Design Point Effect Due to Severe Storm Conditions on the Reliability Assessment of Offshore Structures: Case Study

2005 ◽  
Author(s):  
Ahmed Mostafa Tawfik
Keyword(s):  
Wave Height ◽  
Environmental Conditions ◽  
Current Velocity ◽  
Offshore Structures ◽  
Structural Safety ◽  
Design Stage ◽  
Design Point ◽  
Reliability Method ◽  
Storm Wave

Structural reliability is of an intense significance for the evaluation of failure probability and safety levels of offshore structures in their structural design stage, especially when the variables are eminently random. Hence, the environmental conditions are considered among the most important parameters in the design of offshore structures whose effect of great contribution to structural safety. The 100 year storm wave height and current velocity constitute the majority of uncertainty in the environmental conditions. Eventually, these values are used as stochastic values i.e. mean values in addition to standard deviation. This paper uses the stochastic values of 100 year storm wave height and current velocity to estimate the probability of failure. These simulations had been encountered in the structural analysis and design on practical case study representing an offshore structure located in the Mediterranean Sea to predict the reliability level. The outcome of these simulations uses the Response Surface Method with design point technique for both stress and displacement limit states. The results of this Reliability method lead to an acceptable level for reliability analysis and risk assessments.

Reliability Analysis of Offshore Wind Turbines Using Copula

2018 ◽  
Author(s):  
Weifei Hu ◽  
Zhiyu Jiang ◽  
Yeqing Wang
Keyword(s):  
Reliability Analysis ◽  
Environmental Conditions ◽  
Joint Distribution ◽  
Environmental Parameters ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Design Stage ◽  
Offshore Structure ◽  
Distribution Models ◽  
Restricted Form

Offshore structures are subject to severe environmental conditions and require high operating and maintenance costs. At the design stage of an offshore structure, it is necessary to perform load analysis and to consider representative environmental conditions characterized by statistical models. However, many available joint distribution models of the environmental parameters can only describe the correlation of these parameters in a very restricted form. The use of simple probabilistic models without correctly addressing their correlation may lead to significant bias in the reliability analysis. Here, the correlation between three offshore environmental parameters including the significant wave height, wave peak period, and mean wind speed is described by copula. The copula density functions and theoretical derivations of copula correlation parameters using actual sea state data are provided for general applications of reliability analysis of offshore structures. Hindcast data of two representative sites are used to fit the best copula. The developed copula-based joint distribution can be used for accurate reliability analysis of offshore structures considering long-term fatigue loads and extreme responses.

Design Parameter Estimation Under Multivariate Extreme Ocean Environmental Conditions in the Bohai Sea

2007 ◽  
Author(s):  
Sheng Dong ◽  
Liang Wang ◽  
Xinyu Fu
Keyword(s):  
Parameter Estimation ◽  
Wind Speed ◽  
Wave Height ◽  
Environmental Conditions ◽  
Current Velocity ◽  
Bohai Sea ◽  
Distribution Model ◽  
Logistic Distribution ◽  
Mathematical Form ◽  
The Bohai Sea

On the basis of 21 years hindcasted data in the Bohai Sea, a Trivariate Nested Logistic Distribution model is utilized to calculate the joint probability of extreme environmental conditions, such as wind speed, significant wave height, and current velocity, which simultaneously occur during storm processes. Statistical analysis shows that this approach is simple in mathematical form, explicit in its expression, and can be easily applied to parameter estimation. It involves hierarchical dependence and can be applied to a wider field than the symmetric Logistic model. The ocean environmental contours in three demensions are created rather than the usual two. The contours as slices through return periods of wind speed is displayed to find the mode of wave height and current velocity. Based on the multivariate extreme value distribution theory, the determination of environmental parameter values will be objective and reasonable in engineering design.

Response Statistics of U-Oscillating Water Column Energy Harvesters Exposed to Extreme Storms: Application to the Case Study of Roccella Jonica (Italy)

2020 ◽  
Author(s):  
Felice Arena ◽  
Valentina Laface ◽  
Giovanni Malara ◽  
Saveria Meduri ◽  
Andrea Pedroncini
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Environmental Conditions ◽  
Extreme Event ◽  
Time History ◽  
Structural Safety ◽  
Sea Waves ◽  
Energy Harvesters ◽  
Storm Model

Abstract This article deals with the case study of a marina located in Roccella Jonica (Italy), where a wave energy harvester belonging to the family of U-Oscillating Water Columns (U-OWC) is going to be installed. U-OWCs are wave energy harvesters composed by a water column exposed to the action of random sea waves and an air pocket connected to the atmosphere by a Power Take - Off (PTO) system. In Roccella Jonica, this device is going to be embedded in a vertical breakwater expanding the main layout of the infrastructure. For ensuring the structural safety of the system, to characterize statistically its response peaks in severe environmental conditions is important. In this context, one of the main difficulties is utilizing appropriate environmental conditions representing real extreme events at the installation site. This article proposes to adopt the DNV trapezoidal storm model for representing the time history of an extreme event in conjunction with a nonlinear U-OWC model. Relevant Monte Carlo simulations show that the DNV storm model provides peak distributions that are rather close to the ones obtained by processing real storm time histories. Thus, it can be adopted for checking the performance of the system in extreme conditions.

The Concept of the Optimum Alignment of Discharge Pipelines Due to the Minimization of the Wave Forces

1992 ◽  
Vol 25 (9) ◽  
pp. 211-216
Author(s):  
A. Akyarli ◽  
Y. Arisoy
Keyword(s):  
Wave Height ◽  
Wave Force ◽  
Wave Forces ◽  
Wave Direction ◽  
Incoming Wave ◽  
Pipeline Route ◽  
Optimum Alignment ◽  
The Cost ◽  
Resultant Wave

As the wave forces are the function of the wave height, period and the angle between the incoming wave direction and the axis of the discharge pipeline, the resultant wave force is directly related to the alignment of the pipeline. In this paper, a method is explained to determine an optimum pipeline route for which the resultant wave force becomes minimum and hence, the cost of the constructive measures may decrease. Also, the application of this method is submitted through a case study.

scholarly journals Preventing Dampness Related Health Risks at the Design Stage of Buildings in Mediterranean Climates: A Cyprus Case Study

Buildings ◽  
2018 ◽  
Vol 8 (5) ◽  
pp. 66
Author(s):  
Ugochukwu Elinwa ◽  
Cemil Atakara ◽  
Ifeoluwa Ojelabi ◽  
Abiola Abiodun
Keyword(s):  
Health Risks ◽  
Design Stage

Method for Redesign of District Heating Networks within Transition from the 2nd to the 3rd Generation

2014 ◽  
Vol 657 ◽  
pp. 689-693
Author(s):  
Răzvan Corneliu Lefter ◽  
Daniela Popescu ◽  
Alexandrina Untăroiu
Keyword(s):  
District Heating ◽  
Design Stage ◽  
Heating Systems ◽  
Load Duration ◽  
Load Duration Curve ◽  
District Heating Systems ◽  
Consumption Rates ◽  
Heat Loads ◽  
Heating Networks

Important investmentsare made lately in the area of district heating, as a technology capable ofhelping countries to reach sustainability goals. In Romania, European fundswere spent for transition from the 2nd to the 3rdgeneration of district heating systems. The lack of appropriate monitoringsystems in old district heating systems makes optimisation nowadays very difficult,especially because nominal values used in the first design stage areoverestimated. Realistic nominal heat loads are necessary to make goodestimations of hydraulic parameters to be used for redesign. This studyproposes a method that uses the heat load duration curve theory to identify theappropriate nominal heat loads to be used for redesign. Comparison betweenresults obtained by applying the nominal heat loads of each consumer, as theywere established in the first design stage, and the ones identified by theproposed method are analyzed in a case study. The results show that errors arein the +/- 3% band, between the metered heat consumption rates and the proposedrates. The new method can be used for the sizing of pumps and district heatingnetworks after retrofit, in order to get better adjustments of the circulationpumps and increase of the energy efficiency.

Study on the impacts of peaking factors on a water distribution system in Germany

2010 ◽  
Vol 10 (2) ◽  
pp. 165-172 ◽  
Author(s):  
K. Diao ◽  
M. Barjenbruch ◽  
U. Bracklow
Keyword(s):  
Energy Consumption ◽  
Distribution System ◽  
Water Distribution ◽  
Water Distribution System ◽  
Water Distribution Network ◽  
Design Stage ◽  
Water Age ◽  
Specific System ◽  
Average Water

This paper aims to explore the impacts of peaking factors on a water distribution system designed for a small city in Germany through model-based analysis. As a case study, the water distribution network was modelled by EPANET and then two specific studies were carried out. The first study tested corresponding system-wide influences on water age and energy consumption if the peaking factors used at design stage are inconsistent with ones in real situation. The second study inspected the possible relationship between the choice of peaking factors and budgets by comparing several different pipe configurations of the distribution system, obtained according to variety of peaking factors. Given the analysis results, the first study reveals that average water age will increase if peaking factors estimated at design stage are larger than real values in that specific system, and vice versa. In contrast, energy consumption will increase if peaking factors defined for system design are smaller than ones in real case, and vice versa. According to the second study, it might be possible to amplify peaking factors for design dramatically by a slight increase in the investment on this system. However, further study on budget estimation with more factors and detailed information considered should be carried out.

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