One of the major challenges for the oil and gas industry is to keep buried metal pipes safe from faulting. This paper discusses about a solution to keep buried pipes safe. In this study, after examining the different dimensions of the effect of wave connection on improving the performance of buried metal pipes, by changing the geometric shape of the wave connection such as doubling it, the behavior of the pipe is greatly improved. Waved connections, by their local deformation, create a rotational joint in a limited area so that other parts of the pipe remain intact. In this paper, the behavior of buried pipes due to slip direction fault displacement by modelling with Abacus software version 2017 and selection of 4-node shell element and 8-node shell element have been used for pipe and soil modelling, respectively. In this paper, by comparing to a single waved connection with a double waved connection, the performance of the pipe due to the faulting phenomenon was evaluated. The results show the improvement of the excellent performance of the double joint by reducing the plastic strain values. In addition to increasing the ductility of the pipe, the double connection has been able to reduce the strain values by about 50% compared to the single connection. In general, this paper shows that the use of wave connections can significantly increase the level of safety of buried gas pipelines without increasing the cost.
Abstract:In the present paper, seismic performance of a high concrete arch dam is evaluated based on both the stress and strain criteria. For this purpose, the finite element model of the selected arch dam-reservoir-foundation system was provided. Reservoir was modeled using Eulerian approach as a compressible domain and the foundation rock was assumed to be massless. Dynamic equilibrium equations for the coupled system were solved using Newmark's time integration algorithm. Seismic performance evaluation of dam-foundation-reservoir systems were performed considering parameters such as demand-capacity ratio, cumulative inelastic duration and extension of overstressed (or overstrained) areas obtained from linear elastic analyses and compared with the real crack profile from nonlinear analysis. It was found that although results obtained for the stress and strain rules have similarities, performance evaluation based on the strain gives different results which can be lead to different decision making in dam safety related projects.
Recent earthquakes have damaged many lifeline structures. Buried gas pipelines are also no exceptions.Sometimes, theses pipes are subjected to a thinning of the wall thickness due to corrosion. Therefore, it is important to evaluate the strength of the pipes undergoing local wall thinning to maintain the integrity of the piping systems. The main purpose of this study is to understand failure aspects of buried pipeline caused by earthquake and degradation of metal due to corrosion through FEM. In dynamic analysis, corroded pipeline approaches to critical criteria (reaching the yield stress) in much less time. In this case, if the corroded pipe thickness be half, the yielding angle is reduced to a quarter.
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