ssc-367 - Ship Structure Committee

Verification of a member’s structural integrity due to VIV fatigue
is difficult due to the-interactivenature of the vortices shed and
the vibration of the member. State-of-the-artprocedures developed
to determine the responseamplitudesof amember incorporateseveral
approximations. It is reconunendedthat some of the more important
of these approximationsare carefully considered before starting a
VIV analyses:
●
Experimental data used to correlate parameters in the
development of empirical procedures are limited. Published
data is not available for in-line VIV in uniform oscillatory
flOw.
●
Accuratedeterminationof structuraldamping ratios in air and
inwater isdifficult. Thedamping ratios directly affect the
stability parameter and may contribute to either
underestimationor overestimationof the vibration amplitudes
and stresses.
●
Tubulars extendingover multiple supportsneed to reevaluated
by considering support sleeve tolerances and spanwise
correlation of varying lengths and fixity prior to the
determinationof natural frequencies.
8-7
/ y_.