A New Approach to Identify Active Frequencies of Dynamic Ratcheting- Inducing Ground Motion

Dynamic ratcheting (DR) is a phenomenon that occurs in nonlinear systems and one aspect of complicated nonlinear dynamic behaviors. DR behavior have a strong effect on the magnitude of plastic deformation in single-degree of freedom (SDOF) hysteretic damping systems, therefore there is need to precisely examine this phenomenon caused by earthquake excitations. DR-inducing frequencies of ground excitation are called “active frequencies”. A new method is proposed in this study to identify active frequencies of DR-inducing ground excitation using wavelet transform. The identification method is based on a reduced dimensionality and filtered frequency content of original record according to closeness of displacement time history of SDOF system under both original and modified record. The objective of this study is divided into two main parts: In the first part of this study, applying the proposed method for a DR- inducing ground motion and it was an example that how the method could be utilized to identify active frequencies of DR- inducing ground motion. The second part of this study is devoted to identify the DR- inducing ground motions between a set of ground motions records, containing 504 records up to the year 2012, in Iran. The reduced representation of ground motion is a useful technique for extracting active frequencies from ground motion.