SUMMARYNear-fault ground motions impose large demands on structures compared to 'ordinary' ground motions. Recordings suggest that near-fault ground motions with 'forward' directivity are characterized by a large pulse, which is mostly orientated perpendicular to the fault. This study is intended to provide quantitative knowledge on important response characteristics of elastic and inelastic frame structures subjected to near-fault ground motions. Generic frame models are used to represent MDOF structures. Near-fault ground motions are represented by equivalent pulses, which have a comparable e ect on structural response, but whose characteristics are deÿned by a small number of parameters. The results demonstrate that structures with a period longer than the pulse period respond very di erently from structures with a shorter period. For the former, early yielding occurs in higher stories but the high ductility demands migrate to the bottom stories as the ground motion becomes more severe. For the latter, the maximum demand always occurs in the bottom stories. Preliminary regression equations are proposed that relate the parameters of the equivalent pulse to magnitude and distance. The equivalent pulse concept is used to estimate the base shear strength required to limit story ductility demands to speciÿc target values.

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SUMMARYNear-fault ground motions with forward directivity are characterized by a large pulse. This pulse-like motion may cause a highly non-uniform distribution of story ductility demands for code-compliant frame structures, with maximum demands that may considerably exceed the level of code expectations. Strengthening techniques for multi-story frame structures are explored with the objective of reducing maximum drift demands. One option is to modify the code-based SRSS distribution of story shear strength over the height by strengthening of the lower stories of the frame. The modiÿed distribution reduces the maximum story ductility demand, particularly for weak and exible structures. However, this strengthening technique is less e ective for sti structures, and is almost ine ective in cases in which the maximum demand occurs in the upper stories, i.e. strong and exible structures. As an alternative, the beneÿts of strengthening frames with elastic and inelastic walls are evaluated. The e ects of adding walls that are either ÿxed or hinged at the base are investigated. It is demonstrated that strengthening with hinged walls is very e ective in reducing drift demands for structures with a wide range of periods and at various performance levels. Wall inelastic behavior only slightly reduces the beneÿts of strengthening with hinged walls.

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