• Wind and Structures
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• v.25 no.3
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• pp.283-299
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• 2017

Two types of aerodynamic admittance function (AAF) that have been adopted in bridge aerodynamics are addressed. The first type is based on a group of supposed relations between flutter derivatives and AAFs. In so doing, the aero-elastic properties of a section could be used to determine AAFs. It is found that the supposed relations hold only for cases when the gust frequencies are within a very low range. Predominant frequencies of long-span bridges are, however, far away from this range. In this sense, the AAFs determined this way are of little practical significance. Another type of AAFs is based on the relation between the Theodorsen circulation function and the Sears function, which holds for thin airfoil theories. It is found, however, that an obvious illogicality exists in this methodology either. In this article, a viewpoint is put forward that AAFs of bluff bridge deck sections are inherently dependent on oncoming turbulent properties. This kind of dependence is investigated with a thin plate and a double-girder bluff section via computational fluid dynamics method. Two types of wind fluctuations are used for identification of AAFs. One is turbulent wind flow while the other is harmonic. The numerical results indicate that AAFs of the thin plate agree well with the Sears AAF, and show no obvious dependence on the oncoming wind fields. In contrast, for the case of bluff double-girder section, AAFs identified from the turbulent and harmonic flows of different amplitudes differ among each other, exhibiting obvious dependence on the oncoming wind field properties.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.166-172
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• 2019

A case study was performed in order to develop well-designed of thin plate door impact beam. The conventional impact beam was consisted of steel-pipe welded two brackets on the both side, which causes low productivity and high cost. In order to overcome those disadvantage, it is necessary to develop a new type of door impact; thin plate impact beam. The thin plate impact beam was not needed a welding procedure, which can lead low cost and high productivity. In order to maximally resist from an external force, the cross-section design should be well designed. 6 different cross-section design were proposed based on engineer's experience. Three point bending test was simulated those 6 different impact beam and compared the reaction forces. Among them, one case was chosen and redesigned for detail design.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1096-1101
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• 2004

Generally, the buckling of thin-walled structures has studied for rectangular sections or circular sections. Rectangular sections have small stiffness and circular sections have large stiffness when they are compared with rectangular sections for local buckling. But both of them have similar stiffness to column buckling. Therefore in this paper, we are going to analyze the local buckling for the box section with rounded comer and compare with rectangular section. Also we confirm that the rounded comer section has larger local buckling strength than rectangular section.

• Journal of Mechanical Science and Technology
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• v.19 no.11
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• pp.2016-2024
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• 2005

In this work, a mixed beam approach that combines both the stiffness and the flexibility methods has been performed to analyze the coupled composite blades with closed, two-cell cross-sections. The Reissner's semi-complementary energy functional is used to derive the beam force-displacement relations. Only the membrane part of the shell wall is taken into account to make the analysis simple and also to deliver a clear picture of the mixed method. All the cross section stiffness coefficients as well as the distribution of shear across the section are evaluated in a closed-form through the beam formulation. The theory is validated against experimental test data, detailed finite element analysis results, and other analytical results for coupled composite blades with a two-cell airfoil section. Despite the simple kinematic model adopted in the theory, an accuracy comparable to that of two-dimensional finite element analysis has been obtained for cases considered in this study.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.6
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• pp.107-113
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• 2004

This paper presents the pillar section optimization technique considering the reliability of the vehicle body structure consisted of complicated thin-walled panels. The response surface method is utilized to obtain the response surface models that describe the approximate performance functions representing the system characteristics on the section properties of the pillar and on the mass and the natural frequencies of the vehicle B.I.W. The reliability-based design optimization on the pillar sections Is performed and compared with the conventional deterministic optimization. The FORM is applied for the reliability analysis of the vehicle body structure. The developed optimization system is applied to the pillar section design considering the fundamental natural frequencies of passenger car body structure. By applying the proposed RBDO technique, it can be possible to optimize the pillar sections considering the reliability that engineers require.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.135-140
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• 2001

This study was developed high-quality a large size precast channel structure using polymer concrete to improve quality of the product as well as to enhance construction quality. Precast PC represent the fastest growing segment of the polymer concrete industry. The fast curing, high strength, and low impermeability permit thin section and rapid reuse of moulds. Developed precast channel structure will be structural experiment and analysis. Also, through an example to construct will be develop the most suitable section survey and make practicable.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.121-132
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• 2009

Thin bonded continuously reinforced concrete overlay(CRCO) was constructed on He existing jointed plain concrete pavement(HCP) surface at Seo-Hae-Ahn express highway in South Korea in order to evaluate its applicability and performance. Two sections of road were considered for this evaluation. In the first section, the concrete overlayer was placed and cut down to the existing layer to form transverse joints while CRCO was constructed on top of the existing layer in the second section. Early strength concrete(Type III) was utilized for both overlay sections. The depth of milling and the thickness of overlaid layer were 5 cm and 10 cm, respectively. Several vibrating wire gauges(VWG) were installed to evaluate the performance of CRCO with respect to curling, delamination, and crack propagation. As a result of the strength test, it was found that strength of the material reaches the design criteria within 1-3 days. Analysis with vibrating wire gauge(VWG) showed CRCO effectively restricts joint movement. High adhesive strength also was observed from the material regardless of length of aging. Meanwhile, transverse cracks were observed on the middle of the section where JPCP overlay was applied whereas arbitrarily cracks in transverse direction were observed on the section where CRCP was applied.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.69-73
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• 2003

A open section thick composite beam model is suggested in this study. In the model, the primary and secondary warping and transverse shear effects are incorporated. The rigidities associated with thick channel composite beam and thin channel composite beam are obtained and compared. The results show that the difference among rigidities of the thick and thin composite beams increase as the wall thickness increases.

• Journal of Mechanical Science and Technology
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• v.17 no.4
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• pp.501-510
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• 2003

The spot welded sections of automobiles such as the hat and double hat section members, absorb the most of the energy during the front-end collision. The purpose of this study was to analyze the collapse characteristics of spot welded section members with respect ttl the pitch or spot welds on flanges. through impact experiments and computation for para-closed sections and perfectly closed sections. The hat shaped section members were tested at the impact collapse velocities of 4.72 m/sec, 6.54 m/sec and 7.19 m/sec and double hat shaped section members were tested at the impact collapse velocities of 6.54 m/sec, 7.19 m/sec and 7.27 m/sec. A commercial LS-DYNA3D was used to simulate the collapse behavior of the hat and double hat shaped section members. The validity of the simulation was to be proved by comparing the simulation results and the experimental results.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.2
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• pp.77-85
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• 2009

A two-dimensional cross-section analysis program based on the finite element method has been developed for composite blades with arbitrary cross-section profiles and material distributions. The modulus weighted approach is used to take into account the non-homogeneous material characteristics of advanced blades. The CLPT (Classical Lamination Plate Theory) is applied to obtain the effective moduli of the composite laminate. The location of shear center for any given cross-sections are determined according to the Trefftz' definition while the torsion constants are obtained using the St. Venant torsion theory. A series of benchmark examples for beams with various cross-sections are illustrated to show the accuracy of the developed cross-section analysis program. The cross section cases include thin-walled C-channel, I-beam, single-cell box, NACA0012 airfoil, and KARI small-scale blades. Overall, a reasonable correlation is obtained in comparison with experiments or finite element analysis results.