STR-833: EVALUATION OF THE CONTRIBUTION OF PANEL ZONES TO THE GLOBAL PERFORMANCE OF MOMENT RESISTING FRAMES UNDER SEISMIC LOAD

Before the 1994 Northridge Earthquake, the seismic design strategy for moment resisting frames considered the yielding of the panel zone when calculating the required level of ductility. Following the unacceptable performance of conventional moment resisting frame (MRF) connection details during the Northridge seismic event, prequalified connections were developed to concentrate beam yielding away from the column face, preserving the connection. With these new connection strategies, the panel zone deformation may not contribute as significantly to the overall behaviour of an MRF. Therefore, considering the increased use of advanced dynamic modeling techniques, it is important for both designers and researchers to know what level of modelling detail is required to properly capture the behaviour of an MRF. This paper examines the influence of the panel zone model on the global performance of a moment resisting frame. The nine-storey SAC building is used as a model to evaluate the influence of this variation. The beam-to-column connections use reduced beam sections and are modeled with OpenSees using nonlinear elements that that capture cyclic deterioration. In one case, the panel zones are modelled as rigid offsets with no shear yielding. In the other case, the panel zones are modeled using a rotational spring box, in which rigid links are arranged in a rectangle and connected at the four corners by three pins and one nonlinear spring that captures the shear distortion in the panel zone. An Incremental Dynamic Analysis with 7 ground motions is conducted to determine the differences in global performance. The more refined panel zone model results in a longer first mode period and less energy dissipation in the plastic hinges of the beams. However, the difference in engineering demand parameters at design level events is minimal and may not justify the increase in computational requirements unless collapse assessment is desired