  The paper is concerned with the development of efficient and accurate
solution procedures for the isogeometric boundary element method (BEM) when
applied to problems that contain inclusions that have elastic properties
different to the computed domain. This topic has been addressed in previous
papers but the approach presented here is a considerable improvement in terms
of efficiency and accuracy.
  One innovation is that initial stresses instead of body forces are used. This
then allows a one step solution without iteration. In addition, a novel
approach is used for the computation of strains, that avoids the use of highly
singular fundamental solutions. Finally, a new type of inclusion is presented
that can be used to model reinforcement bars or rock bolts and where analytical
integration can be used. Test examples, where results are compared with Finite
Element simulations, show that the proposed approach is sound.
