Abstarct: Earthquakes are among the most critical natural phenomena, causing significant economic losses and human casualties due to structural failures. Near-fault earthquakes, in particular, generate pulse-like waveforms in the velocity time history of ground motion, exhibiting forward directivity effects. Past occurrences of such earthquakes have demonstrated their potential to cause substantial destruction. In this thesis, the seismic behavior of medium-rise reinforced concrete moment frxames subjected to near-fault earthquakes with forward directivity effects is analyzed. The study incorporates soil-structure interaction (SSI) and utilizes a two-dimensional numerical simulation baxsed on the Beam-on-Nonlinear-Winkler-Foundation (BNWF) method. The objective of this research is to compare the seismic performance of fixed-baxse structures and structures situated on soil type III under near-fault and far-fault earthquakes. In this thesis, three medium-rise reinforced concrete moment frxames with 4, 8, and 12 stories are designed as two-dimensional models in Etabs software and then modeled in Opensees. These frxames are subjected to two sets of 20 earthquake records, and their seismic performance is evaluated using Incremental Dynamic Analysis (IDA). Finally, fragility curves are developed by considering different performance levels as defined in the Hazus guideline. The analysis results indicate that the inter-story drift responses of soil-structure interaction (SSI) models significantly increase compared to fixed-baxse models. Additionally, as the height of the structures increases, their behavior reveals earlier entry into the nonlinear range, leading to a reduction in their capacity. Consequently, the vulnerability of the structures rises across various performance levels. However, the rate of increase in the probability of complete collapse decreases under both categories of earthquakes.