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.

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.

Residual Strength Assessment of Semi-Submersible Platform Column Due to Supply Vessel Collision

2008 ◽  
Author(s):  
Diogo do Amaral Amante ◽  
Leandro Trovoado ◽  
Segen F. Estefen
Keyword(s):  
Ultimate Strength ◽  
Residual Strength ◽  
Structural Damage ◽  
Oil And Gas ◽  
Safety Margin ◽  
Element Model ◽  
Gas Production ◽  
Small Scale ◽  
Cross Sectional ◽  
Strength Assessment

The new structural concept of semi-submersible oil and gas production platforms is based on column square cross sectional area. A successful design is strongly dependent on optimized column structural arrangement. The columns are constituted of longitudinal stiffened panels having their ultimate strength characterized by buckling under compressive loads. A structural damage which may occur in these columns is the effect caused by supply vessel collision. Normally, such damage is in the form of local dents. The aim of the present paper is to evaluate the ultimate buckling residual strength of typical column of semi-submersible platforms damaged by a supply vessel collision. The buckling analysis was validated using a finite element model considering geometric and material nonlinearities considered in previous correlation studies with small scale experiments. Residual strength results from the damaged column are compared with the ultimate strength of equivalent intact column to estimate the safety margin associated with the column structural capability after supply vessel collision.

Korelasi Dukungan Keluarga Dengan Respon Cemas Anak Saat Pemasangan Infus

2018 ◽  
Vol 3 (3) ◽  
pp. 467
Author(s):  
Diah Merdekawati ◽  
Dasuki Dasuki
Keyword(s):  
Coping Strategies ◽  
Family Support ◽  
Sampling Technique ◽  
Correlation Study ◽  
Research Data ◽  
School Age ◽  
Cross Sectional ◽  
Positive Correlation ◽  
Purposive Sampling ◽  
And Coping

<p><em>Pre-school age is particularly vulnerable to the effects of stress and fear during hospitalization. Children under the age of 6 are less able to think about an event as a whole, have not been able to determine behavior that can overcome the fear based on experience ever experienced and coping strategies ever done. The aims of this research to know correlation family support with child anxious response during infusion. This study was a quantitative with correlation study using cross sectional method. There were 51 respondents participated in this research. Data were collected through observation with purposive sampling technique. Then, data were analysed through univariate and bivariate. The result of univariate statistic test revealed that as much as 64.7% had good family support and 56.9% experienced an anxious response during infusion. The result of  bivariate statistic test showed that there was a positive correlation with moderate strength between family support and child's anxious response during infusion. This riset showed that families should provide support when children experience fear, anxiety and pain during infusion.</em></p><p><em><br /></em></p><p>Usia pra sekolah sangat rentan terhadap efek stress dan ketakutan selama rawat inap. Anak- anak dibawah usia 6 tahun kurang mampu berpikir tentang suatu peristiwa secara keseluruhan, belum bisa menentukan perilaku yang dapat mengatasi ketakutan berdasarkan pengalaman yang pernah dialami dan strategi koping yang pernah dilakukan. Tujuan penelitian ini adalah untuk mengetahui korelasi dukungan keluarga dengan respon cemas anak saat pemasangan infus. Penelitian ini merupakan penelitian kuantitatif studi korelatif dengan metode <em>cross secsional</em>. Sebanyak 51 responden terlibat dalam penelitian ini. Pengumpulan data melalui observasi. Pengambilan sampel dilakukan secara <em>purposive sampling. </em>Analisis data dilakukan secara <em>univariat </em>dan<em> bivariat. </em>Dari hasil uji statistik univariat diketahui sebanyak 64,7% memiliki dukungan keluarga baik dan 56,9% mengalami respon cemas saat pemasangan infus. Hasil uji statistik bivariat menunjukkan ada korelasi positif dengan kekuatan sedang antara dukungan keluarga dengan respon cemas anak saat pemasangan infus. Penelitian ini menunjukkan bahwa keluarga sebaiknya memberikan dukungannya pada saat anak mengalami ketakutan, kecemasan dan rasa nyeri pada saat pemasangan infus.</p><p><em><br /></em></p>

Self Management Menentukan Kualitas Hidup Pasien Diabetes Mellitus

2019 ◽  
Vol 4 (2) ◽  
pp. 402
Author(s):  
Iskim Luthfa ◽  
Nurul Fadhilah
Keyword(s):  
Quality Of Life ◽  
Diabetes Mellitus ◽  
Correlation Study ◽  
Self Management ◽  
Rank Test ◽  
P Value ◽  
Cross Sectional ◽  
Spearman Rank ◽  
Consecutive Sampling

<p><em>People with diabetes mellitus are at risk of developing complications, so that it affects the quality of life. These complications can be minimized through self-care management. This study aims to determine the relationship between self management with the quality of life for people with diabetes mellitus. This research is a kind of quantitative research with correlation study. This research used cross sectional design. The sampling technique uses non probability with estimation consecutive sampling. The number of respondents in this research are 118 respondents. Instrument for measuring self management used diabetes self management questionnaire (DSMQ), and instruments to measure quality of life used quality of life WHOQOL-BREEF. The data obtained were processed statistically by using spearman rank test formula and p value of 0,000 There is a significant relationship of self management with the quality of life of people with diabetes mellitus.</em></p><p> </p><p><em>Penderita </em><em>Diabetes mellitus </em><em>beresiko mengalami komplikasi yang dapat mempengaruhi kualitas hidupnya. Komplikasi tersebut dapat diminimalkan melalui manajemen perawatan diri (self management). Penelitian ini bert</em><em>ujuan </em><em>untuk</em><em> menganalisis hubungan self management dengan kualitas hidup pasien diabetes melitus. </em><em>Jenis p</em><em>enelitian ini </em><em>adalah</em><em> deskriptif korelasi</em><em> dengan desain cross sectional</em><em>. Teknik pengambilan sampel menggunakan non probability </em><em>sampling </em><em>dengan pendeka</em><em>t</em><em>an consecutive sampling</em><em>.</em><em> </em><em>J</em><em>umlah </em><em>sampel sebanyak</em><em> </em><em>118 responden.</em><em> </em><em>Instrumen </em><em>penelitian </em><em>untuk mengukur self management </em><em>menggunakan</em><em> </em><em>diabetes self management questionnaire</em><em> (DSMQ), </em><em>dan instrumen untuk mengukur kualitas hidup menggunakan </em><em>quality of life </em><em>WHOQOL-BREEF.</em><em> Analisis data menggunakan spearman rank dan didapatkan hasil nilai </em><em>p value 0,000</em><em> dan r 0,394.Terdapat </em><em>hubungan </em><em>antara </em><em>self management</em><em> dengan kualitas hidup pasien diabetes mellitus</em><em> dengan arah korelasi positif.</em></p>

SUBMERGED CITRIC ACID FERMENTATION OF SUGAR BEET MOLASSES: INCREASE IN SCALE

1955 ◽  
Vol 1 (5) ◽  
pp. 299-311 ◽  
Author(s):  
R. Steel ◽  
C. P. Lentz ◽  
S. M. Martin
Keyword(s):  
Citric Acid ◽  
Scale Up ◽  
Aeration Rate ◽  
Small Scale ◽  
Acid Fermentation ◽  
Inoculum Level ◽  
Cross Sectional ◽  
Factors Affecting ◽  
Beet Molasses ◽  
Initial Ph

Factors affecting the production of citric acid in the submerged fermentation of ferrocyanide-treated beet molasses by Aspergillus niger were studied in 2.5 and 36 liter fermenters. The small fermenters were used to determine the effects of changes in sterilization technique, phosphate supplement, ferrocyanide treatment, inoculum level, initial pH, fermentation temperature, and aeration rate. The relation between ferrocyanide concentration and inoculum level was also studied. Four different samples of molasses were fermented successfully. An average yield of 8.2% citric acid (64% conversion) was obtained from 51 small-scale fermentations. Comparable yields were obtained in the large fermenters under comparable conditions. Most of the information obtained with the small fermenters was applicable to the larger-scale fermenters, but in the latter the fermentation was significantly more stable. Aeration was the main problem in the scale-up and aeration rates approximately double those calculated on a fermenter cross-sectional area basis were required for comparable results in the large fermenters.

Dynamic Characterization and Modeling of Carbon Composite Ballistic Behavior

2016 ◽  
Author(s):  
Chian-Fong Yen ◽  
Robert Kaste ◽  
Jian Yu ◽  
Charles Chih-Tsai Chen ◽  
Nelson Carey
Keyword(s):  
Composite Material ◽  
Progressive Failure ◽  
Laminated Composite ◽  
Carbon Composite ◽  
Ballistic Impact ◽  
Impact Testing ◽  
Material Behavior ◽  
Failure Behavior ◽  
Failure Model ◽  
Carbon Composite Material

Design of the new generation of aircraft is driven by the vastly increased cost of fuel and the resultant imperative for greater fuel efficiency. Carbon fiber composites have been used in aircraft structures to lower weight due to their superior stiffness and strength-to-weight properties. However, carbon composite material behavior under dynamic ballistic and blast loading conditions is relatively unknown. For aviation safety consideration, a computational constitutive model has been used to characterize the progressive failure behavior of carbon laminated composite plates subjected to ballistic impact conditions. Using a meso-mechanics approach, a laminated composite is represented by a collection of selected numbers of representative unidirectional layers with proper layup configurations. The damage progression in a unidirectional layer is assumed to be governed by the strain-rate dependent layer progressive failure model using the continuum damage mechanics approach. The composite failure model has been successfully implemented within LS-DYNA as a user-defined material subroutine. In this paper, the ballistic limit velocity (V50) was established for a series of laminates by ballistic impact testing. Correlation of the predicted and measured V50 values has been conducted to validate the accuracy of the ballistic modeling approach for the selected carbon composite material. The availability of this modeling tool will greatly facilitate the development of carbon composite structures with enhanced ballistic and blast survivability.

Geometrical Stiffness of Thin-Walled I-Beam Element Based on Rigid-Beam Assemblage Concept

2012 ◽  
Vol 28 (1) ◽  
pp. 97-106 ◽  
Author(s):  
J. D. Yau ◽  
S.-R. Kuo
Keyword(s):  
Stiffness Matrix ◽  
Virtual Work ◽  
Bending Moment ◽  
Beam Element ◽  
Narrow Beam ◽  
Cross Sectional ◽  
Geometric Stiffness ◽  
Buckling Behavior ◽  
Post Buckling ◽  
Thin Walled

ABSTRACTUsing conventional virtual work method to derive geometric stiffness of a thin-walled beam element, researchers usually have to deal with nonlinear strains with high order terms and the induced moments caused by cross sectional stress results under rotations. To simplify the laborious procedure, this study decomposes an I-beam element into three narrow beam components in conjunction with geometrical hypothesis of rigid cross section. Then let us adopt Yanget al.'s simplified geometric stiffness matrix [kg]12×12of a rigid beam element as the basis of geometric stiffness of a narrow beam element. Finally, we can use rigid beam assemblage and stiffness transformation procedure to derivate the geometric stiffness matrix [kg]14×14of an I-beam element, in which two nodal warping deformations are included. From the derived [kg]14×14matrix, it can take into account the nature of various rotational moments, such as semi-tangential (ST) property for St. Venant torque and quasi-tangential (QT) property for both bending moment and warping torque. The applicability of the proposed [kg]14×14matrix to buckling problem and geometric nonlinear analysis of loaded I-shaped beam structures will be verified and compared with the results presented in existing literatures. Moreover, the post-buckling behavior of a centrally-load web-tapered I-beam with warping restraints will be investigated as well.

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