DYNAMIC RESPONSE OF SPAR PLATFORM SECURED WITH MOORING SYSTEM USING ANSYS-AQWA

Oil and gas exploration has moved to deeper water in recent years and the type of
offshore structures used are also changing. A spar has a deep draft cylindrical hull
and is suitable for use in deep water regions. Since spar is a floating structure, it uses
mooring lines to hold its position even though the wave and current loading will
cause a motion response on the spar. To understand the motion as well as the tension
loadings in the mooring lines, a dynamic analysis has been conducted in the time
domain. The analysis uses a regular wave profile with 6m height and a period of 10s.
The spar is secured with four mooring lines and is subjected to this wave loading and
using the Linear Airy Wave Theory for computation. The forces acting on the spar
and mooring lines is governed by the Morrison’s Equation. The responses of surge,
heave, pitch and tension is then compared to a benchmark case obtained from
previous study for validation purpose. Upon validation parametric study on the crosssectional
area of mooring lines and the number of mooring lines was performed.
Simulation was performed using ANSYS AQWA finite element software and the
results obtained are consistent with previous studies.