• 대한건축학회논문집:구조계
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• 제34권8호
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• pp.3-11
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• 2018

In this study, total nine R/C beams, designed by the PVA Fiber with ground granulated blast furnace slag and recycled fine aggregate were constructed and tested under monotonic loading. In the material development, micromechanics was adopted to properly select the optimized range of the composite based on steady-state cracking theory and experimental studies on the matrix and interracial properties. Experimental programs were carried out to improve and evaluate the structural performance of the test specimens: the load-displacement, the failure mode, the maximum strength, and ductility capacity were assessed. Test results showed that test specimens (BSPR-20, 40) was increased the maximum load carrying capacity by 3~6% and the ductility capacity by 9~14% in comparison with the standard specimen (BSS). And the specimens (BSPR-60, 80, 100) was decreased the maximum load carrying capacity by 0~4% and the ductility capacity by 79% in comparison with the standard specimen (BSS) respectively.

• 대한건축학회논문집:구조계
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• 제34권11호
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• pp.11-18
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• 2018

In this study, seven R/C beams, designed by the steel fiber with ground granulated blast furnace slag and recycled fine aggregate were constructed and tested under monotonic loading. In the material development, micromechanics was adopted to properly select the optimized range of the composite based on steady-state cracking theory and experimental studies on the matrix and interracial properties. Experimental programs were carried out to improve and evaluate the structural performance of the test specimens: the load-displacement, the failure mode, the maximum strength were assessed. Test results showed that test specimens (BSSR-20, 40, 60, 80) were increased the maximum load carrying capacity by 2~9% and the ductility capacity by 10~22% in comparison with the standard specimen (BSS) respectively. And the specimens (BSSR-100) was decreased the maximum load carrying capacity by 5% and the ductility capacity by 44% in comparison with the standard specimen (BSS) respectively.

• Steel and Composite Structures
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• 제38권2호
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• pp.189-211
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• 2021

An analytical solution is presented to analyze the thermoelastoplastic response of a rotating thick-walled cylindrical pressure vessel made of functionally graded material (FGM). The analysis is based on Tresca's yield condition, its associated flow rule and linear strain hardening material behaviour. The uncoupled theory of thermoelasticity is used, and the plane strain condition is assumed. The material properties except for Poisson's ratio, are assumed to vary nonlinearly in the radial direction. Elastic, partially plastic, fully plastic, and residual stress states are investigated. The heat conduction equation for the one-dimensional problem in cylindrical coordinates is used to obtain temperature distribution in the vessel. It is assumed that the inner surface is exposed to an airstream and that the outer surface is exposed to a uniform heat flux. Tresca's yield criterion and its associated flow rule are used to formulate six different plastic regions for a linearly hardening condition. All these stages are studied in detail. It is shown that the thermoelastoplastic stress response of a rotating FGM pressure vessel is affected significantly by the nonhomogeneity of the material and temperature gradient. The results are validated with those of other researchers for appropriate values of the system parameters and excellent agreement is observed.

• Advances in nano research
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• 제10권2호
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• pp.129-138
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• 2021

In present article, utilizing the Love shell theory with volume fraction laws for the cylindrical shells vibrations provides a governing equation for the distribution of material composition of material. Isotopic materials are the constituents of these rings. The position of a ring support has been taken along the radial direction. The Rayleigh-Ritz method with three different fraction laws gives birth to the shell frequency equation. Moreover, the effect of height- and length-to-radius ratio and angular speed is investigated. The results are depicted for circumferential wave number, length- and height-radius ratios with three laws. It is found that the backward and forward frequencies of exponential fraction law are sandwich between polynomial and trigonometric laws. It is examined that the backward and forward frequencies increase and decrease on increasing the ratio of height- and length-to-radius ratio. As the position of ring is enhanced for clamped simply supported and simply supported-simply supported boundary conditions, the frequencies go up. At mid-point, all the frequencies are higher and after that the frequencies decreases. The frequencies are same at initial and final stage and rust itself a bell shape. The shell is stabilized by ring supports to increase the stiffness and strength. Comparison is made for non-rotating and rotating cylindrical shell for the efficiency of the model. The results generated by computer software MATLAB.

• Advances in nano research
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• 제13권1호
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• pp.29-45
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• 2022

The optimization for dynamic response associated with a cylindrical shell which is made of laminated composites embedded in a piezoelectric layer which is subjected to temperature rises and is resting on an elastic foundation is investigated for the first time. The first shear order theory (FSDT) is utilized in order to obtain the strain relations of the shell. Then, using the energy method, the equations of motions as well as boundary condition of the problem are attained. The formulation of this study together with the solution procedure which is a numerical solution method, differential quadrature method (DQM) is validated using other researches. This paper presents a thorough study on the parameters which impacts the vibration frequency of the laminated shell. The results of this paper shows that any type of laminated composite shell can reduce the vibration frequency providing that the angle related to layer are higher than 85 degrees. Also, in order to reduce the effect of temperature rises, the laminated composites instead of orthotropic one can be used.

• Steel and Composite Structures
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• 제42권3호
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• pp.397-405
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• 2022

The existing researches on the dynamics of the fluid-conveying pipes only focus on stability and vibration problems, and there is no literature report on the wave propagation of the fluid-conveying pipes. Therefore, the purpose of this paper is to explore the propagation characteristics of longitudinal and flexural waves in the fluid-conveying pipes. First, it is assumed that the material properties of the fluid-conveying pipes vary based on a power function of the thickness. In addition, it is assumed that the material properties of both the fluid and the pipes are closely depended on temperature. Using the Euler-Bernoulli beam equation and based on the linear theory, the motion equations considering the thermal-mechanical-fluid coupling is derived. Then, the exact expressions of phase velocity and group velocity of longitudinal waves and bending waves in the fluid-conveying pipes are obtained by using the eigenvalue method. In addition, we also studied the free vibration frequency characteristics of the fluid-conveying pipes. In the numerical analysis, we successively studied the influence of temperature, functional gradient index and liquid velocity on the wave propagation and vibration problems. It is found that the temperature and functional gradient exponent decrease the phase and group velocities, on the contrary, the liquid flow velocity increases the phase and group velocities. However, for vibration problems, temperature, functional gradient exponent parameter, and fluid velocity all reduce the natural frequency.

• Steel and Composite Structures
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• 제42권3호
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• pp.375-388
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• 2022

In this work, limit elastic speed analysis of functionally graded porous rotating disks has been reported. The work proposes an effective approach for modeling the mechanical properties of a porous functionally graded rotating disk. Four different types of porosity models namely: uniform, symmetric, inner maximum, and outer maximum distribution are considered. The approach used is the variational principle, and the solution has been achieved using Galerkin's error minimization theory. The study aims to investigate the effect of grading indices, aspect ratio, porosity volume fraction, and porosity types on limit angular speed for uniform and variable disk geometries of constant mass. To validate the current study, finite element analysis has been used, and there is good agreement between the two methods. The study yielded a decrease in limit speed as grading indices and aspect ratio increase. The porosity volume fraction is found to be more significant than the aspect ratio effect. The research demonstrates a range of operable speeds for porous and non-porous disk profiles that can be used in industries as design data. The results show a significant increase in limit speed for an exponential disk when compared to other disk profiles, and thus, the study demonstrates a range of FG-based structures for applications in industries that will not only save material (lightweight structures) but also improve overall performance.

• Steel and Composite Structures
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• 제43권5호
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• pp.661-672
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• 2022

The solution of contact problems is extremely important as we encounter many situations involving such problems in our daily lives. One of the most important parameters effective in solving contact problems is the materials of the parts in contact. While it is relatively easy to solve the contact mechanics of the systems created with traditional materials with a homogeneous microstructure and mechanical distribution, it may be more difficult to solve the contact problem of new generation materials that do not show a homogeneous distribution. As a result of this situation, it is seen that studies on contact problems of materials that do not exhibit such a homogeneous internal structure and mechanical properties are extremely limited in the literature. In this context, in this study, analytical and numerical analyzes of a contact problem created using functionally graded materials were carried out and the results were evaluated mutually. It has been decided that the contact areas and contact pressures acquired from numerical method are reasonably appropriate with the results obtained from the analytical method.

• Advances in nano research
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• 제10권5호
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• pp.423-435
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• 2021

This paper examines the thermal post-buckling behaviors of graphene-reinforced metal matrix composite (GRMMC) laminated cylindrical panels which possess in-plane negative Poisson's ratio (NPR) and rest on an elastic foundation. A panel consists of GRMMC layers of piece-wise varying graphene volume fractions to obtain functionally graded (FG) patterns. Based on the MD simulation results, the GRMMCs exhibit in-plane NPR as well as temperature-dependent material properties. The governing equations for the thermal post-buckling of panels are based on the Reddy's third order shear deformation shell theory. The von Karman nonlinear strain-displacement relationship and the elastic foundation are also included. The nonlinear partial differential equations for GRMMC laminated cylindrical panels are solved by means of a singular perturbation technique in associate with a two-step perturbation approach and in the solution process the boundary layer effect is considered. The results of numerical investigations reveal that the thermal post-buckling strength for (0/90)_5T GRMMC laminated cylindrical panels can be enhanced with an FG-X pattern. The thermal post-buckling load-deflection curve of 6-layer (0/90/0)_S and (0/90)_3T panels of FG-X pattern are higher than those of 10-layer (0/90/0/90/0)_S and (0/90)_5T panels of FG-X pattern.

• Steel and Composite Structures
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• 제43권1호
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• pp.67-77
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• 2022

In the current study, ordinary design of Represstessed Pre-Flex (RPF) girder by classical beam theory and numerical model taking buckled shape into consideration were compared with field-survey data to find imperfections on the RPF girder before prestressing and after preflexion. It should be noted that the ordinary design do not consider deformed shape of steel girder in RPF beam. The deformed shapes of steel girder due to the incomplete fabrication that could be caused by self-weight, preflexion misalignment, existence of lateral bracing at mid-span and stiffness of reaction frame were found using a newly developed model which was verified against a deformation survey conducted on actual RPF girder in the field. The final observed deformed shapes of RPF after concrete shrinkage and before prestressing were classified into W, C and Unsymmetric shapes in regard to both survey and analytical results. The deformation survey showed negligible amount of unwanted deformation compared to the large size of the RPF girders. The shallower width of the bottom flange of steel girder caused amount of lateral torsional buckling under self-weight and preflexion thereby affecting the unwanted final overall shape of the RPF girders. However, it was found that the unwanted deformation of RPF girders by fabrication errors even though it is negligible compared to the size of the girder, caused unsymmetrical stress contours in concrete and additional tensile stress and raise some safety issues.