Progressive Collapse Analysis and Reliability of a Damaged Hull Girder

2014 ◽  
Author(s):  
Achinike U. Ibekwe ◽  
YongChang Pu ◽  
Wan L. Ham ◽  
Robert S. Dow
Keyword(s):  
Ultimate Strength ◽  
Structural Reliability ◽  
Numerical Technique ◽  
Progressive Collapse ◽  
Limit State ◽  
Neutral Axis ◽  
Statistical Characteristics ◽  
Structural Safety ◽  
State Function ◽  
Hull Girder

With the expectation of hull girder asymmetry and corresponding shift in elastic neutral axis resulting from collision damages and other forms of structural deteriorations, the interaction of vertical and horizontal hull girder capacities become quite significant in the assessment of ship structural safety. This paper therefore extends the application of a previously proposed interactive-numerical probabilistic based methodology for structural safety to assess the hull girder ultimate strength reliability of a damaged ship by means of a user-defined numerical framework. Hull girder capacity is calculated using the NS94D ultimate strength code, which is based on the Smith’s progressive collapse method. The resulting deterministic responses have been interactively linked to the NESSUS probabilistic framework so that the reliability of the damaged hull girder is predicted using an implicit limit state function defined based on a transformation of coordinates to appropriately account for any shift in the neutral axis. Random deviations of the constituent variables are directly applied to calculate the ultimate strength deterministic responses, thereby circumventing the need to characterize any correlated strength variable, which is at best subjective. The conventional approach of characterizing ultimate strength by an assumed coefficient of variation and distribution type was found to be conservative in predicting structural safety of ships relative to the proposed method. Application of the interactive-numerical technique for structural reliability is therefore considered significant for problems involving correlated random variables with unknown statistical characteristics. The method is being considered to predict the safety of cracked hull girders by accounting for the residual strength and further load bearing capabilities of deteriorated and adjacent elements.

Ultimate Strength and Structural Reliability Analysis of FPSO Hull Girder

2002 ◽  
Author(s):  
Eldho Paul ◽  
Appapillal Thavalingam ◽  
Pumendu K. Das
Keyword(s):  
Reliability Analysis ◽  
Ultimate Strength ◽  
Cross Section ◽  
Structural Reliability ◽  
Strength Analysis ◽  
State Function ◽  
Ultimate Capacity ◽  
Hull Girder ◽  
Structural Reliability Analysis ◽  
Wave Induced

The aim of this paper is to provide some results from an investigation on available simplified formulations for ultimate strength analysis of the gull girder and the possibility of extending these methods in order to couple with reliability computations. This particular study is based on an analytical method proposed by Paik and Mansour. The procedure is enhanced to include structural reliability analysis of FPSOs based on probabilistic approach where uncertainties for both capacity and loading of the structure are taken into account. The estimation of the Ultimate longitudinal capacity and the probability of failure of the FPSO are carried out by dividing the cross section of the hull girder into beam column elements considering the different loads acting on the hull. The limit state function is formulated considering the loads acting on the hull girder and ultimate capacity. The ultimate capacity of the hull is taken as a function of variety of random variable (e.g. area of cross section and yield stresses of the different ship components, etc). The loads acting on the hull girder, both still water and wave induced are calculated using IACS and DNV rules and margins are provided to take care of the long-term deployment of FPSO at sea. Some results from the sensitivity analysis are also provided which has been carried out to study the influence of several factors on the structural reliability of the ship under extreme wave induced bending moment loads.

Temperature Effects on FPSO Ultimate Strength: A Reliability Based Approach

2003 ◽  
Author(s):  
Ioannis Moatsos ◽  
Purnendu K. Das
Keyword(s):  
Reliability Analysis ◽  
Ultimate Strength ◽  
Temperature Effects ◽  
Structural Reliability ◽  
Combination Method ◽  
Structural Safety ◽  
Hull Girder ◽  
Reliability Method ◽  
The Subject ◽  
Effects Of Temperature

Structural Reliability analysis is based on probability theory and a significant amount of literature exists on the subject and continues to be a subject of ongoing research. When the structural safety of a ship’s hull is considered, the ultimate hull girder strength should be evaluated. Existing literature on the subject often neglects the effect of temperature. This paper aims to determine the effects of temperature in ship structural reliability and to propose a procedure for analysing structures by taking into account temperature effects. The ultimate strength of the hull girder was calculated using a component approach, where the behaviour of the hull is evaluated based on the behaviour of the single structural components. A sample analysis for Tanker/FPSO structures is provided where the reliability analysis was carried out using a First and Second Order Reliability Method (FORM and SORM) analysis. The loading component was handled using extreme wave statistics and the Ferry Borges-Castanheta load combination method. Annual reliability indices and probabilities of failure were calculated for hogging and sagging conditions showing the effects of temperature along with Partial Safety Factors for all variables taken into account.

Probabilistic Assessment of Hull Girder Strength and Stiffness

2006 ◽  
Author(s):  
Magnu´s Arason ◽  
John S. Kent
Keyword(s):  
Ultimate Strength ◽  
Structural Reliability ◽  
Limit State ◽  
Computational Effort ◽  
Strength Prediction ◽  
Load Prediction ◽  
Probabilistic Prediction ◽  
Hull Girder ◽  
Section Modulus ◽  
Strength And Stiffness

The paper summarises recent work on a probabilistic prediction of hull girder strength and stiffness. This addresses a requirement within the UK Ministry of Defence to introduce structural reliability based methods for naval ship structures, which can have benefits in design as well as inservice assessment. A Monte Carlo simulation scheme, which samples a number of probability distributions, has been developed for application with an ultimate strength prediction tool. This tool uses 2D representation of hull girder sections. The section models are divided into regions that are assumed to have the same statistical properties within each simulation cycle. It is demonstrated that a lognormal distribution describing the ultimate strength of a hull girder section can be derived with relatively little computational effort. The results indicate that whilst standard deterministic strength predictions fall below mean values, there is a significant probability that actual hull girder strengths may be lower. This is of the order of 5%. Modelling uncertainties associated with the simplified strength prediction method are also outlined and quantified. The same method can be used for calculating hull section modulus. Results can be used directly when transforming measured strains to applied bending moments as part of work on load prediction and validation of hydrodynamic tools. The work presented forms part of a larger research programme that aims to produce recommendations for a limit state based assessment of hull girder strength against wave induced bending.

An Efficient Response Surface Method Using Givens Transformation for Structural Reliability Analysis

2012 ◽  
Vol 532-533 ◽  
pp. 408-411
Author(s):  
Wei Tao Zhao ◽  
Yi Yang ◽  
Tian Jun Yu
Keyword(s):  
Response Surface ◽  
Response Surface Method ◽  
Structural Reliability ◽  
Limit State ◽  
State Function ◽  
Limit State Function ◽  
Surface Method ◽  
Mathematical Techniques ◽  
Input Variables ◽  
Improved Accuracy

The response surface method was proposed as a collection of statistical and mathematical techniques that are useful for modeling and analyzing a system which is influenced by several input variables. This method gives an explicit approximation of the implicit limit state function of the structure through a number of deterministic structural analyses. However, the position of the experimental points is very important to improve the accuracy of the evaluation of failure probability. In the paper, the experimental points are obtained by using Givens transformation in such way these experimental points nearly close to limit state function. A Numerical example is presented to demonstrate the improved accuracy and computational efficiency of the proposed method compared to the classical response surface method. As seen from the result of the example, the proposed method leads to a better approximation of the limit state function over a large region of the design space, and the number of experimental points using the proposed method is less than that of classical response surface method.

Response surface method strategies coupled with NLFEA for structural reliability analysis of prestressed bridges

2021 ◽  
Author(s):  
Silvia J. Sarmiento Nova ◽  
Jaime Gonzalez-Libreros ◽  
Gabriel Sas ◽  
Rafael A. Sanabria Díaz ◽  
Maria C. A. Texeira da Silva ◽  
...  
Keyword(s):  
Reliability Analysis ◽  
Response Surface ◽  
Response Surface Method ◽  
Structural Reliability ◽  
Limit State ◽  
Material Behavior ◽  
Nonlinear Material ◽  
State Function ◽  
Surface Method ◽  
Highly Nonlinear

<p>The Response Surface Method (RSM) has become an essential tool to solve structural reliability problems due to its accuracy, efficacy, and facility for coupling with Nonlinear Finite Element Analysis (NLFEA). In this paper, some strategies to improve the RSM efficacy without compromising its accuracy are tested. Initially, each strategy is implemented to assess the safety level of a highly nonlinear explicit limit state function. The strategy with the best results is then identified and used to carry out a reliability analysis of a prestressed concrete bridge, considering the nonlinear material behavior through NLFEA simulation. The calculated value of &#120573; is compared with the target value established in Eurocode for ULS. The results showed how RSM can be a practical methodology and how the improvements presented can reduce the computational cost of a traditional RSM giving a good alternative to simulation methods such as Monte Carlo.</p>

An Efficient Reliability Analysis Method for Structures With Epistemic Uncertainty Using Evidence Theory

2014 ◽  
Author(s):  
Zhe Zhang ◽  
Chao Jiang ◽  
G. Gary Wang ◽  
Xu Han
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Epistemic Uncertainty ◽  
Limit State ◽  
Computational Cost ◽  
Evidence Theory ◽  
State Function ◽  
Limited Information ◽  
Design Point ◽  
Engineering Problems

Evidence theory has a strong ability to deal with the epistemic uncertainty, based on which the uncertain parameters existing in many complex engineering problems with limited information can be conveniently treated. However, the heavy computational cost caused by its discrete property severely influences the practicability of evidence theory, which has become a main difficulty in structural reliability analysis using evidence theory. This paper aims to develop an efficient method to evaluate the reliability for structures with evidence variables, and hence improves the applicability of evidence theory for engineering problems. A non-probabilistic reliability index approach is introduced to obtain a design point on the limit-state surface. An assistant area is then constructed through the obtained design point, based on which a small number of focal elements can be picked out for extreme analysis instead of using all the elements. The vertex method is used for extreme analysis to obtain the minimum and maximum values of the limit-state function over a focal element. A reliability interval composed of the belief measure and the plausibility measure is finally obtained for the structure. Two numerical examples are investigated to demonstrate the effectiveness of the proposed method.

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.

Reliability Analysis of Foundation Pit by Improved Response Surface Method

2011 ◽  
Vol 147 ◽  
pp. 197-202 ◽  
Author(s):  
Jiang Zhou ◽  
Jing Cao ◽  
Yu He ◽  
Jie Song
Keyword(s):  
Reliability Analysis ◽  
Response Surface ◽  
Structural Reliability ◽  
Lateral Displacement ◽  
Limit State ◽  
Uniform Design ◽  
Design Parameters ◽  
State Function ◽  
Foundation Pit ◽  
Improved Response Surface Method

Lacking of explicit limit state function (LSF) will result large quantities of computational efforts for a FEAM based structural reliability analysis. An improved response surface (RS) method is proposed to analyze the failure probability of foundation pit through combining uniform design (UD) and non-parametric regression (NPR). Deferent levels of design parameters are first delicately selected according to UD and then FEAM is used to analysis corresponding pit response parameters including maximum lateral displacement of wall, settlement of ground, safety factor of overall stability, safety factors of against overturning, heave and piping. The RS relationship is then established through NPR based on inputs and responses. At last, a direct Mont Carlo Simulation is carried out to obtain the probability density function of response parameters.

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