• Journal of the Korean Society of Safety
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• v.19 no.2
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• pp.125-129
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• 2004

In masive concrete placement, cracking problem due to hydration heat is frequently encountered. One of measure to solve this problem is to make a construction joint. However, it is cumbersome to make it by chipping the surface of joint. In this study, push-out test for 18 specimens was conducted to compare the interface shear strength of consturction joints whose surfaces were prepared with three methods; chipping, rib-lath, folded rib-lath. Compared to the specimens made with conventional surface chipping, those with rib-lathe showd excellent preformance increasing shear resistance capacity and the role of shear key conceived by folding rib-lath played important role in enhancing shear resistance.

• International journal of advanced smart convergence
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• v.9 no.2
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• pp.49-57
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• 2020

We have not identified on what gender difference during gait at a pace of one's preferred velocity effects on the function of bilateral lower limb. This study was undertaken to investigate a difference of gait strategy by gender during gait at a one's preferred velocity of participants of adult male and female (n=20). Cinematographic data for motion analysis, ground reaction force (GRF) variables, and muscle volume of lower limb were analyzed. Significant difference of variables on movement of center of mass whole body, joint angle and moment of lower limb, and ground reaction force were tested by 2-way ANOVA analysis (P<0.05). Male group showed more muscle volume than female, and both showed more volume in dominant leg than non-dominant. Main effect by bilateral leg during gait showed higher difference in right than left leg in change of vertical position of center of mass (maximal, minimal). Main effect by gender in vertical change of position and velocity of center of mass showed higher difference in male than female (maximal, minimal). Hip joint showed more flexed and extended angle in male than female, and also dorsiflexion of ankle and flexion moment of knee and hip joint showed higher in male than female group. Therefore, this result was assumed that dominant showed furthermore more contribution for propulsive function than non-dominant leg. Gender difference showed in strategy controlling of biomechanical characteristics, and perhaps influenced by muscle volume.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.397-398
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• 2023

To design the shear connections for vertical construction joints of slurry walls, it is necessary to create a force-displacement curve that represents the structural performance of the shear connections. This paper proposes a method for preparing the force-displacement curve of the shear connections including major considerations.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.121-128
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• 1996

In this study design and construction technique for joint-less integral abutment for short to mid span bridges was developed. Expansion of superstructure due to thermal effect was absorbed in the flexible pile-type abutment in stead of expansion joint in the conventional bridges. Design method for pile subject to vertical and horizontal force was proposed. Backfill, approach slab and details of its connection joint with pavement was also proposed.

• Magazine of the Korea Concrete Institute
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• v.8 no.4
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• pp.181-189
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• 1996

It is well-known that the hearing strength in vertical joints of precast concrete large panel system is affected by grout compressive strength angle of shear key and bearing area. 21 vertical joint specimens were tested to investigate the effects of these parameters The analysis of test results shows that : 1. The higher be grout compressive strength, the higher will shear strength be. And the bearing strength does not so increase in proportion of bearing area. 2. The shear key with the angle of $20^{\circ}$shows the highest bearing strength among three angle variables of $20^{\circ}$, $25^{\circ}$, $30^{\circ}$.

• Korean Journal of Applied Biomechanics
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• v.17 no.1
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• pp.53-60
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• 2007

Recently tennis techniques has been changed in stance patterns. Stance is consist of square stance, open stance and semi-open stance. The purpose of this study was to analyze the kinematics variables of racket head velocity during forehand stroke by stance patterns. Eight high school tennis players were chosen for the study who use semi western grip right-handed person more than career 7 years. They performed horizontal swing and vertical swing that it was done each five consecutive trial in the condition of square, open and semi-open stance. The results showed that racket head velocity significant difference was not observed in stance types between swings at impact. Y and Z components of racket head velocity for horizontal and vertical swing at second prior to impact and at impact were that y components velocity was faster horizontal swing than vertical swing and z components velocity was later horizontal swing than vertical swing. Statistically significant variable to racket head velocity and Pearson's correlation were drawn as follows. 1. Z components of racket head velocity in square stance was significant correlation by right knee joint. 2. Y components of racket head velocity in semiopen stance was significant correlation by left hip joint. 3. Y components of racket head velocity in open stance was significant correlation by left ankle joint.

• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.417-424
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• 2003

A bearing failure in RCS(Reinforced Concrete Column and Steel Beam) system is recognized as one of the distinct joint failure modes for the composite frames. Vertical and transverse reinforcement in addition to concrete are effective for better transfer of vortical forces through concrete bearing. To examine the effect of the vertical bars, tie bars, a U-type detail developed in this study and concrete confinement, local bearing tests were conducted using 22 small-scale concrete block specimens. Test results show that vertical reinforcement and tie bars mainly contribute to the bearing capacity. However larger amounts of tie reinforcement are required than those recommend from ASCE guidelines, to apply the nominal concrete strength as 2 $f_{ck}$ over the bearing area. Cross ties are proved to be highly effective for resisting the vertical forces. Maximum bearing strength can be increased upto 2.5 $f_{ck}$ . An accurate prediction model for bearing strength is proposed for better design of the composite Joint.

• Earthquakes and Structures
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• v.7 no.5
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• pp.705-718
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• 2014

This paper presents an analytical model for determining the transverse reinforcement required for reinforced concrete exterior beam-column joints subjected to reversed cyclic loading. Although the joint aspect ratio can affect joint shear strength, current design codes do not consider its effects in calculating joint shear strength and the necessary amount of transverse reinforcement. This study re-evaluated previous exterior beam-column joint tests collected from 11 references and showed that the joint shear strength decreases as the joint aspect ratio increases. An analytical model was developed, to quantify the transverse reinforcement required to secure safe load flows in exterior beam-column joints. Comparisons with a database of exterior beam-column joint tests from published literature validated the model. The required sectional ratios of horizontal transverse reinforcement calculated by the proposed model were compared with those specified in ACI 352R-02. More transverse reinforcement is required as the joint aspect ratio increases, or as the ratio of vertical reinforcement decreases; however, ACI 352R-02 specifies a constant transverse reinforcement, regardless of the joint aspect ratio. This reevaluation of test data and the results of the analytical model demonstrate a need for new criteria that take the effects of joint aspect ratio into account in exterior joint design.

• Korean Journal of Applied Biomechanics
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• v.27 no.3
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• pp.189-195
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• 2017

Objective: The aim of this study was to examine the effect of foot landing type (forefoot vs. rearfoot landing) on kinematics, kinetics, and energy absorption of hip, knee, and ankle joints. Method: Twenty-five healthy men performed single-leg landings with two different foot landing types: forefoot and rearfoot landing. A motion-capture system equipped with eight infrared cameras and a synchronized force plate embedded in the floor was used. Three-dimensional kinematic and kinetic parameters were compared using paired two-tailed Student's t-tests at a significance level of .05. Results: On initial contact, a greater knee flexion angle was shown during rearfoot landing (p < .001), but the lower knee flexion angle was found at peak vertical ground reaction force (GRF) (p < .001). On initial contact, ankles showed plantarflexion, inversion, and external rotation during forefoot landing, while dorsiflexion, eversion, and internal rotation were shown during rearfoot landing (p < .001, all). At peak vertical GRF, the knee extension moment and ankle plantarflexion moment were lower in rearfoot landing than in forefoot landing (p = .003 and p < .001, respectively). From initial contact to peak vertical GRF, the negative work of the hip, knee, and ankle joint was significantly reduced during rearfoot landing (p < .001, all). The contribution to the total work of the ankle joint was the greatest during forefoot landing, whereas the contribution to the total work of the hip joint was the greatest during rearfoot landing. Conclusion: These results suggest that the energy absorption strategy was changed during rearfoot landing compared with forefoot landing according to lower-extremity joint kinematics and kinetics.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.10
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• pp.64-74
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• 2007

Because of the size and environment in the shipbuilding process, the portable type robot is required for the automatic seam tracking. For this reason, the structure of laser sensor should be considered in the initial design step and the coordinate transformation between welding robot and laser sensor, which is joint finder, must be identified exactly and the real time tracking algorithm based on these consideration could be developed. In this research, laser displacement sensor in which its structure is laser beam's vertical projection, is developed to recognize the location of weld joint. In practical applications, however, images of weld joints are often degraded because of the surface specularity or spatter. To overcome the problem, the constrained joint finding algorithm is proposed. In the approach of coordinate conversion rule for the visual feedback control among welding torch, robot body and laser sensor is applied by the same reference point method. In the real time seam tracking algorithms we propose constrained sampling method which uses look ahead distance. The RLS(Recursive Least Square) filter is applied to obtain the smooth tracking path from the sensitive edge data. From the experimental results, we could see the possibility that the developed laser sensor with proposed processing algorithm and real time seam tracking method can be used as a welding under the shipbuilding condition.