SUMMARYThe coupling of Finite Element Method (FEM) with a Boundary Element Method (BEM) is a desirable result that exploits the advantages of each. This paper examines the e$cient symmetric coupling of a Symmetric Galerkin Multi-zone Curved Boundary Element Analysis method with a Finite Element Method for 2-D elastic problems. Existing collocation based multi-zone boundary element methods are not symmetric. Thus, when they are coupled with FEM, it is very di$cult to achieve symmetry, increasing the computational work to solve the problem. This paper uses a fully Symmetric curved Multi-zone Galerkin Boundary Element Approach that is coupled to an FEM in a completely symmetric fashion. The symmetry is achieved by symmetrically converting the boundary zones into equivalent ¯o "nite elements', that are symmetric, so that symmetry in the coupling is retained. This computationally e$cient and fast approach can be used to solve a wide range of problems, although only 2-D elastic problems are shown. Three elasticity problems, including one from the FEM-BEM literature that explore the e$cacy of the approach are presented.

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The recent development of the symmetric Galerkin approach to boundary element analysis (BEA) has been demonstrated to be superior to the collocation method for medium to large problems. This fact has been shown in both heat conduction and elasticity. Accounts of collocation multi‐zone analysis techniques have also been prevalent in the literature, dealing with multiple boundary integral relations associated with portions of overall objects. This technique results in overall system matrices with a blocked, sparse, but unsymmetric character. It has been shown that multi‐zone techniques can produce smaller solution times than a single zone analysis for large problems. These techniques are useful for multi‐material problems as well. This paper presents an approach for combining the benefits of both techniques resulting in a Galerkin multi‐zone method, that is overall unsymmetric but contains a significant amount of block symmetry. A condensation technique in the multi‐zone solver is shown to exploit the symmetry of the Galerkin formulation as well as the blocked sparsity of the multi‐zone technique. This method is compared to collocation multi‐zone on two elasticity problems from the literature. It is concluded that an appropriate implementation of the symmetric Galerkin multi‐zone BEA indeed has the potential to be superior to the collocation based multi‐zone BEA, for medium to large‐scale elasticity problems. © 1997 John Wiley & Sons, Ltd.

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SUMMARYWhen the different parts of a structure are modelled independently by BEM or FEM methods, it is sometimes necessary to put the parts together without remeshing of the nodes along the part interfaces. Frequently the nodes do not match along the interface. In this work, the symmetric Galerkin multi-zone curved boundary element is a fully symmetric formulation and is the method used for the boundary element part. For BEM-FEM coupling it is then necessary to interpolate the tractions in-between the non-matching nodes for the FEM part. Finally, the coupling is achieved by transforming the finite element domains to equivalent boundary element domains in a block symmetric formulation. This system is then coupled with a boundary element domain with non-matching nodes in-between.