Elevated pipelines are commonly encountered in petro-chemical and industrial applications. Within these applications, pipelines normally span hundreds of meters and are thus analysed using beam-type one-dimensional finite elements when the global behaviour of the pipeline is sought at a reasonably low computational cost. Standard beam-type elements, while computationally economic, are based on the assumption of rigid cross-section. Thus, they are unable to capture the effects of cross-sectional localized deformations. Such effects can be captured through shell-type finite element models. For long pipelines, shell models become prohibitively expensive. Within this context, the present study formulates an efficient numerical modelling which effectively combines the efficiency of beam-type solutions while retaining the accuracy of shell-typesolutions. An appealing feature of the model is that it is able to split the global analysis based on simple beam-type elements from the local analysis based on shell-type elements. This is achieved through domain-decomposition procedure within the framework of the bridging multi-scale method of analysis. Solutions based on the present model are compared to those based on full shell-type analysis. The comparison demonstrates the accuracy and efficiency of the proposed method.
The purpose of this study is to develop a stiffness update technique to be used in a computationally efficient finite element solution for the analysis of columns undergoing local deformations, within the procedure of iterative global-local analysis. The computational problem that arises is that the stiffness matrix is formulated according to the global model, and as a result, considerably large number of iterations is required when the local deformations are significant. To overcome this difficulty, a stiffness update technique is presented in which the displacement field of the global model is altered at each step to consider the locally induced softening behaviour in order to accelerate the convergence. This goal is achieved by introducing embedded discontinuities in the beam element.
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