Marine Structures 1(1988) 139-183 Redesign of Marine Structures by Perturbation

Finite element (FE) methods are extensively used for analysis of static and dynamic behavior of marine structures. Often predicted response is unacceptable from the point of view of design or operation. Improvement of response then, becomes a design goal which can be achieved by redesign or reduction of operational threshold. Traditional trial and error techniques using FE methods make redesign expensive and are often inconclusive. In this paper a perturbation-based method is developed to solve redesign problems with both static and modal dynamic objectives using data only from the FE analysis of the baseline structure. Code RE STRUCT implements his method and functions as postprocessor to general or special purpose FE codes. Several simple numerical applications are used to illustrate the efficiency of this redesign method and how it can be used to resolve conflicts caused by incompatible redesign requirements. A 192-degree-of-freedom tower with repeated eigenvalues i redesigned subject o frequency and displacement constraints. Finally the impact of perturbation-based redesign on marine structural design is discussed Key words: Redesign, marine structures, perturbation, static and modal dynamic objectives, finite elements