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The design of flexible earth retaining structures against seismic loading is a challenging geotechnical problem, and it is typically conducted using pseudo-static approaches, which do not adequately represent the transient loading conditions of earthquake motions. Numerical analyses of designed walls with simplified material models showed high stresses in the structure when subjected to both dynamic and pseudo-static conditions, and a very large amount of reinforcement would be required to avoid the formation of plastic hinges. On the other hand, detailed simulations with inelastic material behaviour would yield more realistic estimations of the retaining structural response and improve the efficiency of the design, at the expense of additional computational cost. In this paper, we present numerical analyses of cantilever retaining structures subjected to seismic loading conducted by means of the FE computer code DYNAFLOW. A multi-yield plasticity constitutive model with Mohr-Coulomb yield functions is adopted for the soil elements, and an elastic model for the structural components of the 2D numerical model. Absorbing elements are placed around the truncated numerical domain to avoid spurious reflections, and the input motion is prescribed by means of effective forcing functions to allow absorption of scattered waves. Results are presented in terms of accelerations, bending moments and displacements. Previous simplified analyses and pseudo-static approaches are then compared to the more realistic yet elaborate elasto-plastic simulations.