Statistical Uncertainties in Wave Heights and Combined Loads on Offshore Structures

1991 ◽  
Vol 113 (2) ◽  
pp. 156-161
Author(s):  
S. R. Winterstein ◽  
S. Haver
Keyword(s):  
Environmental Variables ◽  
Probabilistic Models ◽  
Offshore Structures ◽  
Annual Maximum ◽  
Storm Events ◽  
Base Shear ◽  
Combined Loads ◽  
Wave Heights ◽  
Gumbel Model ◽  
Non Gaussian

Probabilistic models of combined environmental variables are shown, and their effect on the probability distribution of annual maximum base shear is estimated. A new “generalized Gumbel” model is introduced for the critical wave height parameter. By preserving higher statistical moments, this model better follows extreme storm events. Uncertainty in this model is included through statistical uncertainty in these moments. Corresponding reliability confidence intervals are also shown as a function of the sample size of hindcast data. Finally, models of the non-Gaussian crest and the drag parameter are found to be of similar importance in predicting the 100-yr base shear.

Erosion monitoring of coastal cliffs of geoheritage significance – an example from north east England.

2020 ◽  
Author(s):  
Lesley Dunlop ◽  
Matthew J Westoby ◽  
Michael Lim
Keyword(s):  
Environmental Variables ◽  
Laser Scanning ◽  
Cost Effective ◽  
Storm Events ◽  
Storm Activity ◽  
North East ◽  
Environmental Controls ◽  
Coastal Cliffs ◽  
Wave Heights ◽  
Offshore Wave

<p>The coastline of County Durham and Tyne and Wear, north east of England, is of geological interest as it displays extensive cliff and foreshore exposures of the dolomites and limestones of later Permian age. The coastline is covered by multiple designations ranging from being a Site of Special Scientific Interest for geological factors to other forms of national and international protection. However, the high cliffs and nature of the deposits means that it is subject to much erosion, rockfalls and exposure to storm activity. For this reason, a lengthy monitoring programme using terrestrial laser scanning (Westoby et al, 2018), photogrammetry (Westoby et al, 2012) and geophysical techniques has been taking place in order to characterise the erosion, recognise points of issue and recommend potential action.</p><p> </p><p>The carbonate rocks, also known as the Magnesian Limestone, were deposited in the Zechstein Sea in a relatively shallow landlocked sea. Straddling latitude 30° north during Late Permian times, the Zechstein Sea was subjected to high evaporation rates leading to evaporate sequences being present. The Permian concretionary limestone is most common in the headlands, stacks and arches, whereas the bays are cut into a weaker dolomite. Marsden Bay includes beach, rock and cliff features and is a classic locality for beach process studies (King, 1953). Whitburn was previously a quarry and coal mine, later infilled and now subject to erosion, undercutting and sink hole appearance.</p><p> </p><p>Rockfalls are often characterised as episodic and unpredictable events, leading to uncertainty and risk for infrastructure and people. As a result of the monitoring it is possible to demonstrate that there are lithologically distinct responses to the passage of the largest storm events.  Foreshore morphology is significant for modulating the relative importance of subaerial and marine erosion drivers. The influence of external environmental controls, notably storm activity, is clearly detectable through regression analysis of rockfall descriptors and environmental variables. Increased storminess, associated with increases in offshore wave heights and cumulative precipitation, corresponds with an increase in total and mean rockfall volume rockfalls at the cliff top during these periods.</p><p> </p><p>The study demonstrates that it is possible to quantify links between environmental variables, in this case offshore wave heights, and erosion prediction. From a hazard and geosite management perspective this finding and framework is significant because it represents an effective new tool for quantifying temporal convergence in rockfall dynamics at lithologically complex rocky coasts over timescales that are relevant for hazard assessment.</p><p> </p><p>King, C.A.M. (1953) The relationship between wave incidence, wind direction and beach changes at Marsden Bay, County Durham. Transactions of the Institute of British Geographers, 19, 13–23.</p><p>Westoby, M.J., Brasington, J., Glasser, N.F., Hambrey, M.J., and Reynolds, J.M., 2012, ‘Structure-from-Motion’ photogrammetry: A low-cost, effective tool for geoscience applications: Geomorphology, v. 179, p. 300-314, https://doi.org/10.1016/j.geomorph.2012.08.021 .</p><p>Westoby, M.J., Lim, M., Hogg, M., Pound, M.J., Dunlop, L., and Woodward, J., 2018, Cost-effective erosion monitoring of coastal cliffs: Coastal Engineering, v. 138, p. 152-164, https://doi.org/10.1016/j.coastaleng.2018.04.008.</p>

scholarly journals Modelling with star-shaped distributions

2020 ◽  
Vol 8 (1) ◽  
pp. 45-69
Author(s):  
Eckhard Liebscher ◽  
Wolf-Dieter Richter
Keyword(s):  
Probabilistic Models ◽  
Arbitrary Dimension ◽  
Probability Density Functions ◽  
Density Functions ◽  
Wide Range ◽  
Gaussian Density ◽  
Spherical Distributions ◽  
Data Points ◽  
Non Gaussian ◽  
General Method

AbstractWe prove and describe in great detail a general method for constructing a wide range of multivariate probability density functions. We introduce probabilistic models for a large variety of clouds of multivariate data points. In the present paper, the focus is on star-shaped distributions of an arbitrary dimension, where in case of spherical distributions dependence is modeled by a non-Gaussian density generating function.

scholarly journals Comprehensive Wind and Wave Statistics and Extreme Values for Design and Analysis of Marine Structures in the Adriatic Sea

2021 ◽  
Vol 9 (5) ◽  
pp. 522
Author(s):  
Marko Katalinić ◽  
Joško Parunov
Keyword(s):  
Adriatic Sea ◽  
Extreme Values ◽  
Wave Climate ◽  
Offshore Structures ◽  
Model Parameters ◽  
Peak Period ◽  
Significant Wave ◽  
Wave Statistics ◽  
Wave Heights ◽  
Almost All

Wind and waves present the main causes of environmental loading on seagoing ships and offshore structures. Thus, its detailed understanding can improve the design and maintenance of these structures. Wind and wave statistical models are developed based on the WorldWaves database for the Adriatic Sea: for the entire Adriatic Sea as a whole, divided into three regions and for 39 uniformly spaced locations across the offshore Adriatic. Model parameters are fitted and presented for each case, following the conditional modelling approach, i.e., the marginal distribution of significant wave height and conditional distribution of peak period and wind speed. Extreme significant wave heights were evaluated for 20-, 50- and 100-year return periods. The presented data provide a consistent and comprehensive description of metocean (wind and wave) climate in the Adriatic Sea that can serve as input for almost all kind of analyses of ships and offshore structures.

scholarly journals Wave Height Distributions and Rogue Waves in the Eastern Mediterranean

2021 ◽  
Vol 9 (6) ◽  
pp. 660
Author(s):  
Sagi Knobler ◽  
Daniel Bar ◽  
Rotem Cohen ◽  
Dan Liberzon
Keyword(s):  
Wave Height ◽  
Eastern Mediterranean ◽  
Rogue Waves ◽  
Distribution Model ◽  
Storm Events ◽  
Order Model ◽  
Deep Seawater ◽  
Wave Heights ◽  
Storm Characteristics ◽  
Buoy Data

There is a lack of scientific knowledge about the physical sea characteristics of the eastern part of the Mediterranean Sea. The current work offers a comprehensive view of wave fields in southern Israel waters covering a period between January 2017 and June 2018. The analyzed data were collected by a meteorological buoy providing wind and waves parameters. As expected for this area, the strongest storm events occurred throughout October–April. In this paper, we analyze the buoy data following two main objectives—identifying the most appropriate statistical distribution model and examining wave data in search of rogue wave presence. The objectives were accomplished by comparing a number of models suitable for deep seawater waves. The Tayfun—Fedele 3rd order model showed the best agreement with the tail of the empirical wave heights distribution. Examination of different statistical thresholds for the identification of rogue waves resulted in the detection of 99 unique waves, all of relatively low height, except for one wave that reached 12.2 m in height which was detected during a powerful January 2018 storm. Characteristics of the detected rogue waves were examined, revealing the majority of them presenting crest to trough symmetry. This finding calls for a reevaluation of the crest amplitude being equal to or above 1.25 the significant wave height threshold which assumes rogue waves carry most of their energy in the crest.

scholarly journals ON THE IMPORTANCE OF CONSIDERING MULTIPLE SEASTATE REALIZATIONS WHEN ESTIMATING DESIGN LOADS IN MULTI-DIRECTIONAL SHALLOW-WATER WAVES

2020 ◽  
pp. 46
Author(s):  
Andrew Cornett ◽  
Scott Baker
Keyword(s):  
Shallow Water ◽  
Water Waves ◽  
Offshore Structures ◽  
Scale Model ◽  
Offshore Structure ◽  
Wave Condition ◽  
Directional Waves ◽  
Wave Heights ◽  
Design Loads ◽  
Peak Pressures

The objectives of this work are to close some of the knowledge gaps facing designers tasked with designing new offshore structures or upgrading older structures located in shallow waters and exposed to energetic multi-directional waves generated by passing hurricanes or cyclones. This will be accomplished by first investigating and characterizing the natural variability of the maximum wave heights and crest elevations found in multiple 2-hour long realizations of several short-crested shallow-water near-breaking seastates. Following this, the variability and repeatability of peak pressures and peak loads exerted on a 1/35 scale model of a gravity-based offshore structure are explored. The analysis focuses on establishing extreme value distributions for each realization, quantifying their variability, and exploring how the variability is diminished when results from multiple seastate realizations and repeated tests are combined. The importance of considering multiple realizations of a design wave condition when estimating peak values for use in design is investigated and highlighted.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/16bCsMd0OMc

Scale Effect in Ice Flexural Strength

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Mohamed Aly ◽  
Rocky Taylor ◽  
Eleanor Bailey Dudley ◽  
Ian Turnbull
Keyword(s):  
Flexural Strength ◽  
Sea Ice ◽  
Probabilistic Models ◽  
Scale Effects ◽  
Offshore Structures ◽  
Bridge Piers ◽  
Freshwater Ice ◽  
Flexural Failure ◽  
Ice Loads ◽  
Ice Strength

Ice flexural strength is an important parameter in the assessment of ice loads on the hulls of ice-class ships, sloped offshore structures, and sloped bridge piers. While scale effects in compressive ice strength are well known, there has been debate as to the extent of scale effects in ice flexural strength. To investigate scale effects during flexural failure of both freshwater and saline ice, a comprehensive up-to-date database of beam flexural strength measurements has been compiled. The database includes 2073 freshwater ice beam tests with beam volumes between 0.00016 and 2.197 m3, and 2843 sea ice beam tests with volumes between 0.00048 and 59.87 m3. The data show a considerable decrease in flexural strength as the specimen size increases, when examined over a large range of scales. Empirical models of freshwater ice flexural strength as a function of beam volume, and of saline ice as function of beam and brine volumes have been developed using regression analysis. For freshwater ice, the scale-dependent flexural strength is given as: σf=839(V/V1)−0.13 For sea ice, the dependence of flexural strength has been modeled as: σ=1324(V/V1)−0.054e−4.969vb. Probabilistic models based on the empirical data were developed based on an analysis of the residuals, and can be used to enhance probabilistic analysis of ice loads where ice flexural strength is an input.

scholarly journals The effects of road crossings on stream macro-invertebrate diversity

2019 ◽  
Vol 29 (3) ◽  
pp. 729-745 ◽  
Author(s):  
Blanka Gál ◽  
András Weiperth ◽  
János Farkas ◽  
Dénes Schmera
Keyword(s):  
Alien Species ◽  
Environmental Variables ◽  
Human Population ◽  
Knowledge Gap ◽  
Storm Events ◽  
Freshwater Biodiversity ◽  
Negative Effects ◽  
Invertebrate Diversity ◽  
Negative Effect ◽  
The Subject

AbstractAlthough it is well known that the increasing size of the human population has a negative effect on freshwater biodiversity, the subject of whether or how the intersection of roads and streams (hereafter road crossings) influence the diversity of stream macro-invertebrates is under-researched. To fill this gap in our knowledge, we collected stream macro-invertebrates from road crossings (bridges and culverts) and compared their diversity with upstream and downstream sections. We found that road crossings had negative effects on the richness and abundance of native macro-invertebrates, as well as on the number of protected taxa. Our results showed also that alien individuals were more abundant at road crossings. These findings support the assumption that road crossings contribute to the spread of alien species. The assessment of environmental variables indicated that road crossings caused habitat modifications, and based on these it can be assumed that habitat modifications and associated phenomena (e.g. pollutants and storm events) were the major drivers of the observed patterns in biodiversity. Our results fill a knowledge gap and contribute to the deeper understanding of the effect of road crossings on freshwater biodiversity.

Vehicle Risk Level Estimation by Using Experimental Trajectories in Bend

2011 ◽  
Author(s):  
Abdourahmane Koita ◽  
Dimitri Daucher ◽  
Michel Fogli
Keyword(s):  
Probability Density ◽  
Reliability Analysis ◽  
Probabilistic Models ◽  
Hermite Polynomials ◽  
Probabilistic Methods ◽  
Risk Level ◽  
General Context ◽  
Risk Levels ◽  
Modelling Uncertainties ◽  
Non Gaussian

This paper tackles the general context of road safety, focussing on the light vehicles safety in bends. It consists to use a reliability analysis in order to estimate the failure probability of vehicle trajectories. Firstly, we build probabilistic models able to describe measured trajectories in a given bend. The models are transforms of scalar normalized second order stochastic processes which are stationary, ergodic and non-Gaussian. The process is characterized by its probability density function and its power spectral density estimated starting from the experimental trajectories. The probability density is approximated by a development on the Hermite polynomials basis. The second part is devoted to apply a reliability strategy intended to associate a risk level to each class of trajectories. Based on the joint use of probabilistic methods for modelling uncertainties, reliability analysis for assessing risk levels and statistics for classifying the trajectories, this approach provides a realistic answer to the tackled problem.

Assessing Climate Change in the North Atlantic Wave Regimes

2020 ◽  
Author(s):  
M. Bernardino ◽  
M. Gonçalves ◽  
C. Guedes Soares
Keyword(s):  
System Integration ◽  
Wave Model ◽  
Offshore Structures ◽  
Future Climate ◽  
Wave Direction ◽  
Peak Period ◽  
Significant Wave ◽  
The North ◽  
Wave Heights ◽  
Mean Wave Period

Abstract An improved understanding of the present and future marine climatology is necessary for numerous activities, such as operation of offshore structures, optimization of ship routes and the evaluation of wave energy resources. To produce global wave information, the WW3 wave model was forced with wind and ice-cover data from an RCP8.5 EC-Earth system integration for two 30-year time slices. The first covering the periods from 1980 to 2009 represents the present climate and the second, covering the periods from 2070–2099, represents the climate in the end of the 21st century. Descriptive statistics of wind and wave parameters are obtained for different 30-year time slices. Regarding wind, magnitude and direction will be used. For wave, significant wave height (of total sea and swell), mean wave period, peak period, mean wave direction and energy will be investigated. Changes from present to future climate are evaluated, regarding both mean and extreme events. Maps of the theses statistics are presented. The long-term monthly joint distribution of significant wave heights and peak periods is generated. Changes from present to future climate are assessed, comparing the statistics between time slices.

scholarly journals Wave current interaction: Effect on force prediction for fixed offshore structures

2018 ◽  
Vol 203 ◽  
pp. 01011
Author(s):  
Mohamed Latheef ◽  
Nasir Abdulla ◽  
Mohd Faieez Mohd Jupri
Keyword(s):  
Vertical Structure ◽  
Offshore Structures ◽  
Base Shear ◽  
Sea State ◽  
Clear Trend ◽  
The North ◽  
Relative Water ◽  
The North Sea ◽  
Current Interaction ◽  
Typical Design

MetOcean conditions in the South China Sea (SCS) indicates that unlike other locations such as the North Sea, the magnitude of the currents can be relatively large. In addition, these currents are strongly sheared. The present study focused on the typical design problem of calculating the ultimate base shear and overturning moments for slender fixed structureswiththe inclusion of the interaction between the currents and the wave field. It has been found that the loads on average can be around 15% larger when this interaction is accounted for in the calculation of the loads, highlighting the importance. In addition, the level of these amplifications were found to be dependent on the sea state steepness and the relative water depth. While no clear trend was found (changed case by case) in the present work, incorporating the vertical structure of the current was found to change the pattern of the amplification of the loads.

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