Response of a Semi-sub Platform to Environmental Load

The increasing usage of floating platforms such as semi-submersibles in the
exploration and production of oil & gas has increase the number of research on
floating platforms. One of the important researches is to investigate and predict the
movement of floating platforms caused by environmental loads. One of the major
components in the design of a semi-submersible platform is to predict its motion
response due to waves. Nowadays, engineers have computer software to do the
calculation and simulation to predict the response of a floating structure. Not many
would do an experiment to compare and see if there is any agreement between the
computer analysis value and the experimental value. So from this research, exclusive
experimental value will be achieved and a comparison can be made between
computer analysis value and experimental value. Later these results can and will
contribute to the designs of future semi-submersibles platform. This research will be
based on real life model testing of a scaled down semi-submersible platform. The
model was based on a prototype semi-submersible platform design for Malaysian
waters by a group of students from a foreign university. The study targets to fill a
vacuum in the design of such important structures by conducting physical modelling.
Changing the wave height, wave period, and ballast conditions, a series of laboratory
tests was achieved at 20 mx 10 mx 1.2 m wave basin of the Coastal Engineering
Laboratory, Universiti Teknologi PETRONAS, under regular waves and random
waves while the semi-submersible is moored by 16 mooring lines connected to the
basin floor. The dynamic response of the semi-submersible was monitored by
photographic methods and the heave, surge and pitch of the structure were plotted vs.
time. The analysis of the maximum responses showed the significance of the wave
period and ballast condition. The scale modelling data show a satisfactory similarity
with the prototype. An equation of motion for heave motion was also constructed and
it can be applied to predict the motion response of the semi-submersible. A force test
was also conducted to get the value of force from wave and current towards the semisubmersible
model. The force calibration result can later be applied to compare
theoretical force calculation with experimental values.