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Four 5-, 10-, 20- and 30-story moment frames, representing low-, mid-, and two high-rise structures, were subjected to a great number of idealized directivity pulses. The amplitudes and periods of pulses vary from 0.02 g to 1.0 g and 0.5 to 12 sec, respectively. Over 1400 nonlinear dynamic analyses of low- to high-rise moment frames were performed which were feasible through using modified fish-bone model. The distribution of interstory drift along the height was studied and two applied contours were proposed: (i) the maximum interstory drift contour, and (ii) the critical story contour. These contours were demonstrated versus the ratio of natural period of the structure to the pulse period and the response modification coefficient (R-factor). Hence, the contours could provide the possibility of investigating the measure of damage, its location and also the conditions leading to collapse based on these parameters. These investigations justify the vulnerability of flexible buildings versus long-period directivity pulses. They also show that some near-fault directivity pulses could impose serious damage to low-rise buildings.

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