4 - Memorial University of Newfoundland DAI

een recorded, then it is beneficial to compan cnlculated design qtmntilies,
or data fmm existins structures with mults fmm teats on model struetsrca.
Such models can be used to 1-1 mathematical models; lo Bnd possiblecflects
of structural modifications; or to provide design quantities directly.
Furthermore, sinn ofshore structures are eosLly and tho cnvimsmnttnl
conditions in which they have to operate are hostile, it is very impartant lltd
all available knowledge and experience sre used in their design. Evidu~tiy,
computer programs can be written to evaluate rtmes in the stranrtum for
variaua conditions of wave and current foma acling on the atmctare. Still,
the vibrational characterislics of the structure are tdsunliy difficult lo rums-
lyre. There vibrstiona, which can be induced by vortcx shedding as 1110 an
flows past structural members, can enuac fatigue failare. Ib gnin eos(ida,cc
in a proposed ddgn before fabricalien commoncea, or lo gnin snmc ~wtdcr-
standing of the vibration characteristics of an existing oflahorn slractarc, it
is, therefore, dwirable to build a scale model, md to tost it uudcr rcnlisth:
aeamnditions in atrnk with a pseudo random wavc-making fnciiily. 11) this
treatise, the model testing and analysis appmach is doptcd.
1.1 Background
loere~ad activity toexplore hydro-carbons in Lho ocean has m^s~xltcd in strue-
lures being installed in deeper waters and more hostile envlmnrncnts. 'rb~~,
unba =me cheapw alternative source of energy (not oil or gas) is found,
this affinity towards the ocean is expnled to inereare in lhe hd!se. 110-
velopments in water depths over 300 m are using mmplinnt strtlctural con-
cepts, auch u gupd tower platforms, tension Iq platforms, or dynamically
pmitisned semi-submeraihle rtrudum. Future developmentn may unc aub