• Journal of Korean Society of Steel Construction
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• v.26 no.6
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• pp.499-509
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• 2014

This study focuses on mixing steel fiber in the concrete to improve the ductility and toughness of the columns. The purpose of the study is to evaluate the load capacity and deformation capacity associated with the amount of steel fiber and loading condition and to analyze the interplay between the steel fiber reinforced concrete and the welding built-up square tube in terms of structure and fire resistance performance. Reinforcement of concrete with steel fiber(Vf=0.375%), when cross-section shape and boundary condition (load ratio) remained unchanged, improved fire resistance performance by 1.1~1.3 times. It is deemed that the area resisting thermal load increased and fire resistance performance was improved since the concrete reinforced with steel fiber restrained cracking. In addition, the fact that the cross-sections of the concrete were barely damaged indicates that load share capacity was greatly improved.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.71-74
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• 2005

In manufacturing automotive parts, such as engine cradles, frame rails, subframes, cross-members, and other parts from circular tubes, pre-bending and pre-forming operations are often required prior to the subsequent tubular hydroforming process. During some pre-forming operations, the cross section of a bent circular tube is crushed into an oval-like shape to ensure proper geometry and sufficient clearance in the hydroforming dies. For such applications, the use of oval Instead of circular tubes could be an effective means of eliminating the pre-forming step. The oval tube could also be produced with less thinning and with less strain on the outside of the bend when controlled by a booster system without the use of mandrel. Hence, the understanding of the issues that occur in the bending of oval tubes is worthy of Investigation. This paper presents parametric studies on the bending of oval tubes without a mandrel. The finite element modeling technique is used to examine the deformation characteristics for both circular and oval tubes. In the simulations, the bending process parameters of bend radius, aspect ratio of the tube ovalness, and tube wall thickness are varied. Observations are made to obtain a hoop-buckle limit diagram in terms of a non-dimensional shape degradation factor. Suggestions based upon developed criteria are made on the acceptability of bend tubes suitable for hydroforming applications without the need ofa pre-forming step or the used of a mandrel.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.611-620
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• 2007

The beam-column connection is the critical design section of general steel frame structures owing to the behavioral characteristics of the structural system. As most members of a frame structure are composed of rolled section beams, the cross-section of the beam members is governed by the negative bending moment near beam-column connections. Such a design concept leaves a redundant load-carrying capacity at the positive bending regions of the beam members leading to design inefficiency. Therefore, it is of utmost importance to redistribute the beam end moments and reduce the stresses at the beam-column connections for a more efficient design of steel frame structures. In this study, reaction-moment prestressing method (RMPM) was proposed for the innovative design and construction of steel frame structures. The RMPM is a prestressing method utilizing the elastic bending deformation of a beam member induced by temporary prestressing for the distribution of a relatively large bending moment to other sections for the efficient use of the beam section. By the application of the RMPM, the negative bending moment at the beam-column connections can be significantly reduced, ultimately leading to possible use of smaller beam sections. Through a series of model tests and numerical analyses of steel frame structures, the moment distributing effect and feasibility of the RMPM was verified.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.141-150
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• 1987

The Soyanggang Dam completed in 1973 was well instrumented during construction period. The measured results for stresses and movements of the embankment have already been published elsewhere, but theoretical analyses have not been made until now. This study intends to analyze the stress and deformation behavior of the embankment numerically which have been subjected to the load of materials during construction and water load during impounding. The constitutive law used for the analyses is hyperbolic model developed by Duncan et al., and a nonlinear incremental finite element analysis simulating its contruction steps is. used in this study. Hyperbolic parameters for each Zone are estimated from literature. The results obtained from the theoretical analyses clearly show deformation characteristics and stress vectors in arbitrary section of the dam. The analytical results ate well agreed with the measured deformations at the maximum cross section, however, there are some discrepancy in horizontal movements and in stresses generated in the core zone. From the numerical analyses and its comparison with the measured values, it is charaterized that relatively large construction settlements occurred in core zone, overburden pressure in the core zone was considerably reduced by arching effect, and tension zones might occur near both abutments because of the large horizontal displacement.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.29-36
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• 2006

Steel reinforced concrete(SRC) columns, which have been widely employed in high-rise buildings, exhibit a time-dependent behavior because of creep and shrinkage of concrete. This long-term behavior may cause a serious serviceability problem in structural systems, so it is very important to predict the deformation due to creep and shrinkage of concrete. However, it was found from the previous experimental studies that the long-term deformation of SRC columns was quite dissimilar from that of RC columns. A new method is required to quantitatively predict the long-term deformation of SRC columns. In this study, the causes of the discrepancy between the behaviors of RC and SRC columns are investigated and discussed. SRC columns exhibit a time-dependent relative humidity distribution in a cross section differently from that of reinforced concrete(RC) columns owing to the presence of a inner steel plate, which interferes with the moisture diffusion of concrete. This relative humidity distribution may reduce the drying shrinkage and the drying creep in comparison with RC columns. Therefore it is suggested that the differential moisture distribution should be taken into account in order to reasonably predict column shortening of SRC columns.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.659-672
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• 1997

Thermal response induced from nonlinear temperature distribution in composite box gilder bridges depends on several variables(environmental conditions, physical and material properties, location and orientation of bridge, and cross-section geometry). In this paper, parametric study are conducted in order to find the effects of variations of seasons, location and orientation of bridge, sectional geometry and some material properties on the axial deformation, curvature and stresses in composite box girder bridge. A two-dimensional transient finite element model to conduct this parametric studies is briefly presented. Firstly, the effects of the parameters on the diurnal variation of curvature are considered, and for the time of maximum curvature, on the distribution of temperature and stresses of composite box girder sectional are considered. Finally, some considerations about the influence of the parameters on the daily maximum values of axial deformation, curvature and stresses are carried out. The influence of thermal effect on structures is important as much as the influence of live or dead load in some cases. In the design of steel composite bridges, the thermal stresses calculated on the supposition that the temperature difference between the concrete slab and steel girder is $10^{\circ}C$ and the temperature distributions are uniform in concrete slab and steel girder can be underestimated.

• Journal of Conservation Science
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• v.31 no.1
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• pp.65-73
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• 2015

The purposes of this study are helping the understanding on the Dae-hwe kind relics, verifying the deformation rate stability during conservation treatment and enhancing the conservation treatment work by investigating the status and analyzing the material of Taejo's portrait mounting decorative knots in the National Palace Museum of Korea collection. The result of material analysis on the decorative knots was that the outer threads are silk threads, inner threads are cotton threads, the width of the metal threads was $500{\sim}600{\mu}m$ and the major component of it was 55wt% copper. The result of verification on the deformation rate during the form correction of the bell tassel was that it has been found as stable by having the deformation rate of 1 TPCM or less. The result of glue selection test to be used on the repairing of tassel cross-section with its thread cut was that wheat starch adhesive has been found most appropriate because it has the highest tensile strength at all concentrations. The conservation and treatment procedure was established based on above results of analysis and test on the relic and the conservation treatment work including packaging has been completed in accordance with the established procedure.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.892-899
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• 2002

Among the methods for enhancement of load-carrying capacity on flexural concrete member, recently, a concept is being investigated which replaces the steel in a conventional reinforced concrete member with a fiber reinforced polymer(FRP) shell. This study focuses on modeling of the structural behavior of concrete surrounded with FRP shells in flexural bending members. A numerical model of fiber cross-sectional analysis is proposed to predict the stress and deformation state of the FRP shell and concrete. The stress-strain relationship of concrete confined by a FRP shell is formulated to be based on the constitutive law of concrete in multi-axial compressive stress state, in assuming that the compression response is dependent on the radial expansion of the concrete. To describe the FRP shell behavior, equivalent orthotropic properties of in-plane behavior from classical lamination theory are used. The present model is validated to compare with the experiments of 4-point bending tests of FRP shell concrete beam, and has well predicted the moment-curvature relationships of the members, axial and hoop strains in the section, and the enhancement of confinement effect in concrete surrounded by FRP shell.

• Journal of Radiation Protection and Research
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• v.2 no.1
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• pp.17-23
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• 1977

The neutron dosimetrical parameters, i. e., the fission neutron spectrum-averaged cross-sections and the fluence-to-dose conversion factors have been calculated for some threshold detectors with the aid of a computer. The threshold detectors under investigation were the $^{115}In(n,\;n')^{115m}In,\;^{32}S(n,\;p)^{32}P$ and $^{27}Al(n,\;{\alpha})^{24}Na$ reactions. It is revealed that the average cross-sections($\bar{\sigma}$) for the $^{32}S(n,\;p)^{32}P$ reaction are independent of the spectral functions, namely, the Watt-Cranberg and Maxwellian forms. In the case of the $^{27}Al(n,\;{\alpha})^{24}Na$ reaction a variation of the $\bar{\sigma}$ values appears to be highly dependent on the fissioning types. It seems that both the average cross-section for the $^{115}In(n,\;n')^{11m}In$ reaction and the conversion factor are insensitive to the spectral deformation of fission neutrons. These phenomena make it applicable to use indium as a possible integral fast neutron dosimeter in nuclear criticality accidents provided that the virgin fission neutrons are completely free from the scattered neutrons.

• Journal of Korea Water Resources Association
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• v.42 no.2
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• pp.141-148
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• 2009

Each river in each country has peculiar channel characteristics at every section. Korea consists of mountains at the rate of 70%. Due to this, the sections that display unique channel form are scattered. One of the typical features is the narrow pass of channel section that presents in the process of the generation of alluvial channel and deformation channel. Around as this narrow pass of channel, it often comes to be regular flood disaster section. Regardless of this situation, investigations and plans that reflect channel characteristics at the narrow pass of channel have been wholly wanting until now. In accordance with this, we have investigated and analysed hydraulic significance and channel form of the narrow pass of channel in Seonsan in this study. The study has found real minute classification of sediment phenomenon at river bed of low flow channel on investigation section which is sand-bed river, but it was vaguely difficult to conclude that classification of sediment arises from explicit natural force. We were able to assume that the phenomenon comes from gentle bed slope, supply of river bed materials which is nearly uniformity. However, classification of sediment would come from collecting an aggregate rather than natural force. And we found that compound cross section conversion has been developing dramatically with channel form of movable bed section referring to movement which was active before at drainage district of the narrow pass of channel. With this, we could find the phenomenon that river width of low flow channel diminished largely. This kind of situation implies that it may cause compound section weighting, flood dimension decreasing, revetment at low flow channel or the local scour at bottom of levee when extraordinary flood occurs.