Buckling Strength of Damaged Stiffened Panels

2011 ◽  
Author(s):  
Diogo do Amaral Amante ◽  
Segen F. Estefen
Keyword(s):  
Numerical Models ◽  
Strength Loss ◽  
Correlation Study ◽  
Small Scale ◽  
Failure Behavior ◽  
Geometric Imperfection ◽  
Stiffened Panels ◽  
Shell Elements ◽  
Buckling Strength ◽  
Parametric Studies

Numerical and experimental simulations for small scale damaged stiffened panels are performed. Six small scale stiffened panels were fabricated following special techniques to keep them in accordance with usual tolerances related to initial geometric imperfections due to fabrication. Ultimate buckling strength analyses were carried out in order to perform a correlation study to adjust the numerical model for further use in parametric studies. The damage was imposed with a local indentation on the panels. Measurements of the geometric imperfection distributions and damage shapes were accomplished using the equipment laser tracker. It is a portable contact measurement equipment that uses laser technology with sub-millimeter accuracy. The numerical models are represented by shell elements assuming finite membrane strains and large rotations, considering both geometric and material nonlinearities. The aim of the work is to study the failure behavior up to and beyond buckling to evaluate the strength loss due to the damage imposed to the panel. Additionally, some numerical simulations of damaged stiffened panels were performed. In these analyses the damage was done with explicit nonlinear finite element code from ABAQUS program. Therefore the distortions and the residual stresses due to the damage are both considered in subsequent compression analysis.

Experimental and Numerical Analyses of Dented Stiffened Panels

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Diogo do Amaral M. Amante ◽  
John Alex Chujutalli ◽  
Segen F. Estefen
Keyword(s):  
Numerical Models ◽  
Strength Loss ◽  
Correlation Study ◽  
Numerical Analyses ◽  
Small Scale ◽  
Geometric Imperfection ◽  
Stiffened Panels ◽  
Shell Elements ◽  
Before And After ◽  
Parametric Studies

Numerical–experimental correlation study for small scale damaged stiffened panels was performed. Six small scale models were fabricated. Two of them were employed for the correlation of intact panels and the remaining four for the correlation of dented panels. Ultimate strength analyses were carried out in order to adjust the numerical model for further use in parametric studies. The damage was imposed by a local indentation of the panels. Measurements of geometric imperfection distributions and damage shapes have been performed before and after the damage using a laser tracker equipment. The numerical models were represented by shell elements assuming finite membrane strains and large rotations, considering both geometric and material nonlinearities. Results obtained showed very good agreement between experimental and numerical analyses for both intact and dented panels. Additionally, numerical simulations of damaged stiffened panels were performed. The aim of the parametric study was to evaluate the behavior up to and beyond buckling, to observe the strength loss due to the presence of the damage on the panel. The explicit nonlinear finite element code from abaqus program was employed to simulate the dent damage. Therefore, distortions and the residual stresses due to the damage were both considered in subsequent numerical compression analyses.

Influence of the Geometric Imperfection on the Buckling Behavior of Floating Platform Column Under Axial Load

2007 ◽  
Author(s):  
Tiago P. Estefen ◽  
Daniel S. Werneck ◽  
Segen F. Estefen
Keyword(s):  
Progressive Failure ◽  
Correlation Study ◽  
Gas Production ◽  
Small Scale ◽  
Failure Behavior ◽  
Floating Platform ◽  
Cross Sectional ◽  
Geometric Imperfection ◽  
Stiffened Panels ◽  
Buckling Behavior

The present work focuses on the design of the new generation of semi-submersible platforms for oil&gas production offshore that is based on column square cross-sectional area. The platform column is based on an arrangement of stiffened flat panels having their ultimate strength characterized by buckling under in-plane compressive loading. Distortions induced by fabrication have considerable influence on the buckling behavior and are discussed in order to provide design recommendations. The aim of the paper is to study a segment of the column structural arrangement between robust transverse frames to analyze the failure behavior of the stiffened panels. Previous research demonstrated the strong influence of both mode and magnitude of the geometric imperfection distribution, as well as the boundary conditions. Numerical and experimental simulations for small scale isolated panels are carried out in order to perform a correlation study to adjust the numerical model for further use in more complex numerical simulations of the structural failure of the column arrangement. The stiffened panels are analyzed to identify the buckling initiation on a particular panel and then the interaction between plates, longitudinal stiffeners and the robust transverse frames during the progressive failure of the whole column.

Residual Strength of Dented Stiffened Panels

2013 ◽  
Author(s):  
Diogo do Amaral Amante ◽  
John Alex Chujutalli ◽  
Segen F. Estefen
Keyword(s):  
Compressive Strength ◽  
Numerical Models ◽  
Compressive Load ◽  
Strength Loss ◽  
Failure Behavior ◽  
Stiffened Panels ◽  
Shell Elements ◽  
Residual Compressive Strength ◽  
Large Rotations ◽  
Indentation Damage

The residual compressive strength of dented stiffened panels is investigated. Numerical simulations were performed using the finite elements program ABAQUS. The analysis is carried out in two steps. First the panel indentation 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 verified. Local damage was simulated by a dynamic collision due to an object fall. Therefore the distortions and the residual stresses due to the damage are both considered in the subsequent compression analysis. The aim of the work is to study the failure behavior up to and beyond buckling to evaluate the strength loss due to the damage imposed to the panel. The numerical models are represented by shell elements assuming finite membrane strains and large rotations, considering both geometric and material nonlinearities.

Hull Girder Ultimate Strength of Intact and Damaged Double Hull Tankers

2016 ◽  
Author(s):  
Diogo do Amaral M. Amante ◽  
John Alex Chujutalli ◽  
Segen F. Estefen
Keyword(s):  
Numerical Model ◽  
Ultimate Strength ◽  
Numerical Models ◽  
Experimental Tests ◽  
Small Scale ◽  
Box Girders ◽  
Shell Elements ◽  
Hull Girder ◽  
Damage Scenarios ◽  
Double Hull

The aim of this work is to accomplish an assessment of the hull girder ultimate strength of intact and damaged double hull tankers. First, the paper presents the validation of the numerical model through comparisons with experimental tests of small-scale box girders. The numerical models are represented by shell elements assuming finite membrane strains and large rotations, considering both geometric and material nonlinearities. Simulation results show very good agreement with experimental tests. Then, a numerical model of a double hull tanker was developed and analyzed in the intact and damaged conditions. Several damage scenarios were investigated.

scholarly journals A Computational Approach to Solve a System of Transcendental Equations with Multi-Functions and Multi-Variables

Mathematics ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 920
Author(s):  
Chukwuma Ogbonnaya ◽  
Chamil Abeykoon ◽  
Adel Nasser ◽  
Ali Turan
Keyword(s):  
Numerical Models ◽  
Problem Formulation ◽  
Science And Engineering ◽  
Physical Systems ◽  
Engineering Problems ◽  
Parametric Studies ◽  
Independent Variable ◽  
Transcendental Equations ◽  
The Waves ◽  
Modelling Approach

A system of transcendental equations (SoTE) is a set of simultaneous equations containing at least a transcendental function. Solutions involving transcendental equations are often problematic, particularly in the form of a system of equations. This challenge has limited the number of equations, with inter-related multi-functions and multi-variables, often included in the mathematical modelling of physical systems during problem formulation. Here, we presented detailed steps for using a code-based modelling approach for solving SoTEs that may be encountered in science and engineering problems. A SoTE comprising six functions, including Sine-Gordon wave functions, was used to illustrate the steps. Parametric studies were performed to visualize how a change in the variables affected the superposition of the waves as the independent variable varies from x1 = 1:0.0005:100 to x1 = 1:5:100. The application of the proposed approach in modelling and simulation of photovoltaic and thermophotovoltaic systems were also highlighted. Overall, solutions to SoTEs present new opportunities for including more functions and variables in numerical models of systems, which will ultimately lead to a more robust representation of physical systems.

scholarly journals The Effectiveness of Ensemble-Neural Network Techniques to Predict Peak Uplift Resistance of Buried Pipes in Reinforced Sand

2021 ◽  
Vol 11 (3) ◽  
pp. 908
Author(s):  
Jie Zeng ◽  
Panagiotis G. Asteris ◽  
Anna P. Mamou ◽  
Ahmed Salih Mohammed ◽  
Emmanuil A. Golias ◽  
...  
Keyword(s):  
Neural Network ◽  
Numerical Models ◽  
Correlation Coefficients ◽  
Network Models ◽  
Small Scale ◽  
Offshore Platforms ◽  
Neural Network Models ◽  
Buried Pipes ◽  
Ensemble Techniques ◽  
Uplift Resistance

Buried pipes are extensively used for oil transportation from offshore platforms. Under unfavorable loading combinations, the pipe’s uplift resistance may be exceeded, which may result in excessive deformations and significant disruptions. This paper presents findings from a series of small-scale tests performed on pipes buried in geogrid-reinforced sands, with the measured peak uplift resistance being used to calibrate advanced numerical models employing neural networks. Multilayer perceptron (MLP) and Radial Basis Function (RBF) primary structure types have been used to train two neural network models, which were then further developed using bagging and boosting ensemble techniques. Correlation coefficients in excess of 0.954 between the measured and predicted peak uplift resistance have been achieved. The results show that the design of pipelines can be significantly improved using the proposed novel, reliable and robust soft computing models.

scholarly journals Observational aspects of prominence oscillations

2007 ◽  
Vol 3 (S247) ◽  
pp. 152-157 ◽  
Author(s):  
Oddbjørn Engvold
Keyword(s):  
Magnetic Structure ◽  
Numerical Models ◽  
Small Scale ◽  
Solar Prominences ◽  
Scale Structures ◽  
Oscillations And Waves ◽  
Available Information ◽  
Small Scale Structures

AbstractSeismology has become a powerful tool in studies of the magnetic structure of solar prominences and filaments. Reversely, analytical and numerical models are guided by available information about the spatial and thermodynamical structure of these enigmatic structures. The present invited paper reviews recent observational results on oscillations and waves as well as details about small-scale structures and dynamics of prominences and filaments.

Coupled Thermo-Hydro-Geochemical Models of Engineered Barrier Systems: The Febex Project

2000 ◽  
Vol 663 ◽  
Author(s):  
J. Samper ◽  
R. Juncosa ◽  
V. Navarro ◽  
J. Delgado ◽  
L. Montenegro ◽  
...  
Keyword(s):  
Large Scale ◽  
Reference Model ◽  
Numerical Models ◽  
Full Scale ◽  
Small Scale ◽  
Model Parameters ◽  
In Situ Test ◽  
Wide Range ◽  
Engineered Barrier

ABSTRACTFEBEX (Full-scale Engineered Barrier EXperiment) is a demonstration and research project dealing with the bentonite engineered barrier designed for sealing and containment of waste in a high level radioactive waste repository (HLWR). It includes two main experiments: an situ full-scale test performed at Grimsel (GTS) and a mock-up test operating since February 1997 at CIEMAT facilities in Madrid (Spain) [1,2,3]. One of the objectives of FEBEX is the development and testing of conceptual and numerical models for the thermal, hydrodynamic, and geochemical (THG) processes expected to take place in engineered clay barriers. A significant improvement in coupled THG modeling of the clay barrier has been achieved both in terms of a better understanding of THG processes and more sophisticated THG computer codes. The ability of these models to reproduce the observed THG patterns in a wide range of THG conditions enhances the confidence in their prediction capabilities. Numerical THG models of heating and hydration experiments performed on small-scale lab cells provide excellent results for temperatures, water inflow and final water content in the cells [3]. Calculated concentrations at the end of the experiments reproduce most of the patterns of measured data. In general, the fit of concentrations of dissolved species is better than that of exchanged cations. These models were later used to simulate the evolution of the large-scale experiments (in situ and mock-up). Some thermo-hydrodynamic hypotheses and bentonite parameters were slightly revised during TH calibration of the mock-up test. The results of the reference model reproduce simultaneously the observed water inflows and bentonite temperatures and relative humidities. Although the model is highly sensitive to one-at-a-time variations in model parameters, the possibility of parameter combinations leading to similar fits cannot be precluded. The TH model of the “in situ” test is based on the same bentonite TH parameters and assumptions as for the “mock-up” test. Granite parameters were slightly modified during the calibration process in order to reproduce the observed thermal and hydrodynamic evolution. The reference model captures properly relative humidities and temperatures in the bentonite [3]. It also reproduces the observed spatial distribution of water pressures and temperatures in the granite. Once calibrated the TH aspects of the model, predictions of the THG evolution of both tests were performed. Data from the dismantling of the in situ test, which is planned for the summer of 2001, will provide a unique opportunity to test and validate current THG models of the EBS.

scholarly journals Numerical models of slab migration in continental collision zones

Solid Earth ◽  
2012 ◽  
Vol 3 (2) ◽  
pp. 293-306 ◽  
Author(s):  
V. Magni ◽  
J. van Hunen ◽  
F. Funiciello ◽  
C. Faccenna
Keyword(s):  
Subduction Zone ◽  
Plate Tectonics ◽  
Numerical Models ◽  
Continental Collision ◽  
Force Balance ◽  
Small Scale ◽  
Dip Angle ◽  
External Forces ◽  
Stress Dependent ◽  
Subduction System

Abstract. Continental collision is an intrinsic feature of plate tectonics. The closure of an oceanic basin leads to the onset of subduction of buoyant continental material, which slows down and eventually stops the subduction process. In natural cases, evidence of advancing margins has been recognized in continental collision zones such as India-Eurasia and Arabia-Eurasia. We perform a parametric study of the geometrical and rheological influence on subduction dynamics during the subduction of continental lithosphere. In our 2-D numerical models of a free subduction system with temperature and stress-dependent rheology, the trench and the overriding plate move self-consistently as a function of the dynamics of the system (i.e. no external forces are imposed). This setup enables to study how continental subduction influences the trench migration. We found that in all models the slab starts to advance once the continent enters the subduction zone and continues to migrate until few million years after the ultimate slab detachment. Our results support the idea that the advancing mode is favoured and, in part, provided by the intrinsic force balance of continental collision. We suggest that the advance is first induced by the locking of the subduction zone and the subsequent steepening of the slab, and next by the sinking of the deepest oceanic part of the slab, during stretching and break-off of the slab. These processes are responsible for the migration of the subduction zone by triggering small-scale convection cells in the mantle that, in turn, drag the plates. The amount of advance ranges from 40 to 220 km and depends on the dip angle of the slab before the onset of collision.

The Effect of Stitching on Compression Behavior of Stiffened Composite Panels

2001 ◽  
Author(s):  
Sung S. Suh ◽  
H. Thomas Hahn ◽  
Nanlin Han ◽  
Jenn-Ming Yang
Keyword(s):  
Beneficial Effect ◽  
Compression Behavior ◽  
Stiffened Panels ◽  
Shell Elements ◽  
Stitch Density ◽  
Stiffened Composite Panels ◽  
Out Of Plane ◽  
Post Buckling ◽  
Post Impact ◽  
Good Agreement

Abstract Failure of stiffened panels under compression is preceded by buckling of their skin and hence is affected by the presence of out-of-plane stresses. One of the promising methods of preventing premature delamination is stitching. The present paper discusses the effect of such stitching on compression behavior of blade-stiffened panels that were fabricated from plain weave AS4/3501-6 through resin film infusion process. Kevlar 29 yarn was used at a stitch density of 9.92 stitches per cm2. Some of the panels were damaged by drop-weight impact before compression testing. For comparison purposes unstitched panels with the same materials and dimensions were also tested under the same loading conditions. Stitching resulted in a 10% improvement in strength in the absence of any intentional damage. The beneficial effect of stitching was most obvious when the panels were impacted on a flange: a 50% improvement was observed in post-impact strength. However, stitching could not prevent stiffener from failure when impacted directly. Thus stitching had no beneficial effect when impact occurred on a stiffener. A buckling and post-buckling analysis was carried out using 3-D shell elements on the Abaqus. Predictions were in fairly good agreement with the experimental data.

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