Analysis and Probabilistic Modeling of the Unstationary Ice Loads Stochastic Process, Based on Experiments With Models of Offshore Structures

2015 ◽  
Author(s):  
Petr Zvyagin ◽  
Kirill Sazonov
Keyword(s):  
Stochastic Process ◽  
Time Series ◽  
Statistical Analysis ◽  
Probabilistic Modeling ◽  
Offshore Structures ◽  
Offshore Structure ◽  
Sample Mean ◽  
Ice Loads ◽  
Time Series Simulation ◽  
Fuzzy C Means Algorithm

Experiments with models of platforms and offshore structures with vertical and inclined panels, which were conducted at Krylov Research Center (St. Petersburg), demonstrated that sometimes ice loads time series registered in these experiments cannot be considered as stationary. At the same time until nowadays methods and algorithms of probabilistic modeling were mainly based on the assumption of ice loads time series stationarity. That is because the analysis and modeling for stationary stochastic process is easier than for those unstationary. In the paper the method for determining the presence of unstationarity in ice loads time series, based on statistical analysis, is described. This method employs sample mean normality. Fuzzy C-means algorithm is used to cluster autocorrelation vectors, which are built for different fragments of time series. In the paper ice loads time series, got in experiments in ice tank with offshore structure columns and basement models, are investigated on their unstationarity. The algorithm of unstationary ice loads time series simulation is offered.

Time Series Simulations of Wide-Band Spectra for Fatigue Tests of Offshore Structures

1984 ◽  
Vol 106 (4) ◽  
pp. 466-470 ◽  
Author(s):  
N. K. Lin ◽  
W. H. Hartt
Keyword(s):  
Time Series ◽  
Fatigue Testing ◽  
Wide Band ◽  
Simulation Method ◽  
Offshore Structures ◽  
Fatigue Tests ◽  
Time Series Model ◽  
Long Time ◽  
Band Spectra ◽  
Time Series Simulation

A time-series simulation method, based on the principle of time series modeling for dynamic systems, is used to reproduce a wide-band stress history from a prescribed stress spectral model for fatigue testing of offshore structures. The optimization procedures and stability of the time series model for the prescribed spectrum are presented and discussed. The optimization procedures are developed on the basis of the Levison-Durbin algorithm, which usually produces a stable time series model if the order of the time series model is even. An example is presented to demonstrate the applicability of the proposed method to long-time, high-cycle fatigue testing.

Study on Distribution Law and Stationarity of Global Ice Loads Registered in Experiments in Ice Tank

2016 ◽  
Author(s):  
Aleksei Dobrodeev ◽  
Petr Zvyagin ◽  
Kirill Sazonov
Keyword(s):  
Time Series ◽  
Offshore Structures ◽  
Research Center ◽  
Distribution Law ◽  
Size And Shape ◽  
State Research ◽  
Ice Loads ◽  
Process Variance ◽  
The Moment

Being confident in ice loads time series distribution law is extremely important for analysis, as well as for performing simulations. Strong autocorrelation, which usually exist in registered data, obstructs making outcomes on process distribution. Furthermore, at the moment there are only cautious suggestions exist about connection of ice loads distribution law with size and shape of structure or its fragment. In the paper new results about distribution law of ice loads time series, which were registered in experiments with indenters and models of offshore structures in Krylov State Research Center ice tank (St. Petersburg), are presented. Experiments with four thin indenters were taken in consideration. Also results of tests on process’ variance and means constancy for mentioned time series are presented. Such analysis was performed using methods and software, developed in St. Petersburg State Polytechnic University and Krylov State Research Center. As a result, hypotheses on ice loads stationarity are tested. Results are discussed.

Response Statistics of Moored Offshore Structures

1995 ◽  
Vol 117 (3) ◽  
pp. 159-165 ◽  
Author(s):  
T. Kinoshita ◽  
S. Takase
Keyword(s):  
Experimental Data ◽  
Time Series ◽  
Extreme Values ◽  
Offshore Structures ◽  
Theoretical Estimation ◽  
Floating Structure ◽  
Correlation Parameter ◽  
Random Seas ◽  
Limited Length ◽  
Time Series Simulation

This paper discusses the prediction of extreme values for total first and second-order responses of a floating structure moored in random seas. It is hard to estimate the extreme values from time series simulation or experimental data of limited length. Several methods of theoretical estimation of the extreme values are examined. They are the SRSS formula introduced by Naess (1987, 1989), the modified SRSS with a correlation parameter, the SRSS with Naess (1987, 1989) corection factor, the approximate SRSS (Naess, 1989), and the formula proposed by authors previously. The results of those methods are compared, and it is confirmed that the last one is very promising.

Results From Model Testing of Ice Protection Piles in Shallow Water

2006 ◽  
Author(s):  
Arne Gu¨rtner ◽  
Joachim Berger
Keyword(s):  
Model Test ◽  
Oil And Gas ◽  
Offshore Structures ◽  
Full Scale ◽  
Offshore Structure ◽  
Oil And Gas Fields ◽  
Ice Loads ◽  
Drifting Ice ◽  
Ice Model Test ◽  
Gas Fields

The development of oil and gas fields in shallow icy waters, for instance in the Northern Caspian Sea, have increased the awareness of protecting offshore structures by means of ice barriers from the impacts of drifting ice. Protection could be provided by Ice Protection Piles (IPPs), installed in close vicinity to the offshore structure to be protected. Piles then take the main loads from the drifting ice by pre-fracturing the advancing ice sheet. Hence, the partly shielded offshore structure could be designed according to significant lower global design ice loads. In this regard, various configurations of pile arrangements have been model tested during the MATRA-OSE research project in the Ice Model Test Basin of the Hamburg Sip Model Basin (HSVA). The main objective was to analyse the behaviour of ice interactions with the protection piles together with the establishment of design ice loads on an individual pile within the pile arrangement. The pile to pile distances within each arrangement were varied from 2 to 8 times the pile diameter for both, vertical and inclined (30° to the horizontal) pile arrangements. Two test runs with 0.1 m and 0.5 m thick ice (full scale values) were conducted respectively. The full scale water depth was 4 m. Based on the model test observations, it was found that the rubble generation increases with decreasing pile to pile distances. Inclined piles were capable to produce more rubble than vertical piles and considerable lower ice loads were measured on inclined arrangements compared to vertical arrangements. As initial rubble has formed in front of the arrangements, the rubble effect accelerated considerable. Subsequent to the build-up of rubble accumulations, no effect of the pile inclination on the exerted ice loads could be observed. If piles are used as ice barriers, the distance between the piles should be less than 4D for inclined piles and 6D for vertical piles to allow sufficient rubble generation. Larger distances only generated significant ice rubble after initial grounding of the ice had occurred.

Analysis and Probabilistic Modeling of the Stationary Ice Loads Stochastic Process With Lognormal Distribution

2014 ◽  
Author(s):  
Petr Zvyagin ◽  
Kirill Sazonov
Keyword(s):  
Stochastic Process ◽  
Stochastic Processes ◽  
Normal Distribution ◽  
Autocorrelation Function ◽  
Strain Gauge ◽  
Lognormal Distribution ◽  
Probabilistic Modeling ◽  
Stationary Stochastic Process ◽  
Strain Gauge Transducer ◽  
Ice Loads

Until recent times researchers who investigated ice loads stochastic processes usually stated the fact of normal distribution for them. In the paper the model of a stationary stochastic process with a lognormal distribution for ice loads is offered. This model relates to the strain gauge transducer ice loads measurements as well as to some examples considered in different papers that were published earlier. For this model dependencies of the autocorrelation function were found that allows to simulate the ice loads process relatively easily. The procedure of such a simulation is described in details and the example of the analysis and simulation ice loads measurements is provided.

scholarly journals Probabilistic Modeling of the Bio-Colonization Effects on Hydrodynamic Forces With Several Combinations of Sea-State Condition: A Study on Jacket-Platforms in the Gulf of Guinea

2013 ◽  
Author(s):  
Franck Schoefs ◽  
Hamed Ameryoun
Keyword(s):  
Probabilistic Modeling ◽  
Offshore Structures ◽  
Hydrodynamic Forces ◽  
Screen Effect ◽  
Gulf Of Guinea ◽  
Offshore Structure ◽  
Environmental Loading ◽  
Sensitivity Studies ◽  
Wind Sea ◽  
Support Cost

During the stage of designing or re-assessment of a jacket-type offshore structure, one of the most important phases is the re-evaluation of environmental loads, which are exerted by the waves, the wind and the currents, and updating the new data (e.g. meteocean, new regulation, structural damaging etc.). The former is mainly caused by the randomness or uncertainty nature of the marine environment as well as the presence of marine growth that makes the modeling of environmental loading more complicated. The general species of marine growth may be divided into two main categories: vegetable (e.g. algae) and animal (e.g. mussel, anemones, and corals). Indeed, the structures can be covered by many marine organisms quickly (in the first weeks). The influence of bio-colonization on an offshore structure can be measured at several levels: obstruct or prohibits a visual inspection of the subjacent support, cost of procedures of cleaning for oil industries and increasing the hydrodynamic forces on the structure. Considering the latter, loading change due screen effect and added mass are shown to be the most relevant. This study aims to provide a probabilistic modeling of marine growth colonization in the Gulf of Guinea. A physical matrix response surface is used in view to provide a probabilistic modeling of the environmental loading on Jacket type offshore structures for quasi-static behavior in the presence of marine growth. The paper focuses on uncertainty and sensitivity studies respecting to the effects of wave, wind-sea and currents.

Experimental Study of Combined Wave and Ice Loads on a Fixed Offshore Structure

2021 ◽  
Author(s):  
Shafiul Mintu ◽  
David Molyneux
Keyword(s):  
Offshore Structures ◽  
Numerical Code ◽  
Ocean Engineering ◽  
Offshore Structure ◽  
Engineering Research ◽  
Combined Loads ◽  
Individual Wave ◽  
Ice Loads ◽  
Ice Floes ◽  
Memorial University Of Newfoundland

Abstract Ice floes in the marginal ice zone (MIZ) are exposed to wind, wave, and current forces which greatly influence the dynamics of the ice floes. ISO 19906 recommends considering combined wave and ice actions while designing offshore structures for arctic and cold regions. Few studies have focused on ice-structure interactions in waves. There are not many tools available to estimate these combined loads on structures. A numerical tool “SAMICE” has been developed to simulate the hydrodynamics of wave-ice interactions, but there exists a lack of data for a realistic MIZ under wave actions for validation studies of the numerical code. To address this gap and to investigate the hydrodynamics of ice floes under waves, a set of experiments was conducted at the wave tank of Ocean Engineering Research Center (OERC) of Memorial University of Newfoundland. A six-component dynamometer was used to measure the loads on a model scale aluminum cylindrical gravity-based offshore structure. Loads were measured for five regular waves of various steepness in combination with three current speeds. Two ice concentrations with various floe sizes of random shapes were prepared from polypropylene sheets to represent the MIZ. Most of the tests were repeated three times and a statistical approach was used to analyze the loads. The preliminary analysis shows that the average wave-ice loads may be determined by ISO guidelines, but the predictions of impulse loads from individual wave-driven ice floes are very uncertain.

scholarly journals Proposal for Tower Crane Productivity Indicators Based on Data Analysis in the Era of Construction 4.0

Buildings ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 21
Author(s):  
Thomas Danel ◽  
Zoubeir Lafhaj ◽  
Anand Puppala ◽  
Sophie Lienard ◽  
Philippe Richard
Keyword(s):  
Time Series ◽  
Data Analysis ◽  
Statistical Analysis ◽  
Data Collection ◽  
Structural Phase ◽  
Sampling Technique ◽  
Construction Site ◽  
Data Logger ◽  
Tower Crane ◽  
Productivity Indicators

This article proposes a methodology to measure the productivity of a construction site through the analysis of tower crane data. These data were obtained from a data logger that records a time series of spatial and load data from the lifting machine during the structural phase of a construction project. The first step was data collection, followed by preparation, which consisted of formatting and cleaning the dataset. Then, a visualization step identified which data was the most meaningful for the practitioners. From that, the activity of the tower crane was measured by extracting effective lifting operations using the load signal essentially. Having used such a sampling technique allows statistical analysis on the duration, load, and curvilinear distance of every extracted lifting operation. The build statistical distribution and indicators were finally used to compare construction site productivity.

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