Investigation on the nonlinear behavior of semi-rigid connections and its effect on the braced steel frames

Connections are one of the main components in the construction of a steel structure. Assumptions in the structural analysis divide them into two categories of rigid and pinned connections, however these connections represent an intermediate behavior in the practice. Recognizing the precise semi-rigid behavior of these connections is a significant factor in identification of nonlinear behavior of structure in the earthquake. For instance, in the case of perfectly pinned behavior, no moment will transmit to columns and they will present higher capacity when subjected to axial load. In case of transmitting moment to the column in a structure with pinned connection, the expected capacity of column will be reduced. Accurate data about rigidity of connections have high application specifically in identification of response modification factor of structures with corresponding methods. Three samples of typical steel connections introduced in the Iranian journals are modeled and analyzed with finite element method and the rigidity behavior of them are inspected in this article. Then the effect of simultaneous application of two different type of bracings on the rigidity of these connections as well as the level of ductility in the steel frames are examined. The results suggest that simultaneous application of bracings with 20% of the required capacity increases ductility and rigidity of connections with the acceptable limit

Keywords:

steel connections , semi-rigid connections , rigidity of connection , cross bracing , frame ductility