This work addresses the relationships between Interface Stress Element Method (ISEM) and Applied Element Method (AEM). We investigated the similarities and discrepancies between the two methods in theory by comparing their model compositions and stiffness matrixes. The results indicate that Applied Element Method is a special case of Interface Stress Element Method. Numerical examples also verify this finding.

1.1 Rigid body spring model

There are mainly two kinds of numerical methods. One is based on continuum material equations, like Finite Element Method (FEM) and Boundary Element Method (BEM). The other is based on discontinuous material model, like Discrete Element Method (DEM) and Discontinuous Deformation Analysis (DDA). However, for structural analysis, we usually need to follow the behavior of structures from small deformation to crack initiation and propagation, fracture of structural members, even till total collapse. It is a typical continuum-discontinuum problem.

To solve this problem, Rigid Body Spring Model (RBSM) was proposed at first (Kawai & Kondou 1976). It regards the material in continuum status as rigid discrete elements connected by springs, and simulates the damage of material as fracture of springs. This method can follow most behavior of structures from zero loading up to complete collapse. However, the accuracy of RBSM in small deformation range is usually less than that of FEM. The accuracy of analysis results in other ranges is also affected due to this reason.

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