فهرست مطالب

  • Volume:4 Issue: 16, 2019
  • تاریخ انتشار: 1398/07/09
  • تعداد عناوین: 6
  • Fatemeh Ghanbari*, Mehdi Adjami, H.Soheil Ataei Pages 1-8

    Measuring cross-shore profiles is very important in coastal engineering studies, since the cross-shore profile determines the behavior of the sea in the coastal area and determines the process of depth changes in this region. As a result of waves, cross-shore profiles change, which will vary in stormy waves (erosion profile) in compare to normal wave conditions (cumulative profile). Considering the great changes in the Caspian Sea level, the purposes of this study are to investigate and determine the erosion or accumulation of coastal profiles based on Sunamura and Horikawaꞌs studies , determine the number of bars in profiles by Short and Aagaardꞌs equations and also determine the relations between coastal parameters with the wave steepness and changes in water level. The results show that for all the coastal areas in the Caspian Sea, the C-parameter is above 8; in other word a stormy erosional nature is dominant. Also according to  -parameter, for all regions the values are above 100 which means a very high possibility to form multi bars profiles (three bars) very high. As the wave's steepness rises, the location of the formation of the bars moves toward the coast, and the depth of water decreases at the beginning and the ends of the bars; also, in terms of lowering in the water level with the change in the height of the waves, the position and the geometric shape of the bars will not follow a certain trend

    Keywords: Cross-shore, Profile, Bars, Erosion profile, Geometric shape, steepness
  • Seyed MohammadHossein Sharifi*, Mahdi Tasdighi Pages 9-15

    Subsea pipelines due to the reduction of transfer costs and expedite the offshore operations is one of the all-purpose structures in marine industries. Subsea pipelines are exposed to a variety of hazards, including corrosion and fatigue Etc. Free span exacerbates the fatigue required parameters due to a phenomenon called the Vortex Induced Vibration (VIV). In this research, the influence of the span's length on the free span subsea pipeline has been reviewed with ABAQUS standard code. In this study the previous result has been expanded. The results of the VIV fatigue life are extensible to all of the depth. Achieved Results indicate that the fatigue life of the pipeline even in the worst condition is much higher than the required amount that it represents the upstream design of DNV-RP-F105. In this study the backrest pipeline has been investigated and result show that the pipeline under the different conditions in the backrest, by creating more vibration and displacement on one side of the pipeline reduces the fatigue life of 113 percent compared to snap. The VIV fatigue life has undergone a lot of changes due to span length changes, maximum changes occur between cable and behavioral which the amount of these changes is reduced by 75%. The free span length is another factor in VIV fatigue. VIV fatigue life will be increased by reducing the span length. As well as increasing the flow velocity that is the main factor in creating the VIV is increased fatigue. Therefore, in terms of the accuracy in the choice of the existing conditions of very high importance for the pipeline. Comparison between effect parameters in VIV fatigue life was shown that span length is the most effective parameter.

    Keywords: Upheaval Buckling, Pipeline, ABAQUS, Vortex Induced Vibration, Free Span
  • Sirous Yasseri* Pages 17-31

    A fundamental challenge facing security professionals is preventing loss; be that asset, production, or third-party losses. This is not dissimilar to what safety professionals have to face. Techniques and methodologies used by the safety professionals could potentially benefit the security experts. Physical security is about taking physical measures to protect personnel and prevent unauthorized access to installations, material, and documents, which also include protection against sabotage, willful damage, and theft. The characteristics of physical security controls include measures for deterrence, detection, delay, and responses aimed at risk mitigation and enhanced operational effectiveness.This paper outlines a systems engineering framework for implementing security goals, which are suitable for meeting the challenge of providing physical security for complex systems, which includes oil and gas facilities.  The proposed framework builds security requirements into system requirements and moves it in parallel with the system development for the entire system’s life cycle; particularly during the concept and design phases. This is a top-down process for use by a multidisciplinary team of security, operations, and industry experts to identify and prevent the system from entering into vulnerable states which could lead to losses. This framework shifts the focus of the security analysis away from threats, being the immediate cause of losses, and focuses instead on the barriers, i.e. safeguards that prevent systems from entering into vulnerable states, which would allow an unfolding event to disrupt the system leading to loses.The need for such a method comes from the recent experience of the securing complex systems that combine a large amount of hardware, software hazardous materials, and control elements. The method takes advantage of systems engineering and encourages the use of goal-based security requirements instead of using a strict prescriptive approach that is common among security professionals.  Using this framework helps both to identify threats associated with the system, as well as weak points within the system. This framework also encourages communication between the security professional, safety engineers, and system designers. This paper draws from the existing literature as listed in the references.

    Keywords: Physical Security, Security Assurance, Systems Engineering, Defence in depth, Security threats
  • AmirReza Valyani, Naser Feghhi Farahmand*, Soleyman Iranzadeh Pages 33-42

    Today complicated and risky environment makes risk assessment and identification one of the main steps of proper project management and realization of project objectives. Marine construction projects are key and strategic projects, and their specific nature adds to their importance. This study aimed to propose a method for risk assessment and ranking critical risks in marine construction projects in Iran. To this end, the risk assessment team was formed to identify serious marine construction project risks using risk breakdown structure. Afterward, the team defined risk assessment measures. All risks were assessed in each criterion based on the Taguchi loss function. It allowed decision-makers to define a measurable risk threshold for each criterion and assess risks by developing a common language called loss score. Finally, critical risks were determined based on their priority. The results can be used to improve effective risk management, and consequently, project management.

    Keywords: Marine projects, construction projects, risk assessment, project risk management, Taguchi loss function
  • MahmudReza Abbasi* Pages 43-46

    Wind waves are one of the most important phenomena that should be considered in coastal and offshore activities. They have many effects on coastal environments such as wave-induced erosion, sediment and pollution transport and even in the worst cases destruction the marine ecosystems. Therefore, knowing the wave characteristics is very important for environmental research. In this paper, the accuracy of CEM semi-empirical method in forecasting the wind-induced waves characteristics in the Strait of Hormuz (SOH) have been studied. Initially, the characteristics of the waves have been calculated by employing the CEM based on wind data from local synoptic stations. Then, the evaluating process have been done by comparing the forecasting values (wave heights and periods) of this method with same recorded value of wave buoys in the SOH. According to the performed study, the accuracy of semi-empirical method in forecasting wave characteristics were in close agreement with measurements values and the SMB method is suitable for determining the wave characteristics in this area. The results show that there is a good correlation coefficient between observations and forecasting data in the CEM and the CEM method has a very small bias error. So, this method is suitable for determination the wave characteristics in this area.

    Keywords: Wind Wave, CEM, modeling, Hormuz Strait, Forecasting
  • Negar Sadeghi Gargari*, Hassan Akbari, Roozbeh Panahi Pages 47-52

    A combination of linear and non-linear models results in a more accurate prediction in comparison with using linear or non-linear models individually to forecast time series data. This paper utilizes the linear autoregressive integrated moving average (ARIMA) model and non-linear artificial neural network (ANN) model to develop a new hybrid ARIMA-ANN model for prediction of container vessel traffic volume. The suggested hybrid method consists of an optimized feed-forward, back-propagation model with a hybrid training algorithm. The database of monthly traffic of Rajaee Port for thirteen years from 2005-2018 is taken into account. The performance of the developed model in forecasting short-term traffic volume is evaluated using various performance criteria such as correlation coefficient (R), mean absolute deviation (MAD), mean squared error (MSE) and mean absolute percentage error (MAPE). The developed model provides useful insights into container traffic behavior. Comparing the results with the real data-sets demonstrates the superior performance of the hybrid models than using models individually in forecasting traffic data.

    Keywords: Forecasting Container Traffic, Neural Network, ARIMA model, Hybrid ARIMA-NN Model