ReviewNonlinear structural consequence analysis of FPSO topside blastwalls
Highlights
► Topsides of offshore platforms are most likely to be exposed to hydrocarbon explosion. Structural damage can be categorized as a P–I curve in the pressure/impulse space. ► The SDOF method was used primarily as a rapid tool to predict the structural response. ► The MDOF method produces reliable results under explosion actions.
Introduction
The offshore structures such as FPSO and Offshore Platform were developed due to moving focus on developing the natural resources from land to ocean. There are various loading conditions such as explosion, fire, extreme wave load and dropped object, etc. Especially, explosion in offshore structure is extremely hazardous. They involve extreme explosion actions which can have serious consequences for health, safety, and the surrounding environment (Paik et al., 2011). Therefore, considerable interests in explosion and blast wall have been increased since the Piper Alpha (6 July 1988). Fig. 1 shows photo of Piper Alpha accident, which resulted in tremendous damage (killing 167 men, $ 1.7billion loss) to the outlying area and huge fires (Cullen, 1990). Since the Piper Alpha accident took place, a substantial amount of effort has been directed towards the management of explosions and fire in offshore installations. Risk-based approaches have begun to replace traditional prescriptive approaches in offshore design, and 26 joint industry projects have been undertaken since 1990 (Paik and Chung, 1999, Paik and Czujko, 2009). In spite of these efforts, accidents occurred continuously, as evidenced by the recent Deepwater Horizon incident which occurred on 20 April 2010 in the Gulf of Mexico as shown in Fig. 2. Therefore many researches are required for the quantitative gas explosion risk assessment and management ofFPSOs.
Marine structures accidents like explosion and fire accidents have been serious matter of the industrial world and considerable interests in explosion and blast wall have been increased since Piper Alpha and Deepwater horizon accidents. However, there is dearth of reliable knowledge and understanding on the explosion accident. Explosion proof that can prevent or minimize accidents is divided into active explosion proof and passive explosion proof. Active explosion proof is the kind of protection method that prevents gas ignitions before gas is ignited and passive explosion proof is the method that minimizes consequence of explosion accidents after gas ignitions occur (Czujko, 2001).
While active explosion proof costs too much, passive explosion proof comes inexpensive. So that Passive explosion proof is considered efficient method in terms of cost-benefit. Our study in this paper focuses on nonlinear structural response analysis of blast wall structures that is typical passive explosionproof.
Corrugated blast walls are among some of the common passive protection systems that have been developed to protect personnel and/or important assets from hydrocarbon explosion. Most of the blast walls are designed using the single degree of freedom (SDOF) method as recommended in the design guidance and a time-domain finite element commercial software should use for predicting the response of blast wall panel by the Technical Note 5 (TN5) issued by the Fire and Blast Information Group (FABIG, 1996, FABIG, 1999, FABIG, 2002, FABIG, 2007).
This study presents the numerical study on the analysis of FPSO topside blast walls subjected to blast loading generated from typical hydrocarbon explosions for the above purposes (Czujko, 2005). One of the uncertainties in blast walls design remains in the accurate evaluation of the explosion loading. As such, they are normally designed against a nominal pressure of 0.5 bar (HSE, 2004) which often results in the elastic response of the section. However, recent large scale explosion tests on the blast walls have shown the possibility of as high as 4 bar overpressure with a shorter duration in a typical module (Fischer and Häring, 2009, HSE, 2003, HSE, 2004, HSE, 2006a). A variety of explosion loading cases consisted of diversity of peak pressure and duration time are considered for those reasons. Moreover, the P–I curve comparisons between time-domain nonlinear finite element methods (NLFEM) and the single degree of freedom (SDOF) method based on charts that provide the maximum response are used. Particular attention is given to the plastic response of the blast walls (HSE, 2004, HSE, 2006a).
This paper is a summary of the results obtained techniques, using the nonlinear finite element method (NLFEM) and the single degree of freedom (SDOF) method that were performed in the present study. In addition, appropriate guidance for nonlinear structural consequence analysis of explosion will also be presented.
Section snippets
The procedure of nonlinear structural consequence analysis
Fig. 3 presents the procedure for the nonlinear structural consequence analysis of FPSO topsides in explosion scenarios (Paik, 2011). The structural system of the FPSO topsides is defined to include the decks, support members, blast wall and pipelines. The several explosion loading cases considered in this chapter include peak pressure and duration time determined on the basis of the exceedance curve and load curve. Three methods of determining the dynamic structural response of a structural
Pulse pressure test panel under explosion loading for validation
Drawing on HSE research reports 124 and 404, which are based on studies conducted by the University of Liverpool, the pulse pressure test results of 1/4-scale blast wall panels were considered suitable for validating between experimental and numerical study. Fig. 6 shows a typical blast wall construction made of corrugated stainless steel sheet with end connections at the top and bottom. They are designed to be efficient energy-absorbing systems (HSE, 2003, HSE, 2004, HSE, 2006a).
Fig. 7
Dynamic structural response of FPSO topside blast walls under explosion loads
Drawing on HSE research reports 124 and 404, which are based on studies conducted by the University of Liverpool, the pulse pressure test results of 1/4-scale blast wall panels were conducted for validating between experimental and numerical study. The FE simulation results for displacement–time histories and deformed shape were in good agreement compared with the experimental method (Fischer and Häring, 2009, HSE, 2004, HSE, 2006a). The experimental method is the best way of obtaining results,
Conclusions
The aim of the present study has been to develop a practical procedure of nonlinear structural consequence analysis for FPSO topside blast walls under explosion. In addition, appropriate guidance will also be presented on the use of the finite element numerical tool and be introduced of maximum response of single-degree elasto-plastic systems maximum for the above purpose. Based on the results obtained from the present study, the following conclusions can be drawn.
- 1)
The procedure of nonlinear
Acknowledgment
The present study is part of the EFEF JIP (Phase II and III). The authors are pleased to acknowledge the support of their partners in this project: American Bureau of Shipping, ComputIT AS, Daewoo Shipbuilding and Marine Engineering, Gexcon AS, the UK Health & Safety Executive, University of Liverpool, and Samsung Heavy Industries. This research was also supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education,
References (24)
- et al.
Quantitative assessment of hydrocarbon explosion and fire risks in offshore installation
Mar. Struct.
(2011) User's Manual (Version 12.0)
(2011)Introduction to Structural Dynamics
(1964)The Public Inquiry into the Piper Alpha Disaster
(1990)Design of Offshore Facilities to Resist Gas Explosion Hazard: Engineering Handbook
(2001)- Czujko, J., 2005. Computational methods in the analysis of explosion resistant barriers. In: Proceedings of the...
Consequences of explosions in various industries
Safety and Reliability of Industrial Products, Systems and Structures (SAFERELNET 2007)
(2007)- et al.
Strain-Hardening and Strain-Rate Effects in the Impact Loading of Cantilever Beams
(1957) Technical Note 4: Explosion Resistant Design of Offshore Structures
(1996)Technical Note 5: Design Guide for Stainless Steel Blast Walls
(1999)
Technical Note 7: Simplified Methods for Analysis of Response to Dynamic Loading
Technical Note 10: An Advanced SDOF Model for Steel Members Subject to Explosion Loading: Material Rate Sensitivity
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