• Journal of Korean Society of Steel Construction
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• v.26 no.6
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• pp.581-594
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• 2014

In this paper, flexural resistance of hybrid girder under uniform bending moment was evaluated, which is composed of HSB800 and HSB600 steel for the flange and web, respectively. Doubly-symmetric and monosymmetric sections with noncompact or compact flange and slender, noncompact or compact web were considered. Nonlinear analyses with 3-dim. shell element model were performed to determine the 'flexural resistance of section' and the 'lateral torsional buckling strength' by taking initial imperfection and residual stress into account. The numerical results were compared with the AASHTO LRFD and Eurocode 3 specifications and also the applicability of AASHTO LRFD appendix A6 was examined for the sections with noncompact and compact web.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.9
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• pp.82-87
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• 2003

This research is concerned with ground experiments for satellite solar array deployment as well as the validation of theoretical modeling technique presented in the previous paper. We carried out the experiments on the strain energy hinge with stopper to investigate he buckling characteristics of the SEH, which affects the shape and the speed of the solar array deployment. The moment-angle diagram obtained from the experiments was later combined with the theoretical deployment model. This paper also presents the details of the ground experiments performed at the Korea Aerospace Research Institute(KARI) . It was found that the ground experimental results were in good agreement with the theoretical predictions thus validating the dynamic modeling technique.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.81-91
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• 2003

Recently, many high-rise reinforced concrete(RC) bearing-wall structures of multiple uses have been constructed, which have the irregularities of weak(or soft) story and torsion at the lower stories simultaneously. The study stated herein was performed to investigate seismic performance of such a high-rise RC structure through a series of shaking table tests of a 1: 12 model. Based on the observations of the test results, the conclusions are drawn as follows: 1) Accidental torsion due to the uncertainty on the properties of structure can be reasonably predicted by using the dynamic analysis than by using lateral force procedure. 2) The mode coupled by translation and torsion induced the overturning moments not only in the direction of excitations but also in the perpendicular direction: The axial forces in columns due to this transverse overturning moment cannot be adequately predicted using the existing mode analysis technique, and 3) the hysteretic curve and the strength diagram between base shear and torque(BST) clearly reveal the predominant mode of vibrations and the failure mode.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.11
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• pp.1236-1244
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• 2012

A equivalent stiffness modeling has been performed for extracting the equivalent stiffness properties which are orthotropic elastic model from a large scale wind turbine rotor blade so that structure model can be constructed more simply for the three dimensional static aeroelastic analysis. In order to present the procedure of equivalent stiffness modeling, NREL 5MW class wind turbine rotor having the three stiffness information which are flapewise, edgewise and torsional stiffness was chosen. This method is based on applying unit moment at the tip of the blade as well as fixing all degree of freedom at the blade root and calculating the displacement from the load analysis to obtain the elastic modulus corresponding to equivalent stiffness referred to the NREL reports on blade divided into 5 sections respectively. In addition, one section was divided into 3 parts and the trend functions were used to make the equivalent stiffness model more correctly and quickly. Through the comparison of stiffness between the reference values and calculated values from equivalent stiffness model, the investigation of the accuracy on the stiffness values and the efficiency for constructing the model was conducted.

• Journal of Korean Society of Steel Construction
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• v.18 no.5
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• pp.515-524
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• 2006

Cross-sectional distortions take place when steel box girders a re subjected to torsional moment, as a consequence of which distortional warping stresses are necessarily developed. Additional normal stresses due to the distortion are should be included at the design stage. The relative magnitude with respect to the maximum bending stress are kept less than the specific values, i.e., at 5~10%, by properly spaced intermediate diaphragms that could prevent the distortional deformation of the box girder. However, current design equations for the stiffness of intermediate diaphragms were derived based on BEF. In this study, the area required by the intermediate diaphragm members are investigated through three-dimensional finite element analyses. The results of the analyses indicate that the current equations give to conservative values for the intermediate diaphragm of box girder bridges. Finally, an improved equation for the area of the intermediate diaphragm is derived from a regression analysis from the finite element analysis results.

• Wind and Structures
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• v.30 no.2
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• pp.181-198
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• 2020

In the traditional buffeting response analysis method, the spanwise incomplete correlation of buffeting forces is always assumed to be same as that of the incident wind turbulence and the action of the signature turbulence is ignored. In this paper, three typical bridge decks usually adopted in the real bridge engineering, a single flat box deck, a central slotted box deck and a two-separated paralleled box deck, were employed as the investigated objects. The wind induced pressure on these bridge decks were measured via a series of wind tunnel pressure tests of the sectional models. The influences of the wind speed in the tests, the angle of attack, the turbulence intensity and the characteristic distance were taken into account and discussed. The spanwise root coherence of buffeting forces was also compared with that of the incidence turbulence. The signature turbulence effect on the spanwise root coherence function was decomposed and explained by a new empirical method with a double-variable model. Finally, the formula of a sum of rational fractions that accounted for the signature turbulence effect was proposed in order to fit the results of the spanwise root coherence function. The results show that, the spanwise root coherence of the drag force agrees with that of incidence turbulence in some range of the reduced frequency but disagree in the mostly reduced frequency. The spanwise root coherence of the lift force and the torsional moment is much larger than that of the incidence turbulence. The influences of the wind speed and the angle of attack are slight, and they can be ignored in the wind tunnel test. The spanwise coherence function often involves several narrow peaks due to the signature turbulence effect in the high reduced frequency zone. The spanwise coherence function is related to the spanwise separation distance and the spanwise integral length scales, and the signature turbulence effect is related to the deck-width-related reduced frequency.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.1
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• pp.35-44
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• 1990

Most of the medium-size ships are powered by large-bore, long-stroke, slow-speed and two-stroke diesel engines in order to improve the fuel efficiency. Such a propulsion plant develops low-frequency excitation forces/moments of significant magnitude. A RO/RO car/truck carrier is also one of the cases. In this paper, the rational methods for analysis of vertical and coupled horizontal-torsional vibrations are presented. Taking account of unusual characteristics of the hull form and structural systems, the emphasis is put on modelling methods based on beam analogy, calculation of system parameters such as added mass and its center, polar added-mass moment of inertia, shear coefficient of hull sections and coupling degree in antisymmetric modes, and modal analysis of forced vibrations.

• Journal of Biosystems Engineering
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• v.29 no.1
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• pp.29-36
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• 2004

The geometric characteristics of the Altari radish were measured for the purpose of mechanization of the kimchi processing. In this study, geometric characteristics such as the sectional area and volume of the radishes(pyeong-gang and sa-chul) were calculated using the image processing method, and physical properties such as the compressive strength, the cutting force of the radish and the torsional moment of the radish leaf-stems were measured by using a universal testing machine. In case of the radish(pyeong-gang), the weight was ranged 215.0∼465.0 g, the length of the radishes(body) was 86.3∼129.2 mm, the diameters were 43.3∼58.1 mm, and the length of the leaves was 261.3-368.2 mm. And the vertical compressive strengths were ranged 83.8∼171.7 N/$\textrm{cm}^2$, the horizontal compressive strengths were 113.0∼176.3 N/$\textrm{cm}^2$, the shearing forces were 86.0∼114.6 N, and the surface hardness was ranged 51.1∼52.1 N/$\textrm{cm}^2$. In case of the radish(sa-chul), the weight was ranged 203.5∼412.2 g, the length of the bodies was 67.5∼127.0 mm, the diameters were 22.3∼59.8 mm and the length of the leaves was 245.6∼312.6 mm respectively. And the vertical compressive strengths were ranged 91.3∼168.3 N/mm, the horizontal compressive strengths were 132.6∼186.9 N/$\textrm{cm}^2$, the shearing forces were 89.4∼116.5 N, and the surface hardness was ranged 52.4∼67.8 N/$\textrm{cm}^2$, respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.183-191
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• 2003

A four-story reinforced concrete moment resisting frame damaged from an ultimate limit state earthquake is upgraded with prestressing cable bracing. The purpose of this study is to investigate the bracing configuration effects on the 3-D building response using thee different locations of the bracing systems for the retrofitted building. Since the previous work done by the author proved that static incremental loads to collapse analysis as a substitute to dynamic non-linear time history analysis was a valid alternative tool. Thus, static load to collapse analysis is solely applied to evaluate the seismic performance parameters of both the original and upgraded buildings in this study. In results, the exterior bracing system is effective in restraining torsional behavior of the structure under seismic loads, and no sudden failure occurs in this system that enhances the ductility of the building due to the gradual change of building stiffness as the lateral load increases.

• Steel and Composite Structures
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• v.39 no.1
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• pp.65-80
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• 2021

Irregularities of a building in plan and elevation, which results in the change in stiffness on different floors highly affect the seismic performance and resistance of a structure. This study motivated to investigate the seismic responses of high-rise steel-frame buildings of twelve stories with various stiffness irregularities. The building has five spans of 3200 mm distance in both X- and Z-directions in the plan. The design package SAP2000 was adopted for the design of beams and columns and resulted in the profile IPE500 for the beams of all floors and box sections for columns. The column cross-section dimensions vary concerning the number of the story; one to three: 0.50×0.50×0.05m, four to seven: 0.45×0.45×0.05 m, and eight to twelve: 0.40×0.40×0.05 m. Real recorded ground accelerations obtained from the Vrancea earthquake in Romania together with dead and live loads corresponding to each story were considered for the applied load. The model was validated by comparing the results of the current method and literature considering a three-bay steel moment-resisting frame of eight-story height subject to seismic load. To investigate the seismic performance of the buildings, the time-history analysis was performed using ABAQUS. Deformed shapes corresponding to negative and positive peaks were provided followed by the story drifts and fragility curves which were used to examine the probability of collapse of the building. From the results, it was concluded that regular buildings provided a seismic performance much better than irregular buildings. Furthermore, it was observed that building with torsional irregularity was more vulnerable to seismic failure.