4 - Memorial University of Newfoundland DAI

~~lidity of the results war rompsrod to known msults fmm actual plstforma.
it war also polsible to determine the maximum increase in member loading
resulting fmm such failure. These vesulla were most helpful in putting the
frequencies and load rnsitivities into a general perspective.
Rofcroncc 1271 discussed the main features of a joint revarch project un-
dcrtakcn in 1980 by Leper1 el ol. about technique using the dynamic pmp
crtios 01 an obhore skzl structure to detect structural damage. A relation
was oslnbliahed between the occurrence of a failure and the modification of
thc dynamic pmpcrties of the structur.. Baed on many parts of experi-
ments, using the scale modol of s platform, and on modal analysis theory,
lhc investigation showed that such a relation exinls which depends on the size
and position ol tho dcfat. From that invetignlian, two methods for the me
chanical detection of damages were prernted and compared, both from the
technical and ~conomical viewpoints. A third method, using the sdjuatrnenl
of a lhmreticnl model by the mesauted modal pnrameters, was pmpoaed to
monitor the midual integrity for a damaged platform. Next vibmdetection
was prented as a poworlul tool for future olTahore surveys, and an efficient
complemml to the conventional non-destructive ksting methods. It wns em-
~phnsizd thnl the technique can directly relatenny structural damqe to the
resulting loss of integrity of tho affected structure.
B~lrke el al. Pa] pmse..ced a IensCsqu- method far calcttlating a n-
sponae shape wtor at each discrete frequency of the matrix auto and cross-
spectral density functions. The resulting shape vectors provided: (1) a single
function of frequency (the squared norm) for displaying peaka in the spectral
densily fitnetion, (2) a quantitative mearure of the mode shape ls-iated
with the peaks, and (3) a measure of the godnea of fit of the vecta data