When steel tall frames are subjected to near-fault ground motions, collapse mechanism of a steel tall frame tends to be localized into single or lower several stories. This paper examines the feasibility of resolving this issue by adding base-hinged core trusses. Case studies are performed on the response of 20 story moment resisting frames designed in accordance with the Japanese design practice of high-rise buildings. In these studies, the response of the frames with core trusses to near-fault ground motions are examined by incremental dynamic analyses, wherein degradation due to local buckling at beam ends are taken into consideration. The results of the parametric analysis demonstrate that addition of relatively small amount of base-hinged core trusses leads to formation of global mechanism and significant reduction of response to near-fault ground motions.
