• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.6
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• pp.515-522
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• 2017

In this paper, an isogeometric analysis for multipatch problem is investigated, in which two or more geometries are connected at the interface in a conforming or non-conforming conditions. To express higher continuity at the patch interface, two approaches such as Nitsche based method and master-slave method are formulated for the linear elasticity problem and discretized using the isogeometric approach using NURBS basis functions. A short comparison between two approaches in formulations reveals the pros and cons of them with the applicability in the isogeometric multipatch problem. In addition, a NURBS based stress recovery is adopted to express a better stress continuity through the post-processing. Numerical examples indicate the effectiveness of Nitsche method in the non-conforming patch, following the exact solution well. For the stress concentration problem with the conforming patch, introduced two methodologies show comparative results, meanwhile the NURBS based stress recovery presents an improved smooth stress contour in the whole domain including the patch interface.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.5
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• pp.345-352
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• 2024

In this paper, a multipatch isogeometric analysis method is developed for a multi-connected NURB patch model and applied to geometrically exact shell element analysis. When connecting different NURBS patches, isogeometric analysis may become inaccurate due to the density of control point meshes and discontinuity between patches. To solve this problem, Nitsche's method is applied to the isogeometric analysis method to ensure the compatibility of the displacement and traction between two patches by using a potential function defined as the product of the displacement difference and traction of the two patches. The final derived governing equation is formed as a symmetric stiffness matrix from this potential function. Since the added system matrices from the compatibility boundary conditions are calculated as a boundary integral between patches, the computational cost does not increase significantly. For the positive definiteness of the system equation, appropriate stability parameters are calculated through generalized eigenvalue analysis, and the stability parameters and solution accuracy are analyzed according to the density of the integration meshes between the two patches. This multipatch isogeometric analysis method is applied to geometrically exact shell elements considering first-order shear deformation, and it is confirmed that by using Nitsche's method in this shell analysis with multiple connected patches results in improved stress continuity as well as displacement continuity between patches.