While it is generally perceived that ground motion duration will influence structural performance, previous research on the topic has produced mixed conclusions, which has led to the effect of duration being largely ignored in structural design practice. The believed reasons for the inconclusive results are the use of non-deteriorating structural models, attention not paid to behavior near collapse and the use of inefficient metrics to characterize duration. This paper summarizes preliminary results of a study that employs non-linear incremental dynamic analyses to assess the effect of ground motion duration on the estimated collapse risk of reinforced concrete bridge piers. Spectrally equivalent long and short duration record sets are used to isolate the effect of duration from that of other ground motion characteristics like response spectral amplitude and response spectral shape, and quantify its influence on estimated seismic collapse risk. Sensitivity of the effect of duration to model parameters is studied to help identify classes of structures most susceptible to long duration shaking. Preliminary findings and their implications on research and structural design practice are presented.