1,721,013 research outputs found
Design tool for an offshore harbour
No full textIn this report a design tool has been developed for offshore harbours. The main objective of the design tool is to recommend an optimum value for the offshore distance of the berth, the breakwater length and the breakwater type. This recommendation has to be made based on CAPEX and OPEX estimates for the various structures the offshore harbour consists of, and based on downtime caused by wave action. After the determination of the functionality and usability requirements the design tool has to fulfill, an overview of all relevant design parameters and processes is presented. These parameters and processes are incorporated in the design tool via four modules: a cost module, a breakwater design module, a wave calculation module and a waiting cost module. Three verifications have been performed on the design tool, as well as a sensitivity analysis in order to obtain insight in the performance of the tool and the sensitivity of its model formulations to uncertainties in the input. Based on the results of these analyses, conclusions can be drawn with regard to the reliability and sensitivity of the design tool.Civil Engineering and GeosciencesHydraulic EngineeringPorts & Waterway
Sedimentation in the Botlek Harbour - A research into driving water exchange mechanisms.
No full textSiltation of harbour basins and navigation channels is a serious problem in the port of Rotterdam as well in many other harbours all over the world. Due to siltation, basins and channels require frequent maintenance dredging to guarantee safe navigational depths. The costs associated with these dredging activities are quite high. To keep the channels and harbours in Rotterdam navigable, Rijkswaterstaat and the Port of Rotterdam are dredging approximately 15 million m3 of sediment a year. The dredging cost of the Botlek Harbour only is already about 3 million Euros a year. It is a task to keep the costs in the Port of Rotterdam as low as possible to compete with other ports. Reducing maintenance dredging costs is in line with the goal of the Port of Rotterdam to be the most competitive, innovative and sustainable port in the world. Most sedimentation within the maintenance area of the Port of Rotterdam occurs in the Botlek. According data, between 1.5 and 3 million m3/year is dredged in the Botlek Harbour. Although the current dredging philosophy more or less works, the question arises whether there are solutions that are more cost-effective. However, the problem is so complex that it narrowed down for the sake of research quality. The main causes of siltation in general and specifically in the Botlek Area form an important part of the study. Hydrodymical models (SIMONA & Delft3D), were used to gain insight in the sedimentation problem. The focus in this thesis was more on the hydrodynamics. The exchange mechanisms between the river and Botlek Harbour were investigated, which were needed to examine the effectiveness of certain solutions. In practice a lot of solutions are proposed in literature, however in this study only a couple of ‘hard’ measures are investigated. The first possible solution that was examined was the use of a Current Deflecting Wall. It turned out that the hydrodynamics were very sensitive to the configuration of the CDW. While sometimes it would lower the exchange flow, at other cases it would even make the problem worse. The second solution was to make a gap in the Geulhaven dam. However this was not a good solution as high exchange flows occurred. The last proposed solution, the filling of the underwater dam, seemed more feasible as it would decrease the exchange flow according the numerical models. The research has first order results which can be used in further studies. According to this results, certain solutions will decrease the exchange flows. On turn it would very likely result in lower sedimentation rates in the Botlek Area. It is expected that some CDW configurations and the filling of the underwater dam would have a positive effect when it comes to sedimentation. However, this research is the first step of an extensive study that must made to deal with the problem. First of all many things can be done to improve the models, for example by using a higher spatial resolution. Secondly, other sets of conditions must be modelled to see what kind of effect this has on exchange flows. In addition, sediment must be included in the models to have more insight on the sedimentation itself. The next step would be a feasibility study, including a cost benefit analysis. It would be wise to improve the models further and to make a scale model for the most feasible solution. In the ideal case, were all steps are positive and hard conclusion can be made, it would be a good idea for the Port of Rotterdam to start a pilot.Hydraulic EngineeringHydraulic EngineeringCivil Engineering and Geoscience
Analyzing the hydraulic design for the new basin in the IJmuiden outer harbor
No full textTo improve the lightering conditions of bulk carriers in the outer harbor of IJmuiden, the lightering facility will be transfered to a new harbor basin that will be implemented at the location of the dredging depot in the former Averij harbor. The Dutch Directorate-General for Public Works and Water Management (RWS) demands that down time of the lightering operations inside the new basin does not exceed 5% of the operating time of 365 days a year, 24 hours a day. Down time of the lightering operation can be caused by several issues. This thesis investigates the contribution of long waves with wave periods between 10 and 250 seconds to the down time conditions. Theoretically this long wave climate can cause high ship response as incoming wave periods are close to the bulk carrier's natural periods. The long waves can also cause resonance in the new basin or in the outer harbor as a whole. A coupled system of basin resonance and ship response is also investigated as the two separate resonance systems can enforce each other for certain wave periods. Investigating a 200.000 DWT bulk carrier's Response Amplitude Operators for an open water situation concludes that the bulk carrier experiences enforced movement in its horizontal motions for wave periods around 250 seconds and in its vertical motions for wave periods between 15 and 20 seconds. In the real time situation the ship's horizontal motions will be damped by the mooring system and the high resonance periods will not be met. The numerical wave model PHAROS has been used to analyze whether resonance patterns arise in the outer harbor basins for a wave period band between 10 and 250 seconds. It is concluded that the new basin can experience resonance for wave periods between 100 and 250 seconds. The highest wave amplification of 4.5 times the incoming wave height at sea occurs for an incoming wave period of 147 seconds. The amplified wave height inside the new basin will not contribute to down time conditions as the amplified wave height is lower than the critical wave height of 0.80 meter. The implementation of the new basin has a positive ffect on the area of the outer harbor behind the Fort island. Especially in the Hoogoven harbor and at the Noorder ship lock wave agitation decreases. However, standing waves may arise between the new basin and the opposing IJmond harbor if sufficient wave energy is present in the incoming wave climate. The results of the coupled system of basin resonance and bulk carrier vertical response do not result in a contribution to the down time criteria. Although amplified waves can become a factor 4.5 larger than the incoming wave heights, earlier investigation and observations and analyses in this study show that the incoming wave energy for long waves is low and the probability of incoming waves amplifying into waves of critical wave heights that cause down time to the lightering process is very little. The contribution to the down time of the new basin is very small in comparison to the contribution of wind and locally generated wind waves.Ports and WaterwaysHydraulic EngineeringCivil Engineering and Geoscience
Berthing loads in structural design: Validation of partial factors
No full textStructural design of these marine facilities is not implicitly covered in EN1990 (European Norm), and the types of loads and load combinations that are to be considered are different from those for buildings and bridges, since they concern operational loadings from vessels berthing and mooring, and also loads from vessels moored acting indirectly through mooring lines and fenders. The overall objective is to find and recommend action and combination factors for the safe and cost-effective structural design of marine facilities using the deterministic limit-state design methodology of EN1990.Hydraulic EngineeringHydraulic EngineeringCivil Engineering and Geoscience
``Slibvaren’’: Adjustment of the harbour admittance policy by reduction of the minimal required under keel clearance (UKC)
No full textAll harbours require frequent dredging to cope with sedimentation. In certain cases the deposited sediment/silt forms a weak soil layer referred to as fluid mud. The top layer is often used as nautical bottom, while its presence is not necessarily harmful to the vessel. This could lead to the conclusion that the safety margin underneath a vessel (i.e., Under Keel Clearance (UKC)) is too large/safe and can be reduced. Research indicates that the UKC can be decreased to smaller (<10%) or negative (0 to -10%) values. Reducing the UKC leads to less dredging and allowance of higher draught vessels. This can create economic benefits for the port authority and, depending on the chosen strategy, shipping company. Less dredging is also likely to reduce the amount of sediment that is re-suspended and could thus assist the system in reducing turbidity. Altered vessel behaviour by a smaller UKC and the possible resulting safety impairments create application challenges. These effects are caused by undulations in the water-mud interface (when sailing close to the fluid mud) or a too strong mud layer (when sailing through the mud). A discussion is instigated as the result of different end-user objectives: navigational safety versus optimal port profit. Extensive knowledge from various scientific fields is required to make a sound consideration between safety and benefits. Within this thesis, the alignment between end-users and required scientific topics is studied using a Decision Support Model (DSM). The DSM is based on a Frame of Reference approach by van Koningsveld [2003] which is meant to improve communication and aid decision making. For conceiving the DSM, various objectives from end-users are categorized into three management context: economy, ecology and safety. In reducing the UKC the benefits (economy and ecology) are opposed by the potential downsides (safety). Knowledge from literature led to relevant topics in each management context. Three strategies where used for quantification: draught increase, dredging decrease or draught increase with maintaining the current UKC requirement. The general DSM was applied to the case of Delfzijl where fluid mud and UKC reduction are topics of discussion. Weighing the strategies results in a dredging reduction being optimal. Relative small visiting vessels and high turbidity in the area cause this outcome. Difficulties in quantifying sub-elements are the result of knowledge gaps which might be resolved by further research. After addressing the topics of research, a sound decision on application can be made. The complete DSM and the outcomes where presented to port authority, harbour masters and pilot at Delfzijl. Based on the DSM, these end-users where able to point out topics of concern and provide additional feedback. These topics, mainly regarding safety, where subsequently assessed with a probabilistic tidal window model as proposed by Bouw [2005]. The model copes with the request for extra safety and can be easily extended when new knowledge on survey error and vessel velocity is obtained. From this thesis it was apparent that the main challenge for an UKC reduction is the absence of a means to designate the strength based nautical bottom. Port authorities have no means of assessing the strength of the bottom and corresponding effects on vessel behaviour. This affects the decision whether to start experimentally reducing the UKC for visiting vessels. Resulting in no possibilities to gain experience in the concept. In addition, the port authority is not able to determine the depth contour change induced by an envisioned dredging reduction.Civil Engineering and GeosciencesHydraulic Engineerin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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