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CONTENTS
Volume 45, Number 4, November25 2022
 


Abstract
In present work, bending and free vibration studies are carried out on different kinds of sandwich FGM beams using recently proposed (Chakrabarty et al. 2011) C-0 finite element (FE) based higher-order zigzag theory (HOZT). The material gradation is assumed along the thickness direction of the beam. Power-law, exponential-law, and sigmoidal laws (Garg et al 2021c) are used during the present study. Virtual work principle is used for bending solutions and Hamilton's principle is applied for carrying out free vibration analysis as done by Chalak et al. 2014. Stress distribution across the thickness of the beam is also studied in detail. It is observed that the behavior of an unsymmetric beam is different from what is exhibited by a symmetric one. Several new results are also reported which will be useful in future studies.

Key Words
bending; finite element; free vibration; HOZT; sandwich FGM beam

Address
Simmi Guptaa and H.D. Chalak:Department of Civil Engineering, National Institute of Technology, Kurukshetra, Haryana 136119, India

Abstract
In this study, a two-dimensional model of the contact problem has been examined using the finite element method (FEM) based software ANSYS and based on the multilayer perceptron (MLP), an artificial neural network (ANN). For this purpose, a functionally graded (FG) half-infinite layer (HIL) with a crack pressed by means of two rigid blocks has been solved using FEM. Mass forces and friction are neglected in the solution. Since the problem is analyzed for the plane state, the thickness along the z-axis direction is taken as a unit. To check the accuracy of the contact problem model the results are compared with a study in the literature. In addition, ANSYS and MLP results are compared using Root Mean Square Error (RMSE) and coefficient of determination (R2), and good agreement is found. Numerical solutions are made by considering different values of external load, the width of blocks, crack depth, and material properties. The stresses on the contact surfaces between the blocks and the FG HIL are examined for these values, and the results are presented. Consequently, it is concluded that the considered non-dimensional quantities have a noteworthy influence on the contact stress distributions, and also, FEM and ANN can be efficient alternative methods to time-consuming analytical solutions if used correctly.

Key Words
artificial neural network; contact mechanics; finite element method; functionally graded

Address
Murat YayIaci and Sevval Ozturk:Department of Civil Engineering, Recep Tayyip Erdogan University, 53100, Rize, Turkey

Ecren Uzun YayIaci:Surmene Faculty of Marine Science, Karadeniz Technical University, 61530, Trabzon, Turkey

Mehmet Emin Ozdemir:Department of Civil Engineering, Cankiri Karatekin University, 18100, Cankiri, Turkey

Sevil Ay:Department of Civil Engineering, Artvin Coruh University, 08100, Artvin, Turkey

Abstract
This study presents similarities and differences between Turkish Building Code for Steel Structures, which are TS 648 and SDCCSS (Specification for Design, Calculation and Construction of Steel Structures) in terms of the design of the members. Hot-rolled I-shaped steel sections for symmetrical and U-shaped steel sections (i.e., channels) for monosymmetric sections were elaborated in detail. The design strength of tension members under tensile load, compression members under axial load and flexural members under flexure and shear were examined separately. Connection details for tension members, slenderness for compression members and distance between lateral supports for flexural members were considered as prime variables. Analysis results revealed the design strength of the tension members where at least one of the cross-sectional parts is not connected to the connection plates, I-shaped compression members where a slenderness ratio is below 39 (λ〈39), U-shaped compression members and flexural members where Lb is between Lp and Lr (Lp〈Lb≤Lr) designed based on TS 648 are greater than those designed based on SDCCSS 2018. Strength differences between the specification can reach 79% for tensile members, 13% for compression members and 9% for flexural members.

Key Words
building; SDCCSS 2018; specification; steel; strength; TS 648

Address
Mehmet Bakir Bozkurt, Abdulkerim Ergut:Department of Civil Engineering, Manisa Celal Bayar University, 45140, Manisa, Turkey

Yasin Onuralp Ozkilic:Department of Civil Engineering, Necmettin Erbakan University, 42100, Konya, Turkey

Abstract
The memory response of nonlocal systematical formulation size-dependent coupling of viscoelastic deformation and thermal fields for piezoelectric materials with dual-phase lag heat conduction law is constructed. The method of the matrix exponential, which constitutes the basis of the state-space approach of modern control theory, is applied to the non-dimensional equations. The resulting formulation together with the Laplace transform technique is applied to solve a problem of a semiinfinite piezoelectric rod subjected to a continuous heat flux with constant time rates. The inversion of the Laplace transforms is carried out using a numerical approach. Some comparisons of the impacts of nonlocal parameters and time-delay constants for various forms of kernel functions on thermal spreads and thermo-viscoelastic response are illustrated graphically.

Key Words
dual-phase lag; laplace transform; memory-dependent derivative; size-dependent thermo-viscoelastic coupling; thermo-piezoelectricity

Address
Magdy A. Ezzat:1)Department of Mathematics, College of Science and Arts, Qassim University, Al Bukairyah, Saudi Arabia
2)Department of Mathematics, Faculty of Education, Alexandria University, Alexandria, Egypt

Zeid I.A. Al-Muhiameed:Department of Mathematics, Faculty of Science, Qassim University, Buraydah 51452, Saudi Arabia

Abstract
This paper studies the static stability of an axially graded column with the power-law gradient varying along the axial direction. For a nonhomogeneous column with one end linked to a rotational spring and loaded by a compressive force, respectively, an Euler problem is analyzed by solving a boundary value problem of an ordinary differential equation with varying coefficients. Buckling loads through the characteristic equation with the aid of the Bessel functions are exactly given. An alternative way to approximately determine buckling loads through the integral equation method is also presented. By comparing approximate buckling loads with the exact ones, the approximate solution is simple in form and enough accurate for varying power-law gradients. The influences of the gradient index and the rotational spring stiffness on the critical forces are elucidated. The critical force and mode shapes at buckling are presented in graph. The critical force given here may be used as a benchmark to check the accuracy and effectiveness of numerical solutions. The approximate solution provides a feasible approach to calculating the buckling loads and to assessing the loss of stability of columns in engineering.

Key Words
axially graded column; buckling; critical load; exact solution; power-law gradient

Address
X.F. Li, L. Lu, Z.L. Hu, and B.J. Xiao:School of Civil Engineering, Central South University, Changsha 410075, China

Y Huang:School of Mathematics and Big Data, Foshan University, Foshan, Guangdong 528000, China

Abstract
Improving the mechanical properties of concrete in the construction industry in order to increase resistance to dynamic and static loads is one of the essential topics for researchers. In this work, vibration analysis of elastic nanocomposite beams reinforced by nanoparticles based on mathematical model is presented. For modelling of the strucuture, sinusoidal shear deformation beam theory (SSDBT) is utilized. Mori-anak model model is utilized for obtaining the effective properties of the strucuture including agglomeration influences. Utilizing the energy method and Hamilton'sprincipal, the motion equations are calculated. The frequency of the elastic nanocomposite beam is obtanied by analytical method. The aim of this work is investigating the effects of nanoparticles volume percent and agglomeration, length and thickness of the beam on the frequency of the structure. The results show that the with enhancing the nanoparticles volume percent, the frequency is increased. In addition, the water absorption of the concrete is presented in this article.

Key Words
analytical method; beam; frequency response; nanoparticles; SSDBT

Address
Suxia Hou, Jijun Luo:Shaanxi Engineering Research Center of Controllable Neutron Source, School of Electronic Information,
Xijing University, Xi

Abstract
This paper presents experimental and numerical investigations of a new seismic enhancement method for existing reinforced concrete (RC) frames by using an external sub-structure, the hybrid seismic retrofit method (HSRM) system. This retrofit system is an H-shaped frame bolt-connected to an existing RC frame with an infilled-concrete layer between their gaps. Two RC frames were built, one with and one without HSRM, and tested under cyclic loading. The experimental findings showed that the retrofitted RC frame was superior to the non-retrofitted specimen in terms of initial stiffness, peak load, and energy dissipation capacity. A numerical simulation using a commercial program was employed for verification with the experiments. The results obtained from the simulations were consistent with those from the experiments, indicating the finite element (FE) models can simulate the seismic behaviors of bare RC frame and retrofitted RC frame using HSRM.

Key Words
cyclic loading; FEM; LS-DYNA; retrofitted RC frame; seismic retrofit method

Address
Nguyen-Vu Luat:1)Deep Learning Architecture Research Center, Department of Architectural Engineering, Sejong University,
209 Neungdong-ro, Gwangjin-gu, Seoul 05006, South Korea
2)Institute of Postgraduate and Short-term training, Mien Dong Innovative Technology University, Thong Nhat, Dong Nai 76400, Vietnam

Hongseok Lee:Deep Learning Architecture Research Center, Department of Architectural Engineering, Sejong University,
209 Neungdong-ro, Gwangjin-gu, Seoul 05006, South Korea

Jiuk Shin:Department of Architectural Engineering, Gyeongsang National University, Jinju, 52828, South Korea

Ji-Hun Park:Division of Architecture and Urban Design, Incheon National University, 119 Academy-ro, Yeonsu-gu, Incheon 22012, South Korea

Tae-Sang Ahn:Research Center, Korea Disaster Prevention Technology, 6-1 Neejinmal-gil, Docheok-myeon, Gyeonggi-do, South Korea

Kihak Lee:Deep Learning Architecture Research Center, Department of Architectural Engineering, Sejong University,
209 Neungdong-ro, Gwangjin-gu, Seoul 05006, South Korea


Abstract
One of the biggest problems in structural steel calculation is the design of structures using the lowest possible material weight, making this a slow and costly process. To achieve this objective, several optimization methods have been developed and tested. Nevertheless, a method that performs very efficiently when applied to different problems is not yet available. Based on this assumption, this work proposes a hybrid metaheuristic algorithm for geometric and dimensional optimization of space trusses, called Simulated Squirrel Search Algorithm, which consists of an association of the wellestablished neighborhood shifting algorithm (Simulated Annealing) with a recently developed promising population algorithm (Squirrel Search Algorithm, or SSA). In this study, two models are tried, being respectively, a classical model from the literature (25-bar space truss) and a roof system composed of space trusses. The structures are subjected to resistance and displacement constraints. A penalty function using Fuzzy Logic (FL) is investigated. Comparative analyses are performed between the Squirrel Search Algorithm (SSSA) and other optimization methods present in the literature. The results obtained indicate that the proposed method can be competitive with other heuristics.

Key Words
fuzzy logic; simulated annealing; space trusses; squirrel search algorithm; structural optimization

Address
Mateus P. Pauletto and Moacir Kripka:Departament of Civil Engineering, University of Passo Fundo Campus 1, 99001-970, Passo Fundo, RS – Brazil

Abstract
The flexural strengthening of reinforced concrete beams by external bonding of composite materials has proved to be an efficient and practical technique. This paper presents a study on the flexural performance of reinforced concrete continuous beams with three spans (one span and two cantilevered) strengthened by bonding carbon fiber fabric (CFRP). The model is based on equilibrium and deformations compatibility requirements in and all parts of the strengthened continuous beam, i.e., the continuous concrete beam, the FRP plate and the adhesive layer. The adherend shear deformations have been included in the present theoretical analyses by assuming a linear shear stress through the thickness of the adherends. Remarkable effect of shear deformations of adherends has been noted in the results. The theoretical predictions are compared with other existing solutions that shows good agreement, and It shows the effectiveness of CFRP strips in enhancing shear capacity of continuous beam. It is shown that both the normal and shear stresses at the interface are influenced by the material and geometry parameters of the composite beam.

Key Words
composite plate; continuous RC beam; interfacial stresses; shear lag effect; strengthening

Address
Rabahi Abderezak, Tahar Hassaine Daouadji and Benferhat Rabia
1)Laboratory of Geomatics and sustainable development, University of Tiaret, Algeria
2)Department of Civil Engineering, Ibn Khaldoun University of Tiaret, Algeria


Abstract
The tensile behavior of the Thread-fixed One-side Bolt (TOB) at high temperatures was studied using the Finite Element Modeling (FEM) to explore the structural responses that could not be measured in tests. The accuracy of the FEM was verified using the test results from the failure mode, load-displacement curve as well as yielding load. Three typical failure modes of TOB connected T-stubs were observed, which were the Flange Yielding (FY), the Bolt Failure (BF) and the Coupling Failure mode (CF). The influence of the flange thickness tb and the temperature exceeded 700°C. The failure modes of T-stubs were mainly decided by the flange thickness, which relates to the anchorage of the hole threads and the bending resistance of flange. The failure mode could also be changed by the high temperature. Design equations in EN 1993-1-8 were modified and verified by the FEM results. The results showed that these equations could predict the failure mode and the yielding load at different temperatures with satisfactory accuracy.

Key Words
bolted T-stub; design method; failure mode; high temperature; thread-fixed one-side bolt

Address
Yang You:1)School of Transportation and Civil Engineering, Shandong Jiaotong University, 5001 Haitang Road, Changqing District, Jinan,
Shandong Province, People


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