Effect of Pressure on Collapse Behaviour of Stiffened Panel

2014 ◽  
Author(s):  
Lei Jiang ◽  
Shengming Zhang
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Lateral Pressure ◽  
Initial Pressure ◽  
Offshore Structures ◽  
Numerical Results ◽  
Stiffened Panel ◽  
Longitudinal Stress ◽  
Stiffened Panels ◽  
Hull Girder

During normal operations, ship and offshore structures, are subjected to combined lateral pressure and in-plane stresses. The effect of the lateral pressure is often ignored in hull girder ultimate assessments. This paper investigates the influence of the lateral pressures on the nonlinear collapse behavior of stiffened panels subjected to in-plane longitudinal stress. In this study, nonlinear finite element analyses were first conducted for the desired pressure alone; the longitudinal stress was then applied up to and beyond the collapse of the structures. Four representative stiffened panels taken from the bottoms of different double hull oil tankers were considered. The nonlinear analyses were performed using LR’s in-house finite element program VAST and following the procedure for nonlinear collapse analysis developed by LR. The numerical results indicated that the application of the initial pressure loads not only reduced the ultimate load carrying capacity of the panels significantly, but also changed the failure modes of the structures. The sensitivity of the ultimate strength to lateral pressure was dependent upon the panel geometry and whether the pressure was applied on the plate or the stiffener side. The numerical results and findings from this study are presented in this paper.

Finite Element Analysis of Top-Hat–Stiffened Panels of Fiber-Reinforced–Plastic Boat Structures

2007 ◽  
Vol 44 (01) ◽  
pp. 16-26
Author(s):  
Ömer Eksik ◽  
R. Ajit Shenoi ◽  
Stuart S. J. Moy ◽  
Han Koo Jeong
Keyword(s):  
Finite Element ◽  
Lateral Pressure ◽  
Three Dimensional ◽  
Element Model ◽  
Stiffened Panel ◽  
Element Analysis ◽  
Stiffened Panels ◽  
Fiber Reinforced Plastic ◽  
Reinforced Plastic ◽  
Experimental Findings

This paper describes the development of a finite element model in order to assess the static response of a top-hat-stiffened panel under uniform lateral pressure. Systematic calculations were performed for deflection, strain, and stress using the developed model based on the ANSYS three-dimensional solid element (SOLID45). The numerical modeling results were compared to the experimental findings for validation and to further understand an internal stress pattern within the different constituents of the panel for explaining the likely causes of the panel failure. Good correlation between experimental and numerical strains and displacements was achieved.

Ultimate Strength of Stiffened Plates Subjected to Longitudinal Compression and Lateral Pressure

2014 ◽  
Author(s):  
Karan Doshi ◽  
Suhas Vhanmane
Keyword(s):  
Finite Element ◽  
Ultimate Strength ◽  
Lateral Pressure ◽  
Stiffened Plates ◽  
Stiffened Panel ◽  
Element Analysis ◽  
Stiffened Panels ◽  
Linear Finite Element ◽  
Non Linear ◽  
Compressive Loads

This paper presents a non-linear finite element analysis (FEA) and subsequent formula development for ultimate strength of stiffened panels of ship structures. A review of studies on ultimate strength of ship plating subjected to lateral pressure was carried out. The present work takes into account, the influence due to the lateral pressure on the ultimate strength of stiffened plates with initial imperfections subject to longitudinal compressive loads. ANSYS non-linear FE software was used for non linear finite element analyses of stiffened panels (864 cases) considering VLCC hull. Based on regression analysis, a set of semi-analytical formulae were proposed and described. It is observed that depending upon the failure mode, scantlings of the stiffened panel and magnitude of lateral pressure, ultimate strength of the stiffened panels in compression is affected.

scholarly journals The Prediction of Buckling Load of Laminated Composite Hat-Stiffened Panels Under Compressive Loading by Using of Neural Networks

2018 ◽  
Vol 12 (1) ◽  
pp. 468-480 ◽  
Author(s):  
Shashi Kumar ◽  
Rajesh Kumar ◽  
Sasankasekhar Mandal ◽  
Atul K. Rahul
Keyword(s):  
Neural Network ◽  
Finite Element ◽  
Network Architecture ◽  
Laminated Composite ◽  
Buckling Load ◽  
Stiffened Panel ◽  
Stiffness Ratio ◽  
Data Set ◽  
Stiffened Panels ◽  
Structural Problems

Background:Stiffened panels are being used as a lightweight structure in aerospace, marine engineering and retrofitting of building and bridge structure. In this paper, two efficient analytical computational tools, namely, Finite Element Analysis (FEA) and Artificial Neural Network (ANN) are used to analyze and compare the results of the laminated composite 750-hat-stiffened panels.Objective:Finite Element (FE) is an efficient and versatile method for the analysis of a complex problem. FE models have been used to generate data set of four different parameters. The four parameters are extensional stiffness ratio of skin in the longitudinal direction to the transverse direction, orthotropy ratio of the panel, the ratio of twisting stiffness to transverse flexural stiffness and smeared extensional stiffness ratio of stiffeners to that of the plate.Results and Conclusion:For training of ANN, multilayer feedforward back-propagation has been used as a network function with two-hidden layers in the neural network. The good network architecture is achieved after several iterations to predict the buckling load of the stiffened panel. ANN prediction for unknown new data set is in good agreement with FEA results of different cases, which show that ANN tool can be used for the design of complex structural problems in civil engineering and optimization of the laminated composite stiffened panel.

On the Ductile Response of Stiffened Panels Subjected to Lateral Indentation: Experimental and Numerical Analysis

2010 ◽  
Author(s):  
Hagbart S. Alsos ◽  
Jo̸rgen Amdahl
Keyword(s):  
Finite Element ◽  
Plate Thickness ◽  
Offshore Structures ◽  
Instability Criterion ◽  
Potential Hazard ◽  
Explicit Finite Element ◽  
Stiffened Panels ◽  
Environmental Consequences ◽  
Structural Capacity ◽  
Indentation Tests

Reliable prediction of ductile fracture is essential in analysis of accidental response of ships and offshore structures. The consequences of fracture are significant. It may imply a significant reduction in structural capacity. It may also pose a potential hazard for human safety, as well as lead to an environmental and economical loss, e.g. caused by tanker collision or grounding. A series of five steel-plate indentation tests were conducted at the Norwegian University of Science and Technology (NTNU), Department of Mariner Technology, during late fall 2007. These are performed quasi-statically on various configurations of stiffened panels. The tests represent hull or deck plates in ships or platform structures subjected to accidental actions from ship-ship collisions, ship grounding or dropped object impacts. Various configurations of stiffened panels are tested, all laterally by a cone shaped indenter until fracture occurred. The specimen dimensions represent a 1:3 scale of the dimensions found in medium sized tankers, i.e. plate thickness of 5 mm. Naturally, because damaged hull and cargo tanks may cause severe environmental consequences, focus is on the plastic deformation and fracture resistance of the panels. The panel tests are primarily intended to serve as verification for advanced finite element simulations using a failure criterion based on instability mechanisms, i.e. local necking. This is implemented into the non linear explicit finite element code LS-DYNA and is referred to as the BWH instability criterion. In addition, the influence of the element size with respect to onset of failure is studied using three different element sizes for the various test cases. Although, attention is primarily placed on accidental scenarios, such as ship collision and grounding, the experimental results are of considerable relevance for other types of abnormal actions, e.g. dropped objects on deck and subsea structures, and stiffened panels subjected to explosion or ice actions.

Time-Variant Reliability Assessment of FPSO Hull Girder With Long Cracks

2006 ◽  
Vol 129 (2) ◽  
pp. 81-89 ◽  
Author(s):  
Efrén Ayala-Uraga ◽  
Torgeir Moan
Keyword(s):  
Brittle Fracture ◽  
Fatigue Cracking ◽  
Stiffened Panel ◽  
Stress Effect ◽  
Mean Stress ◽  
Stiffened Panels ◽  
Hull Girder ◽  
Mean Stress Effect ◽  
Hull Structure ◽  
The Mean

An efficient time-variant reliability formulation for the safety assessment of an aging floating production storage and offloading (FPSO) vessels with the presence of through-thickness cracks (i.e., long cracks), is presented in this paper. Often in ship structures, cracks are detected by means of close visual inspection when they have already propagated through the thickness. The propagation of long cracks in stiffened panels is therefore considered, as they may be present in critical details of the deck and/or bottom plating of the vessel. Although it has been found that stiffened panels are tolerant to fatigue cracking, the safety of such structural components with the presence of long cracks may be threatened when exposed to overload extreme conditions, i.e., brittle or ductile fracture may occur. The probability of brittle fracture of an aging hull structure, i.e., a stiffened panel at the bottom plating with the presence of long cracks is studied in this paper. The mean stress effect due to the continuously varying still-water loading as well as residual stresses is explicitly accounted for in the crack growth calculation procedure presented herein. An analytical model is established for determining the equivalent long-term stress range including the mean stress effect. The continuously varying still-water load effects due to the operational nature of FPSOs introduce additional uncertainties in the estimation of fatigue damage as well as in the likelihood of fracture failure mode. In the present case study it is found that the time-invariant approach is a good approximation when dealing with the time-variant reliability problem. One of the main conclusions drawn from this study is that the still-water mean stress has a significant effect on the failure probabilities of stiffened panels with long cracks under brittle fracture mode.

scholarly journals Influence of boundary condition and stiffener type on collapse behaviours of stiffened panels under longitudinal compression

2019 ◽  
Vol 11 (10) ◽  
pp. 168781401988476
Author(s):  
Jin Pan ◽  
Na Li ◽  
Zhao Jun Song ◽  
Ming Cai Xu
Keyword(s):  
Boundary Condition ◽  
Finite Element ◽  
Carrying Capacity ◽  
Biaxial Stress ◽  
Stiffened Panel ◽  
Load Carrying Capacity ◽  
Longitudinal Compression ◽  
Stiffened Panels ◽  
Biaxial Stress State ◽  
Load Carrying

A series of stiffened panels with different dimensions and types of stiffener are simulated under longitudinal compression in finite element code ANSYS. Two bays/spans model with periodic boundary condition is adopted to consider the influence of neighbouring members. The stiffened panel adopted in the finite element mode is generally cut from the deck or bottom of a ship hull girder, and thus, the constraint on their edges depends to some extent on the relative structural response of the adjacent members. Hence, to understand the effects of constraint condition on the collapse behaviour, an extensive parametric study is carried out, employing a wide geometrical range for bulk carrier and very large crude carrier. Moreover, considering various collapse modes, the load-carrying capacities of the stiffened panels are also investigated for various stiffener types. It is found that the biaxial stress state caused by longitudinal constraint could increase or decrease the load-carrying capacity of the stiffened panel, which depends on the collapse mode and should be noticed. The transverse constraint on the longitudinal edges could cause biaxial stress state, which might increase or decrease the load-carrying capacity of the stiffened panel, which depends on the collapse modes.

Residual Compressive Strength of Dented FPSO Side Shell Panel

2014 ◽  
Author(s):  
Diogo do Amaral Amante ◽  
John Alex Chujutalli ◽  
Segen F. Estefen
Keyword(s):  
Finite Element ◽  
Compressive Strength ◽  
Compressive Load ◽  
Stiffened Panel ◽  
Finite Element Program ◽  
Stiffened Panels ◽  
Residual Compressive Strength ◽  
Element Program ◽  
Shell Panel ◽  
Dent Depth

This paper presents a non-linear finite element study to obtain the ultimate compressive strength of dented FPSO side stiffened panels. The finite element program ABAQUS was used to perform numerical analysis. The analysis is carried out in two steps. First the supply collision damage is imposed using the ABAQUS explicit code program. After the indentation, a compressive load is applied and then the panel residual compressive strength is obtained. A parametric study was accomplished to evaluate the influence of the dent depth on the stiffened panel strength. Damages occurring on the stiffener and between the stiffeners are compared.

Optimization of stiffened panels under compression

1986 ◽  
Vol 21 (3) ◽  
pp. 153-158
Author(s):  
Li Weiji
Keyword(s):  
Design Process ◽  
Numerical Results ◽  
Stability And Convergence ◽  
Stiffened Panel ◽  
Feasible Direction ◽  
Stiffened Panels ◽  
Feasible Direction Method ◽  
Design Variables ◽  
Effectiveness And Efficiency

The optimization of the angle-stiffened panel under compression using the feasible direction method is studied in this paper. We could only take the most critical constraint into account for each iteration when using the feasible direction method, with the result that the process of calculation is greatly simplified. It is beneficial for stability and convergence of the design process that the design variables in each iteration are modified once by some experience formulae, if necessary. The illustrative examples and the comparison of the numerical results of this paper with those of another paper indicate the effectiveness and efficiency of the method presented here.

Evaluation of Cumulative Collapse of a LNG Carrier Hull Girder Under Dynamic Cyclic Bending Moments

2021 ◽  
Author(s):  
Jian Ji ◽  
Bin Liu ◽  
Lin Chen ◽  
Xianting Liao ◽  
C. Guedes Soares
Keyword(s):  
Finite Element ◽  
Ultimate Strength ◽  
Failure Modes ◽  
Ship Hull ◽  
Bending Moments ◽  
Nonlinear Finite Element Method ◽  
Cyclic Bending ◽  
Hull Girder ◽  
Hull Structure ◽  
The Difference

Abstract The present paper continues the recent work reported by Liu and Guedes Soares [1] where finite element simulations were conducted to investigate the ultimate strength of a container ship hull girder under cyclic bending moments. Here a membrane LNG carrier is investigated to evaluate the “cyclic ultimate strength” of this specialized ship hull structure including double bottoms, sides and decks. The paper aims to analyze the ultimate strength and to compare the collapse modes of a LNG carrier hull girder under monotonic and dynamic cyclic bending moments, revealing the difference in their failure modes. Nonlinear finite element method is employed, using the explicit LS-DYNA solver, to analyze the ultimate strength of hull structures. The numerical results show that the cyclic ultimate strength of hull structures is about 20% lower than the monotonic ultimate strength in the present study.

Bond Strength Testing and Simulation for Grouted Pile/sleeve Connections in Aged Structures

2021 ◽  
Author(s):  
Raja Srinivasa Rao Mohan Aita ◽  
Tarek Omar ◽  
Anjan Amulyaratan Sarkar ◽  
Michael Roy ◽  
Xing Sun ◽  
...  
Keyword(s):  
Finite Element ◽  
Bond Strength ◽  
Failure Modes ◽  
Load Capacity ◽  
Offshore Structures ◽  
Material Strength ◽  
Mechanical Resistance ◽  
Geometrical Parameters ◽  
Strength Tests ◽  
Shear Keys

Abstract Recently the old accommodation platform (OAP) was decommissioned in Offshore Abu Dhabi. This platform was founded on four legs with piles inside and duly grouted inside pile and annulus. The main objective of this to carry out bond strength tests and finite element (FE) analysis for retrieved OAP grouted samples to investigate if any ageing effect on the bond strength of the grouted pile/sleeve connections for aged offshore structures. Nine Sleeve/Pile samples of varying lengths from 240mm to 1200mm were extracted for testing from the decommissioned platform. Dimensional analysis was carried out to assess the thickness loss and eccentricity. A bespoke testing rig with the maximum load capacity of 15,000kN was built at TWI Ltd. to perform bond strength tests. Finite element (FE) simulation of the testing was carried out and compared to the test results to calibrate and fine-tune material constitutive behaviour parameters and interfacial (friction and bond) parameters. Specimen measurements revealed a significant scatter in annulus grout thicknesses of various sleeve/pile specimens with maximum variations of up to 52%. These results indicate that pile alignment is strongly variable. Shear keys in the form of steel rings welded alternately onto the leg's inner surface and the pile outer surface providing mechanical resistance to relative sliding of the grout between the two bodies. The testing results shown that the ultimate loads varied significantly among various specimens, ranged between 9920kN for 1m specimen and 1800kN for 1.2m specimen. FE simulations agreed well with the observed failure modes and were used to investigate how the measured failure loads were influenced by grout material properties, cohesive bond behaviour and geometrical parameters such as shear keys and eccentricity. From the FE studies, it was found that different cohesive (surface) parameters are required to give the best fit, with the higher cohesive stiffness and strength associated with a higher failure load. Grout strength is also a significant parameter, but the effect of surface cohesion is less significant compared to material strength. The majority of the tested values were found to be meeting the minimum bond strength resulting from available standards (eg. ISO 19902). This type of real time testing output will provide insight into various parameters that contribute to bond strength in pile leg grouted connections. Moreover, these test and assessment results will form an integral and important input to various ongoing researches associated with ADNOC's grouted connections being carried out as part of another JIP led by National University of Singapore which is aimed at deriving design equations applicable to grouted connections beyond codal limits.

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