology
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• v.38 no.5
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• pp.307-314
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• 2024

To minimize the production time of floating liquefied natural gas (FLNG) units, which are eco-friendly offshore structures, builders are exploring methods to extend the length of piperacks. This approach aims to reduce the number of installations and equipment required. In this study, a static stability analysis (in-place analysis) was conducted using the structural analysis computer system (SACS), a program for analyzing topside structures, to assess the effects of piperack enlargement. Two models were analyzed: the original piperack and a version with double the length. Both models were based on data from an existing FLNG unit, with identical environmental loads applied. The results showed that while relative displacement increased linearly with length, the stress did not follow the same linear pattern. However, stress levels in some braces at the base of the structure increased, indicating the need for larger structural members. From the perspective of in-place analysis, piperack enlargement appears feasible. However, further investigation, including fatigue analysis and assessments of operational and maintenance challenges, is recommended to confirm its long-term viability.

• Construction Engineering and Management
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• v.11 no.4
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• pp.5-11
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• 2010

• Architectural research
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• v.15 no.3
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• pp.151-158
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• 2013

Offshore oil and gas process plants are exposed to hazardous accidents such as explosion and fire, so that the structural components should resist such accidental loads. Given the possibilities of thousands of different scenarios for the occurrence of an accidental hazard, the best way to predict a reasonable size of a specific accidental load would be the employment of a probabilistic approach. Having the fact that a specific procedure for probabilistic accidental hazard analysis has not yet been established especially for explosion and fire hazards, it is widely accepted that engineers usually take simple and conservative figures in assuming uncertainties inherent in the procedure, resulting either in underestimation or more likely in overestimation in the topside structural design for offshore plants. The variation in the results of a probabilistic approach is determined by the assumptions accepted in the procedures of explosion probability computation, explosion analysis, and structural analysis. A design overpressure load for a sample offshore plant is determined according to the proposed probabilistic approach in this study. CFD analysis results using a Flame Acceleration Simulator, FLACS_v9.1, are utilized to create an overpressure hazard curve. Moreover, the negative impulse and frequency contents of a blast wave are considerably influencing structural responses, but those are completely ignored in a widely used triangular form of blast wave. An idealistic blast wave profile deploying both negative and positive pulses is proposed in this study. A topside process module and piperack with blast wall are 3D FE modeled for structural analysis using LS-DYNA. Three different types of blast wave profiles are applied, two of typical triangular forms having different impulse and the proposed load profile. In conclusion, it is found that a typical triangular blast load leads to overestimation in structural design.