A Hydraulic Absorber for Wideband Vibration Reduction in Ship Hulls

1994 ◽  
Vol 116 (1) ◽  
pp. 43-48 ◽  
Author(s):  
W. J. Hsueh ◽  
Y. J. Lee
Keyword(s):  
Vibration Reduction ◽  
Stochastic Theory ◽  
Optimal Level ◽  
Hull Girder ◽  
Ship Hulls ◽  
Optimal Theory ◽  
Hydraulic Servo ◽  
Efficient Level ◽  
Oil Tanker ◽  
Multi Mode

A vibration reduction of ship hulls by an active absorber system is proposed. In the scheme, a tuned mass is moved according to the hull vibration as measured by a multi-mode sensing system in order to generate a suitable active force for vibration reduction of hull girder. In order to supply the large amount of required power, a hydraulic servo system is implemented. Then the dynamic characteristic of the hydraulic system is considered for system design. Based on stochastic theory and optimal theory, the control law of the system is derived in order to approach the optimal level of vibration reduction. A 10-t absorber is applied to a 87,000-t oil tanker to demonstrate the feasibility of this scheme. The results show that the multi-peak values of resonance are suppressed in frequency response. Moreover, the vibration excited by propeller and engine is reduced to an extremely efficient level by this scheme.

Hull girder fatigue strength of corroding oil tanker

2010 ◽  
pp. 149-154
Author(s):  
J Parunov ◽  
K _iha ◽  
P Mage ◽  
P Juri_i_
Keyword(s):  
Fatigue Strength ◽  
Hull Girder ◽  
Oil Tanker

Hull-Girder Reliability of a Chemical Tanker

2009 ◽  
Vol 46 (04) ◽  
pp. 192-199
Author(s):  
Jôsko Parunov ◽  
Maro Corak ◽  
C. Guedes Soares
Keyword(s):  
International Association ◽  
Progressive Collapse ◽  
Bending Moment ◽  
Single Step ◽  
Hull Girder ◽  
Structural Rules ◽  
Term Operation ◽  
Reliability Method ◽  
Reliability Bound ◽  
Oil Tanker

The aim of the paper is to calculate hull-girder reliability of chemical tanker according to the reliability model proposed by International Maritime Organization (IMO). The probability of hull-girder failure is calculated using a first-order reliability method for two operational profiles—one typical for oil tanker and the other one modified in order to reflect differences between oil tanker and chemical tanker. The evaluation of the wave-induced load effects that occur during long-term operation of the ship in the seaway is carried out in accordance with International Association of Classification Societies (IACS) recommended procedure. The stillwater loads are defined on the basis of a statistical analysis of loading conditions from the loading manual. The ultimate collapse bending moment of the midship cross section, which is used as the basis for the reliability formulation, is evaluated by progressive collapse analysis and by single-step procedure. The reliability analysis is performed for "as-built" ship and for "corroded" ship according to corrosion deduction thickness from new Common Structural Rules for double-hull oil tankers. It is shown that hull-girder failure probability of "as-built" chemical tanker is well above the upper reliability bound proposed by IMO, while the "corroded" ship is slightly unconservative since the reliability index is lower than IMO lower reliability bound.

The BP Oil Tanker Structural Monitoring System

1995 ◽  
Vol 32 (04) ◽  
pp. 277-296
Author(s):  
David J. Witmer ◽  
Jack W. Lewis
Keyword(s):  
Monitoring System ◽  
Structural Damage ◽  
Prolonged Exposure ◽  
North Pacific Ocean ◽  
The United States ◽  
Management Program ◽  
Structural Monitoring ◽  
Hull Girder ◽  
Response Data ◽  
Oil Tanker

BP Oil Company time-charters a fleet of American-flag tankers for the ocean transportation of crude oil and petroleum products to the East, West and Gulf Coasts of the United States. Commencing in 1991, ship response and structural monitoring instrumentation was installed on the four ships of the Atigun Pass-class. These crude carriers are operated in the Trans-Alaska Pipeline Service, or "TAPS" trade, sailing the waters of the North Pacific Ocean and Gulf of Alaska. The structural monitoring systems were designed to measure the effects of subjecting a ship to the typical loads and forces encountered while at sea: hogging, sagging, slamming, hydrostatic pressure, and hull girder springing. Additionally, BP was interested in developing a system that could provide shiphandling guidance to the master or watch officer so that the detrimental effects of prolonged exposure to such loads and forces could be effectively minimized. The paper describes in detail the physical arrangement of the BP Oil Tanker Structural Monitoring System (BPSMS), including the suite of sensors employed to measure ship responses and hull girder stresses. It explains how the response data collected by the sensors is analyzed by the onboard computer located on the ship's bridge and how ship response data are presented back to the deck officers via a family of display monitor screens. These displays provide the officers with a "tool" that can be used to effectively monitor the physical and structural response of their ship to waves, and to quantify, in terms of lowering the wave bending moment and reducing the risk of slamming, the result of an action or actions taken to minimize the risk of incurring structural damage. Onboard ship response and structural monitoring is now an integral part of BP's tanker fleet structural management program. The units have greatly increased the awareness of the ship's officers regarding their role in helping to control the amount of structural damage done to the ships. Data from the units have also helped management make more informed decisions regarding operational requirements placed on the ships.

Designed-Oriented Methods of Ultimate Hull Girder Strength

2006 ◽  
Author(s):  
Enrong Qi ◽  
Weicheng Cui
Keyword(s):  
Single Step ◽  
Software System ◽  
Element Analysis ◽  
Hull Girder ◽  
Structural Rules ◽  
Ship Hulls ◽  
Calculation Results ◽  
Long Time ◽  
Common Structural Rules ◽  
Double Hull

Based on long-time theoretical and experimental work in authors group, assessment methods of ultimate strength of ship hulls are analyzed and improved. Nonlinear finite element analysis method (FEM), idealized structural unit method (ISUM), simplified method (SM) and analytical method (AM) are integrated into a software system of direct calculations of large tankers. Using this software system, a comparative calculation is performed on ultimate hull girder strength of a 300,000dwt double hull tanker and the calculation results are also compared with the single step procedure of Common Structural Rules for double hull tankers (JTP CSR).

Rapid Assessment of Hull Girder Collapse for Corroded Double Hull Oil Tanker After Collision

2016 ◽  
Author(s):  
Sung Hwan Noh ◽  
Jung Kwan Seo ◽  
Jeom Kee Paik ◽  
Samy A. M. Youssef
Keyword(s):  
Finite Element ◽  
Structural Damage ◽  
Rapid Assessment ◽  
Probabilistic Approach ◽  
Hull Girder ◽  
The Alps ◽  
Oil Tankers ◽  
Double Hull ◽  
Oil Tanker ◽  
Probability Density Function Pdf

Corroded tankers might be subjected to a very serious structural damage if involved in collision accidents. For understanding or preventing the collision accidents, various studies are being proposed by researchers to improve the analysis method. In this paper, four types of double hull oil tankers (Panamax, Aframax, Suezmax and VLCC) are used. Probabilistic approach is used to create ship-ship collision scenarios for each target structure and the ultimate longitudinal hull girder strength of the hypothetical oil tanker’s hull cross-section. The ALPS/HULL is used to simulate and is intelligent supersize finite element method (ISFEM) software. A relevant probability density function (PDF) is introduced using the results from finite element simulations of the ship-ship collisions, which is commonly used to predict residual strength.

Reduction of Hull Whipping in Slamming by Active Control System

1994 ◽  
Vol 38 (02) ◽  
pp. 115-122
Author(s):  
Wen-Jeng Hsueh ◽  
Ya-Jung Lee
Keyword(s):  
Control System ◽  
Active Control ◽  
High Speed ◽  
Active Vibration Control ◽  
Mathematical Formulation ◽  
Active System ◽  
Hull Girder ◽  
Hydraulic Servo ◽  
Active Vibration ◽  
Active Control System

The reduction of hull girder whipping in slamming by an active control system is investigated. Under the consideration of hull flexibility, a mathematical formulation is developed for the whipping of a hull, subject to slamming, and including an active vibration control system consisting of a tuned mass and hydraulic servo system. Using the optimal theory, the control law of the active system is determined. In addition, a closed-loop estimator is introduced to estimate the distribution of hull motion, which is required to compute the actuator output of the active system. Finally, a numerical example of an application to a 205-ton high-speed craft is described. The results show that the whipping will be reduced significantly. The whipping acceleration and induced stress in particular are reduced more than 95% within 2 sec by this scheme.

scholarly journals Distortionary Taxes and the Provision of Public Goods

1992 ◽  
Vol 6 (3) ◽  
pp. 117-131 ◽  
Author(s):  
Charles L Ballard ◽  
Don Fullerton
Keyword(s):  
Public Goods ◽  
Public Good ◽  
Optimal Level ◽  
Marginal Rate ◽  
The Public ◽  
Lump Sum ◽  
Marginal Rates Of Substitution ◽  
Efficient Level ◽  
Distortionary Taxes ◽  
The Cost

Economists have long been concerned with finding an efficient level of public expenditure. The classic statement of the problem was given by Paul Samuelson (1954). An optimal level of expenditure is where the sum of the marginal rates of substitution between the public good and a reference good equals the marginal rate of transformation between the public good and the reference good (ΣMRS = MRT). However, Samuelson's formula assumes that all of the revenue needed to finance public goods can be raised with lump-sum taxes. Since this is not generally possible, the formula must be modified to account for the distortionary effects of the tax system. An appropriate modification is to multiply the cost side of the equation by a term that is commonly called the marginal cost of public funds (MCF). In the case of Samuelson's formula, where government is entirely financed with lump-sum taxes, the MCF would be exactly 1.0. In the traditional view of economists, distortionary taxes cause the MCF to be greater than one, thus raising the cost of providing public goods. In this paper, we discuss some cases where the MCF may be less than one. We will illustrate this possibility using numerical examples for labor taxes.

Energy Harvesting From Building Seismic Isolation With Multi-Mode Resonant Shunt Circuits

2014 ◽  
Author(s):  
Mincan Cao ◽  
Lei Zuo
Keyword(s):  
Energy Harvesting ◽  
Vibration Control ◽  
Seismic Isolation ◽  
Large Scale ◽  
Base Isolation ◽  
Numerical Study ◽  
Vibration Reduction ◽  
Host Structure ◽  
Multi Mode ◽  
Shunt Circuit

A novel electromagnetic transducer shunt circuit is proposed in this paper for dual-functional energy harvesting and vibration control of building seismic isolation. In recent decades, base isolation systems are widely used in low and middle rise buildings. Even though base isolation can filter out high frequency excitation from earthquake, it still necessary to consider higher order modes’ vibration in host structure. The new design extends the multi-mode shunt circuit technology in piezoelectric area in order to achieve good vibration suppression into the seismic isolation of multi degree of freedoms (MDOF) of host structure of buildings, and use multi-mode circuit to achieve both energy harvesting and seismic vibration control. A numerical study of simplified two degree of freedom base isolation is presented in this paper. This passive system is also examined by giving recorded earthquake excitation. The stimulation results show that this new design could take advantage both of low-pass filtering capacity of base isolation system and resonant vibration reduction of electromagnetic shunt circuit. It is also observed that parameters selected for vibration reduction of building can effectively achieve large-scale energy harvesting at same time.

Hull-Girder Reliability of an Aged Oil Tanker

2008 ◽  
Author(s):  
Josˇko Parunov ◽  
Paulo Mage ◽  
C. Guedes Soares
Keyword(s):  
Transfer Functions ◽  
International Association ◽  
Single Step ◽  
Hull Girder ◽  
Structural Rules ◽  
Term Operation ◽  
Strip Theory ◽  
Reliability Method ◽  
Years Of Service ◽  
Oil Tanker

The aim of the paper is to assess the hull-girder reliability of an existing single-hull oil tanker after 25 years of service using a reliability method and assumptions very similar to those proposed recently by International Maritime Organization (IMO). The evaluation of the wave-induced load effects that occur during long-term operation of the ship in the seaway is carried out in accordance with the International Association of Classification Societies (IACS)-recommended procedure, while transfer functions are calculated using the linear strip theory. The still-water loads are defined on the basis of statistical analysis of data recorded on single-hull oil tankers. The ultimate collapse bending moment of the midship cross section, which is used as the basis for the reliability formulation, is evaluated by progressive collapse analysis and by a single-step procedure according to Common Structural Rules (CSR). The reliability analysis is performed for three states of the hull: as built ship with scantlings of the new ship, CSR corroded state with net thicknesses of the structural members according to the corrosion deduction thickness proposed by CSR and survey state with scantlings according to the thickness measurements after 25 years of service. The yearly probability of structural failure is calculated using the first-order reliability method, while sensitivity analysis and a parametric study are performed to investigate the variability of the results with changes of the random variables within their plausible ranges. Results of the analysis are compared with recommended target reliability indices proposed by IMO and also with the results of the reliability assessment of the new double-hull tanker. Such comparison is possible since similar reliability methods and uncertainty models are employed. Results of the analysis may have several useful applications related to the decision-making aspects of the future of an aged oil tanker.

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