zahra omrani

This paper proposes a homotopy analysis method to simulate Wave-perforated breakwaters interaction. This method is an analytic technique for strongly nonlinear problems. The solid boundary condition is used for analyzing the problem. It is extremely complicated for wave motion through a permeable plate accompanied with the wave energy dissipation and phase shift. Thus, some assumptions are needed in the theoretical study to ease solution. The method of assuming the permeable plate to be a rigid homogeneous porous medium is generally employed. The flow of a fluid past a porous plate is considered. However, the plate thickness is neglected in solving the fluid regions around the breakwater because it is very small compared with the wavelength and water depth. An exact analytical solution of the governing non-linear differential equation is constructed using homotopy analysis method. It is observed that the relevant perturbation solution corresponds to a special case of the presented solution.

The purpose of risk management is managing the uncertainties by considering activities for identifying, assessing, monitoring, and reducing the impact of risks. Three strategies may be used to deal with the kind of risks that exist in projects: risk acceptance, risk transfer, and risk reduction. Events that can affect the economical goals of a project must be identified and evaluated so that they can be appropriately managed. Fixed jacket-type offshore platform (JTOP) as an expensive and necessary structure in energy facilities. in this research, the effect of knowledge increasing on the risk reduction and cost optimization for JTOP is studying. This paper focuses on optimizing the pile length of the fixed jacket-type offshore platforms and reducing the conservative design by using the risk reduction approach. Fixed offshore platform in South Pars Gas Fields of Iran as a case study.Increasing the Geotechnical knowledge and reducing the pile lengths is performed as considering similar geotechnical study at this regions and pile dynamic driving test (PDA), updating the pile bearing capacity base on increased knowledge for geotechnical data, and finally assessing the result based on inplace analyzing Pile driving result shows increasing the longterm soil bearing capacity, So first of all the required strength and parameters extracted from the existing data with analyzing and comparing where to adjust and matches with the lower limit of the theoretical equations. Finally, this new assumption is used for optimizing the pile length design. This research shows that that the numerical analysis and assumptions that have been used in the design procedure are conservative and a proper risk management program with the knowledge increasing could have resulted in risk reduction. The analysis process that has been used in the present research leads to the pile cost reduction by 11% that is considerable for stakeholders in such an expensive structure. The most important innovation in this paper is the use of the results of pile driving operation for optimal pile design because, in pile driving operation, piles with design diameter are used.

Fixed pile-founded offshore platforms require careful consideration during their analysis, design, and assessment because uncertainty in design variables can decrease the reliability of the structures. The present study investigated the sensitivity of seismic engineering demand parameters to stochastic and epistemic modelling variables for a fixed pile-founded jacket platform. Tornado diagram analysis and the first-order second-moment techniques were employed to examine the effects of 11 variables on engineering demand parameters under real earthquake loads and the importance of each variable was determined. As the nonlinear response of the pile foundation is a crucial source of nonlinearity in offshore platform response, a robust model considering soil-pile-structure-fluid interaction was employed. This study varied from previous research as it employed a three-dimensional model, fluid environment modelling, and earthquake actions in perpendicular directions. These differences resulted in more realistic approximations of the seismic behaviour of the platforms. It was found that the effects of different variables, especially water depth, should be considered in order to produce better performance evaluations of a structure for a more efficient and cost-effective design.

In this paper, a numerical study of the dynamic propagation of buckles initiated in long pipes under external pressure is presented. The model accounts for the inertia of the pipe, the nonlinearity introduced by contact between the collapsing walls of the pipe while the material is modeled as a finitely deforming elastic plastic solid. The buckling and collapse are assumed to take place in vacuum. The numerical results, obtained from nonlinear finite element analysis are compared with the results of the experimental study on small-scale models, undertaken by Kyriakides & Netto (2000). Comparison shows that the finite element results have very close agreement with the experimental behavior. The effect of external pressure on the velocity of dynamic buckle propagation for different diameter to thickness ratios is separately investigated and their proper relations are derived.