بهسازی اتصالات صلب فولادی متداول از طریق کاهش مقطع بال

Abstract
The moment connections sustained by many steel buildings were damaged during the
recent earthquakes due to brittle fractures in the special moment resistant frames.
Previous studies showed that although the top beam flange resisted due to the interaction
of concrete slab, many damages are created because of weld cracking between the bottom
beam flange and the column flange. Different methods of retrofit and rehabilitation could
be used to prevent weld cracking and brittle fracture of the joints. The reduction of the
bottom flanges of steel beams near the beam-column joints in the special moment resistant
frames is currently an acceptable alteration of a connection because the top flange is
located in the concrete slab and removing of concrete slab has financial and technical
problems. RBS connection is one of the different kinds of Post-Northridge connections in
which by cutting some parts of the flange near the end of the beam (where the possibility
of making plastic hinges is high), the plastic hinge moves by the side of the column into
the area within the beam. By using this method, the connection is altered from the special
moment frame into a more ductile connection that has more ability to endure in plastic
rotation, and generally ductility increases. The ductility of the panel zone is one of the
parameters, which undoubtedly affects the manner of the yield of beams with RBS
connection. Our findings in this work showed that new method causes the beam plastic
rotation to increase by 30%. In addition, the applied force at the panel zone (according to
the capacity of panel zone) is decreased. When compared to the frames without cuts, these
reductions result in a 52% decrease in the plastic rotation of the panel zone, we also
investigated the amount of dissipated energy by beams in the conditions before and after
retrofitting. ANSYS software was used to study and analyze the non-linear behavior in the
area of connections.