Recent studies have demonstrated the effect of earthquake ground motion duration on structural collapse capacity. They have also proposed methods to explicitly account for this effect of duration in structural design and assessment procedures via an adjustment to the design ground motion intensity. The objective of this study is to explore an alternative method to account for the effect of duration by adjusting the permissible peak deformations instead. This paper describes preliminary investigations into the effect of ground motion duration on the dynamic deformation capacity of ductile reinforced concrete framed structures. The dynamic deformation capacities of the structures under short and long duration ground motions are estimated by conducting incremental dynamic analysis (IDA) on realistic, deteriorating nonlinear structural models. Sets of spectrally equivalent short and long duration ground motions are employed to control for the effect of response spectral shape. Preliminary results indicate a reduction in the dynamic deformation capacity of the analysed structures under the increased cyclic demands imposed by long duration ground motions. These results will be assimilated to propose a modification to the peak deformation acceptance criteria employed by seismic design and assessment procedures to explicitly account for the effect of duration