This work focuses on the seismic design of reinforced concrete structures in highly seismic areas such as Goma and Bukavu. Entitled ‘Contribution to the Structural Design of Buildings type G+9 in the Seismic Zones of Goma and Bukavu’, the study aims to analyze the influence of soil properties on the seismic behavior of a (G+9) or 10 storey building in accordance with the provisions of Eurocode 8. The analyses and designs were carried out according to the norm RPA99 modified 2003, MATLAB (for simplified manual calculations), Robot structural Analysis Professional (for automated calculations), Eurocode 8, Eurocode 2, Reinforced concrete to limit States 91 (mod.99). The building is a ten-storey reinforced concrete structure without shear walls or bracing systems, in order to clearly observe the effect of soil type on dynamic behavior. Two types of analyses were carried out: a manual static analysis for the preliminary design of structural elements (beams, columns, footings), and a modal response spectrum analysis according to Eurocode 8 for seismic evaluation. The results reveal that soft soil from Bukavu (Class C) produces higher internal forces, with an average increase in base shear forces of approximately 41%, and a 42% increase in lateral displacements compared to hard soil from Goma (Class A). This is due to the amplification of seismic waves in soft soils, which significantly affects tall buildings. Finally, the generated reinforcement plans were adapted to the specific loads for each soil type, highlighting the importance of adjusting the design to local ground conditions. This study underlines the critical impact of soil type on seismic analysis and structural design. It emphasizes the importance of prior geotechnical investigations and strict adherence to Eurocode 8 provisions to ensure structural safety in seismic regions.