The seismic demand imposed by a ground motion is related to its amplitude and duration. The amplitude of the ground motion is usually represented by the Cyclic Stress Ratio (CSR) and the effects of the duration of a ground motion have usually been represented through an equivalent number of uniform amplitude cycles (N).

This thesis begins with a review of methods used to determine N, as well as important factors known to influence the evaluation of N. Discrepancies between the current cycle counting methods and the known influential factors are identified. A new procedure based on pore pressure generation is proposed and compared to two modern cycle counting procedures from the literature using a small suit of records in the NGA-West2 ground motion database. The study identified parameters that influenced the N results for all three procedures, including soil unit weight, depth, fines content, cycle amplitude, and cycle sequencing.