Effect of various span lengths on seismic demand on column splices in steel moment frames

Steel moment frames have gone through intensive investigation to understand the cause of the damage since the 1994 Northridge–California earthquake. A research conducted by the SAC Joint Venture has helped to improve the current code requirements for steel special moment frame design. One major outcome of these research efforts was on the enhanced design requirements for column splices. For example, AISC 341 Seismic Provisions require that column splices in intermediate and special moment frames, when not made using complete joint penetration welds, be designed to develop the expected flexural strength of the smaller connected column and the shear demand associated with flexural hinging at the top and bottom of the spliced column. This paper focuses on the effect of various span lengths on seismic demands on column splices in steel moment-resisting frames. A comprehensive nonlinear analytic investigation was undertaken to evaluate the seismic responses of 4- and 9-story moment-resisting frames with constant and various span lengths subject to an ensemble of 20 strong ground motions. The results indicate that the structural response is sensitive to the span length and variable span length within the frame might significantly increase the seismic demand on column splices.