Dynamic characteristics and VIV of deepwater riser with axially varying structural properties

► Another lift copy uttered by instantaneous motion, rather than final response amplitude, to examine dynamic characteristic. ► The presented approach avoids costly iterations and is more efficient for the time domain calculation using FE codes. ► The influence of axially varying structural properties on dynamic characteristic and VIV of the deepwater riser is explored. ► Axially varying structural parameters can efficiently change the modal wave length as well as the modal displacement. ► Vibration amplitude of riser VIV reply is partial by complex effect of factors relating axial stress and modal wave length.