scholarly journals Probabilistic strength assessment through analytical modelling of pillars found in ship structures

2021 ◽  
Vol 349 ◽  
pp. 03007
Author(s):  
Angelos S. Vasileiou ◽  
Konstantinos N. Anyfantis
Keyword(s):  
Cross Sections ◽  
Slenderness Ratio ◽  
Statistical Nature ◽  
Ship Structures ◽  
Strength Assessment ◽  
Sample Data ◽  
Stratified Sample ◽  
Regulatory Bodies ◽  
Input Variables ◽  
Probabilistic Nature

The compressive strength of pillars found in ship structures is studied under a reliability perspective. Monte Carlo Simulations (MCS) are applied, aided by a stratified sample scheme (i.e. Latin Hypercube), to account for uncertainty within the problem’s input variables (yield stress, elastic modulus, initial bow imperfection). MCSs were applied for three slenderness ratio values (low, medium, high), for hollow-circular, hollow-square and “H” shape cross-sections, and multiple geometries per slenderness ratio, per cross-section. The pillar’s strength is calculated based on the Perry-Robertson formula. The probabilistic resistance per pillar was modelled by generating the probability density function that best describes the statistical nature of the sample data. In this paper we illustrate the probabilistic nature of the compression column resistance, and compare it to the deterministic resistance suggested by regulatory bodies.

Estimate of the Ultimate Load on Structural Members Subjected to Lateral Loads

2001 ◽  
Vol 38 (03) ◽  
pp. 169-176
Author(s):  
L. Belenkiy ◽  
Y. Raskin
Keyword(s):  
Finite Element ◽  
Limit Analysis ◽  
Ultimate Load ◽  
Limit Load ◽  
Plastic Behavior ◽  
Lateral Loads ◽  
Ship Structures ◽  
Strength Assessment ◽  
Stiffened Panels ◽  
Plate Elements

This paper examines plastic behavior of typical ship structures, specifically beams, grillages, and plates subjected to predominantly lateral loads. The ultimate loads, determined on the basis of the theorems of limit analysis [1,2], are evaluated using nonlinear finite-element plastic analysis. The relationships between analytical and finite-element models for prediction of ultimate loads of beams, stiffened panels, and grillages are illustrated. It has been shown that the ultimate loads, obtained from the theorems of limit analysis, can be successfully used for strength assessment of stiffened ship structures subjected to lateral loads. The effect of shear force on ultimate load is analyzed using the finite-element method. This paper confirms that in the case of beams and grillages under lateral loading, the ultimate load may characterize the threshold of the load at which a stiffened ship's structure fails by the development of excessive deflections. For plate elements, on the other hand, the plastic deflections represent the permissible limit of external load better than the ultimate limit load.

Fatigue Strength Assessment of a Butt-Welded Joint in Ship Structures Based on Time-Domain Strain Approach

2020 ◽  
pp. 1-16
Author(s):  
Yan Dong ◽  
Yordan Garbatov ◽  
Carlos Guedes Soares
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Time Domain ◽  
Welded Joint ◽  
Stress Strain ◽  
Ship Structures ◽  
Strength Assessment ◽  
Variable Amplitude ◽  
Notch Stress ◽  
Fatigue Strength Assessment

Fatigue strength assessment of a butt-welded joint in ship structures based on a time-domain strain approach is performed in this study. The service life load histories applied to the butt-welded joint located on the deck of a bulk carrier are generated, accounting for the still-water and wave-induced loads. The rainflow counting method is applied to analyze the load histories, and the long-term distributions of the load range are compared with those based on the conventional spectral fatigue analysis. An approach of converting the load history to a series of closed notch stress-strain hysteresis loops and several open notch stress-strain hysteresis curves is proposed and demonstrated under variable amplitude loading. The approach is based on analytical notch stress-strain estimations and consists of several steps to consider the material memory effect, overcoming some limitations of the existing methods. To determine the fatigue damage for the variable amplitude loading, a design fatigue curve is derived considering the uncertainty in the fatigue lives and load sequence effects. The intrinsic fatigue limit concept is used to filter the small amplitude cycles that do not have a damaging effect. The fatigue strength of the butt-welded joint is analyzed, taking the weld-induced residual stress and misalignment effects into account explicitly. The notch mean stresses or strain amplitudes of the cycles are significantly enhanced because of the presence of a high level of weld-induced tensile residual stress or misalignment, resulting in highly severe fatigue damage. 1. Introduction Complex ship structures containing geometrical and material discontinuities are prone to fatigue because of cyclic loads. Therefore, fatigue strength assessment has been an important criterion in the ship structural design (Guedes Soares & Moan 1991). Various fatigue design concepts for the assessment of welded joints, where fatigue failures mostly originate, are applied (Xu 1997; Radaj et al. 2006), and they can be classified into two types. The first one is based on S-N curves in combination with the Palmgren-Miner rule, and the second one is based on the crack propagation models and failure criteria.

Non-Dimensional Kinetoelastostatic Maps for Compliant Mechanisms

2013 ◽  
Author(s):  
Santosh D. B. Bhargav ◽  
Harish I. Varma ◽  
G. K. Ananthasuresh
Keyword(s):  
Cross Sections ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Slenderness Ratio ◽  
Element Analysis ◽  
Output Displacement ◽  
Static Responses ◽  
Slender Beams ◽  
Applied Forces ◽  
The Cross

How do we assess the capability of a compliant mechanism of given topology and shape? The kinetoelastostatic maps proposed in this paper help answer this question. These maps are drawn in 2D using two non-dimensional quantities, one capturing the nonlinear static response and the other the geometry, material, and applied forces. Geometrically nonlinear finite element analysis is used to create the maps for compliant mechanisms consisting of slender beams. In addition to the topology and shape, the overall proportions and the proportions of the cross-sections of the beam segments are kept fixed for a map. The finite region of the map is parameterized using a non-dimensional quantity defined as the slenderness ratio. The shape and size of the map and the parameterized curves inside it indicate the complete kinetoelastostatic capability of the corresponding compliant mechanism of given topology, shape, and fixed proportions. Static responses considered in this paper include input/output displacement, geometric amplification, mechanical advantage, maximum stress, etc. The maps can be used to compare mechanisms, to choose a suitable mechanism for an application, or re-design as may be needed. The usefulness of the non-dimensional maps is presented with multiple applications of different variety. Non-dimensional portrayal of snap-through mechanisms is one such example. The effect of the shape of the cross-section of the beam segments and the role of different segments in the mechanism as well as extension to 3D compliant mechanisms, the cases of multiple inputs and outputs, and moment loads are also explained. The effects of disproportionate changes on the maps are also analyzed.

The Fatigue Crack Propagation of the Ship Structures in Random Sea States

2012 ◽  
Author(s):  
Guoqing Feng ◽  
Junwei Cao ◽  
Huilong Ren ◽  
Hui Li
Keyword(s):  
Fatigue Strength ◽  
Fracture Mechanics ◽  
Traditional Method ◽  
Stress Cycle ◽  
Stress History ◽  
Ship Structures ◽  
Strength Assessment ◽  
Fatigue Stress ◽  
History Of ◽  
Fatigue Strength Assessment

The traditional method for the fatigue strength assessment of ship structures is based on S-N curves and Miner linear cumulative damage rules. However, with the development of the ship mechanics, the fracture mechanics method has aroused people’s attention. Some researchers have begun to use the fracture mechanics method to perform the fatigue strength assessment of ship structures. A fracture mechanics based approach for the fatigue assessment of ship structures in random sea states is presented. First, the fatigue stress history of the ship structures in random sea states is simulated. Then, the stress intensity factor in random sea states is calculated through the weight function and the fatigue stress of the ship structures in random sea states. Finally, the crack growth is calculated using Pairs equation for each stress cycle throughout the fatigue stress history of the ship structures in random sea states.

Design Loads Used for Direct Strength Assessment of Merchant Ship Structures

2004 ◽  
Author(s):  
Tingyao Zhu ◽  
Toshiyuki Shigemi
Keyword(s):  
Irregular Waves ◽  
Estimation Methods ◽  
Regular Waves ◽  
Bulk Carrier ◽  
Ship Structures ◽  
Strength Assessment ◽  
Hull Girder ◽  
Merchant Ship ◽  
Bulk Carriers ◽  
Design Loads

This paper summarizes the results of extensive research on the design loads used for strength assessment of merchant ship structures such as tankers, bulk carriers and container ships. The main aim of the research was to develop practical estimation methods of design loads having rational technical backgrounds acting on primary structural members of tankers, bulk carriers and container ships. During this study: 1) The design sea states that closely resemble the actual sea states which are considered as the most severe for hull structures are proposed. 2) The practical estimation methods of the design sea states are proposed by parametric studies using the results of series calculation of representative merchant ships. 3) The practical estimation methods of design regular waves resulting in the same level of stresses with that induced in irregular waves under the design sea states are proposed. 4) The practical estimation methods of the design loads such as ship motions, accelerations, hull-girder bending moments and hydrodynamic pressures that are induced under design regular waves are briefly introduced. The findings in this study have been summarized and implemented in the new design standards for tanker, bulk carrier and container ship structures. (Guidelines for Tanker Structures, 2001, Nippon Kaiji Kyokai. Guidelines for Bulk Carrier Structures, 2002, Nippon Kaiji Kyokai. Guidelines for container Carrier Structures, 2003, Nippon Kaiji Kyokai.)

Buckling and Ultimate Strength Assessments of Ship Structures

2013 ◽  
Author(s):  
Shengming Zhang
Keyword(s):  
Ultimate Strength ◽  
Fe Analysis ◽  
Development Work ◽  
Ship Structures ◽  
Element Analysis ◽  
Strength Assessment ◽  
Stiffened Panels ◽  
Development History ◽  
Bulk Carriers ◽  
Oil Tankers

This paper presents buckling and ultimate strength assessment methods for ship structures. Buckling and collapsing analysis approaches for plates, stiffened panels and hull girders are described and their development history and employments in ship design assessments are reviewed and discussed. Examples using non-linear finite (FE) element analysis are given and comparisons between results obtained by formulae and FE analysis are carried out. Lloyd’s Register’s recent research and development work on ultimate strength and its applications to existing oil tankers and bulk carriers are also presented.

Fatigue Strength Assessment of Ship Structures Based on the Crack Propagation Theory

2009 ◽  
Author(s):  
Song Niu ◽  
Guoqing Feng ◽  
Huilong Ren ◽  
Jian Zhang
Keyword(s):  
Crack Propagation ◽  
Function Method ◽  
Failure Modes ◽  
Analysis Method ◽  
Propagation Theory ◽  
Ship Structures ◽  
Element Analysis ◽  
Fatigue Assessment ◽  
Strength Assessment ◽  
Simplified Procedures

Fatigue damage is one of the main failure modes of ship structures. At present, the fatigue assessment of ship structures is mainly based on S-N method, such as the simplified procedures by classification societies or the spectral fatigue analysis method, etc. Because the initial flaw or crack can not be taken into account in S-N method, the fatigue assessment of ship structures based on fracture mechanics or crack propagation theory is worth to be studied. In this paper, the crack propagation theory based fatigue assessment of ship structures is studied. First, the calculation of stress intensity factor based on finite element analysis and weight function method are given, then Paris model is used to predict the crack propagation life. Finally, a numerical example is given to show the procedure of fatigue assessment of ship structures.

Buckling Behaviour of Stainless Steel Square Hollow Sections

2016 ◽  
Vol 853 ◽  
pp. 301-305
Author(s):  
Shameem Ahmed ◽  
Mahmud Ashraf ◽  
Mohammad Anwar-Us-Saadat
Keyword(s):  
Stainless Steel ◽  
Strain Hardening ◽  
Cross Sections ◽  
Design Method ◽  
Numerical Models ◽  
Slenderness Ratio ◽  
Design Guidelines ◽  
Material Nonlinearity ◽  
Cross Sectional ◽  
Steel Design

Structural stainless steel design guidelines should appropriately recognise its characteristic beneficial properties such as material nonlinearity and significant strain hardening. The Continuous Strength Method (CSM) exploits those through a strain based approach for both stocky and slender cross-sections. In this paper, a new design method is proposed that combines the CSM with Perry type buckling curves. Numerical models were developed to investigate effects of various parameters on column strength and to develop full column curves. It was observed that material nonlinearity significantly influence column strengths, and hence, different column curves were developed for a total of 20 material property combinations by calibrating imperfection factor and limiting slenderness ratio for each set. Proposed method includes the strain hardening benefits for stocky section, and abolished the necessity of calculating effective cross-sectional properties for slender sections. Performance of the proposed technique is compared against those obtained by the Eurocode EN1993-1-4.

scholarly journals Assessment the strength of steel ship structures in collision damaged by simulation method

2015 ◽  
Vol 18 (4) ◽  
pp. 94-101
Author(s):  
Vu Van Huynh
Keyword(s):  
Simulation Method ◽  
Ship Structures ◽  
Strength Assessment ◽  
Bulbous Bow ◽  
Assessment Results

This paper presents the strength assessment results in collision damaged condition between the 20000 DWT steel ship with bulbous bow of another ship by simulation method. The simulation collision studies have been performed using the FEM through the Abaqus/Explicit. This research investigates six cases which three cases the striking ship velocity is 5 knot and three cases expand.

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