• Steel and Composite Structures
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• v.28 no.6
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• pp.719-734
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• 2018

Prior to the introduction of modern seismic guidelines, it was a common practice to provide straight bar anchorage for beam bottom reinforcement of gravity load designed building. Exterior joints with straight bar anchorages for beam bottom reinforcements are susceptible to sudden anchorage failure under load reversals and hence require systematic seismic upgradation. Hence in the present study, an attempt is made to upgrade exterior beam-column sub-assemblage of a three storied gravity load designed (GLD) building with single steel haunch. Analytical formulations are presented for evaluating the haunch forces in single steel haunch retrofit. Influence of parameters that affect the efficacy and effectiveness of the single haunch retrofit are also discussed. The effectiveness of the single haunch retrofit for enhancing seismic performance of GLD beam-column specimen is evaluated through experimental investigation under reverse cyclic loading. The single steel haunch retrofit had succeeded in preventing the anchorage failure of beam bottom bars of GLD specimen, delaying the joint shear damage and partially directing the damage towards the beam. A remarkable improvement in the load carrying capacity of the upgraded GLD beam-column sub-assemblage is observed. Further, a tremendous improvement in the energy dissipation of about 2.63 times that of GLD specimen is observed in the case of upgraded GLD specimen. The study also underlines the efficacy of single steel haunch retrofit for seismic upgradation of deficient GLD structures.

• Journal of the Korean Society for Precision Engineering
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• v.3 no.4
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• pp.53-63
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• 1986

In this study, the stress distribution of rectangular bar under torsion, when warping of both ends is free or constrained, is investigated. Method of separation of variable and Fourier Series are used for the theoretical analysis, and 3dimensional photoelastic stress-freezing method for experimental analysis. The main results are as follows; 1) In the case of warping-constrained rectangular bar, the normal stresses are negligible because they are less then 0.5% of the shear stresses. The maximum normal stress is placed on the point of y=0.61 b when b/a=1 and it gradually moves to the corner y=b when the value of b/a is increased. 2) According to increase of the value of b/a, on the crossection, the maximum shear stress is placed on the middle point of the long side (x=${\pm}a$, y=0) when warping of both ends is free but the middle of the short side (x=0, y=${\pm} b$) when warping is constrained. The stress distribution is straight line when warping is constrained, namely, the stress distribution is proportional to the distance from the axis of centroid, but parabolic when warping is free. 3) The values of the combined stress of warping-constrained bar, if the influence of the loaded point is neglected, are generally smaller than those of warping-free.

• Korean Journal of Construction Engineering and Management
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• v.13 no.1
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• pp.106-117
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• 2012

The proportion of rebar factory manufacturing which has been settled down in Korea recently seems to increase because of their strength such as high decreasing rate of rebar loss and manufacturing accuracy and the external factors such as an increase of downtown projects and a decrease of skilled workers. However, factory manufacturing using straight rebars causes a certain amount of rebar loss and an environmental problem including $CO_2$ emissions. To solve these problems, Bar in coil (BIC) has been introduced; however its application is very rare because it has not been produced so far in Korea and manufacturing machines of BIC are very expensive. Also, although BIC's application is expected to expand due to its strengths, few analysis of its application has been conducted. Therefore in this study, analysis of the BIC's characteristics and the influence to the rebar manufacturing industry are conducted for the advancement of rebar work as a basic research. To achieve this, inquiry on the present condition of rebar manufacturing industry in Korea is implemented. Then, the validation of BIC's applications by aspects of industry and the analysis of stakeholders' economical profit and loss are conducted.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.1181-1185
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• 1991

Unlike printed character, the recognition of Hand written one has various kinds of difficulties due to the existence of the huge pattern associated with the person who writes. Therefore, in general, recognition of Hand written characters requires an algorithm which takes into consideration of the individual differences. Hangul characters are basically made of straight lines and circles. They can be represented in terms of feature parameters such as the end point of the straight line, the length and the angle. Then all Hangul characters can be represented by the number of basic segments(-, /, vertical bar, O) multiplied by the feature parameters respectively. In this study we propose a method for recognizing Hand written Hangul characters in terms of fuzzy inference.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.546-551
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• 1997

New typology of failure mechanisms for uniform compression fields are presented based on the classical theory of plasticity, in particular th normality rule, and the limit theorem. The concrete is assumed as a rigid-perfectly plastic material obeying the modified Coulomb failure criteria with zero tension cut-off. The failure mechanisms are capable of explaining flexural types of crushing failure in uniaxial uniform compression stress fields which are called struts in truss models. The failure mechanisms consist of sliding failure along straight failure lines or hyperbolic failure curves and rigid body rotation. The failure mechanisms involving straight failure lines are explained by constant strain expansion in the first principal direction and rigid body rotation motion. The failure mechanisms presented are applied to the explanation of bond failure of bar combined with concrete crushing failure and flexural crushing failure of concrete.

• Structural Engineering and Mechanics
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• v.49 no.2
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• pp.273-283
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• 2014

According to deformation features of pre-twisted bar, its elastic bending and torsion buckling equation is developed in the paper. The equation indicates that the bending buckling deformations in two main bending directions are coupled with each other, bending and twist buckling deformations are coupled with each other as well. However, for pre-twisted bar with dual-axis symmetry cross-section, bending buckling deformations are independent to the twist buckling deformation. The research indicates that the elastic torsion buckling load is not related to the pre-twisted angle, and equals to the torsion buckling load of the straight bar. Finite element analysis to pre-twisted bar with different pre-twisted angle is performed, the prediction shows that the assumption of a plane elastic bending buckling deformation curve proposed in previous literature (Shadnam and Abbasnia 2002) may not be accurate, and the curve deviates more from a plane with increasing of the pre-twisting angle. Finally, the parameters analysis is carried out to obtain the relationships between elastic bending buckling critical capacity, the effect of different pre-twisted angles and bending rigidity ratios are studied. The numerical results show that the existence of the pre-twisted angle leads to "resistance" effect of the stronger axis on buckling deformation, and enhances the elastic bending buckling critical capacity. It is noted that the "resistance" is getting stronger and the elastic buckling capacity is higher as the cross section bending rigidity ratio increases.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.3
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• pp.155-161
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• 2009

An investigation of the deformation behavior of ${\gamma}'-Ni_3Al$ single crystals containing fine dispersion of disordered ${\gamma}$ particles was performed for several different crystal orientations. Deformation structures were observed by the weak-beam method of transmission electron microscopy (TEM). The critical resolved shear stress (CRSS) for (111) [$\bar{1}$01] slie. increases with increasing temperature in the temperature range where (111) slip operates. The CRSS for (111) [$\bar{1}$01] slip is dependent on crystal orientation in the corresponding temperature range. The temperature where the strenjlth reaches a maximum is dependent on crystal orientation; the higher the ratio of the Schmid factors of (010) [$\bar{1}$01] to that of (111) [$\bar{1}$01], the higher the peak temperature. The peak temperatures were increased by the precipitation of y particles for the samples of all orientations. Electron microscopy of deformation induced dislocation arrangements under peak temperature has revealed that most of dislocations are straight screw dislocations. The mobility of screw dislocations decreases with increasing temperature. Above the peak temperature, dislocations begin to cross slip from the (111) [$\bar{1}$01] slip system to the (010) [$\bar{1}$01] slip system, thus decreasing the strength.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.3
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• pp.398-404
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• 2013

The simulation of the ballistic trajectory of penetrator into the spaced multi-layer RC targets is very important to predict the hitting condition in subsequent target. Because of perturbation by lateral load of penetrator caused by asymmetric hitting position between penetrator and steel bar reinforcement, penetrator rotates and deviates from the straight path. Therefore, penetration capability of penetrator is decreased in the subsequent targets. This paper presents the result of the penetration of steel-bar-reinforced concrete target by using the explicit finite element code LS-DYNA. A series of computations is performed and compared to experimental data and the computed results are in good agreement with the experimental results over a wide range of velocities. And then we conduct the simulation according to various RC target hitting condition and impact velocities.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.15-26
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• 2003

This study was conducted to investigate the performance times, CM position and CM speed, pole chord length and pole chord angle, whole body angular momentum(X axis), and grip width in pole vault event according to the event and phase; touch down, pole plant, take-off, maximum pole bending pole straight, pole release, peak height, and foot contact, pole contact, free flight. The pole vaulting of four male elite vaulters including six trial were filmed using two video digital cameras at 60 Hz at 56th national athletic match, and data were collected through the DLT method of three dimensional cinematography. In general the better jumper is, the longer the performance time is. And the greater CM speed is, and the better his transformation ability of CM horizontal speed into vertical speed is. As he uses a longer pole, his grip is higher, and it is a enough for him to rock back his body, so that he pulls and pushes the pole well keeping his hips close to. An greater maximum angular momentum and early positioning of the hips parallel to the bar makes his body far side of the bar and his bar clearance easier. Specially our national jumper needs to have more powerful braking force during foot contact phase, and take his body on the pole after maximum pole bending, and pull and push the pole strongly keeping his hips close to. Also he needs to have stronger muscular strength in order to control the longer pole and use the pole of proper tension more efficiently.

• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.4
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• pp.24-35
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• 2014

An experimental study on the structural behavior of connection types between approach slab and integral abutment has been done for three typical bar connections. Typical hinge style reinforcing bar detail for its connection is preferred in order to accommodate rotation of the approach slab among engineers. However, the straight horizontal bars can be used as connection detail accomodate structural capacity. Total six specimens with three types of rebar detail are tested for direct tensile and bending load. The characteristic structural behaviors are carefully monitored and all the strain gauge data obtained are analyzed. It is shown that the structural performance of all the specimens well exceed its design allowance. Several design suggestions are given based on careful reviews on the experiment.