A Method for the Frequency Domain Seakeeping Analysis of Offshore Structures in the Early Design Stage

2020 ◽  
Author(s):  
Maximilian Liebert
Keyword(s):  
Frequency Domain ◽  
Cross Sections ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Offshore Structures ◽  
Design Stage ◽  
Design Environment ◽  
Early Design ◽  
Early Design Stage ◽  
Response Amplitude Operators

Abstract The motion analysis of floating offshore structures is a major design aspect which has to be considered in the early design stage. The existing design environment E4 is an open software framework, which is being developed by the Institute of Ship Design and Ship Safety, comprising various methods for design and analysis of mainly ship-type structures. In context of the development to enhance the design environment E4 for offshore applications this paper presents a method to calculate the response motions of semi-submersibles in regular waves. The linearised equations of motion are set up in frequency domain in six degrees of freedom and the seakeeping behaviour is calculated in terms of the amplitudes of the harmonic responses. The hydrodynamic forces onto the slender elements of the semi-submersible are accounted for by a Morison approach. As the drag and damping forces depend quadratically on the amplitudes, these forces are linearised by an energy-equivalence principle. The resulting response amplitude operators of the semi-submersible are validated by comparison with model tests. The method represents a fast computational tool for the analysis of the seakeeping behaviour of floating offshore structures consisting of slender elements with circular cross sections in the early design stage.

Determination of Hydrodynamic Masses and Roll Periods of Ships in Shallow Water

2021 ◽  
Author(s):  
Larissa Jannsen ◽  
Stefan Krüger
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Hydrodynamic Forces ◽  
Ship Design ◽  
Design Stage ◽  
Ship Motions ◽  
Design Environment ◽  
Early Design ◽  
Early Design Stage ◽  
Water Effects

Abstract Due to the fast increase of the vessels’ size over the past few years the actual water depth is becoming more and more relevant for seakeeping problems. The highly frequented sea route TSS Terschelling – German Bight for example is a shallow water route for large vessels which are now affected by the reduced keel clearance. Many shallow water depth areas occur also in coastal areas or inland seas. If a vessel is travelling in shallow water sea states, the hydrodynamic forces will change compared to deep water sea states and they are essential for further seaway calculations. Furthermore, a rough but easy evaluation of the incoming seaway is the roll period. Shallow water effects should be taken into account for calculating roll periods and thereby predicting a manageable or risky seaway situation. This paper presents the implementation of shallow water effects into an existing 2D panel code. With this panel code the hydrodynamic forces for the vessel’s frames are calculated based on the potential theory in the frequency domain, which is a validated approach in the early design stage. The panel code is part of the ship design environment E4 which is being developed by the Institute of Ship Design and Ship Safety, among others. With the expanded method it is possible to calculate hydrodynamic forces also in shallow water in all degrees of freedom. Therefore, the frame motions are converted to global ship motions. Furthermore, for the usage in the early design stage the calculations should be fast but also accurate. The obtained calculation results are therefore validated with full scale measurement using Inertial-Measurement-Units.

scholarly journals A Mobile Design Environment for Building Form Generation

2020 ◽  
pp. 131-142
Author(s):  
Mehmet Emin Bayraktar ◽  
Gülen Çağdaş
Keyword(s):  
Design Thinking ◽  
Tall Buildings ◽  
Digital Design ◽  
Design Stage ◽  
Design Environment ◽  
Modeling Tools ◽  
Early Design ◽  
Early Design Stage ◽  
Mobile Design ◽  
Current Design

Computer technology has affected architectural studies as well as other professions. Architectural tools are used in every stage of the design and their primary goals are transferring and sharing the ideas of the architects’ mind. Nevertheless, in the early design phase, digital design tools remain ineffective in terms of idea development. Current design software and modeling tools are insufficient for the architect to quickly share ideas and generate alternative suggestions for fast sketching and modeling. In this paper, a mobile design application is developed. It aims to support open-ended design thinking and to be fast and effective in terms of improving ideas. It is based on augmented reality and it works on mobile phones. In order to evaluate the application, a set of images consisting of tall buildings are shown to users. Then they are asked to model a similar form of their own. At the end, results are assessed with a questionnaire. Using the obtained data, the effectiveness of the digital mobile tool in the early design stage is discussed.

Identification of Human Errors During Early Design Stage Functional Failure Analysis

2018 ◽  
Author(s):  
Lukman Irshad ◽  
Salman Ahmed ◽  
Onan Demirel ◽  
Irem Y. Tumer
Keyword(s):  
Failure Analysis ◽  
Human Error ◽  
System Level ◽  
Design Stage ◽  
Human Factors Engineering ◽  
Human Errors ◽  
Functional Failure ◽  
Early Design ◽  
Early Design Stage ◽  
Early Design Stages

Detection of potential failures and human error and their propagation over time at an early design stage will help prevent system failures and adverse accidents. Hence, there is a need for a failure analysis technique that will assess potential functional/component failures, human errors, and how they propagate to affect the system overall. Prior work has introduced FFIP (Functional Failure Identification and Propagation), which considers both human error and mechanical failures and their propagation at a system level at early design stages. However, it fails to consider the specific human actions (expected or unexpected) that contributed towards the human error. In this paper, we propose a method to expand FFIP to include human action/error propagation during failure analysis so a designer can address the human errors using human factors engineering principals at early design stages. To explore the capabilities of the proposed method, it is applied to a hold-up tank example and the results are coupled with Digital Human Modeling to demonstrate how designers can use these tools to make better design decisions before any design commitments are made.

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