10-10-2014, 02:14 PM
The objectives of this paper are (i) to identify the basic parameters which control
the earthquake response of torsionally coupled offshore gravity type platform
systems composed of resisting elements providing force interaction during
yielding. (ii) To clarify the differences in response between systems subjected to
single component ground motion and systems subjected to double component
ground motion. (iii) To clarify the differences in response between systems with
the torsional stiff nesses of the columns about their own centroidal axes
neglected and systems with the torsional stiff nesses of the columns considered
in the yielding criteria. (iv) To evaluate the maximum ductility requirements in
the effects of magnitude of eccentricities on the ductility.
A typical offshore gravity type of platform with a square deck and four resisting
columns was used to examine these objectives First. Dimensionless equations of
motion were formulated and a yield criteria to include the interaction of the
torsional stiffness of the columns was assumed. ElCentro, May 1940, earthquake
was used as input and the equations of motion were numerically integrated
using linear acceleration-method.