Semnan University International Journal of Nonlinear Analysis and Applications 2008-6822 2026 02 20 Nonlinear dynamic soil-structure coupling analysis in steel structures on a wide foundation under near- and far-fault earthquakes using viscous energy absorbing systems 10494 10.22075/ijnaa.2025.38563.5515 EN Ali Sanaeirad Department of Civil Engineering, Faculty of Engineering, Arak University, Arak, Iran Reza Mohammadi Department of Civil Engineering, Faculty of Engineering, Arak University, Arak, Iran Journal Article 2025 06 05 Analysis of dynamic soil-structure interaction in steel structures with a wide foundation, as well as the use of appropriate energy-absorbing systems in structures whose members do not perform properly, is of great importance. This is because by absorbing seismic energy, these systems ensure that the structural members remain within the elastic range during an earthquake. Viscous dampers are among the energy dissipation devices that have been widely considered in modern seismic design methods. Given that loading codes change every few years, existing structures often no longer meet the provisions of new regulations and require retrofitting. This makes the idea of using a type of damper in these structures very significant. When performing correctly, these earthquake energy absorbers delay the structure's reaching the limit state during severe earthquakes, which is highly effective in improving structural performance. In this study, to investigate the role of interaction, the response of structures was compared from the perspective of inter-story drift and the behavior of structural members, both with and without considering dynamic soil-structure interaction and under near- and far-fault earthquakes. For this purpose, three two-dimensional steel moment frames with 10, 5, and 15 stories were used as low-rise, mid-rise, and high-rise structures, respectively. Then, the frames, which had been previously designed with viscous damper reinforcement and considering soil-structure interaction in loose soils, were analyzed. For the nonlinear dynamic analysis, seven accelerograms were used, and the results were compared. Based on the findings, it is observed that the reduction in floor response when using viscous dampers is not necessarily guaranteed; it can also increase depending on the earthquake record and the characteristics of the structure. The response of structures equipped with viscous dampers is close to that of structures without dampers, and in some cases, they are schematically almost identical. The results of the study indicate a significant increase in structural response in the presence of interaction and successive earthquakes, especially in low-rise buildings compared to high-rise buildings. These findings can be effective in improving seismic design criteria and evaluating the performance of structures against sequential earthquake events. https://ijnaa.semnan.ac.ir/article_10494_7d90ca24dfbc4ba4465647f0cd89c245.pdf