• Advances in aircraft and spacecraft science
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• v.5 no.6
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• pp.671-689
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• 2018

Bending, buckling and free vibration responses of functionally graded (FG) higher-order beams resting on two parameter (Winkler-Pasternak) elastic foundation are studied using a new inverse hyperbolic beam theory. The material properties of the beam are graded along the thickness direction according to the power-law distribution. In the present theory, the axial displacement accounts for an inverse hyperbolic distribution, and the transverse shear stress satisfies the traction-free boundary conditions on the top and bottom surfaces of the beams. Hamilton's principle is employed to derive the governing equations of motion. Navier type analytical solutions are obtained for the bending, bucking and vibration problems. Numerical results are obtained to investigate the effects of power-law index, length-to-thickness ratio and foundation parameter on the displacements, stresses, critical buckling loads and frequencies. Numerical results by using parabolic beam theory of Reddy and first-order beam theory of Timoshenko are specially generated for comparison of present results and found in excellent agreement with each other.

• Steel and Composite Structures
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• v.17 no.4
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• pp.371-386
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• 2014

This paper presents a tri-linear restoring force model based on the test results of 12 circular RC columns strengthened by CFRP strips under low cyclic loading. The pre-stress of CFRP strips and axial load ratio of specimens are considered as the affect parameters of the proposed model. All essential characteristics of the hysteretic behavior of the proposed model, including the hysteretic rules, main performance points, strength degradation, stiffness degradation and confinement effects are explicitly analyzed. The calculated results from the proposed model are in good agreement with the experimental results, which shows that the recommended model can be reliably used for seismic behavior predictions of circular RC columns strengthened by pre-stressed CFRP strips.

• Nuclear Engineering and Technology
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• v.52 no.3
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• pp.614-620
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• 2020

In a previous study, delayed hydride cracking (DHC) assessment of pressurized water reactor (PWR) spent fuel during dry storage using the threshold stress intensity factor (K_IH) was performed. However, there were a few limitations in the analysis of the cladding properties, such as oxide thickness and mechanical properties. In this study, those models were modified to include test data for irradiated materials, and the cladding creep model was introduced to improve the reliability of the DHC assessment. In this study, DHC susceptibility of PWR spent fuel during dry storage depending on the axial elevation was evaluated with the improved assessment methodology. In addition, the sensitivity of affecting parameters such as fuel burnup, hydride thickness, and crack aspect ratio are presented.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.1-4
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• 2005

To investigate the effective seismic strengthening methods for masonry walls in developing countries, a total of four confined masonry (CM) walls were constructed and tested. In order to investigate the effect of the height of application point of lateral loads and reinforcing steel bars in walls and columns for the improvement of the seismic behavior of confined concrete block masonry walls, an experimental research program is conducted. The heights of inflection point considered were 0.67 and 1.11 times the height of the wall measured from the top of foundation beam. The constant vertical axial stress applied was 0 MPa. During the test, cracking patterns, load-deflection data, and strains in reinforcement and walls in critical locations was measured. From test data, it was showed that the seismic performance of confined concrete block masonry walls was significantly affected by test variables.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.71-73
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• 2003

A CFD analysis has been made for fully developed turbulent flows in a triangular bare rod bundle with pitch to diameter ratio (P/D) of 1.123. The nonlinear turbulence models predicted the turbulence­driven secondary flow in the triangular subchannel. The nonlinear quadratic $\kappa-\omega$ models by Speziale and Myong-Kasagi predicted turbulence structure in the rod bundle fairly well. The nonlinear quadratic and cubic $\kappa-\omega$ models by Shih et al. and Craft et al. showed somewhat weaker anisotropic turbulence. The differential Reynolds stress model appeared to overpredict the turbulence anisotropy in the rod bundle.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.325-332
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• 2006

Membrane structures, a kind of lightweight soft structural system, are used for spatial structures. The design procedure of membrane structures are needed to do shape finding, stress-deformation analysis and cutting pattern generation, because the material property has strong axial stiffness, but little bending stiffness. The problem of cutting pattern is highly varied in their size, curvature and material stiffness. So, the approximation inherent in cutting pattern generation methods is quite different. Therefore the ordinary computer software of structural analysis & design is not suitable for membrane structures. In this study, we develop the program for cutting pattern generation using geodesic line, and investigate the result of example's cutting pattern in detail.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.365-370
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• 1999

SKD11 is one of the most difficult workpiece for machining, so it is necessary to evaluate the machining characteristics of SKD11. The workpiece was made to be the pipe form and heat-treated to HRC45. In this paper, the orthogonal cutting experiment of this material was carried out with TiAlN coated WC cutting tool of 4 kinds of rake angle. After cutting experiment, cutting characteristics of SKD11 were investigated according to variation of cutting speed, feedrate and rake angle.

• Structural Engineering and Mechanics
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• v.59 no.3
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• pp.475-502
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• 2016

Nanobeams are widely used as a structural element for nanodevices and nanomachines. The development of nano-sized machines depends on proper understanding of mechanical behavior of these nano-sized beam elements. Small length scales such as lattice spacing between atoms, surface properties, grain size etc. are need to be considered when applying any classical continuum model. In this study, Eringen's nonlocal elasticity theory is incorporated into classical beam model considering the effects of axial extension and the shear deformation to capture unique static behavior of the nanobeams under continuum mechanics theory. The governing differential equations are obtained for curved beams and solved exactly by using the initial value method. Circular uniform beam with concentrated loads are considered. The displacements, slopes and the stress resultants are obtained analytically. A detailed parametric study is conducted to examine the effect of the nonlocal parameter, mechanical loadings, opening angle, boundary conditions, and slenderness ratio on the static behavior of the nanobeam.

• Journal of Korean Association for Spatial Structures
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• v.13 no.4
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• pp.67-74
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• 2013

The Age-adjusted effective Modulus Method(AEMM) is one of the methods adopted for the construction stage analysis of concrete structures. The AEMM uses the aging factor to consider the effects of the varying concrete stress. In the aspects of computation time and the accuracy of the results, the AEMM is considered as one of most appropriate methods for construction stage analysis of tall building structures. Previous researches proposed appropriate values of the aging factor in the forms of graphs or using very simple equations. In this paper, an equation for estimating the aging factor as a function of rebar ratio in the section, compressive strength of concrete, notional member dimension, and age of concrete at the load application. The validity of aging factor proposed in this paper were examined by the comparison with the results of step-by step method.

• Structural Engineering and Mechanics
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• v.53 no.1
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• pp.27-40
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• 2015

The rational analytical solutions are presented for functionally graded beams subjected to arbitrary tractions on the upper and lower surfaces. The Young's modulus is assumed to vary exponentially along the thickness direction while the Poisson's ratio keeps unaltered. Within the framework of symplectic elasticity, zero eigensolutions along with general eigensolutions are investigated to derive the homogeneous solutions of functionally graded beams with no body force and traction-free lateral surfaces. Zero eigensolutions are proved to compose the basic solutions of the Saint-Venant problem, while general eigensolutions which vary exponentially with the axial coordinate have a significant influence on the local behavior. The complete elasticity solutions presented here include homogeneous solutions and particular solutions which satisfy the loading conditions on the lateral surfaces. Numerical examples are considered and compared with established results, illustrating the effects of material inhomogeneity on the localized stress distributions.