Mechanical and Civil Engineering Seminar

Aboveground storage tanks (ASTs) are often used for bulk storage of hazardous materials, including a variety of fuels and chemicals at industrial sites, such as petrochemical and oil & gas facilities. Due to their location in coastal areas ASTs can suffer major damage in severe storms resulting in spills with catastrophic social, environmental and economic consequences. Failure of these structures has been attributed to flotation, buckling or damage from debris. Despite significant evidence of tank vulnerability and consequences of failure, understanding of the mechanisms leading to AST failure and the likelihood of damage under multiple storm induced hazards (e.g., surge, wave, wind) is limited.  This presentation explores the vulnerability of this key piece of energy infrastructure, while highlighting the socio-political context in which associated risks have evolved and identifying the prospects for mitigation.  First, the failure modes of ASTs observed in past hurricane events are reviewed.  Then a method for probabilistic modeling of tank performance under multiple hurricane induced loads is presented.  In this approach metamodels are used in the derivation of a flotation and buckling fragility models for ASTs.  As a byproduct, global imperfection models are proposed to account for geometric variations that affect the buckling behavior of tanks.  The impacts of alternative risk mitigation strategies are explored, including structural solutions, operational or procedural strategies that may reduce the potential for damage or spillage of hazardous materials.  A case study is presented in the Houston Ship Channel, where over 4500 tanks exist in the world's second largest petrochemical complex situated alongside one of the US's busiest ports. Through this case study, the risk of damage and spill potential is evaluated for alternative storm scenarios. Results highlight the temporal co-evolution of spill risks and social vulnerability attributed to the increasing industrial development and socio-demographic shifts that occurred from 1970 to 2014. This work provides a basis for future mitigation activities and enhanced understanding of the factors and conditions that affect risks to oil and gas infrastructure in hurricane prone regions.