scholarly journals Optimasi Bentuk Struktur Elemen Cangkang Pada Pondasi Terapung Menggunakan Metode Algoritma Genetik

2018 ◽  
Vol 18 (2) ◽  
pp. 1-11
Author(s):  
Augusta Adha ◽  
Mahadi Kurniawan
Keyword(s):  
Finite Element ◽  
Stress Level ◽  
Contact Area ◽  
Shell Structure ◽  
External Load ◽  
Plate Theory ◽  
Mindlin Plate ◽  
Lower Stress ◽  
Floating Foundation ◽  
Lower Stress Level

[ID] Prinsip dasar pondasi terapung adalah keseimbangan antara berat struktur atas dan total berat tanah (termasuk didalamnya air tanah) yang dipindahkan oleh konstruksi pondasi tersebut sehingga tidak menghasilkan penurunan struktur. Pondasi terapung sangat baik digunakan pada daerah dengan daya dukung tanah yang rendah atau pada daerah yang memiliki tanah dengan derajat pemadatan yang bervariasi. Hal ini dikarenakan karakteristik pondasi terapung yang membagi gaya ke area kontak yang sangat besar sehingga seluruh area kontak tersebut hanya mengalami tegangan yang relatif kecil. Namun demikian, karena kapasitas dukung pondasi terapung sangat tergantung pada luasan area, maka pondasi terapung menjadi tidak efektif untuk diterapkan pada daerah yang kecil. Salah satu solusi yang dapat digunakan untuk mengatasi permasalahan ini adalah dengan penerapan struktur pelat cangkang (shell structure) pada pondasi terapung untuk meningkatkan luas area bidang kontak pondasi terapung dan tanah. Paper ini membahas optimasi bentuk pelat cangkang yang digunakan pada pondasi terapung agar memiliki daya dukung yang cukup untuk menahan gaya yang ditransferkan oleh struktur atas. Metode algoritma genetik digunakan dalam proses optimasi dimana koordinat dari titik yang menyusun bentuk (shape) struktur cangkang (cn) dipakai sebagai desain variabel. Pada penelitian ini, proses optimasi menggunakan pemodelan dengan 11, 13 dan 15 variabel desain untuk melihat sensitivitas desain variable tersebut terhadap hasil optimasi. Tegangan yang terjadi pada struktur cangkang tersebut di evaluasi dengan Analisa Elemen Hingga dengan perilaku element cangkang seperti model teory pelat Reissner-Midlin. Fungsi tujuan pada penelitian ini adalah meminimalkan penggunaan material untuk membentuk sebuah pondasi terapung dengan fungsi penalti tegangan pada elemen cangkang. [EN] The basic principle of floating foundation is counterforce balancing between the weight of the structure and thetotal weight of the soil (including groundwater) which is displaced by the structure. Floating foundation is effective in areas with low soil bearing capacity because the external load is widely spread that resulting lower stress level in contact area; Hence, it is necessary to design the shape of floating structure that provide adequate uplift whilst also create lower stress level by spreading the external load to wider contact area. This paper discusses the shape optimization of the floating foundations to have sufficient capacity to resist the force transferred by the upper structure whilst also minimize the use of material without resulting element overstress. Genetic algorithm method is used in the optimization process where the coordinates of the points that shape the shell structure (cn) are used as variable designs. In this study, the multivariable optimization using finite element model is investigated . The stress that occurs in the shell structure is evaluated by Finite Element Analysis with the behavior of shell elements based on Reissner-Mindlin plate theory.

Frequency Response of a Three-Node Finite Element for Composite Thin and Thick Plates

2004 ◽  
Author(s):  
A. V. S. Ravi Shastry ◽  
Pramod Kumar
Keyword(s):  
Finite Element ◽  
Frequency Response ◽  
Plate Theory ◽  
Composite Plates ◽  
Mode Shapes ◽  
Mindlin Plate ◽  
Integration Scheme ◽  
Shear Locking ◽  
Triangular Finite Element ◽  
Strain Components

A shear-locking free isoparametric three-node triangular finite element is considered for the study of frequency response of moderately thick and thin composite plates. The strain displacement relationship is based on Reissner-Mindlin plate theory that accounts for transverse shear deformations into the plate formulation to circumvent the shear locking effect. The element is developed with full integration scheme; hence the element remains kinematically stable. The performance of the element for the case of static load response using the shear correction terms to shear strain components applied to a composite plate has been studied. The natural frequencies and mode shapes in accordance with varying mode numbers, are deduced and the results are compared with the available analytical and finite element solutions in literature.

The effect of the lower stress level on the cyclic creep behavior of an ods superalloy

1991 ◽  
Vol 18 (6) ◽  
pp. 1029-1033
Author(s):  
William L. Kimmerle ◽  
Vincent C. Nardone ◽  
John K. Tien
Keyword(s):  
Stress Level ◽  
Creep Behavior ◽  
Cyclic Creep ◽  
Lower Stress ◽  
Lower Stress Level

A Mindlin–Reissner Variational Principle to Analyze the Behavior of Moderately Thick Plates

1989 ◽  
Vol 42 (11S) ◽  
pp. S32-S38
Author(s):  
Roberto S. Carnicer ◽  
Stefano Alliney
Keyword(s):  
Finite Element ◽  
Variational Principle ◽  
Plate Theory ◽  
Mindlin Plate ◽  
General Boundary Conditions ◽  
Thick Plates ◽  
Numerical Examples ◽  
Simple Support ◽  
Mindlin Plate Theory ◽  
Moderately Thick Plates

In the present work a method to solve the plate behavior under the assumption of the Mindlin plate theory is analyzed by means of finite element techniques, avoiding the tendency of the thin element to lock when the thickness of the plates becomes very small. A different formulation is developed from the Mindlin–Reissner principle for general boundary conditions. Numerical examples to evaluate the noninfluence of locking on clamped and simple support plates are calculated.

scholarly journals Finite Element Modelling of a Composite Shell with Shear Connectors

Symmetry ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 527 ◽  
Author(s):  
Nguyen ◽  
Canh ◽  
Thanh ◽  
Ke ◽  
Phan ◽  
...  
Keyword(s):  
Finite Element ◽  
Composite Shell ◽  
Plate Theory ◽  
Dynamic Responses ◽  
Mindlin Plate ◽  
Physical Parameters ◽  
Working Process ◽  
Shear Connectors ◽  
Layer Composite ◽  
Mindlin Plate Theory

A three-layer composite shell with shear connectors is made of three shell layers with one another connected by stubs at the contact surfaces. These layers can have similar or different geometrical and physical properties with the assumption that they always contact and have relative movement in the working process. Due to these characteristics, they are used widely in many engineering applications, such as ship manufacturing and production, aerospace technologies, transportation, and so on. However, there are not many studies on these types of structures. This paper is based on the first-order shear deformation Mindlin plate theory and finite element method (FEM) to establish the oscillator equations of the shell structure under dynamic load. The authors construct the calculation program in the MATLAB environment and verify the accuracy of the established program. Based on this approach, we study the effects of some of the geometrical and physical parameters on the dynamic responses of the shell.

scholarly journals A STUDY ON EFFECTS OF YOGA AND ACADEMIC ACHIEVEMENT OF HIGH SCHOOL STUDENTS

2018 ◽  
Vol 6 (7) ◽  
pp. 23-27
Author(s):  
Christal Jeba N
Keyword(s):  
High School ◽  
Academic Achievement ◽  
Academic Performance ◽  
High School Students ◽  
Stress Level ◽  
The Other ◽  
Competitive Performance ◽  
Lower Stress ◽  
School Students ◽  
Lower Stress Level

The article focuses on assessing facts of a study on effects of yoga and academic achievement of high school students’. Transcendental meditation reduces stress and improves academic performance mentally causes increased alertness, and the practice of yoga brings improvement in competitive performance. It is inferred from the present investigation that all the high school students have average level of effect of yoga with respect to all the background variables under study. It was proved that students under consideration scored higher grades and had lower stress level as compared to the other students who do not practice yoga.

scholarly journals The study of the relationship between life limiting factor and stress level for FGH96

2018 ◽  
Vol 165 ◽  
pp. 22031 ◽  
Author(s):  
Didi. Yang ◽  
Yi. Shi ◽  
Guolei. Miao ◽  
Xiaoguang. Yang ◽  
Duoqi. Shi
Keyword(s):  
Fatigue Life ◽  
Stress Level ◽  
Fatigue Tests ◽  
Limiting Factors ◽  
Limiting Factor ◽  
Lower Stress ◽  
Surface Residual Stress ◽  
Nickel Based Superalloy ◽  
Loading Ratio ◽  
Lower Stress Level

FGH96 is a Chinese made powder metallurgy nickel based superalloy. This reserach aims to investigate the effect of stress on the microstructure of the worst fatigue life at 600°C. The specimens were first polished by abrasive paper and then electropolished to elimate the effect of surface residual stress. The fatigue tests were conducted at 600°C, and the loading ratio was 0.05 at the frequency of 5Hz. Tests were conducted at 900, 1000, 1100, 1200MPa respectively. The fatigue life under the same condition were compared and the fractography of specimens were examined under SEM to further identify the life-limiting factors of the material. The initiation mode transferred from facet initiated to inclusion initiated from lower stress level to higher stress level. Meanwhile, the initiation position transferred from internal to surface with the increase of stress level. This means at higher stress level, fatigue life is mainly limited by inclusion at surface while at lower stress level the limit is controlled by internal facet.

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