• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.873-878
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• 2000

Tension stiffening effects of reinforced concrete member with large diameter bar, mainly used at reactor building of nuclear power plant, are studied by uniaxial structural tests. Bond length and stress of steel bar, size of steel bar, and compressive strength of concrete are evaluated to tension stiffening by uniaxial tests. Problems and solution during the uniaxial test are suggested. The prevent splitting cracks, concrete cover-to-bar diameter ratio $c/d_{b}$ is kept 2.6~2.8. Because the bond length is increased as the size of steel bar, the specimen length of the D35 steel bar is required at least 2.0 m. The specimen length must be decided with bond length as well as concrete cover-to-bar diameter ratio to prevent splitting crack.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.6
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• pp.712-723
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• 2015

This study was conducted to develop the SWCC estimation equation using scaling technique, and to investigate relative sensitivity of the SWCC according to the soil water tension, for the four kinds of soil texture such as Sand [S], Sandy Loam [SL], Loam [L] and Clay Loam [CL]. The SWCC estimation equation of scale factor [${\Theta}sc$] (Eq. 1) was developed based on the log function (Eq. 2) and exponential function (Eq. 3). ${\Theta}sc=[({\Theta}-{\Theta}r)/({\Theta}s-{\Theta}r)]$ (Eq. 1) ${\Theta}sc=-0.196ln(H)+0.4888$ (Eq. 2) ${\Theta}sc=0.3804(H)^{(-0.448)}$ (Eq. 3) where, ${\Theta}$: water content (g/g %), ${\Theta}s$: water content at 0.1bar, ${\Theta}r$: water content at 15bar, H: soil water tension (matric potential) (bar) Relative sensitivity of soil water content was decreased as increase soil water tension, those according to soil water tension were 0.952~0.620 compared to 0.1bar case. Relative sensitivity of scale factor was also decreased as increase soil water tension, those according to soil water tension were 0.890~0.577 compared to 0.2bar case.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.130-136
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• 2017

The present work is for an evaluation of tension behavior and surface deterioration of FRP Hybrid Bar due to UV exposure and freezing/thawing(F/T) actions. For the work, FRP Hybrid Bar is subjected to UV exposure test, then F/T test is performed successively to 180 cycles. In FRP Hybrid Bar, no significant surface deterioration is evaluated after UV exposure. Tension hardening performance, a unique engineering advantage of FRP Hybrid Bar, is still maintained after F/T test. The performance in FRP Hybrid Bar exposed to UV is still effective. FRP Hybrid Bar exposed to UV have almost similar tension behavior of FRP Hybrid Bar without UV exposure. Although F/T cycles increase to 180, steel rebar, FRP Hybrid Bar, and FRP Hybrid Bar exposed to UV show no significant changes in tension behavior. In the work, UV exposure and F/T actions are evaluated to have little negative effect on surface deterioration and tensile performance in FRP Hybrid Bar, however spalling of silica coating due to impact should be considered since it affects bonding strength to outer concrete.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.3
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• pp.404-408
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• 2006

In this paper, connection strength between facing block and tie-bar was investigated through experimental study with varying in-fill material such as concrete, soil and crushed stone. Also, connection strength between anchor block and tie-bar was investigated with varying in-fill material. According to the experimental results, in case of using in-fill concrete, connection strength between facing block and tie-bar was larger than allowable tension load of tie-bar. Whereas in case of using in-fill soil or crushed stone, connection strength between facing block and tie-bar was less or similiar to allowable tension load of tie-bar. Connection strength between anchor block and tie-bar for which crushed stone was used as in-fill material, was larger than allowable tension load of tie-bar.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.10a
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• pp.84-88
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• 1997

The Jonhnson-Cook constitutive relation has been used in dynamic plasticities. The constants of the Jonhson-Cook relation of sheet metals for an autobody is not known yet. In this paper, the material properties of SPCEN, SPCC and SPRC in the high strain rate states have been acquired. A new tension split Hopkinson bar was used in high speed tensile tests of sheet metals. The experimental results acquired from the apparatus are used to determine the constants of Johnson-Cook constitutive relation of sheet metals. This results can be used to analysis of crashworthness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.11
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• pp.3415-3423
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• 1996

The compact tension specimen geometry has been widely used for measuring fatigue crack growth rates at elevated temperature when the fatigue load is under tension/tension condition. However, most of the elevated temperature components which have significant crack growth life experience fatigue load under tension/compression conditions. Thus test techniques are required since the compact tension specimen cannot be used for tension/compression loading. In this paper, a simplified test procedure for measureing fatigue crack growth rates is proposed, which employs a round bar specimen with a small surface crack. Fatigue crack growth rates under tension/ tension loading conditions at elevated temperature were measured according to the proposed procedure and compared with those previously measured by C/(T) specimens. Since both the measured crack growth rates were comparable, the fatigue crack growth rates under tension/ compression load can be reliably measured by the proposed procedure. For monitoring crack depth. DC electric potential method is employed and an optimal probe location and current input conditions were proposed.

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.351-358
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• 2007

Unlike external bonded steel plate or carbon fiber, the external unbonded strengthening using hi-strength bar has some advantages in speed and simplicity of installation. It is not required surface preparations and not affected by environmental conditions. A set of nine laboratory tests on RC beams strengthened using the hi-tension bars are reported. Anchoring pin developed in former research is installed at the end of beam to connect the hish-tension bar to RC beam. The test results strengthened by hi-tension bars are compared with those of non-strengthened specimens. The main test parameters are the cross-sectional area of the high-tension bar, distance of stirrups and condition of supports. Test results show that the beams reinforced are superior to reference specimens, especially for the strength and deformation capacity. Also, shear resisting effect of hi-strength bar can be confirmed in the specimens which have lack of stirrups.

• Journal of Ocean Engineering and Technology
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• v.34 no.3
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• pp.155-166
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• 2020

Ductile fracture prediction is critical for the reasonable damage extent assessment of ships and offshore structures subjected to accidental loads, such as ship collisions and groundings. A fracture model combining the Hosford-Coulomb ductile fracture model with the domain of solid-to-shell equivalence model (HC-SDDE), was used in fracture simulations based on shell elements for the punching fracture experiments of unstiffened and stiffened panels. The flow stress and ductile fracture characteristics of JIS G3131 SPHC steel were identified through tension tests for flat bar, notched tension bar, central hole tension bar, plane strain tension bar, and pure shear bar specimens. Punching fracture tests for unstiffened and stiffened panels are conducted to validate the presented HC-DSSE model. The calibrated fracture model is implemented in a user-defined material subroutine. The force-indentation curves and final damage extents obtained from the simulations are compared with experimental results. The HC-DSSE fracture model provides reasonable estimations in terms of force-indentation paths and residual damage extents.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2209-2219
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• 1997

A split hopkinson bar could be used for obtaining the high strain rate material properties of sheet metals for an autobody. In high speed tensile tests of sheet matals, a new design of a tension split Hopkinson bar apparatus is needed. The design of grips and an anvil length are numerically analyzed with ABAQUS/Explicit for the new apparatus of split Hopkinson bars. From the experiments with the new apparatus, the material properties of SPCEN in the high strain rate state have been acquired and compared with quasi-static experimental results. The material properties of SPCEN as well as other sheet metals in an autobody are indispensible for the analysis of crashworthness. Nevertheless the experiment of sheet metal in the high strain rate state has not been done or reported.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.423-428
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• 1999

A high precision hot strip width control method has been developed in this study by applying interstand looper tension measuring system at finishing mill stands. As with deviation of hot rolled steel strip is closely related to abnormal increase in the interstand strip tension, on-line measuring device of looped tension and data analyzing system was developed in this study. To determine dominant factors that will cause local width shortage, the logged data sets of bar width, bar thickness, looper tension, and strip thickness along the strip length were correlated with the data set of strip width change. With the result of the correlation analysis, existing sequence control logic and parameters for looper actuator were modified for strip width quality and the gains of the looper control were refined for the stable operation during the full passage of rolled strip. The on-line tension measurement and tension feedback control for looper system improved strip travelling stability and reduced strip width deviation in the srip top end region.