A Method for Ultimate Strength Assessment of Plates in Combined Stresses

2015 ◽  
Author(s):  
Shengming Zhang ◽  
Lei Jiang
Keyword(s):  
Ultimate Strength ◽  
Structural Engineering ◽  
Fe Analysis ◽  
Strength Analysis ◽  
Element Analysis ◽  
Simple Method ◽  
Strength Assessment ◽  
Industry Standards ◽  
Non Linear ◽  
Offshore Industry

It is becoming a normal practice in structural engineering, including ships and offshore industry, to perform non-linear finite element analysis to assess the structure’s capacity for design or evaluation purposes. However, experience has shown that the quality and accuracy of the non-linear FE analysis results are highly dependent on the person’s skills and analysis procedures used. In some cases, the results could lead to a wrong conclusion. Simplified method with good accuracy is still a preferred approach in design by the industry because it is simple and easy to use. However, even the method for the simple model, a plate under combined loads, has not been addressed completely because of its complexity. This paper has thus developed a simple method for the ultimate strength analysis of square plates under combined longitudinal and transverse compressive stresses. The method is fully validated with a systematic non-linear FE analysis results. The paper has also compared the methods from the industry standards BS5400 and DIN18800. Analysis examples are also provided in the paper for reference and discussions.

A Procedure for Non-Linear Structural Collapse Analysis

2014 ◽  
Author(s):  
Shengming Zhang ◽  
Lei Jiang
Keyword(s):  
Structural Engineering ◽  
Standard Procedure ◽  
Analysis Procedure ◽  
Structural Collapse ◽  
Element Analysis ◽  
Collapse Analysis ◽  
Non Linear ◽  
Mesh Density ◽  
The Difference ◽  
Offshore Industry

It is a normal practice nowadays in structural engineering, including ships and offshore industry, to perform non-linear finite element analysis to assess the structure’s capacity for design or evaluation purposes. However, experience has shown that the quality and accuracy of the non-linear FE analysis results are highly dependent on the skill of the person performing the analysis and the analysis procedure used. The difference between results obtained by different people can be significant. In some cases, the results can be misleading. It is considered that a unified procedure is necessary. This paper is moving a step further and trying to develop a standard procedure which can provide a guideline for structural collapse analysis of stiffened panels under any load combinations. The paper provides the technical background on the analysis procedure and the key steps such as model extent, mesh density, initial imperfections, and boundary conditions. Analysis examples are provided in the paper for reference and discussions.

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.

Application of the Incorporated Meshing Technique to Non-Linear FE Analysis of Hull Girder Ultimate Strength

2016 ◽  
Author(s):  
Chenfeng Li ◽  
Zhiyao Zhu ◽  
Huilong Ren ◽  
Xueqian Zhou
Keyword(s):  
Ultimate Strength ◽  
Limit State ◽  
Computation Time ◽  
Fe Analysis ◽  
Strength Analysis ◽  
Ultimate Limit State ◽  
Hull Girder ◽  
Non Linear ◽  
Promising Solution ◽  
Accuracy Of Results

In the use of non-linear FE analyses for investigating the mechanical behavior and assessing the ultimate strength characteristics of ship hull structures, fine meshes can ensure the accuracy of results they are also, however, computationally expensive in terms of efficiency. Although the incorporated meshing technique, which can effectively reduce the computation time at almost no cost of accuracy, is a promising solution, it has not been systematically investigated. In this paper, the incorporated meshing technique is applied to the nonlinear FE analysis of hull girder ultimate strength based on the assumption of a certain stress distribution of ship section in the ultimate limit state. The computations are carried out with a variety of localized mesh refinements in the compressed zones. The results of ultimate strength analysis for a typical cargo hold shows that, compared to meshing with global refinement, the incorporated meshing technique can effectively improve the computational efficiency without sacrificing the numerical accuracy.

Buckling and Ultimate Strength Assessment of FPSO Structures

2005 ◽  
Author(s):  
Haihong Sun ◽  
Xiaozhi Wang
Keyword(s):  
Ultimate Strength ◽  
Oil And Gas ◽  
Element Analysis ◽  
Strength Criteria ◽  
Strength Assessment ◽  
Stiffened Panels ◽  
Oil And Gas Fields ◽  
Extensive Test ◽  
Offshore Oil And Gas ◽  
Classification Society

Floating production, storage and offloading systems (FPSOs) have been widely used for the development of offshore oil and gas fields because of their attractive features. They are mostly ship- shaped, either converted from existing tankers or purposely built, and the hull structural scantling design for tankers may be applicable to FPSOs. However, FPSOs have their unique characteristics. FPSOs are sited at specific locations with a dynamic loading that is quite different from those arising from unrestricted service conditions. The structures are to be assessed to satisfy the requirements of all in-service and pre-service loading conditions. The fundamental aspects in the structural assessment of FPSOs are the buckling and ultimate strength behaviors of the plate panels, stiffened panels and hull girders. The focus of this paper is to address the buckling and ultimate strength criteria for FPSO structures. Various aspects of the criteria have been widely investigated, and the results of the design formulae proposed in this paper have been compared to a very extensive test database and numerical results from nonlinear finite element analysis and other available methods. The procedures presented in this paper are based on the outcomes of a series of classification society projects in the development of buckling and ultimate strength criteria and referred to the corresponding classification society publications.

A Study on the Simplified Calculation Method for the Residual Ultimate Strength of Damaged Hull Structures

2016 ◽  
Author(s):  
Kimihiro Toh ◽  
Shunsuke Maeda ◽  
Takao Yoshikawa
Keyword(s):  
Ultimate Strength ◽  
Calculation Method ◽  
Fe Analysis ◽  
Structural Members ◽  
Average Strain ◽  
Non Linear ◽  
Compressive Loads ◽  
Calculation Results ◽  
Simplified Calculation ◽  
Simplified Calculation Method

In order to obtain the non-linear average stress-average strain relationships (σ-ε curves) of damaged structural members under both tensile and compressive loads, the systematical calculations are performed using the non-linear FE analysis (FEA) code, LS-DYNA, and the idealized σ-ε curves of damaged structural members are estimated from FEA results. In addition, by introducing the idealized σ-ε curves of damaged structural members to the simplified calculation program, which is developed by authors and based on the Smith’s method, the residual ultimate strength of damaged hull structures is calculated. The residual ultimate strength of damaged hull structures is also calculated utilizing FEA, the calculation results by the simplified calculation program are compared with the results obtained from FE analyses so as to examine the accuracy of simplified calculation method.

PHOTOGRAMMETRY MEASUREMENTS OF INITIAL IMPERFECTIONS FOR THE ULTIMATE STRENGTH ASSESSMENT OF PLATES

2021 ◽  
Vol 156 (A4) ◽  
Author(s):  
A Cubells ◽  
Y Garbatov ◽  
C Guedes Soares
Keyword(s):  
Finite Element ◽  
Ultimate Strength ◽  
Compressive Load ◽  
Initial Imperfection ◽  
Maximum Load ◽  
Surface Shape ◽  
Element Analysis ◽  
Strength Assessment ◽  
Load Carrying ◽  
Geometrical Imperfections

The objective of the present study is to develop a new approach to model the initial geometrical imperfections of ship plates by using Photogrammetry. Based on images, Photogrammetry is able to take measurements of the distortions of plates and to catch the dominant surface shape, including the deformations of the edges. Having this data, it is possible to generate faithful models of plate surface based on third order polynomial functions. Finally, the maximum load- carrying capacity of the plates is analysed by performing a nonlinear finite element analysis using a commercial finite element code. Three un-stiffened and four stiffened plates have been modelled and analysed. For each plate, two initial imperfection models have been generated one, based on photogrammetric measurements and the other, based on the trigonometric Fourier functions. Both models are subjected to the same uniaxial compressive load and boundary conditions in order to study the ultimate strength.

Automated Assessment of Ultimate Hull Girder Strength

2003 ◽  
Vol 125 (3) ◽  
pp. 211-218 ◽  
Author(s):  
M. J. Smith ◽  
N. G. Pegg
Keyword(s):  
Ultimate Strength ◽  
Progressive Collapse ◽  
Three Dimensional ◽  
Strength Analysis ◽  
Cross Sectional ◽  
Strength Assessment ◽  
Hull Girder ◽  
Single User Interface ◽  
Interaction Curves ◽  
The Uk

An automated approach to ultimate hull girder strength assessment using DRDC’s ultimate strength analysis suite (ULTSAS) is described. The analysis suite improves the ability to perform rapid ultimate strength assessments by providing access to UK and Canadian analysis codes and databases under a single user interface. The interface also allows for automatic cross-sectional model generation from three-dimensional ship finite element models with the MGDSA program. The main features of the ULTSAS system are described, including cross-sectional modelling, and the use of load-shortening curve databases. The paper also provides a review of the progressive collapse method for determining ultimate strength, which is now used in both the UK and Canadian analysis codes. Two numerical approaches are described, one based on curvature incrementing and the other on moment incrementing. It is shown that the moment incrementing procedure produces more accurate bi-axial interaction curves in some instances. Results are obtained for two damage configurations of the HALIFAX class frigate.

Finite Element Analysis on the Hull Girder Ultimate Strength of Asymmetrically Damaged Ships

2016 ◽  
Author(s):  
Muhammad Zubair Muis Alie ◽  
Ganding Sitepu ◽  
Juswan Sade ◽  
Wahyuddin Mustafa ◽  
Andi Mursid Nugraha ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Ultimate Strength ◽  
Cross Sections ◽  
Progressive Collapse ◽  
Ship Hull ◽  
Strength Analysis ◽  
Functional Requirements ◽  
Element Analysis ◽  
Hull Girder

This paper discusses the influence of asymmetrically damaged ships on the ultimate hull girder strength. When such damages take place at the asymmetric location of cross sections, not only translation but also inclination of instantaneous neutral axis takes place during the process of the progressive collapse. To investigate this effect, the Finite Element Analysis (FEA) is employed and the damage is assumed in the middle hold. The collision damage is modeled by removing the plate and stiffener elements at the damage region assuming the complete loss of the capacity at the damage part. For the validation results obtained by Finite Element Analysis of the asymmetrically damaged ship hull girder, the simplified method is adopted. The Finite Element method of ultimate strength analysis of a damaged hull girder can be a practical tool for the ship hull girder after damages, which has become one of the functional requirements in IMO Goal Based Ship Construction Standard.

Ultimate Behavior of Single Shear Bolted Connections with Thin-Walled Aluminum Alloys(6061-T6)

2012 ◽  
Vol 446-449 ◽  
pp. 3441-3445 ◽  
Author(s):  
Tae Soo Kim ◽  
Yong Hyun Jo ◽  
Seung Hun Kim ◽  
Yong Taeg Lee
Keyword(s):  
Finite Element ◽  
Ultimate Strength ◽  
Plane Deformation ◽  
Free Edge ◽  
Fe Analysis ◽  
Test Results ◽  
Bolted Connections ◽  
Element Analysis ◽  
Out Of Plane ◽  
Single Shear

The purpose of this study is to investigate the ultimate behaviors of aluminum alloy bolted connections assembled with four bolts. Specimens for single shear bolted connections were tested and finite element analysis based on this test results was conducted. The validity of finite element(FE) analysis for predicting the structural behaviors such as ultimate strength, fracture mode and curling(out-of-plane deformation) occurrence was verified through the comparisons between test results and FE analysis results. It is known that the curling resulted in sudden strength drop. Moreover, FE models with free edge and restrained out-of-plane deformation for curled specimens are analyzed additionally, therefore, the influence of curling on the ultimate strength; strength reduction ratio is estimated.

Corrosion-Dependent Ultimate Strength Assessment of Aged Box Girders Based on Experimental Results

2011 ◽  
Vol 55 (04) ◽  
pp. 289-300 ◽  
Author(s):  
S. Saad-Eldeen ◽  
Y. Garbatov ◽  
C. Guedes Soares
Keyword(s):  
Service Life ◽  
Residual Stresses ◽  
Ultimate Strength ◽  
Bending Moment ◽  
Experimental Results ◽  
Time Dependent ◽  
Strength Analysis ◽  
Box Girders ◽  
Strength Assessment ◽  
Equivalent Time

This paper presents a corrosion-dependent analysis of the ultimate strength analysis of aged box girders based on experimental results. Three multispan corroded stiffened box girders subjected to four-point vertical load are analyzed, idealizing the behavior of midship sections of full ships. The specimens have three levels of corrosion. Two corrosion-dependent formulas for assessing the ultimate strength as well as the ultimate bending moment of corroded structures are proposed. Using a time-dependent corrosion growth model, equivalent time-dependent formulations are developed. The effect of corrosion degradation on the residual stresses during the service life is also analyzed, and a regression equation for predicting the remaining residual stresses along the service life is proposed. Finally, a corrosion-dependent moment-curvature relationship has been developed accounting for the changes in geometrical characteristics and material properties of the tested box girders.

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