Seismic performance enhancement of rigid beam to column moment connection using modified steel slit damper

The high ductile of steel moment-resisting frames (SMRFs) during earthquakes has been challenged due to the brittle fractures of their welded (rigid) beam to column connections. Consequently, SMRFs have suffered severe damages and have produced collapse in main structural members (such as beams and columns). During previous years, energy dissipative devices in connections have been developed by researchers to resolve the ductility problem in rigid beam to column connections of SMRFs. Slit steel damper (SSD) as one of these devices contains a plate or a standard section with a number of slits in its web. The damper can dissipate the seismic input energy with inelastic deformation absorption and also prevent seismic energy transmission to the main structural members (such as beam and column). Due to the uniform strut width of SSD, stress concentration at the end parts of the damper struts is produced and unbalanced distribution of von-Mises stresses along the struts is shown. Furthermore, slit dampers are commonly fractured in the end parts of its struts. The low participation of the middle parts of struts in the energy dissipation is caused. Henec, finding the best shape of slits has been attracted by researchers. In this study, new geometry shape of SSD was proposed for improving rigid beam to column connections of steel structures. For investigating the performance of the proposed damper, the behavior of a rigid connection with the common and proposed SSD was assessed subjected to monotonic and cyclic loads in ABAQUS software. The proposed SSD has the same weight in comparison with that of the common SSD. The results of assessment was shown that in the proposed SSD reducing the width of damper slits in two its ends and increasing its middle parts improved its seismic performance in comparison with that of the common SSD. The proposed damper in comparison with common one subjected to shear load can effectively contribute to about 41% of the total dissipated energy. Furthermore, using the proposed damper in a rigid beam to column connection subjected to cyclic loading can effectively contribute to about 51.8% of the total dissipated energy. The performance of the proposed SSD shows that first, the middle part of strip treat like fuse and the suitable ductility provide. Then, the maximum stresses transfers to the top and bottom of strips. Due to the distribution of stresses in more area, the strength of the proposed damper increases. Therefore, withstanding a large number of loading cycles until the failure in this proposed damper, it can be used instead of welded connection in SMRFs.