Enhancing Robustness of Tubbing Tunnels in Case of Extreme Loads

2012 ◽  
pp. 184-187
Author(s):  
Christoph Niklasch ◽  
Peter-Michael Mayer
Keyword(s):  
Extreme Loads

Turkstra Profiles of North Sea Currents: Wider Than You’d Think

2011 ◽  
Author(s):  
Steven R. Winterstein ◽  
Sverre Haver ◽  
Alok K. Jha ◽  
Borge Kvingedal ◽  
Einar Nygaard
Keyword(s):  
North Sea ◽  
Deep Water ◽  
Current Speed ◽  
Marine Structures ◽  
Marginal Analysis ◽  
Water Currents ◽  
Extreme Loads ◽  
Peak Over Threshold ◽  
Direct Contrast ◽  
Sea Currents

To design marine structures in deep water, currents must be modelled accurately as a function of depth. These models often take the form of T-year profiles, which assume the T-year extreme current speed occurs simultaneously at each depth. To better reflect the spatial correlation in the current speeds versus depth, we have recently introduced Turkstra current profiles. These assign the T-year speed at one depth, and “associated” speeds expected to occur simultaneously at other depths. Two essentially decoupled steps are required: (1) marginal analysis to estimate T-year extremes, and (2) some type of regression to find associated values. The result is a set of current profiles, each of which coincides with the T-year profile at a single depth and is reduced elsewhere. Our previous work with Turkstra profiles suggested that, when applied in an unbiased fashion, they could produce unconservative estimates of extreme loads. This is in direct contrast to the findings of Statoil, whose similar (“CCA”) current profiles have generally been found to yield conservative load estimates. This paper addresses this contradiction. In the process, we find considerable differences can arise in precisely how one performs steps 1 and 2 above. The net finding is to favor methods that properly emphasize the upper tails of the data—e.g., using peak-over-threshold (“POT”) data, and regression based on class means—rather than standard analyses that weigh all data equally. By applying such tail-sensitive methods to our dataset, we find the unconservative trend in Turkstra profiles to essentially vanish. For our data, these tail-fit results yield profiles with both larger marginal extremes, and broader profiles surrounding these extremes—hence the title of this paper.

Powertrain Motion Control Analysis under Quasi-Static Extreme Loads

2016 ◽  
Author(s):  
Tianqi Lv ◽  
Peijun Xu ◽  
Yunqing Zhang
Keyword(s):  
Motion Control ◽  
Control Analysis ◽  
Extreme Loads

A Flexible Connector Design for Multi-Modular Floating Structures

2018 ◽  
Author(s):  
Huai Zhao ◽  
Daolin Xu ◽  
Haicheng Zhang ◽  
Qijia Shi
Keyword(s):  
Finite Element Method ◽  
Structural Model ◽  
Random Waves ◽  
The Finite Element Method ◽  
Floating Platform ◽  
Stiffness Analysis ◽  
Floating Structures ◽  
Extreme Loads ◽  
Strength And Stiffness ◽  
Frequency Domain Approach

The paper aims to provide a novel flexible connector model for the connection of a multi-modular floating platform. The structural model of the connector is presented. To evaluate connector loads, the governing equation for a modularized floating platform is established using the Rigid Module Flexible Connector (RMFC) model. The dynamic analysis for a two-module floating platform is carried out by using the frequency domain approach in random waves and the extreme loads of the flexible connector are estimated. The finite element method is applied for strength and stiffness analysis to assess the performance of the connector.

Fire-induced extreme loads

2019 ◽  
pp. 165-213
Author(s):  
Adnan Ibrahimbegovic ◽  
Naida Ademovicć
Keyword(s):  
Extreme Loads

scholarly journals New vulnerabilities of historic urban centers and archaeological sites: Extreme loads

2016 ◽  
Vol 11 (3) ◽  
pp. 15-26 ◽  
Author(s):  
Alina-Maria Nariţa ◽  
Vlad Gurza ◽  
Răzvan Opriţa ◽  
Alexandra Keller ◽  
Iasmina Apostol ◽  
...  
Keyword(s):  
Archaeological Sites ◽  
Urban Centers ◽  
Extreme Loads

scholarly journals Loads on a Point-Absorber Wave Energy Converter in Regular and Focused Extreme Wave Events

2020 ◽  
Author(s):  
Eirini Katsidoniotaki ◽  
Edward Ransley ◽  
Scott Brown ◽  
Johannes Palm ◽  
Jens Engström ◽  
...  
Keyword(s):  
Wave Energy ◽  
Wave Train ◽  
Offshore Structures ◽  
Wave Energy Converter ◽  
Extreme Waves ◽  
Extreme Wave ◽  
Energy Converter ◽  
Point Absorber ◽  
Wave Energy Converters ◽  
Extreme Loads

Abstract Accurate modeling and prediction of extreme loads for survivability is of crucial importance if wave energy is to become commercially viable. The fundamental differences in scale and dynamics from traditional offshore structures, as well as the fact that wave energy has not converged around one or a few technologies, implies that it is still an open question how the extreme loads should be modeled. In recent years, several methods to model wave energy converters in extreme waves have been developed, but it is not yet clear how the different methods compare. The purpose of this work is the comparison of two widely used approaches when studying the response of a point-absorber wave energy converter in extreme waves, using the open-source CFD software OpenFOAM. The equivalent design-waves are generated both as equivalent regular waves and as focused waves defined using NewWave theory. Our results show that the different extreme wave modeling methods produce different dynamics and extreme forces acting on the system. It is concluded that for the investigation of point-absorber response in extreme wave conditions, the wave train dynamics and the motion history of the buoy are of high importance for the resulting buoy response and mooring forces.

Operability of Ballasting and Lifting Operations of Extreme Loads with Integrated Hydrodynamics (Obelics)

2012 ◽  
Author(s):  
Drs G de Vries ◽  
◽  
Ir E J P M Frickel ◽  
Keyword(s):  
Extreme Loads

Discussion of “Statistical Combination of Extreme Loads”

1978 ◽  
Vol 104 (1) ◽  
pp. 233-234
Author(s):  
Yozo Fujino ◽  
Niels C. Lind
Keyword(s):  
Extreme Loads
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