Environmental Contour Lines for Design Purposes: Why and When?

2004 ◽  
Author(s):  
Sverre Haver ◽  
Gudmund Kleiven
Keyword(s):  
Time Domain ◽  
Exceedance Probability ◽  
Response Analysis ◽  
Short Term ◽  
Structural Problems ◽  
Contour Lines ◽  
Convenient Approach ◽  
Probabilistic Structure ◽  
Term Response

Methods of prediction of structural loads corresponding to a required target annual exceedance probability are reviewed. Particular attention is given to utilization of environmental contour lines for such a purpose. This approach is based on using short term methods for predicting adequate estimates of the q-probability response. The environmental contour line approach is a very convenient approach if complicated structural problems are considered. For such problems one will often have to involve numerical time domain analyses or model tests to reveal the short term probabilistic structure of the response maxima, making a full long term response analysis impossible for most practical problems.

Wave Sector Dependent Contour Lines

2007 ◽  
Author(s):  
Gro Sagli Baarholm ◽  
Sverre Haver ◽  
Carl M. Larsen
Keyword(s):  
Linear Response ◽  
Contour Line ◽  
Exceedance Probability ◽  
Wave Direction ◽  
Short Term ◽  
Sea State ◽  
Extreme Loads ◽  
Contour Lines ◽  
Term Analysis

This paper is concerned with estimating the response value corresponding to given annual exceedance probability. In principle, this requires that a full long term analysis is executed. For a linear response this can easily be done. For a non-linear response quantity however, where time domain simulations are required in order to obtain the short term stochastic structure a full long term analysis will be time consuming. An approximate method to determine the long-term extremes by considering only a few short term sea states is outlined. All sea states corresponding to a certain probability of occurrence and are given by a contour line of Hs, Tp for each wave direction. The advantage of the method is that a proper estimate of the long term extreme can be obtained by considering the most unfavourable sea state along the contour line. This will make possible practical estimation of the extreme loads the structure is exposed to. The purpose of the present paper is to illustrate how to apply directional contour lines in order to obtain a characteristic design value according to requirements regarding the marginal exceedance probability.

Long-Term Extreme Response Analysis of Marine Structures Using Inverse SORM

2017 ◽  
Author(s):  
Finn-Idar G. Giske ◽  
Bernt Johan Leira ◽  
Ole Øiseth
Keyword(s):  
Structural Reliability ◽  
New Method ◽  
Response Analysis ◽  
Marine Structures ◽  
Short Term ◽  
Reliability Method ◽  
Extreme Response ◽  
Improved Accuracy ◽  
Term Response

In this paper the first order reliability method (FORM) found in connection with structural reliability analysis is first used in an inverse manner to efficiently obtain an approximate solution of the full long-term extreme response of marine structures. A new method is then proposed where the second order reliability method (SORM) is used to improve the accuracy of the approximation. This method is compared with exact results obtained using full numerical integration. The new method is seen to achieve improved accuracy for large return periods, yet keep the number of required short-term response analyses within acceptable levels.

Post-Katrina performance of a turret-moored floating storage and offloading unit in the Gulf of Mexico

2009 ◽  
Vol 223 (3) ◽  
pp. 391-398
Author(s):  
J J M Baar
Keyword(s):  
Gulf Of Mexico ◽  
Wind Waves ◽  
Mooring Line ◽  
Response Analysis ◽  
Strong Impact ◽  
Offshore Platforms ◽  
Short Term ◽  
Line Loads ◽  
Term Response

Conventional design of ships and offshore platforms relies on performing a short-term response analysis for metocean conditions with a 100-year return period. This approach is efficient but not necessarily conservative when compared with a comprehensive long-term response analysis that considers platform responses for storms encountered over the lifetime of the platform. Turret-moored floating production, storage and offloading systems are sensitive to non-collinear wind, waves, and current conditions. During hurricanes in the Gulf of Mexico such conditions frequently occur and, depending on the resulting weathervaning characteristics of a turret-moored tanker, they may have a strong impact on vessel motions, mooring line loads, and riser performance. In recent years some very strong hurricanes have occurred in the Gulf of Mexico, e.g. Katrina and Rita in 2005. When including these recent storm data in the long-term response analysis they have a marked effect on the extrapolated 100-year long-term responses. The post-Katrina long-term responses of a generic turret-moored floating storage and offloading unit are evaluated and compared against pre-Katrina analysis results. The results of the analysis are used to stipulate response-based design criteria which are simple short-term design sea states that can reproduce a given long-term response (e.g. roll).

Application of Environmental Contour Lines on a Flexible Riser

2010 ◽  
Author(s):  
Gro Sagli Baarholm ◽  
Sverre Haver
Keyword(s):  
Time Domain ◽  
Linear Response ◽  
Contour Line ◽  
Exceedance Probability ◽  
Response Analysis ◽  
Wave Direction ◽  
Flexible Riser ◽  
Peak Period ◽  
Non Linear

This paper is concerned with estimating the response value corresponding to an annual exceedance probability. In principle, this response needs to be obtained by combining the response statistics in all sea states and wave headings. The probability distribution for a given sea state and wave direction, specified by the significant wave height, Hs, the peak period, Tp, and wave direction, β, can be obtained by frequency domain analysis for linear response. Time domain simulations are, in general, required to obtain the stochastic structure of a non-linear response quantity. To limit the statistical uncertainty, the time domain simulations must be sufficiently long. Therefore, a simplified method is necessary to improve the efficiency of the direct calculation of the long-term response value in the non-linear case. A method to determine the long-term extremes by considering only a few short term sea states is outlined. The sea states have a certain probability of occurrence and are identified by a contour line in the (Hs,Tp) plane. This will make possible practical estimation of the extreme loads the structure is exposed to. The contour line approach is merely suggested as a method for predicting load- and response maxima corresponding to a given annual exceedance probability without having to carry out a full long term analysis. The advantage with this concept is that the environmental and response analysis is decoupled. This is very convenient if the problem under consideration is of a very non-linear nature — in particular if characteristic values for design are to be established directly from model tests. The method is an approximate method, but seems to give results of reasonable accuracy for most problems. The purpose of the present paper is to present the contour line method applied to estimate responses on a flexible riser, lazy wave configuration, located in the North Sea.

Long-Term Extreme Response Analysis of Marine Structures Using Inverse SORM

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Finn-Idar G. Giske ◽  
Bernt Johan Leira ◽  
Ole Øiseth
Keyword(s):  
Structural Reliability ◽  
New Method ◽  
Response Analysis ◽  
Marine Structures ◽  
Short Term ◽  
Reliability Method ◽  
Extreme Response ◽  
Improved Accuracy ◽  
Term Response

In this paper, the first-order reliability method (FORM) found in connection with structural reliability analysis is first used in an inverse manner to efficiently obtain an approximate solution of the full long-term extreme response of marine structures. A new method is then proposed where the second-order reliability method (SORM) is used to improve the accuracy of the approximation, resulting in an inverse SORM (ISORM) approach. This method is compared with exact results obtained using full numerical integration. The new method is seen to achieve significantly improved accuracy, yet keep the number of required short-term response analyses within acceptable levels.

Unfolding the case of returnees: How the European Union and its member States are addressing the return of foreign fighters and their families

2021 ◽  
pp. 1-23
Author(s):  
Carlota Rigotti ◽  
Júlia Zomignani Barboza
Keyword(s):  
European Union ◽  
Perceived Threat ◽  
The European Union ◽  
Security Threat ◽  
Short Term ◽  
Member States ◽  
Foreign Fighters ◽  
Term Response

Abstract The return of foreign fighters and their families to the European Union has mostly been considered a security threat by member States, which consequently adopt repressive measures aimed at providing an immediate, short-term response to this perceived threat. In addition to this strong-arm approach, reintegration strategies have also been used to prevent returnees from falling back into terrorism and to break down barriers of hostility between citizens in the long term. Amidst these different strategies, this paper seeks to identify which methods are most desirable for handling returnees.

An oncology clinical trial design with randomization adaptive to both short- and long-term responses

2017 ◽  
Vol 28 (7) ◽  
pp. 2015-2031 ◽  
Author(s):  
Hao Liu ◽  
Xiao Lin ◽  
Xuelin Huang
Keyword(s):  
Trial Design ◽  
Clinical Trial Design ◽  
Therapeutic Benefit ◽  
Survival Outcome ◽  
Operating Characteristics ◽  
Short Term ◽  
Term Survival ◽  
Long Term Survival ◽  
Term Response

In oncology clinical trials, both short-term response and long-term survival are important. We propose an urn-based adaptive randomization design to incorporate both of these two outcomes. While short-term response can update the randomization probability quickly to benefit the trial participants, long-term survival outcome can also change the randomization to favor the treatment arm with definitive therapeutic benefit. Using generalized Friedman’s urn, we derive an explicit formula for the limiting distribution of the number of subjects assigned to each arm. With prior or hypothetical knowledge on treatment effects, this formula can be used to guide the selection of parameters for the proposed design to achieve desirable patient number ratios between different treatment arms, and thus optimize the operating characteristics of the trial design. Simulation studies show that the proposed design successfully assign more patients to the treatment arms with either better short-term tumor response or long-term survival outcome or both.

scholarly journals Physiological adaptations to sugar‐mimic alkaloids: Insights from Bombyx mori for long‐term adaption and short‐term response

2020 ◽  
Vol 10 (18) ◽  
pp. 9682-9695
Author(s):  
Shunze Jia ◽  
Yinghui Li ◽  
Xiangping Dai ◽  
Xiaotong Li ◽  
Yanyan Zhou ◽  
...  
Keyword(s):  
Bombyx Mori ◽  
Short Term ◽  
Physiological Adaptations ◽  
Term Response
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