DESIGN ISSUES OF LIQUID STORAGE TANKS AND PIPELINES IN SEISMIC AREAS

Abstract eng:
ILF is a major international engineering consultant for structural analysis and design of industrial facilities and components (liquid storage tanks, vessels, piping), as well as pipelines. In this presentation, the evaluation of the effects (probability of cracks) resulting from an impact of fracture bodies (rock) on an intunnel pipeline is presented. FEA was performed with software ABAQUS/Explicit. Input regarding possible sizes of the fracture bodies from a falling height of 1.0m to 2.2m was provided. Integrity of the DN1200 pipeline was checked, based on acceptance criteria set according to relative codes and literature (ASME B31.8, PDAM). Results for several scenarios of rock sizes and falling angles have been investigated. Three risk categories were defined for plain dents, according to the plastic strain of the pipeline and dent depth as a percentage of the diameter: - category L, leakage cannot be excluded (through wall cracks), - category R, cracks occur, but leakage is excluded (not through wall cracks), - category D, remaining plastic strains exist, but no cracks occur. Several scenarios were taken into account. According to the detailed analyses the risk of leakage depends highly on the impact angle of the falling rock (kinked or smooth dent). In a similar project ILF was commissioned to evaluate the effects resulting from an impact of Rockfall, from a slope on buried pipeline segments. For the evaluation of the impact force and soil intrusion of the boulder, critical input parameters are: - impact energy, conditioned by the size and shape of the boulder, the coefficient of restitution of the slope (bouncing factor), the starting height of the boulder and the vegetation and friction conditions of the slope. - Impact angle. - Soil parameters of piping zone. -Depth of cover of the pipeline. The investigation was performed on the basis of the provided data, regarding the most probable scenarios of boulder shapes and sizes as well as impact energy. The analysis showed that a soil cover of 2 m is effective. Soil intrusions of the boulder in the order of 0.3 m resulted in smooth dents with a depth of approx. 30 mm in the pipe without pressure and approx. 5 mm in the pipe under pressure.

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