Spur dikes are hydraulic structures frequently applied to protect rivers' banks. Since flow pattern around a spur dike located in a rivers' bend is particularly complicated due to the existence of secondary flow and helical flow, the effect of submergence ratio on flow patterns around a short T-head spur dike located in a 90° bend has been monitored numerically in this study. The numerical data are verified with experimental data obtained under non-submerged conditions, which indicate the numerical results are in accordance with experimental data. In this research, the numerical simulation based on various submergence ratios is done using FLOW-3D software to analyze. The results showed an increase in dimensions and the number of vortices associated with an increase in submergence ratio so that for the amount of 50% submergence, two vortices form around outer wall and an area downstream of the wing of spur dike, at bed level. Moreover, the length and width of separation zones were estimated to be 1.6 and 1.5 times larger compared to nonsubmerged condition, respectively.
As one of the most important components of an offshore oil and gas complex, Catwalk (access bridge) provides support for equipment and act as a passage for staff. Therefore, any damage in this structure may result in casualties as well as financial and environmental losses. Hence, identifying the location and severity of damage in these structures is of a great importance. As a common SHM method, modal strain energy uses the changes in the dynamic properties of the structure for identifying the damage location and severity. Considering natural frequencies in the process of the damage localization is one of modifications that has been successfully applied to this method. In order to show the robustness of this method for identifying damages in real class offshore structures with a large number of elements, the improved modal strain energy (IMSE) method is applied for damage localization and quantification in the access bridge of Foroozan platform in the Persian Gulf. The results showed that the IMSE damage index is more accurate than the original Stubbs index. Both the single and multiple damages were predicted with a good accuracy with this method. However, the method was more accurate in locating the damages in horizontal elements as well as the elements far from the supports of the structure.
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