• Journal of the Computational Structural Engineering Institute of Korea
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• 제26권6호
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• pp.463-470
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• 2013

In this paper, 2D simple analyses were performed in order to predict the large torsional oscillations in a suspension bridge based on Makenna and Tuama model(2001). The existing model(Makenna and Tuama, 2001) has shown unrealistic results as the wind speed increases and frequency decreases. Furthermore, resonance could not be simulated by the existing model. Therefore, in this study, new model was proposed with a consideration of the torsional resistance. The vertical and rotational behaviors of the deck in the suspension bridge were analyzed. Analysis results showed that at first vertical oscillations were observed and it was gradually transformed to the rotation oscillations. With the consideration of the torsional resistance, it was shown that vertical behavior were stabilized as time passed. However, the rotational behavior was not stabilized and was kept until the end of analysis. Beat periods decreased while the wind speed increased. The resonance of the rotational mode was dependent to the rotational resistance. Obtained results could be applied for the design of the suspension bridge under the wind load.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.255-258
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• 2005

The current ACI design code does not take into account the contribution of concrete for the torsional moment of reinforced concrete(RC) beams subjected to pure torsion. This code is not capable of evaluating the inter-effects between concrete and torsional reinforcement on the torsional resistance of the RC beams. In this study, 9 RC beams subjected to pure torsion were tested. The main parameter of the beams was the amount of torsional reinforcement and the angle of twist. Test results indicated that the current ACI code over-estimated the torsional strength of RC beams that had larger amount of torsional reinforcement.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.287-290
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• 2008

Resistance to lateral torsional buckling of steel I-girder (open section) is a very important design requirement. But, most studies of steel I-girder with corrugated webs were invested in shear behavior. Untill now, most studies about Lateral torsional buckling of I-girder with corrugated webs have been based on Lindner.J's study (Lateral torsional buckling of beamswith trapezoidally corrugated webs,1990). the study includes that the pure torsional constant of I-girder with corrugated webs $J_{cor}$ doesn't different from that of I-girder with flat webs. This paper pesents pure torsional constant of I-girder with corrugated webs by using finite element anaysis.

• The Journal of the Korean dental association
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• 제57권11호
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• pp.672-678
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• 2019

AIM: The purpose of this study was to evaluate and compare the torsional fracture resistances, cyclic fatigue resistance, and bending stiffness of two nickel-titanium (NiTi) rotary instruments made of different heat-treated alloy: Aurum Blue (heat-treated) and Aurum Pro (conventional). Methods: Forty-five Aurum Blue and Aurum Pro NiTi files were selected for the three mechanical tests (n=15). For the torsional resistance test, 3 mm file tip was fixed and the shaft was driven clockwise at 2 rpm until fracture occurred by using a customized device. Cyclic fatigue resistance was evaluated by rotating instruments in artificial canal with dynamic mode. Bending stiffness was tested by observation of the bending moment on attaining a 45° bend. The results were analyzed by student-t tests at a significance level of 95%. The fractured surface of each groups were examined under a scanning electron microscope (SEM). Results: Aurum Blue showed significantly higher toughness, ultimate strength, distortion angle, and number of cycles to failure than those of Aurum Pro (p < 0.05). However, Aurum Blue and Aurum Pro did not differ significantly in terms of bending stiffness. SEM showed typical topographic appearances of the cyclic fatigue and torsional fracture. Conclusions: Under the limitations of this study, heat-treated instruments showed higher flexibility and fracture resistances than conventional NiTi instruments.

• Journal of the Korean Mathematical Society
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• 제44권3호
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• pp.707-717
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• 2007

Arches are constrained with rotational resistance at both edges. An energy method is used to derive variational formulation which is used to prove the existence of equilibrium states of elastic circular arches for the torsional spring constants ${\rho}-\;{\geq}\;0,\;{\rho}+\;{\geq}\;0,\;and\;{\rho}-\;+\;{\rho}+\;>\;0$. The boundary conditions are searched using the existence of minimum potential energy.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.585-588
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• 2008

Resistance to lateral torsional buckling of steel I-girder (open section) is a very important design requirement. But, most studies of steel I-girder with corrugated webs were invested in shear behavior. Until now, most studies about Lateral torsional buckling of I-girder with corrugated webs have been based on Lindner.J's study. the study includes that the pure torsional constant of I-girder with corrugated webs doesn't different from that of I-girder with flat webs. This paper pesents pure torsional constant I-girder with sinusoidally corrugated webs by using finite element analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제35권5호
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• pp.277-286
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• 2022

The elastic and inelastic responses obtained from the experimental and analytical results of two RC building structures under the service level earthquake (SLE) and maximum considered earthquake (MCE) in Korea were used to weinvestigate the characteristics of the mechanisms resisting shear and torsional behavior in torsionally unbalanced structures. Equations representing the interactive effect of translational drift and torsional deformation on the shear force and torsional moment were proposed. Because there is no correlation in the behavior between elastic and inelastic forces and strains, the incremental shear forces and incremental torsional moments were analyzed in terms of their corresponding incremental drifts and incremental torsional deformations with respect to the yield, unloading, and reloading phases around the maximum edge-frame drift. In the elastic combination of the two dominant modes, the translational drift mainly contributes to the shear force, whereas the torsional deformation contributes significantly to the overall torsional moment. However, this phenomenon is mostly altered in the inelastic response such that the incremental translational drift contributes to both the incremental shear forces and incremental torsional moments. In addition, the given equation is used to account for all phenomena, such as the reduction in torsional eccentricity, degradation of torsional stiffness, and apparent energy generation in an inelastic response.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제58권3호
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• pp.578-585
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• 2009

In this paper, we present the design of an electromagnetic scanning mirror with torsional springs. The scanning mirror consisting of torsional springs and electromagnetic coils was designed for the applications of laser animation systems. We analyzed and optimized three types of torsional springs, namely, straight beam springs (SBS), classic serpentine springs (CSS), and rotated serpentine springs (RSS). The torsional springs were analyzed in terms of electrical resistance, fabrication error tolerance, and resonance mode separation of each type using analytical formula or numerical analysis. The RSS has advantages over the others as follows: 1) A low resistance of conductors, 2) wide resonance mode separation, 3) strong fabrication error tolerance, 4) a small footprint. The double-layer coils were chosen instead of single-layer coils with respect to electromagnetic forces. It resulted in lower power consumption. The geometry of the scanning mirror was optimized by calculations; RSS turn was 12 and the width of double-layer coil was $100{\mu}m$, respectively. When the static rotational angle is 5 degrees, the power consumption of the mirror plate was calculated to be 9.35 mW since the resistance of the coil part and a current is $122{\Omega}$ and 8.75 mA, respectively. The power consumption of full device including the mirror plate and torsional springs was calculated to be 9.63 mW.

• Structural Engineering and Mechanics
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• 제18권6호
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• pp.745-757
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• 2004

Lateral-torsional buckling moment resistances of I-shaped stepped beams with continuous lateral top-flange bracing under a single point load on the top flange and negative end moments were investigated. Stepped beam factors and a moment gradient correction factor suggested by Park et al. (2003, 2004) were used to develop new lateral buckling formula for beam designs. From the investigation of finite element analysis (FEA), new lateral buckling formula of beams with singly or doubly stepped member changes and with continuous lateral top-flange bracing subjected to a single point load on top flange and end moments were developed. The new design equation includes the length-to-height ratio factor to account for the increase of lateral-torsional buckling moment resistance as the increase of length-to-height ratio of stepped beams. The calculation examples for obtaining lateral-torsional buckling moment resistance using the new design equation indicate that engineers should easily determine the buckling capacity of the stepped beams.

• Proceedings of the Korean Geotechical Society Conference
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1126-1133
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• 2005

The effects of mean particle size and uniformity coefficient of dredged soils to the liquefaction resistance strength and dynamic characteristics are experimentally studied in this paper. Representative 4 mean particle sizes and 3 uniformity coefficients were selected and 12 representative particle size distribution curves which have different mean particle sizes and uniformity coefficients, were artificially manufactured using the real dredged river soil. Cyclic triaxial tests and torsional shear tests were carried out to analyze the effect of mean particle size and uniformity coefficient to the liquefaction resistance strength and dynamic characteristics of soils.