The principal aim of this study is to study the fracture behavior of offshore platforms subjected to wave loading. A general review of offshore structures, wave loading and their effects on offshore structures are presented. Fracture mechanics aspect on the assessment of crack tip severity under cyclic loading condition is explored. A brief review on the basics of Wavelet analysis is also mentioned in this study. The techniques for modeling wave loading in finite element analyses are described and discussed in detail. A series of 3D analyses are carried out using the ABAQUS finite element software to study the effects on the dynamic response of the change in support conditions at the seabed. The effects of wave height, wave period and wave velocity on platform behavior are studied. The results from time history analysis are characterized using Wavelet Analysis in order to obtain the response pattern due to wave loading. These analyses allow the frequency response of the jacket structures to be described in the time domain. These results give a clear view on the response of jacket structure. The important parameters on offshore modeling have also been identified and discussed in this study. In order to perform the assessment of fracture in welding steel structures under dynamic loading conditions, the conventional fracture assessment parameter i.e. J-integral, does not include the effect of inertia within the equation. Hence, to allow for inertia effects on J-integral calculations, an additional term must be included in the original expression for the J-integral introduced by Rice to restore path independence. The WARP3D finite element program, in which an inertia effect is included in a general J-integral computation facility, is used to calculate J-integral values for centre cracked plate and three point bend (TPB) specimens under dynamic load. Results of J-integral from WARP3D were compared with those obtained from ABAQUS FE program. Both programs showed close agreement for intermediate loading rates. Finite element investigations have been carried out by using the ABAQUS FE program in order to study the inertia effects on cracked specimens, i.e. centre crack plate, three point bend (TPB), and compact tension (CT) specimens. It has been found that increasing loading rates cause a decrease of J-integral values. When loads were held at their maximum, an overshoot situation in J-integral values occurred. The present work also suggests that an approximation method, i.e. area under load-displacement curve and crack tip opening displacement (CTOD), can be used to calculate J-integral for intermediate loading rates. However, assessing the crack tip severity of a critical structural application, i.e. offshore platforms, has been based on highly computational time consuming process. Therefore, the present study proposes the simplified method for assessing the crack tip severity of through-wall crack in minimum structures. In order to get a better understanding of the local behavior of connections, the 3D-submodel of through-wall crack pipe is modeled within the full 3D beam element of the brace caisson. The fracture characterizing parameter (CTOD) is extracted from the crack tip region. The applied CTOD results will be compared with those obtained from the simplified method. From the analyses results, it can be seen that the simplified method can enormously reduce the analysis time and allows design engineers to assess the possibility of connection fractures, or determine approximate values of toughness and defect size requirements for given peak stress levels.