فهرست مطالب

  • Volume:3 Issue:11, 2018
  • تاریخ انتشار: 1397/05/01
  • تعداد عناوین: 6
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  • Alireza Sadat Hosseini , Mohammad Lesani , Mohammad Reza Bahaari Pages 1-9
    The relative stress concentration factors (SCF) on the chord member of a tubular T-joint strengthened with FRP which is subjected to brace axial loading are studied. ABAQUS Finite Element software package is used to perform the numerical analyses. Prior to the main studies, the unstiffened joint was validated against the API and Lloyd’s Register equations together with the experimental data. Six different types of FRP materials such as Glass/Vinyl ester, Glass/Epoxy (Scotch ply 1002), S-Glass/Epoxy, Aramid/Epoxy (Kevlar 49/Epoxy), Carbon/Epoxy (T300-5208) and Carbon/Epoxy (AS/3501) are used as strengthening material in order to enhance the fatigue life of tubular T-joints through lowering the SCFs. Promising results derived from analyses which show that FRP strengthening method can be considered as an effective method for decreasing the SCF values at tubular T-joints. Results of the analyses for 6mm CFRP layup revealed that under the action of axial loading the FRP strengthening could decrease the SCFs up to 30% and 50% at crown and saddle points of the chord member.
    Keywords: Tubular T-joint, Offshore Platforms, FRP-strengthening, SCF, Finite Element Analysis
  • Hasan Mirsane , Yaser Maghsoudi , Rohollah Emadi , Majid Mostafavi Pages 11-20
    The coastline is defined as an edge or land margin by the sea. Managing such ecological environments in terms of continuous changes requires monitoring at different intervals. To do this, it is necessary to use remote sensing techniques to detect and analyze coastline variations. Two study areas located on the coast of the Persian Gulf (South part of the Qeshm Island and the port of Tien to Asaluyeh) have been studied by two types of optical and radar images and wavelet edge detection algorithm for coastline extracting. In this study, the coastline is extracted in two ways, firstly the coastline extracts from both optical and radar images separately, then by images fusion using wavelet-IHS method. The accuracy obtained in Qeshm area in 2009 from optical, radar and fused images was 3.4, 5.5 and 3.2 respectively, and in Asaluyeh region in 2007, 2.1, 3.4 and 2.98 respectively.
    Keywords: Coastline Extraction, Radar, Landsat, Sentinel-1, ALOS, IRS, Fusion, Wavelet, IHS
  • Soheil Ataei H. , Amir Jabari Kh. , Amir Mohammad Khakpour , Mehdi Adjami , Seyed Ahmad Neshaei Pages 21-30
    Due to the great importance of sea level changes especially for coastal regions, identifying and studying the factors affecting these variations makes it easier to predict changes of sea level and will help to determine the riparian zone and changes in coastal lines. In this research, precipitation-evaporation is studied based on ERA-Interim model of ECMWF in order to estimate changes in Caspian Sea (CS) level and the validity of the results is evaluated in a period between 1980 to the end of 2015. Recorded data about the rivers entering the CS were also studied for better prediction of changes in water level. According to satellite and software analyses, in average evaporation has increased with a rate of 0.89 Km3/year, while precipitation and rivers discharge have decreased by the rates of 1.09 Km3/year and 1.41 Km3/year, respectively during the 36 years. The standard deviation of the sea level change caused by Volga discharge (normally entering 249.13 Km3/year into the sea alone) is closer to the recorded standard deviation obtained from change of CS level than the other two factors. Also, the lowest and the highest correlation coefficients relative to the recorded sea level changes were calculated considering simultaneous effect of precipitation-evaporation, and simultaneous effect of all parameters, respectively. As a conclusion, it can be said that the main reason for decreasing the CS level during recent years could be attributed to the rise of evaporation in comparison to precipitation and inlet rivers discharges.
    Keywords: Sea Level Change, Precipitation, Evaporation, Caspian Sea, Volga River, ERA-Interim
  • Sirous Yasseri , Hamid Bahai Pages 31-44
    This paper explores further and describes the System Readiness Level estimation for means of production in the oil and gas industry, through a case study. The concept as Technology Readiness Level (TRL) originally promoted by NASA and was then adopted by government agencies and industries across the USA and Europe. TRL was adopted by API (API 17N) and tailored for the assessing the readiness of subsea components for inclusion in subsea production systems. The API’s TRL has been recently extended by introducing two more metrics namely, the Integration Readiness Level (IRL) and the System Readiness Level (SRL). SRL is a mathematical combination TRL and IRL and is a metric for assessing progress in developing major subsea systems.
    Standard assessment metrics, such as Technology Readiness Levels (TRL), do not sufficiently evaluate the modern complex systems. Building on the previous publications [43] the SRL calculation method is expanded and expounded by adding a system engineering framework for the process of SRL estimation. Explained in some detail, in this paper, which produces more consistent results. Using an error averaging method, SRL is calculated by combining the TRL of each component with IRL, which expresses the readiness of each of these components to be integrated with other components of the system. To facilitate the calculation the Design Structure Matrix (DSM) is used both to visualise components and perform the necessary arithmetic
    Keywords: Oil, Gas Production system, Technology readiness level, Integration readiness level, System readiness level, System Architecture
  • Pedram Edalat , Mohammadsaeid Bagherinia Pages 45-55
    Complexity and costly nature of operations involving in the decommissioning process require huge investments to be done during the lifetime of the field for its decommissioning phase of the total project. This work offers a knowledge-based decommissioning alternative strategy selection system for fixed offshore jacket platforms in the Persian Gulf. In this method, the alternative option of installing offshore wind turbines (OWT) as the most probable economic feasible alternative to decommissioning on an abandoned platform jacket structure in the Persian Gulf is proposed. In this regard, costs and benefits study between two strategies are considered; one total decommissioning and the other installing an OWT on the jacket structure of a local platform in the region. It is found that the second strategy is beneficial and saves near 9 million US dollars for company. Furthermore, the company earns the technology and experiences with OWT installation and operations and would be a technical leader in the region for coming years as well as improve the total rate of greenhouse gas emission production in the region.
    Keywords: Offshore platform, Decommissioning, Strategy selection, Offshore wind turbine
  • Mohammad Pakhirehzan , Maryam Rahbani , Hossein Malakooti Pages 57-65
    Marine areas are affected by different atmospheric phenomena such as wind and storm. In this research the effect of a large scale atmospheric phenomenon, known as Winter Shamal Wind, is investigated on the regime of currents and waves in the northwest part of the Persian Gulf. This wind normally occurs for the period of three to seven days, during December to early March. MIKE21 Coupled Model FM was applied to study the pattern of current and waves for this period. To provide the hydrodynamic data for the model and validate the simulated results, the wind data of ECMWF and mast meteorology of coastal synoptic station of Bushehr and wave data of buoy located offshore of Bushehr was used. The results indicated only a slight increase in current speed with no significant change in current direction during Winter Shamal Wind, showing a stable current pattern in northwest of the Persian Gulf. The significant wave height and wave propagation speed for the period of Winter Shamal Wind in comparison with the days prior to the wind show significant changes. The maximum wave speed in the area under investigation reaches up to 1 m/s and the significant wave height is almost 1 meter higher than that of normal situation.
    Keywords: Persian Gulf, winter Shamal wind, MIKE21