118 research outputs found
Reliability-based Assessment for Fender Systems
No full textPIANC has published several working group reports related to the design of fender systems. The work of PIANC WG33 is widely accepted by the industry and has been used to design marine structures worldwide. However, the existing design approach does not distinguish uncertainties in fender engineering, e.g. uncertainties related to vessel sizes, berthing velocities, and berthing angles. This paper aims to show how to take into account some of these uncertainties into fender design using a reliability-based approach. The influence of multiple fenders contact and multivariate dependence between vessel size, berthing velocity, and berthing angle on the failure probability of a fender system was analysed. These correlations were modelled using a Vine-Copula, while the contribution of multiple fenders contact was investigated by performing simulation. Furthermore, the failure probability of the fender system was determined using the First Order Reliability Method and Monte Carlo simulation. The results show that uncertainty in berthing velocity, the effect of multiple fenders contact, and dependence between design variables largely influence the reliability of a fender system. It is highly recommended to incorporate all these aspects into the design approach to accomplish a cost-effective design solution. The key findings of this study can be used to update the existing design approach of fender systems and help to interpret the berthing records collected by Port Authorities.Civil Engineering | Hydraulic Engineerin
Allowable Hull Loading due to Fender Contact
No full textMarine structures are frequently equipped with rubber fender systems, which absorb the berthing energy in order to protect both the marine structure and the berthing vessel. These fender systems absorb the kinetic berthing energy by elastic deflection and the associated reaction fender force introduces a berthing impact load acting on the vessel’s side hull. In guidelines and rules on ship design, recommendations regarding the structural resistance due to external fenders are not present. On the other hand, special requirements state minimal strengthening for tug resistance, which results in marked areas on a vessel’s side hull at which tug contact is allowed. Also for ships equipped with integrated steel fenders in their side hull, also known as beltings, minimal strengthening is required. Since the use of fender systems in ports is common, and all ships require to berth in a port the maximum hull loading due to fender contact is an important factor to take into account from the vessel’s perspective. PIANC WG33 published design recommendations for the maximum allowable hull pressure in kN/m2 for different types of vessels. The size of the fender contact area is in practice determined by dividing the design reaction force by the maximum allowable hull pressure. However, the hull pressures in this recommendation are based on the pressure on the keel of a fully laden vessel. Based on this background information, not all values are reliable, since some pressures correspond to a draft of 70 meters. Besides that, the pressure formulation does not contain information on the specific geometry of the contact area, i.e. height and width. This thesis systematically analyses the strength of the vessels’ parallel side hull for different failure modes, e.g. yielding in the stiffeners due to excessive bending or shear stresses. The structural geometry of various vessel types is represented by various grillages. Two different pressure distributions were considered: a soft contact area, and a rigid contact area, to cover the most extreme behaviour of a fender panel. The results of this study show that the allowable load is largely influenced by the geometry of the contact area. The fender panels designed using the PIANC WG33 fender design are not always optimal. Especially for fender panels having large widths, the current guidelines seem to be too optimistic. Consequently, it is necessary to define a maximum width to what extent the current guidelines are allowable. This study shows that a specific allowable force in kN for a specific geometry is preferred over the current guidelines. In this study, a general formulation for the maximum allowable hull loading is proposed. This formulation requires the specific structural layout of the vessel that encounters the berthing facility. If the specific ship’s particulars are not known, recommendations are provided for different vessel types. These recommendations consist of a new acceptance criterion for each vessel type, which can be used to optimise the geometry of fender panels. The findings of this study can be used in the design of fender systems and the new design criterion has been submitted to the members of PIANC WG211.Marine Technolog
Loads on fender structures and dolphins by sailing ships
No full textFender structures and dolphins form an important part of the navigable canal. They have many functions: they must be able to guide and slow down ships, they must protect structures aft of ships against impacts from ships, and must protect ships from these structures. In addition, they must act as berthing or waiting places for ships. Fender structures and dolphins are installed where one or more of these functions are required, generally when passing nearby sluices, bridges, harbour entrances, etc. The costs of constructing and maintaining fender structures and dolphins may be considerable, thus savings in construction or maintenance costs, together with efficient operation, are very important. Up until recently schematised calculation methods, with dimensioning approach velocities and angles of the ships, obtained from practical observation, were used by the Netherlands Ministry of Public Works, Locks and Weirs Directorate, for designing fender structures and dolphins. The fender structures built meet the requirements previously laid down. However, at a time when fender structures and dolphins must be designed as economically as possible, and when ships are increasing in both size (e.g. push tows) and speed, there is a need to provide better calculation methods and more broadly based general conditions. For these reasons a study has been carried out to determine the loading of fender structures and dolphins by sailing ships. This Rijkswaterstaat Communication gives a survey of the study carried out. This Rijkswaterstaat Communication is drawn up in two parts. The first part contains an introduction to, and summary of, the study (Chapt. 1), and a determination of the data required for determining the impact forces (Chapters 2 to 5 inclusive). The second part contains the determination of the impact forces by calculations and model investigation (Chapters 6 to 9 inclusive)
Impact resistance of ship hull to berthing loads: quantifying critical fender impact
No full textOver the last two decades, the size and capacity of (container) vessels calling port at the Port of Rotterdam have increased considerably. To moor these huge and heavy ships safely at the quay, fenders are frequently installed. The present guidelines for the “Design of Fender Systems”, which were established in 2002, are due to be updated in 2023. Part of the update of these new guidelines for the design of fenders by working group 211 of the Permanent International Commission for Navigation congresses (PIANC) consists of the verification and validation of the hull pressure criterion, taking into account the recent growth of (container) vessels. Obtaining a generic criterion is challenging due to the enormous diversity in vessel sizes and structural layouts. In addition, fender dimensions and types may also have a significant influence on the fender-induced load. This leads to the following research question: “How can critical fender-induced loads acting on the parallel side hull be quantified, accounting for the diversity of vessels and fenders?” In this research, parallel hull sections are used in numerical simulations to investigate the allowable load of fenders and to derive the influence of panel size and dimensions (tall or wide). Including detailed parallel hull sections for a representative group of vessels, makes it possible to look beyond simplified geometries, such as stiffened panels, and specific case studies. First, the structural response and corresponding governing failure modes were studied. In addition to existing failure modes described in fender-induced loads, tripping of stiffeners as a possible governing failure mode was included. A modification to available analytical formulations was made to describe the critical tripping pressure of stiffeners with a flange under patch loads more accurately. The proposed critical tripping pressure induced by a fender is underestimated by the analytical model in comparison to the numerical simulations of the parallel sections. When the rotational restraint of the web frame attached to the tripping stiffener is considered, a closer correlation between the analytical results and the numerical simulations of the parallel hull is foreseen. For the numerical simulations, a parametric approach was adopted, where different impact locations and contact areas were applied for several vessel types and sizes. The lowest steel grade of vessels currently applied in shipbuilding was implemented to obtain the lower limit of allowable fender-induced loads. The key finding of this study is that allowable fender-induced loads are largely influenced by the vessel's structural dimensions, such as web frame spacing, and the size of the fender panel with respect to the ship's geometry. The constant hull pressure criterion currently used by PIANC can be maintained but should be limited to a total allowable reaction force, because, for large panels, it overestimates the capacity. Furthermore, it has been shown that for large ships, wide panels outperform tall panels because they activate web frame(s). Making panels much wider does not necessarily yield more capacity because the stress concentration remains in the web frames. For small vessels, the trend is less clear, as the web frame is activated at an earlier stage (less far apart) and the capacity does not increase exponentially with the width. In addition, high panels on small vessels sometimes lead to the activation of a deck and thus increase the allowable load. The overall conclusion of this research is that the PIANC criterion should be limited to a total reaction force. Furthermore, by correctly sizing fender panels, more efficient use of the vessel's capacity can be ensured, as web frames provide more capacity. The findings of this research can be used to allow small and large vessels to safely berth onto existing facilities.Marine Technolog
Circinus X-1: survivor of a highly asymmetric supernova
No full textWe have analyzed the kinematical parameters of Cir X-1 to constrain the nature of its companion star, the eccentricity of the binary and the pre-supernova parameter space. We argue that the companion is most likely to be a low-mass (< 2.0 M_sun) unevolved star and that the eccentricity of the orbit is 0.94 +/- 0.04. We have evaluated the dynamical effects of the supernova explosion and we find it must have been asymmetric. On average, we find that a kick of 740 km/s is needed to account for the recently measured radial velocity of +430 km/s (Johnston, Fender & Wu) for this extreme system. The corresponding minimum kick velocity is 500 km/s. This is the largest kick needed to explain the motion of any observed binary system. If Cir X-1 is associated with the supernova remnant G321.9-0.3 then we find a limiting minimum age of this remnant of 60000 yr. Furthermore, we predict that the companion star has lost 10% of its mass as a result of stripping and ablation from the impact of the supernova shell shortly after the explosion
GITAR “FENDER” DALAM POP ART (BENTUK-BENTUK GITAR “FENDER” SEBAGAI GAGASAN DALAM BERKARYA SENI GRAFIS PROSES SCREEN PRINTING DENGAN GAYA POP ART)
No full textDi dunia seni rupa gitar seringkali menjadi ide dalam berkarya, baik dalam berkarya lukis, patung sampai dengan object art. Beberapa seniman terkemuka, diantaranya Pablo Picasso dan Edouard Manet pernah mengangkat gitar sebagai ide dalam berkarya seni. Penulis memilih untuk mengangkat gitar sebagai benda seni populer yang pada umumnya hanya kita dengarkan dan nikmati suaranya dalam sebuah karya seni musik, maka dari itu dalam karya ini penulis ingin menonjolkan segi estetika dari gitar-gitar tersebut, dengan mengerucutkan pilihan kepada gitar dengan merek Fender. Dalam pandangan penulis, bentuk-bentuk gitar Fender yang eksklusif dan tampak elegan akan menarik jika disajikan ke dalam bentuk karya seni rupa. Pengembangan gagasan dan visualisasi bentuk-bentuk gitar Fender ke dalam karya screen printing dengan gaya Pop Art menjadi masalah dalam skripsi penciptaan ini, maka skripsi penciptaan ini bertujuan agar penulis mampu mendeskripsikan gagasan dan visualisasi bentuk-bentuk gitar Fender dalam karya screen printing dengan gaya Pop Art. Penulis menggunakan teknik screen printing untuk menghasilkan karya visualisasi gitar Fender dengan gaya Pop Art. Terdapat lima buah karya. Empat Karya dibuat dalam ukuran 4 x (40 x 40) dan satu karya dalam ukuran 3 x (40 x 40) dan disusun dengan sistem panel yang dimodifikasi dengan bentuk tetris sebagai acuan, Kelimanya dikerjakan dengan tahapan penciptaan sketsa manual, pewarnaan digital dan dipindahkan menjadi karya besar dengan teknik screen printing. Setiap unsur visualisasi karya yang digunakan pada setiap karya disesuaikan dengan karakteristik gitar yang menjadi objek utama. Hasil karya penciptaan ini diharapkan selanjutnya dapat menjadi menginspirasi seniman-seniman lain untuk menghasilkan karya unik yang mudah dimengerti. Selain itu, karya ini diharapkan mampu memotivasi setiap orang yang mengapresiasi melalui kalimat motivasi yang disisipkan dalam karya ini.
Kata kunci : Gitar, Fender, Pop Art, Seni grafis, cetak saring (screen printing)
In the world of art, a lot of artist such as Pablo Picasso and Edouard Manet have been using guitar as their idea for painting, sculpting, object art, etc. Author choose to brought up guitar as a popular art item that usually we heard and enjoyed as an art in a form of music. So in this thesis, author choose “Fender” guitar as an example to show the aesthetic side of a guitar. Author viewed the exclusive and elegant shape of Fender guitar to be looked interesting as a piece of art. Idea development and visualization of Fender guitar shapes into pop art styled screen printing becoming an issue in this thesis so that author can describe the idea and visualization of Fender guitar shapes into a pop art styled screen printing. Author used screen printing technique to create five of this piece of art. Four of this was made in a tetris modified panel system with a size of 4 x (40 x 40 cm) and one in a size of 3 x (40 x 40 cm). The step consist of manual sketching, digital coloring and finalized as screen printing art. Every element of visualization in this works was adjusted by the characteristic of the guitar which become the main object. Hopefully this works will inspired other artist to create some unique art that easy to understand and motivates every other people that give appreciation to this works through motivational words that included in this pieces of art.
Keywords : Guitar, Fender, Pop Art, Printmaking, Screen printin
Ship berthing to a vertical quay-wall: Fender forces and ship motion
No full textIn this report a mathematical model is formulated which is sufficiently accurate to describe the typical behaviour of a ship berthing to a vertical quay-wall fitted with fenders as well as to determine the response of the fenders themselves. In order to achieve this a three-dimensional set of governing equations is drawn up by which the lateral transient motions of shiplike bodies nearby a closed wall with a vertical front can be described adequately. To this end use is made of two separate methods both originating from the mathematical model presented, viz. the so-called 'impulse response function'-technique, which has the restriction that the ship-fluid system is supposed to be linear, and a direct 'timedomain approach' where non-linearities can be taken into account. Both methods enable the inclusion of external forces of arbitrary nature. The 'impulse response function'-technique makes allowance for the fluid reactive forces by means of the hydrodynamic coefficients which are incorporated in the impulse response functions representing the properties of the linear ship-fluid system. Application of the 'timedomain approach' amounts to a direct solution of the governing set of equations which is simplified to a two-dimensional situation (strip theory). The ship is schematized to a prismatic body with a rectangular crosssection so that coupling between the respective ship motions is not present. The closed berthing structure consists of a long, straight wall with an impermeable, vertical front and fitted with one fender, the reaction force of which acts perpendicular to the front side of the berth. Although not essential, the fender applied is ndamped and linear. The influence of a restrictive water depth is taken into account. Since berthing manoeuvres and ship-fender interactions take mainly place in the horizontal plane and the ship is supposed to maintain a lateral motion with its longitudinal axis of symmetry parallel to the face of the berth, only the sway mode of motion needs to be considered; the effect of a forward speed is not included. The 'impulse response function'-technique as well as the direct 'time-domain approach' are applied to the case of shallow water with a horizontal bottom and relatively large horizontal dimensions in front of the berthing structure. Only centric impacts are considered. Each of both methods presented describes the behaviour of the schematized ship during the berthing operation as well as the behaviour of the fender itself. An extensive experimental verification was carried out by means of model tests. Four water depths were regarded. The results of theoretical calculations and model tests show a reasonably good agreement.Hydraulic EngineeringCivil Engineering and Geoscience
Analisis Respon Dinamis Sistem Fender Tipe Super Cone SCN 1800 Akibat Perilaku Beban Operasi Kapal
No full textLNG Bunkering adalah penyediaan bahan bakar untuk kapal-kapal yang beroperasi di sektor transportasi maritim. Dalam beberapa tahun terakhir, permintaan akan bahan bakar ramah lingkungan meningkat, sehingga LNG menjadi pilihan yang menarik sebagai alternatif berkelanjutan. Hal ini menyebabkan pembangunan dan pengembangan fasilitas pelabuhan bunkering yang meningkat. Pelabuhan yang baik memerlukan suatu struktur sandaran kapal yang baik untuk melindungi struktur dari benturan badan kapal ke dermaga yang biasa disebut dengan fender. Maka dari itu, penulis akan menganalisis struktur fender tipe super cone SCN 1800 akibat gaya sandar dan beban lingkungan saat kapal LNG-Fuelled Dry Bulk Carrier beroperasi. Analisis gaya saat sandar dilakukan dengan metode analitik sedangkan gaya dari beban lingkungan dilakukan dengan simulasi time domain menggunakan perangkat lunak berbasis metode elemen hingga. Analisis lokal juga dilakukan untuk mengetahui deformasi dan tegangan struktur fender. Dari hasil analitik didapatkan sudut sandar dan kecepatan kapal yang diperbolehkan karena hasil gaya reaksi yang tidak melebihi kapasitas reaksi fender. Untuk kapal kondisi normal ballast adalah 4 derajat dan 0.180 m/s sedangkan untuk kapal kondisi full load adalah 6 derajat dan 0.105 m/s. Hasil gaya reaksi maksimum fender dengan simulasi time domain saat kapal operasi akibat beban lingkungan adalah 2325 kN. Selanjutnya dilakukan analisis lokal fender dari gaya reaksi fender saat kapal sandar dan beroperasi. Hasil tegangan maksimum terjadi pada bagian terjadi antara panel dan body fender sebesar 33.7 Mpa dengan variasi arah gaya dari sumbu X+. Sedangkan deformasi maksimum sebesar 6.98 m dengan variasi arah gaya di sumbu X+.
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LNG Bunkering is the provision of fuel to ships operating in the maritime transportation sector. In recent years, the demand for environmentally friendly fuels has increased, making LNG an attractive option as a sustainable alternative. This has led to the construction and development of improved bunkering port facilities. A good port requires a good ship berthing structure to protect the structure from the impact of the ship's body on the pier, commonly referred to as fenders. Therefore, the author will analyze the fender type super cone SCN 1800 structure due to berthing forces and environmental loads when the LNG-Fuelled Dry Bulk Carrier ship operates. The analysis of the berthing forces is carried out by analytical methods, while the forces from environmental loads are carried out by time domain simulation using software based on the finite element method. Local analysis was also conducted to determine the deformation and stress of the fender structure. From the analytical results, the berthing angle and ship speed are obtained, which are allowed because the result of the reaction force does not exceed the reaction capacity of the fender. For normal ballast condition, ships are 4 degree and 0.180 m/s, while for full load condition ships are 6 degree and 0.105 m/s. The result of the maximum fender reaction force with time domain simulation when the ship operates due to environmental loads is 2325 kN. Furthermore, a local analysis of the fender is carried out from the reaction force of the fender when the ship is docked and operating. The maximum stress results occurred in the between fender panel and body fender section of 33.7 Mpa with a variation in the direction of the force from the X + axis. In addition, the maximum deformation is 6.98 m with variations in the direction of the force in the X + axis
Algorithms for Efficient Top-Down Join Enumeration
No full textFor a DBMS that provides support for a declarative query language like SQL, the query optimizer is a crucial piece of software. The declarative nature of a query allows it to be translated into many equivalent evaluation plans. The process of choosing a suitable plan from all alternatives is known as query optimization. The basis of this choice are a cost model and statistics over the data. Essential for the costs of a plan is the execution order of join operations in its operator tree, since the runtime of plans with different join orders can vary by several orders of magnitude. An exhaustive search for an optimal solution over all possible operator trees is computationally infeasible. To decrease complexity, the search space must be restricted. Therefore, a well-accepted heuristic is applied: All possible bushy join trees are considered, while cross products are excluded from the search.
There are two efficient approaches to identify the best plan: bottom-up and top-down join enumeration. But only the top-down approach allows for branch-and-bound pruning, which can improve compile time by several orders of magnitude, while still preserving optimality.
Hence, this thesis focuses on the top-down join enumeration. In the first part, we present two efficient graph-partitioning algorithms suitable for top-down join enumeration. However, as we will see, there are two severe limitations: The proposed algorithms can handle only (1) simple (binary) join predicates and (2) inner joins. Therefore, the second part adopts one of the proposed partitioning strategies to overcome those limitations. Furthermore, we propose a more generic partitioning framework that enables every graph-partitioning algorithm to handle join predicates involving more than two relations, and outer joins as well as other non-inner joins. As we will see, our framework is more efficient than the adopted graph-partitioning algorithm. The third part of this thesis discusses the two branch-and-bound pruning strategies that can be found in the literature. We present seven advancements to the combined strategy that improve pruning (1) in terms of effectiveness, (2) in terms of robustness and (3), most importantly, avoid the worst-case behavior otherwise observed.
Different experiments evaluate the performance improvements of our proposed methods. We use the TPC-H, TPC-DS and SQLite test suite benchmarks to evaluate our joined contributions
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