• Nuclear Engineering and Technology
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• v.31 no.3
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• pp.328-334
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• 1999

Based on the Euler beam theory and the elastic strain energy method, the elastic stiffness formula of the holddown spring assembly consisting of several leaves was previously derived. Even though the previous formula was known to be useful to estimate the elastic stiffness of the holddown spring assembly, recently it was reported that the elastic stiffness from the previous formula deviated greatly from the test results as the number of leaves was increased. The objective of this study is to extend the previous formula in order to resolve such an increasing deviation when increasing the number of leaves. Additionally, considering the friction forces acting on the interfaces between the leaves, we obtained an extended elastic stiffness formula. The characteristic test and the elastic stiffness analysis on the various kinds of specimens of the holddown spring assembly have been carried out; the validity of the extended formula has been verified by the comparison of their results. As a result of comparisons, it is found that the extended formula is able to evaluate the elastic stiffness of the holddown spring assembly within the maximum error range of + 12%, irrespective of the number of the leaves.

• Nuclear Engineering and Technology
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• v.30 no.4
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• pp.287-297
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• 1998

The elastic stiffness formula of leaf type holddown spring(HDS) assembly is verified by comparing the values of elastic stiffness with the characteristic test results of the HDS's specimens. The comparisons show that the derived elastic stiffness formula is useful in reliably estimating the elastic stiffness of leaf type HDS assembly. The elastic stiffness sensitivity of leaf type HDS assembly is analyzed using the formula and its gradient vectors obtained from the mid-point formula. As a result of sensitivity analysis, the elastic stiffness sensitivity with respect to each design variable is quantified and design variables of large sensitivity are identified. Among the design variables, leaf thickness is identified as the most sensitive design variable to the elastic stiffness of leaf type HDS assembly. In addition, the elastic stiffness sensitivity, with respect to design variable, is in power-law type correlation to the base thickness of the leaf.

• Nuclear Engineering and Technology
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• v.28 no.6
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• pp.583-593
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• 1996

An elastic stiffness formula of a leaf type holddown spring(HDS) assembly with a uniformly tapered width from $w_0$ to $w_14$ over the length, has been analytically derived based on Euler beam theory and Castigliano's theorem. Elastic stiffnesses of the tapered-width leaf type HDSs(TW-HDSs) designed in the same dimensional design spaces as the KOFA HDSs have been evaluated from the derived formula, in addition, a parametric study on the elastic stiffness of the TW-HDSs has been carried out. Analysis results show that, as the effects of axial and shear force on the elastic stiffness of He TW-HDSs have been 0.15~0.21% of the elastic stiffness, most of the elastic stiffness is attributed to the bending moment, and that elastic stiffnesses of the TW-HDSs have been about 32~33% higher than those of the KOFA HDSs. It is found that the number of leaves composing a HDS assembly could be lessened by one under the conditions that the TW-HDSs have been adopted in KOFA.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.1
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• pp.180-187
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• 1997

A formula for estimating the elastic stiffness of TW-HDS with a uniformly tapered width from w$_{0}$ to w$_{1}$ over the length, has been analytically derived based on Euler beam theory and Castigliano's theorem. Elastic stiffnesses of the TW-HDSs designed in the same dimensional design spaces as the KOFA HDSs have been estimated from the derived formula, in addition, a sensitivity study on the elastic stiffness of the TW-HDSs has been carried out. Analysis results show that elastic stiffnesses of the TW-HDSs have been by far higher than those of the KOFA HDSs, and that, as the effects of axial and shear force on the elastic stiffness have been 0.15-0.21%, most of the elastic stiffness is attributed to the bending moment. As a result of sensitivity analysis, the elastic stiffness sensitivity at each design variable is quantified and design variables having remarkable sensitivity are identified. Among the design variables, leaf thickness is identified as that of having the most remarkable sensitivity of the elastic stiffness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.8
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• pp.1276-1290
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• 1997

The previous elastic stiffness formulas of leaf type holddown spring assemblies(HDSs) have been corrected and extended to be able to consider the point of taper runout for the TT-HDS and all the strain energies for both the TT-HDS and the TW-HDS based on Euler beam theory and Castigliano'stheorem. The elastic stiffness sensitivity of the leaf type holddown spring assemblies was analyzed using the derived elastic stiffness formulas and their gradient vectors obtained from the mid-point formula. As a result of the sensitivity analysis, the elastic stiffness sensitivity at each design variable is quantified and design variables having remarkable sensitivity are identified. Among the design variables, leaf thickness is identified as that of having the most remarkable sensitivity of the elastic stiffness. In addition, it was found that the sensitivity of the leaf type HDS's elastic stiffness is exponentially correlated to the leaf thickness.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.111-118
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• 2006

The elastic buckling strength of a corrugated culvert made of orthotropic material such as FRP was evaluated. The height and length of a corrugated wave and the thickness of the culvert were considered as factors affecting the buckling strength of the culvert. And also, the ratio of the longitudinal stiffness and transverse stiffness was considered as the parameter affecting on the buckling strength of the used orthotropic material. Buckling strengths of various corrugated culvert models with different shapes and stiffness ratio were evaluated by FE analyses and a formula to estimate the elastic buckling strength was suggested from the regression with FE analysis results. Analysis results show that a corrugated culvert has superior buckling strength to a general flat pipe and the suggested formula estimates accurate buckling strength of the corrugated culverts made of orthotropic material.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.119-126
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• 2006

The elastic budding strength of a GFRP pipe reinforced with ribs was evaluated. The height and thickness of a rib and the spacing between two adjacent ribs were considered as factors affecting tlje budding strength of the pipe. And also, the ratio of the longitudinal stiffness and transverse stiffness was considered as the parameter affecting on the budding strength because GFRP is orthotropic material. Buckling strengths of various GFRP pipe models with different shapes and stiffness ratio were evaluated by FE analyses and a formula to estimate the elastic buckling strength of a rib-reinforced pipe made of orthotropic material was suggested from the regression with FE analysis results. Analysis results show that a rib-reinforced pipe has superior buckling strength to a general flat pipe and the suggested formula estimates accurate buckling strength of the rib-reinforced pipe.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.737-746
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• 2006

The elastic buckling strength of a Glass Fiber Reinforced Plastic (GFRP) pipe reinforced with ribs was evaluated. The height and thickness of a rib and the spacing between two adjacent ribs were considered as factors affecting the buckling strength of the pipe. And also, the ratio of the longitudinal stiffness and transverse stiffness was considered as the parameter affecting the buckling strength as the GFRP is orthotropic material. Buckling strengths of various GFRP pipe models with different shapes and stiffness ratios were evaluated by FE analyses and a formula to estimate the elastic buckling strength of a rib-reinforced pipe made of orthotropic material was suggested from the regression with the results from the FE analysis. Analytical results show that a rib-reinforced pipe has a buckling strength superior to a general flat pipe and the suggested formula estimates accurate buckling strength of the rib-reinforced pipe.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.1
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• pp.191-198
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• 2003

The pavement stiffness is scarcely used in structural analysis to design the superstructure of bridge. It is reasonable not to consider it in the case of asphalt concrete pavement over concrete deck because the pavement stiffness compared with the concrete deck plate can be ignored. However, sometimes, the pavement materials have a similar amount of elastic modulus to concrete and are applied to the orthotropic steel deck plate which has relatively less stiffness compared with the concrete deck plate. In this paper, the steel plate deck of a real bridge project was analyzed by considering the pavement stiffness by linear elastic FEM. It was assumed that a perfect bond between the steel plate deck and the pavement exited. The results indicated that the structural behavior of the orthotropic steel deck plate can be estimated enough to affect the evaluation result of structural capacity in some cases. Therefore, the investigations by experimental tests and more advanced numerical model are indispensible in figuring the design formula for considering the effects of pavement stiffness in the structural analysis of an orthotropic bridge.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.109-116
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• 2004

This paper investigates the characteristics of deflection for circular plate that has same supporting boundary condition along the width direction of plate according to the length change of supporting end. For two boundary conditions such as simple supporting and clamping on both ends, this study derives maximum deflection formula of circular plate using differential equation of elastic curve, assuming that a circular plate is a beam with different widths along the longitudinal direction. The deflection formula of circular plate is verified by carrying out finite element analysis with regard to the ratio of length of supporting end to radius of circular plate.