A comparison of recently developed analytical models for steel moment-resisting frame connections

The investigations following the unacceptable performance of moment resisting frames (MRF) in steel structures during the 1994 Northridge Earthquake identified issues in the weld detailing of the connections used. These original MRF connections, commonly known as pre-Northridge connections, have been identified as having a less ductile performance than anticipated. Research efforts immediately following the Northridge earthquake have resulted in the development of a variety of connections that are identified as pre-qualified, allowing these connections to be selected by designers for implementation without the need for component-level validation. Further research has been conducted to develop other alternate connections. Some of this research has resulted in a series of MRF connections that have been developed to allow for full hysteretic behaviour without the resulting damage due to plastic hinging of the beam. Connections such as the sliding hinge joint (SHJ) dissipate large amounts of energy through friction rather than plastic yielding. Modifications to these connections have resulted in a SHJ connection with self centering behaviour (SCSHJ). This paper examines the specific behaviour of some of the available moment resisting connections and the calibration of the analytical tools used to model each connection. A summary of the hysteretic performance of each connection is presented and a comparison is conducted between the hysteretic behaviours of pre-Northridge, several pre-qualified connections and newly developed low-damage connections such as the SHJ and SCSHJ connections. Analytical models are developed for each type of connection in OpenSees based upon the available component test data. The calibration of these models is discussed and the resulting parameters are summarized to enable both researchers and designers to implement these connection models in future frame analyses. Finally, the collapse analysis of a case-study frame incorporating these various MRF connections is presented.