The current study set to investigate the seismic performance of the steel moment-resisting frames equipped with multi-level pipe dampers considering the connection flexibility in the model. Initially, the behavior model of the damper, connections, and steel columns are presented and calibrated based on the experimental results. Then, three steel moment-resisting frames having 4, 8, and 12 stories with poor lateral strength were modeled in the OpenSees software, while the flexibility of the beam-column connection was taken into account. The structural models were then subjected to the one-direction lateral load and evaluated using the nonlinear static analysis. The results revealed that the rehabilitation of steel moment-resisting frames using the multi-level pipe dampers significantly led to enhanced load bearing capacity of frames compared to the corresponding control frame. The maximum load bearing capacity increase was 57%, 56%, and 60% in the 4-, 8-, and 12-story frames, respectively. The ultimate deformation capacity increased as well, while the yield displacement of frames decreased. The maximum increase on the ultimate ductility of strengthened frames was 43%, 34%, and 33% in the 4-, 8-, and 12-story frames, respectively. The findings can be considered as a criterion to compare the performance of this type of damper with the conventional control structures. پرونده مقاله