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The Brazilian oil industry is essentially based on offshore production and exploitation units. The seakeeping analysis is, therefore, imperative to sizing vessels designed to operate in different sea states. Normally, a linear approach is sufficient to predict reasonably the vertical motions of free floating bodies. The characteristics of Brazilian oil fields and the subsea infrastructure drive a tendency to design of very large floating platforms which, in turn, leads to resonant periods out of wave energy zone. Whereas, on the one hand, wave-induced first order motions decrease, on the other hand second order vertical motions become relevant to the seakeeping analysis as far as mooring design is concerned. Potential theory in frequency domain is presented, in which the difficulty in determining the so called Quadratic Transfer Function or simply QTF becomes explicit. The theory is valid for six degrees of freedom and the second order forces are obtained through direct integration of the fluid pressure acting on the instantaneous wetted surface of the body. The second order forces are, therefore, calculated using a commercial potential solver algorithm such as WAMIT for arbitrary body geometry. Irregular wave tests with beam sea incidence have been carried out at IPT (Instituto de Pesquisa Tecnológica do Estado de São Paulo) towing tank for a new concept of FPSO hull idealized to operate on ultra deep waters. The results from these tests showed clearly a roll resonant motion, characterized as second order slow motion, which were used as paradigm to compare the numerical results achieved from complete estimative of QTF. The comparison showed good agreement between them. Obtaining the QFT requires massive computational power and a considerable amount of time. For this reason, this work uses existing approximation methods to estimate the second order roll motion of an FPSO and proposes a new approximation method derived from existing ones, which represents an original contribution of this Thesis. The results from the existing and proposed approximation methods were compared with those obtained with the complete QTF showing that the proposed approximation yields results of improved accuracy compared with the existing ones for roll motion of the FPSO. In light of the assumptions adopted to apply the proposed approximation method, its applicability on the other types of offshore structure may be likewise promises if the transfer function is narrowbanded. LISTA DE ILUSTRAÇÕES ! " # $! " # % & $! " ' # ( & ( $! " " ) ( % * + $! " $ ,. ! $ / &! 0 $ / ! $ / ! 0 " 1 % . ! ,2/ &! ," 2/ ! ,112/ ! ,2 " 0 ,2. ! 3 4/ &! ) / ! " ," 2. ! 3 4/ &! ) / ! " ,112. ! 3 4/ &! ) / ! " ,2. ! 3 4/ &! ) / ! " . ! / &! % " # * ,( * 5 . ! / &! % " ' # ,( * 5 . ! / &! % " " . ! ,2 / &! ,2/ ! ," 2/ ! ," 2/ ! # ,112 / ! ,112/ ! ,2/ )! ,2 " $ # ) ,2 $ ( ,. ! ,2/ &! ," 2/ ! ,112/ ! ,2 $ , ,,$ ' ,( * , . ! ,2/ &! ," 2/ ! ,112/ ! ,2 $ " ,,2. ! / &! $ $ ,," 2. ! / &! $ 1 # ,,112. ! / &! $ 0 ,,2. ! / &! 1 ,( & ( % . ! ,2 / &! ,2 / ! ," 2 / ! ," 2 / ! ,112 / ! ,112 / ! ,2 / )! ,2 / 1 # ,3 . ! ,2 / &! ,2 1 ' # ,3 . ! ,2 / &! ,2 1 " # ,3 . ! ," 2 / &! ," 2 1 $ # ,3 . ! ," 2 / &! ," 2 1 1 # ,3 . ! ,112 / &! ,112 1 0 # ,3 . ! ,112 / &! ,112 1 # ,3 . ! ,2 / &! ,2 1 # ,3 . ! ,2 / &! ,2 1 # ,& ! ,2 / &! ,2 1 # ,& . ! ,2 / &! ,2 1 # ,& ! ," 2 / &! ," 2 1 ' # ,& . ! ," 2 / &! ," 2 1 " # ,& ! ,112 / &! ,112 1 $ # ,& . ! ,112 / &! ,112 1 1 # ,& ! ,2 / &! ,2 1 0 # ,& . ! ,2 / &! ,2 1 # ,( ! ,2 / &! ,2 1 # ,( . ! ,2 / &! ,2 1 # ,( ! ," 2 / &! ," 2 1 # ,( . ! ," 2 / &! ," 2 1 # ,( ! ,112 / &! ,112 1 ' # ,( . ! ,112 / &! ,112 1 " # ,( . ! ,2 / &! ,2 1 $ # ,( . ! ,2 / &! ,2 ( % , ) 78 5 ! # & 1! #$0 ( % , 78 ' " 5 ! ' # 2 2

Modelagem de efeitos de segunda-ordem nos movimentos de roll de plataformas tipo FPSO.