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Application of systems for passive vibration control is an efficient way for seismic protection of structures. Systems for passive vibration control consist of seismic isolation devices and energy dissipation devices. Base isolation of structures is a concept where devices for passive vibration control are placed in foundations of buildings. Various energy dissipation devices have been developed and tested so far, while metallic dampers represent a significant class. Those devices dissipate energy through the yield of metal material which they are made of. The metallic dampers have often been used because of their main advantages reflected in stable hysteretic behavior and well-known models for analytical prediction of the dissipated energy and structural response. Most of the metallic dampers have been developed for application in the beam-column joints or in the bracing system. The innovative energy dissipation device named multi-gap multi-level multi-directional seismic energy absorber, intended for the application in the horizontal seismic dilatation in the system of base isolation, has been developed recently by the group of the authors among whom is one of the authors of this paper. The main parts of the absorber are vertical components with linearly changeable circular cross-section. Due to the lateral displacements of the isolated structure the vertical components bend and energy dissipation is provided by yielding of the steel material they are made of. According to the previous experimental and numerical study of the absorber's vertical components, three-dimensional finite element model of the absorber has been developed and presented in this paper. The aim of the numerical analysis is to determine mechanical properties of the absorber based on the lateral force-displacement diagram. Furthermore, a simplified numerical model using one-dimensional beam finite elements has been proposed. The performance of the absorber has been determined using the available semianalytical solution for elastoplastic deflection of non-prismatic cantilever beams previously developed by the first author as well. The obtained results have been compared and it has been concluded that all three modelling approaches provide reliable mechanical properties of the absorber necessary for dynamic analysis of structures in engineering practice. [ABSTRACT FROM AUTHOR]