An advanced implementation of the boundary element method for plane strain elastoplasticity.

摘要

The primary objective of the present research is to broaden the scope of the direct formulation boundary element method with respect to plane-strain elastoplastic problems, specially for geomechanics applications. This study intends also to improve the computational efficiency and accuracy of the boundary element method, and to make possible the solution of large problems using a limited core space by means of out-of-core storage for the global matrices and vectors.;A FORTRAN computer program having the following major features has been developed: (1) interpolation using quadratic isoparametric elements and plastic cells; (2) numerical integration with variable number of Gauss points, and colomnwise calculation and storage of global matrices; (3) complete treatment of traction discontinuity; (4) option for the division of the body into several regions, with no operations performed for the zero blocks of the resulting global matrices; (5) use of the initial stress method for the iterative algorithm with the previous elimination of the linear degrees-of-freedom; (6) availability of a data generation segment specially designed for boundary elements; and (7) automatic allocation of core space for all global arrays from a single vector.;The program has been tested for elastic and elastoplastic problems. A comparative study has indicated that the boundary element method is more efficient and more accurate than the finite element method for the calculation of stresses around underground excavations. For a problem with widespread plastic flow, the finite element method was superior.