1,513 research outputs found
Lt. Col. R. F. Fender
No full textPortrait of Lt. Col. R. F. Fender. Published in Fort Worth Star-Telegram, morning edition March 12, 1951.https://mavmatrix.uta.edu/specialcollections_startelegram1950s/10106/thumbnail.jp
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
Grain-Fender
No full textPatent for a grain fender to be used as an attachment to a grain table. Illustrations included
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)
Fireplace Fender.
No full textPatent for a Fireplace-Fender used as a protective barrier between burning fireplaces and people. Specifically preventing the sparks from the fire to catch clothing on fire or any other flammable materials, Illustrations included
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
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
Measuring the accretion rate and kinetic luminosity functions of supermassive black holes
No full textWe derive accretion rate functions (ARFs) and kinetic luminosity functions (KLF) for jet-launching supermassive black holes. The accretion rate as well as the kinetic power of an active galaxy is estimated from the radio emission of the jet. For compact low-power jets, we use the core radio emission while the jet power of high-power radio-loud quasars is estimated using the extended low-frequency emission to avoid beaming effects. We find that at low luminosities the ARF derived from the radio emission is in agreement with the measured bolometric luminosity function (BLF) of AGN, i.e., all low-luminosity AGN launch strong jets. We present a simple model, inspired by the analogy between X-ray binaries and AGN, that can reproduce both the measured ARF of jet-emitting sources as well as the BLF. The model suggests that the break in power law slope of the BLF is due to the inefficient accretion of strongly sub-Eddington sources. As our accretion measure is based on the jet power it also allows us to calculate the KLF and therefore the total kinetic power injected by jets into the ambient medium. We compare this with the kinetic power output from SNRs and XRBs, and determine its cosmological evolution
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