Finite Element Numerical Method for Nonlinear Interaction Response Analysis of Offshore Jacket Affected by Environment Marine Forces

In this paper a nonlinear response of a fixed offshore platform under the combined forces of waves, wind and sea currents is presented. Wave force acting on the elements is calculated using Morison equation. Hydrodynamic loads on horizontal and vertical tubular members and the dynamic response of offshore fixed platform coupled with distribution of displacement, axial force, and bending moment along the base of the platform for regular and severe cases have been investigated. The structure must be able maintain production in a one-year wave return period condition and also to be able to continue with one hundred-year storm return period. The results of this study show that bending moment values with a one-year wave return period condition for the base platform and junction of platform to deck are 70 percent and 59 percent, respectively more than bending moment with a one-year wave return period. The direction of wave and wind hit has significant effects on the shift platform response, also nonlinear response is important for the safe design and operation of offshore structures.

Analyzing Factors Affecting Erosion and Sedimentary Deposits Using the Empirical Method of PSIAC

PSIAC empirical method is considered as one of the methods calculating and estimating the amount of erodibility and sedimentation of sedimentary deposits in sedimentary basins and dams’ reservoirs. This method is based on analyzing nine influential factors including: surface geology, solid, weather, runoff, unpaved area, limited plant coverage, land usage, high lands erosion, river erosion and sediment transportation. These factors are rated according to their level of importance. The case study of this research is Lali Water Catchment, Khuzestan, Iran. The amount and intensity of adorability will be ranked as low, moderate and high. This research is based on field work, laboratorial studies and analyzing results obtained from statistics. Results indicated that the unpaved area and high land erosion are identified as the most effective factors, respectively. In contrast, runoff and surface geology are considered as the lowest rate. Other factors reflect moderate effects. Since any significant studies have not been done in this regard, the current research can present a new method to scrutinize the empirical effects of these factors. It is noteworthy to highlight that different methods are compared with each other in order to scrutinize the amount of erodibility in most studies, but the present study has analyzed the influential factors of the sub-methods of one major method. This essay focuses on the affectability of each one of the nine factors, independently. In conclusion, the outcomes of this research can contribute to identify and determine suitable alternatives to stabilize sedimentary basins and increase the life span of dams and watershed management projects and also reduce the destructive effects of floods. Additionally, it contributes civil projects in such lands.

Investigation of sediment transport pattern and beach morphology in the vicinity of submerged groyne （case study： Dahane Sar Sefidrood）

Marine structures, such as Groynes, Sea walls and Detached Breakwaters, are constructed in coast of area to improve coast stability against bed erosions due to changing wave and current pattern. Marine mechanisms and interaction with the hydraulic structures need to be intensively studied. Groynes are one of the most prominent structures that are used in shore protection and littoral sediment. The main hydraulic function of the groyne is to control the long shore current and littoral sediment transport. This structure can be submerged and provide the necessary beach protection without negative aesthetic impact. However, for submerged structures adopted for beach protection, the shoreline response to these structures is not well understood. The objective of this study is to predict sediment transport in the vicinity of submerged groyne and comparison with non-submerged groyne focusing on a part of the coast at Dahane Sar Sefidrood, Guilan Province, Iran, where serious coast erosion has been occurred. The simulations were designed using a one-line model which can be used as a first approximation of shoreline prediction in the vicinity of groyne. The results of the proposed model are compared with experimental data to determine the shape of the coast. The results of predicted beach deformation show that when submerged groyne construct in the beach, sediment accumulation will be slightly less than the non-submerged groyne; because transfer coefficient for the submerged groyne is more than non-submerged groyne. This result will cause more sediment passing on submerged groyne. Finally, the result of the present study show that using submerged groyne is an efficient way to control the sediment and beach erosion without causing severe environmental effect on the coast.