A new definition of strong motion duration and related parameters affecting the response of medium–long period structures

This study presents a new definition of the strong motion duration combining the alternative bracketed and significant duration definitions. Based on the time integral of the absolute ground velocity, a new index is defined, as cumulative absolute displacement (CAD), and used to estimate the strong motion duration. The proposed bracketed-significant duration tbs is found to be well correlated with the strong motion part of the records, especially in the case of near-source events. The duration tbs and the CAD index are used to assess the anticipated structural behavior of medium–long period structures.Two normalized parameters P1 and P2, representing the amplification of structural response and the number of equivalent loading cycles, respectively, are determined in terms of the tbs and CAD and the spectral velocity associated with the medium–long period range. P1 and P2 appear to be better correlated with the structural response than established well-known indices.