Ballast Condition Research Articles

Investigation of hydroelastic ship responses of an ULOC in head seas

Investigation of hydroelastic ship responses has been brought to the attention of the scientific and engineering world for several decades. There are two kinds of high-frequency vibrations in general ship responses to a large ocean-going ship in its shipping line, so-called springing and whipping, which are important for the determination of design wave load and fatigue damage as well. Because of the huge scale of an ultra large ore carrier (ULOC), it will suffer seldom slamming events in the ocean. The resonance vibration with high frequency is springing, which is caused by continuous wave excitation. In this paper, the wave-induced vibrations of the ULOC are addressed by experimental and numerical methods according to 2D and 3D hydroelasticity theories and an elastic model under full-load and ballast conditions. The influence of loading conditions on high-frequency vibration is studied both by numerical and experimental results. Wave-induced vibrations are higher under ballast condition including the wave frequency part, the multiple frequencies part, the 2-node and the 3-node vertical bending parts of the hydroelastic responses. The predicted results from the 2D method have less accuracy than the 3D method especially under ballast condition because of the slender-body assumption in the former method. The applicability of the 2D method and the further development of nonlinear effects to 3D method in the prediction of hydroelastic responses of the ULOC are discussed.

Effect of Partially Filled Spherical Cargo Tanks on the Roll Response of a Bargelike Vessel

Floating liquefied natural gas (FLNG) is an offshore structure which enables liquefaction, storage, and offloading of natural gas. It is a game changer in offshore hydrocarbon development. Side-by-side offloading is a promising way of transferring liquefied natural gas (LNG) from FLNG to an LNG carrier. The roll response of LNG carriers, which plays a critical role, has been observed to be influenced by the liquid cargo motion inside the tanks. Therefore, the operational window for side-by-side offloading may not be estimated robustly using a simplified method which ignores the liquid cargo and considers only the ballast condition. This necessitates a scientific understanding of the roll responses of an LNG carrier at different load conditions. In this study, a series of model tests are conducted on a bargelike vessel with two spherical tanks. The response amplitude operators (RAOs) and response spectra of the vessel in different load conditions and different headings are investigated. The effect of intermediate cargo volumes on global roll response is, for the first time, examined for spherical cargo tanks. It is suggested that intermediate loading conditions with explicit inclusion of the effects of cargo sloshing is utilized in side-by-side operability studies to robustly ascertain offloading availability.

Comparison of Laboratory Testing Using SmartRock and Discrete Element Modeling of Ballast Particle Movement

AbstractTrack performance is largely dependent on ballast performance. Unfavorable ballast conditions cause track geometry roughness and can contribute to increased rates of damage and deterioration to the rail, tie, and fastening components. Recent discrete element modeling (DEM) studies demonstrated a strong relationship between individual ballast particle movement and overall ballast performance. This paper presents a laboratory and numerical study on ballast particle movement under cyclic loading. In the laboratory test, a wireless device called SmartRock was embedded in a ballast box to monitor individual ballast particle movement beneath a crosstie under cyclic loading. In the numerical study, an image-aided DEM approach was utilized to generate DEM particles with a realistic shape of ballast particles and simulate the ballast box test. The laboratory test results recorded by the SmartRock and DEM simulations results were compared. Good agreement was observed between the simulated and recorded parti...

Condições de tração dos tratores agrícolas fabricados e comercializados no Brasil

In Brazil today, beyond there is no mandatory testing center, there are few studies aiming to determine the performance of agricultural tractors. Performance tests of the specimens are made by manufacturers, and because the official reports disclosure is not required, consumers have information only from the own manufacturer. Thus, this study aimed to evaluate the performance the conditions tractor of the agricultural tractors with manufactured and/or sold tires in Brazil in relation to power ranges and type of traction. To do so, from 191 agricultural tractors, we calculated the following parameters maximum traction force at DB and relative traction force/weight. Some ofthese parameters were evaluated under different soil and ballast conditions. The results showed that the power range 147 kW and 4x2 TDA traction type present the best values for estimated maximum traction power. It can be concluded that the maximum traction force is higher for the range tractors 147 kW, power over and traction type 4x2 TDA backed.

Study on added resistance of a tanker in head waves at different drafts

In this study, added resistance was evaluated experimentally and numerically in four draft conditions: full load, ballast, and two intermediate conditions between the full load and ballast conditions. A series of towing-tank experiments for ship motion and added resistance in the four draft conditions was carried out in head sea conditions. The ship motion and added resistance were measured for the wavelength to ship length ratios of 0.4–2.0. In the numerical approach, two different seakeeping analyses were adopted: the strip method and Rankine panel method. For the strip method, analytical or empirical corrections were added in the short wave condition. The experimental and numerical results for the heave and pitch motions and the added resistance were compared for the four draft conditions. The numerical motion responses of both approaches showed good agreement with the experimental data. For the added resistance, the Rankine panel method showed reasonable results in all draft conditions. In contrast, the strip method showed poor results except in the full load condition. Based on the comparison of the experimental and numerical results, the potential application of the two numerical methods to various draft conditions was considered.

Investigation of springing in ship structures using experimental methods and 3-D hydroelastic theory

Large and long ships experience springing behavior. Depending on the trade routes and design of such ocean-going ships, wave-induced vibrations may be due to springing and whipping effects. In this paper, we address the wave-induced vibrations in an ultra-large ore carrier under fully loaded and ballast conditions. The experimental measurements from tests performed using a flexible model of the ship were compared with the numerical predictions from 3-D hydro-elastic theory (THAFTS) (Wu, Hydroelasticity of floating bodies. PH.D thesis, Brunel University, 1984). The measurements showed multiple frequencies between the encountered wave frequency and the 2-node bending frequency that occurred only in ballast conditions, whereas the springing vibrations were more apparent with forward speed under ballast conditions in both regular and irregular waves. The numerical method predicted the vertical bending moment quite well in the fully loaded condition but underestimated it in the ballast condition. This result was primarily due to an inability to capture the prediction of the multiple frequencies between the encountered wave frequency and the 2-node bending frequency. Using THAFTS, a new ship form with a deep draft was introduced, and this vessel was shown to reduce springing vibrations.

실선시험에 의한 DWT 8,000톤 선박의 선회성능 – Semi–balanced rudder and flap rudder –

This study is intended to provide navigator with specific information necessary to assist the avoidance of collision and the operation of ships to evaluate the maneuverability of dead weight tonnage 8,000 tons Oil/Chemical tanker. The actual maneuvering characteristics of ship can be adequately judged from the results of typical ship trials. Author carried out sea trials based full scale for turning test in ballast condition and full load condition, semi balanced rudder and flap rudder. The turning circle maneuvering were performed on the starboard and port sides with rudder angle at the normal continuous rating. The results from tests could be compared directly with the standards of maneuverability of IMO and consequently the maneuvering qualities of the ship is full satisfied with its.

Regulating characteristics of new tamping device exciter controlled by rotary valve

Tamping devices have a common problem that the amplitude and frequency of the tamping tool cannot be adjusted and, thus, are too inflexible to satisfy different working demands. In order to solve this problem, mathematical modeling and analysis of a new tamping arm are developed according to the technical parameters of the existing tamping devices, and the configuration of the new tamping exciter controlled by a rotary valve is analyzed using analytical method. Considering the feasibility and practicability of the new tamping device, the special electrohydraulic exciter and rotary valve are determined. Then, the control characteristic, performance, and dynamic motions of the exciter are studied in view of the ballast condition feature. Finally, the test verifies the theoretical model and the new tamping device exciter shows good performance.

2-D Entropy and Short-Time Fourier Transform to Leverage GPR Data Analysis Efficiency

Accurate detection of singular region using ground-penetrating radar (GPR) is very useful in assessing roadway pavement, bridge deck concrete structure, and railroad ballast conditions. To locate an object within the large radargram involves extensive computational resources and time, especially when the data of interests only possess a small portion of the whole big data set. Therefore, an efficient GPR signal-processing technique is highly demanded. This paper proposes the use of 2-D entropy analysis to narrow down the data scope to the interested regions, which can considerably reduce computational cost for more sophisticated data postprocessing. Joint time-frequency analysis using short-time Fourier transform is then performed for singular region location detection and refinement. The proposed methodology is tested with different laboratory setups. The analysis results show good agreement with physical configurations.

GPR Laboratory Tests For Railways Materials Dielectric Properties Assessment

In railways Ground Penetrating Radar (GPR) studies, the evaluation of materials dielectric properties is critical as they are sensitive to water content, to petrographic type of aggregates and to fouling condition of the ballast. Under the load traffic, maintenance actions and climatic effects, ballast condition change due to aggregate breakdown and to subgrade soils pumping, mainly on existing lines with no sub ballast layer. The main purpose of this study was to validate, under controlled conditions, the dielectric values of materials used in Portuguese railways, in order to improve the GPR interpretation using commercial software and consequently the management maintenance planning. Different materials were tested and a broad range of in situ conditions were simulated in laboratory, in physical models. GPR tests were performed with five antennas with frequencies between 400 and 1800 MHz. The variation of the dielectric properties was measured, and the range of values that can be obtained for different material condition was defined. Additionally, in situ GPR measurements and test pits were performed for validation of the dielectric constant of clean ballast. The results obtained are analyzed and the main conclusions are presented herein.

Comparative Study between Results of Theoretical Calculation and Model Test for Performance Confirmation of "Crown Duct"

Chosun University, in cooperation with SPP shipyard, has developed an energy saving device based on a new concept: "Crown Duct." Crown Duct is composed of a semi-duct with short struts inside and outside the duct. Theoretical calculations for two different designs were carried out using the CFD code "Ship Flow." The design selected from these two different forms by the CFD code analysis was tested in a towing tank at SSPA. The results showed about 4% efficiency gain under a full-load condition and about 7% gain under a ballast condition in the towing tank test.

On the Use of Ballast Inspection Technology For the Management of Track Substructure

The railroad track substructure and specifically its ballast and sub-ballast layers play a key role in the maintenance of the stability and geometry of the track structure. However, because it traditionally has not been readily accessible below the surface of the ballast, very limited information about its conditions was available, without extensive and disruptive excavation techniques. New-generation inspection technology now allows for the access to significant additional information about the ballast and sub-ballast to include its extent, condition, depth, degree of fouling, and any inadequacies in the substructure layer that can lead to loss of track stability or accelerated degradation of the track structure. This paper discusses several of the key track substructure inspection technologies, to include the traditional monitoring of the track geometry and then addresses the new inspection technologies now available to more accurately define the ballast condition. This includes such newly introduced inspection technologies as LIDAR for measurement of the ballast profile, ground penetrating radar inspection for ballast depth deficiency, and other related inspection technologies. These new technologies allow for more accurate ballast deficit and condition analysis.

Design Conditions for Dolphin Berth by Tanker Fleet Analysis

Energy acquisition due to the increase of oil price is one of the most important issues and policy for most countries. Various tankers have been built in the world and sent to the trade market. It is necessary to build the port infrastructure and facilities to give them proper services such as mooring, packing, storing, and transshipment, etc. However, the domestic guidelines or standards for design and construction for the dolphin berth among these facilities are out of date and do not meet the recent trend of tanker types. Therefore, it requires amendment on the guidelines or standards. In this study, a detailed analysis of the tanker fleet, covering 8,000 ships under operation and order to build, is made to estimate the proper PBL(Parallel Body Length) of each tanker class. After discussion and comparison on the dolphin berth design and construction codes of various countries, those are the leading countries of tanker operation and management, suggestion was made to amend on the design code. The referred codes are of Korea, Japan, UK, USA, and Canada. The analysis of tanker fleet shows the PBL as 0.45L under the normal ballast condition. In order to verify the deduced amendment on the domestic design code for dolphin berth, it was selected one of the domestic dolphin berth, located at the Yeosu oil terminal, which is almost completed to construct. The design criteria and expected tankers to moor in that terminal were analyzed and the appropriateness and countermeasure for deficiency were summarized.

Retracted: Influence of Track Support Stiffness of Railway Tracks on Track Impact Factor

Track support stiffness (TSS) is used as a quality index of railway tracks to assess their performance and bearing capacity. TSS depends on the elastic stiffness of the elastic materials and the structural characteristics of the track system. The theoretically designed track impact factor (TIF), which is used to design ballasted and slab tracks in the Republic of Korea, is not detailed enough to describe various track types and TSS. In this study, the relationship between the TSS and the TIF for various types of tracks currently employed in Korean urban transit was assessed by performing field tests using actual vehicles running along the service lines. Field tests were performed on ballasted tracks (with good and bad ballast conditions) and three slab track types (i.e., sleeper-embedded track, rail floating track, and sleeper floating track). The theoretically designed TIF and TSS were compared with the corresponding TIF and TSS measured through field tests for the various track types on the service line. The condition of ballast (gravel) and the spring stiffness of the rail support materials directly affected the TSS. Moreover, the TIF for the service line appeared to increase with the TSS; therefore, it was inferred that the TSS directly affected the TIF.

Behaviour of Track Ballast Under Repeated Loading

Najaf-sea quarry is located in Najaf city about 160 km south west of Baghdad the capital of Iraq. It is the main source that supplies track ballast for maintenance of existing railway network and construction of new railway lines in the middle and southern parts of Iraq. Track ballast experience a complex combination of stresses during its service lifetime, primarily from repeated axial loads of the trains in addition to stresses generated from the environmental conditions. The ideal evaluation of suitability of track ballast must be carried out under real field loading conditions, however such field tests are usually costly and time consuming. On the other hand laboratory model tests simulating field loads under limited boundary conditions can provide satisfactory indication about the suitability of the material. The present paper investigates the deformation characteristics of Najaf-sea track ballast, under repeated loading using model tests simulating ballast conditions under a selected track section. A test setup was designed and manufactured capable of applying both monotonic as well as repeated loading on the track section under different conditions. The repeated model tests which simulate as close as possible the field conditions shed the light on the generated settlement, modulus of deformation and degradation of the ballast particles under different repeated loading levels. Statistical analysis in terms of breakage index and repeated applied load revealed satisfactory correlations that help in understanding the overall performance of the ballast material. The results also demonstrate that 4–5 tamping are capable of controlling both the settlement and modulus of deformation of the ballast material.

A track ballast maintenance and inspection model for a rail network

The geometry of railway track governs the quality of the ride for passengers and, should it deteriorate to an extreme state, can become a safety concern with potential derailment. The geometry is dependent upon a number of different factors, among which is the condition of the ballast. Several options exist to control the condition of the ballast, including manual intervention, tamping and stoneblowing. Ballast condition is monitored implicitly by measuring the geometry of the railway lines using a specially equipped measurement train. By analysing the data collected by this train, the deterioration process of the railway geometry can be understood. Using this understanding, mathematical models can then be constructed, which take account of the possible maintenance and renewal options to predict the track state. This model enables decisions to be made on the best or optimal strategy for maintenance and renewal of the ballast. This article describes a model of the track maintenance process for a railway network. Owing to their flexibility, the model is formulated using a Petri net and combines the deterioration, maintenance and inspection processes for a railway network containing a number of regions. There are a limited number of maintenance machines in the network and the maintenance in each region is organised independently. The model also takes account of the fact that the maintenance of track sections with severe levels of ballast deterioration must take priority over all other maintenance in the network and allows for opportunistic maintenance to be analysed.

Lateral pressure effects on the progressive hull collapse behaviour of a Suezmax-class tanker under vertical bending moments

This paper presents the results of an investigation of the effect of lateral pressure on the progressive hull collapse behaviour of a double-hull oil tanker subject to vertical bending moments in both the sagging and hogging conditions. As an illustrative example, a Suezmax-class double-hull oil tanker designed by the Common Structural Rules (CSR) method is considered. The ANSYS nonlinear finite element method (NLFEM) is employed for the progressive hull collapse analysis. The effects of lateral pressure – static (anchored condition) and dynamic (operating condition) – are investigated in both the full-load and ballast conditions. To check the accuracy of ultimate hull girder strength analysis methods, Dow's test hull is also applied together with Suezmax class oil tanker under conditions of vertical bending moment but without lateral pressure loads. In this regards, the NLFEM method is compared with ALPS/HULL intelligent supersize finite element method (ISFEM) programs and International Association of Classification Societies (IACS) CSR method, which applies the idealized structural unit method (ISUM) (also called the Smith method). The important insights developed from the present study are documented.

Prediction of displacement induced by tilting trains running on ballasted tracks through measurement of track impact factors

In the track design and behavior prediction, the variable contribution of wheel load was evaluated by considering the design load for the tracks. Further, the track impact factor was used to calculate the dynamic wheel load as a single value, which was chosen according to the rail type (i.e., continuous welded rail or joint rail) and the design speed but did not take into consideration the track conditions (i.e., the ballast condition good or bad), train type (i.e., tilting train and EMU), and track components (i.e., sleeper type and fastening type). In this study, the measured track impact factor was applied to the time history function of the FE analysis in order to predict the displacement of ballasted tracks under real conditions, which included curved and the deteriorated tracks, thus increasing the train speed by approximately 20–30% of the existing train speed. Therefore, the dynamic wheel load and the rail and sleeper displacement were measured for two different trains running on four conventional curved track sections with two different sleeper types. The track impact factor was estimated from the measured dynamic wheel load, and the empirical dynamic wheel load was calculated using the measured track impact factor at each site. The measured track impact factors were used for simulating the dynamic wheel loads applied on the derived time history function for fast trains. A finite element analysis model using the derived time history function based on the empirical dynamic wheel load was used to predict the train-induced track displacement. The numerical simulations and field test results were compared with German and Japanese regulations for train-induced track displacement, and the speedup effect of a tilting train was compared with that of a general train (EMU).The empirical track impact factors were 17–18% higher in the R400 sections than in the R600 sections. As the track curvature decreased, the impact on the track increased. Therefore, the empirical track impact factors were 21–23% higher in the WT sections than in the PCT sections. At 70km/h, the impact on the track from a tilting train was 7–11% less than that from EMU. Although the tilting train sped up by 30% (90km/h), its response level was similar to or less than that of the EMU. The analytical results reproduced the experimental results well within about 2–5% difference in the values. Therefore, the derived time history function based on the measured track impact factors is considered to provide sufficiently reliable FEA results in the investigation of the behavior of ballasted tracks. The difference between the maximum displacements for both train types on all the sections was about 15–20%.The analytical results show that the speed limits of the tilting train were higher than those of the EMU by approximately 8–23km/h at each test site. Therefore, the speed limit of each test site was estimated by considering the limit of sleeper displacement. It was shown that the time history function derived using the measured track impact factor on a small track curvature with wooden sleepers was higher than that in other test sections. Therefore, it would be advantageous to increase the weight of sleepers on existing lines to increase the train speed through the speedup effect without increasing the track curvature. The increase in the speed of a tilting train with a small track curvature was much better than that by a track curvature increased by approximately 10%.

A study on the Development of Energy-Saving Device "Crown Duct"

A energy saving device "Crown duct" has been developed and its efficiency gain has been verified experimentally in the towing tank of SSPA. The preswirl stator is well known as one of energy saving devices, which recovering the rotational energy of propeller slipstream. Crown duct has two functions of recovers the rotational energy by three blades on top of duct and of flow concentration by semi-duct. The model tests showed 4.4% efficiency gain with Crown Duct at full load condition and 6.9% at ballast condition compared with the bare hull ones for the middle class tanker.

PARAMETRIC STUDY OF MARINE STEAM TURBINE PLANTS

The steam turbine power plant has until recently been the first choice for very large power main propulsion units. Its advantages of little or no vibration, low weight, minimal space requirements and low maintenance costs are considerable. Furthermore a turbine can be provided for any power rating likely to be required for marine propulsion [1].This research deals with the parametric study of marine steam power plants. It studies the effect of the ambient temperature which is considered as the cooling water inlet to the condenser (from 24oC to 35 oC) also the boiler pressure (from 30 bar to 60 bar) on the performance of the steam power plants in both fully loaded ship and ballast conditions. The performance of the power plant concerned with the thermal efficiency, the fuel consumption, the steam mass flow rate, and the mass flow rate of cooling water inlet to condenser. The procedures have been carried out for METHANE KAREELIN as LNG carrier with steam power plant rated for 29 MW.The results showed that, the sailing in cold weather is more favorable for high thermal efficiency, less fuel and steam consumption, also less mass flow of the cooling water inlet to the condenser. Also, it is better to work under high steam pressure for high thermal efficiency, less fuel and steam consumption, and less mass flow of the cooling water inlet to the condenser. But, this pressure is limited to the metallurgy of metals that are bear this pressure as well as not based on the designer. Finally, carrying more cargo increases both the fuel consumption and steam consumption, to keep the ship speed constant as well as possible.