4 - Memorial University of Newfoundland DAI

detwM from the data roeorded (lateral, wtieal and angular aenwrs) from
lorcc trsnnducora at 17 locations abavhwater on the structure were used ta
provides baris lor a future analytical phase.
Vandiver and Campbell [IS] introduced the Maximum Entropy Method
(MBM) of speetral analysis as a powerful technique far estimating the dy-
namic response pmpcrties of offshore pMforms. This method wsr presented
in makingeslimata 01 natural frequmciea and damping ratias for three sim-
ilar U.S. Navy air combat maneuvering range platforms near Cape Hatteras,
North Csraiin~ Note that MEM has p~oved the capability of producing
nmootit high rrsolutian reaponse spectra from short time histories of deck
acceleration. Also, this capability to use short record lengths substantially
dccrcnsw inherent error8 arising from the necessary assumption 01 stationary
wave excitation loras (ibid.).
Irwin [I91 cxamined tho various methods of conducting tests on small
scale atruelures and the details of simple, low coet vibrating systems suitable
for teala on still modcls wcrc presented. The analysis and interpretation of
thc data dcrived from such experiments wue also considered. In relerence
[ZO], s rational evnluntion of the atructurel Integrity of an offshore structure,
using vibration measurements, was done for the USCG Ambrose Tower-a
lotor-lcggod fixed platform at the entrance to New York harbour. A math-
cmatleal model of the structure was analyzed with the SAP IV computer
pmgrnm while considering the eflecta 01 mas, entrained water, soil support
conditions, equipment, etc. Also, the various parameterr affecting the lower-
mode vibration charactorirtiw d the structure were examined separately,
and their quantitative influence on the structure were investigated. Eiom
tltc resulk dtained, it was verified that the vibration analysis of an offahore