فهرست مطالب

International Journal of Coastal, Offshore and Environmental Engineering
Volume:5 Issue: 2, Spring 2020

  • تاریخ انتشار: 1398/12/22
  • تعداد عناوین: 6
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  • Sirous Yasseri * Pages 1-13

    The ISO requires a two-level seismic qualification, namely Extreme Level Earthquake (ELE) and Accidental Level Earthquake (ALE) where damages that do not lead to leak is acceptable. ISO accepts both the response spectrum method and the time history approach.  Since the spool-soil system behaves non-linearly, the time domain analyses must be performed for both levels. ISO requires 7 real earthquakes scaled for the site to be used for each seismic level and the system must pass at least 50% of the cases.  Best estimate soil models were developed to represent soil conditions at the manifolds locations in Part I. A set of 10 real earthquake time histories were propagated through the soil column for each location. The resulting ground motion at the surface was computed using a nonlinear model. The frequency-dependent ratio of spectra acceleration at the mudline to the stiff soil outcrop spectral acceleration (Spectral Amplification Ratio or SAR) was computed for each time history. The mean SAR was then used to modify the stiff soil hazard results from the PSHA to obtain design response spectra at the mudline. This is the second part of three interlinked papers summarises the state of art for the benefit of practitioners of subsea engineering.

    Keywords: Subsea Spools, Soil- spool interaction, ISO 19902, ISO 19901, earthquake, ALE, ELE
  • Mahdi Saleh, Rouhollah Amirabadi *, Mahdi Sharifi Pages 15-22
    Significant advantages of FPSO in the ability to transfer and extract from offshore wells have led to their widespread applications. Kind of different modules is installed on the top of these platforms, where one of the major engineering concerns is choosing the location of these modules on the FPSO platform deck in order to reduce the effects of environmental forces. Typically, these modules are analyzed and designed based on the maximum linear acceleration extracted from the ship's spectral analysis, using a quasi-static method. The main purpose of this research is the analytical study of these modules response under dynamic excitation due to the wave effect. This research has been done in two parts. First, the dynamic response of different parts of the ship's deck has been analyzed under the effect of wave force and proper location for these modules is recommended. For this purpose, first with modeling and analysis performed in MAXSURF software, the ship's dynamic responses at different points of the deck have been calculated. Then these modules have been analyzed against the deck response considering base isolation at the module bases in the second part. The obtained response has been applied to two modules as a case study in Sap2000 software. The result shows that base shear and displacement have a verity response in the function of base isolation stiffness. Due to the extension of the ship's deck and the serious differences in the acceleration spectrum at different locations of the deck, in order to select the optimal stiffness, the locations of the desired module must also be considered.
    Keywords: Floating Platform, Dynamic analysis, FPSO, time history analysis, Neoprene
  • Hamid Reza Feizian, Mehdi Shafieefar *, Roozbeh Panahi Pages 23-40
    Incorporation of a tuned liquid column damper (TLCD) into a semisubmersible drilling platform is numerically investigated in this paper. First, a governing equation for liquid fluctuation in the TLCD is derived for the planar motion of the TLCD in conjunction with the motion of the platform. Then, the real-time response of the platform under irregular waves is analyzed using radiation/diffraction theory in which TLCD loading is exerted on the platform at each time-step. This facilitates capture of the difference-frequency and sum frequency second order wave forces and the low-frequency motion of the platform. The results show that the effect of the rotational motion of the platform on the TLCD is significant and the TLCD has a reciprocal effect on this rotational motion of the platform. It is shown that the TLCD decreases the low-frequency motion of the platform and has no considerable effect on the wave-frequency motion. Also, the sensitivity of the platform motion to the main specifications of the TLCD is assessed by a parametric study.
    Keywords: Tuned liquid column damper, Semisubmersible platform, Low-frequency motion, Irregular waves
  • Reza Dezvareh *, Mahdi Shafaghat Pages 41-49
    In order to predict changes in coastal profile, it is necessary to investigate the sediment transport rate along the coast. Sediment transport is important in the areas of sedimentology, geomorphology, civil engineering and environmental engineering. The study of sediment transport is often performed to determine the location of erosion or deposition, the amount, timing and distance of its occurrence. Forecasting future coastline changes are as a result of the marine structural development. It provides the conditions for appropriate engineering decision-making. It also makes the grounds for sustainable use of the coast. When spot and local forecasts are necessary, models based on time series like support vector regression and Artificial Neural Network as new solutions are taken into consideration. These methods are one of the ways of machine learning. This study was investigated the importance of the offshore sediment transport rate in this research for the desired beach on the west coast of Hormozgan province. The littoral drift (LITDRIFT) model is used to get this type of transfer rate. To estimate evaluation of the longshore sediment transport rate by support vector machine (SVM); it will be needed two categories of data; one for data training and the other to check the machine for testing. The results of estimation of sediment transport rate using support vector regression and artificial neural network method showed the superiority of support vector regression over the neural network in both training and experimental groups of data.
    Keywords: Artificial intelligence, Long shore Sediment Transport, Support vector regression, Neural Network, coastal engineering
  • Danial Ghaderi, Maryam Rahbani * Pages 51-64
    Coastal cities are among the most important and sensitive regions in the world. They are constantly affected by marine and coastal processes such as waves, currents, and other geological-physical parameters such as sedimentation and deposition. These factors constantly change the shoreline. Thus, evaluation and management at coastal area are very important. In this study, the rate of shoreline changes in the coastal area of Bandar Abbas, south of Iran, was investigated using remote sensing technique and DSAS tools. Landsat 8, 7 and, 5 satellite and Sentinel-2A satellite images were used to detect the rate of changes. Images from the years 1990 to 2020 were selected with 5-year time-interval. Using the NSM, SCE, EPR, and LRR statistical indexes of the DSAS tool, erosion and accretion rates were calculated in about 50 km of shoreline length. According to the EPR index Nakhl e Nakhoda jetty and Shoor River estuary show the maximum and minimum rate of changes, with amount of +31.07 m/yr and +4.83 m/yr, respectively. The average rate of changes was calculated as +12.34 m/yr. We recognized this part of the shoreline as the most sensitive area and suggested that any further development in this area should be undertaken obsessively. Shoreline of urban area of Bandar Abbas generally shows positive rate of change less than +5 m/yr, with the average rate of +2.35 m/yr, which suggests development in this area is in slow pace. In general, only 4% of the shoreline of is detected with high accretion (20.5 to 31.5 m/year) and about 53% is recognized as low accretion (0.5 to 10.5 m/year).
    Keywords: Bandar Abbas, Rate of Shoreline Change, satellite images, Remote Sensing, Landsat, Sential
  • Maryam Kaveh, Majid Fattahi *, Rahman Ghaffari Pages 65-70
    This study aims to identify an appropriate model for developing the transit capacity, known as an instrument that countries use in relation to their geographical locations to diversify their income sources. In international aspects, developing transit capacity can also provide a country with other advantages in foreign affairs. Moreover, it is necessary to develop transit by Iran because of reducing economic vulnerability and increasing deterrence against hostile activities of Iran’s enemies. Therefore, transit opportunities and bottlenecks were identified in addition to reviewing previous studies and interviewing the experts. Considering the semi-structured and in-depth interviews given to 13 informed transit experts, this is a qualitative study in which the grounded theory was employed. Finally, the proper transit capacity development model was proposed by extracting causal, main category, intervening, and contextual conditions and outcomes.
    Keywords: port, transit, Amirabad Port, transit development algorithm, Grounded Theory (GT)