• Journal of Korean Society of Steel Construction
• /
• v.20 no.4
• /
• pp.519-528
• /
• 2008

A simple steel-concrete composite deck is developed for preventing the lateral torsional buckling of girders that are under construction and for reducing the term of works using H-shaped rolled beams as bridge girders. A new type of shear connectors is also developed for the composite behavior between a simple steel-concrete composite deck and the rolled beams by the connecting conditions between the deck and the girders. One is a connector bolt that is lengthened and split or tightened with two nuts and the other is an I-shaped rolled beam welded on a steel plate with a number of holes punched through the web. In this study, to estimate the shear strength of those shear connectors the push-out tests are performed and the test results are compared with that of the previous studies and the codes. The result of the push-out tests of the connector bolts showed that the shear performance is similar to that of the stud connector and revealed that the equation for the shear strength in the Korean Specification of Highway Bridge overestimates the shear capacity of the connector bolt whose diameter is larger than 19mm. From the push-out tests of punched I-shaped rolled beams with varying welding amounts, with the small amount of welding, shear capacity is governed by the shear capacity of welding. On the other hand, shear capacity is governed by the size of the punched I-shaped rolled beams, regardless of the amount of welding.

• Tunnel and Underground Space
• /
• v.20 no.5
• /
• pp.352-359
• /
• 2010

Stability of twin tunnels depends on the pillar width and the ground condition. In this study, large scale model tests were conducted for investigating the influence of the pillar width of twin tunnels on their behavior in the regular horizontal jointed rock mass. Jointed rocks was composed of concrete blocks. Pillar width of twin tunnels varied in 0.29D, 0.59D, 0.88D and 1.18D, where D is the tunnel width. During the test, pillar stress, lining stress, tunnel distortion, and ground displacement were measured. Lateral earth pressure coefficient was kept in a constant value 1.0. As a result, it was found that the pillar stress and the displacement of the ground and tunnel were increased by decreasing pillar width. The maximum displacement rate was measured just after the upper excavation in each construction sequence. And the maximum influence position was the right shoulder of the preceeding tunnel at the pillar side. It was also found that for the stability assessment the inner displacement was more critical than the crown displacement. The influence zone was formed at the pillar width 0.59D~0.88D that was smaller than 0.8D~2.0D, which was proposed by experience for a good ground condition. And it would be concluded that horizontal joints could also influence on the stability of the twin tunnels.

• Journal of the Korean GEO-environmental Society
• /
• v.16 no.7
• /
• pp.23-33
• /
• 2015

This paper is results of numerical study for application of sheet pile retaining wall reinforced with H-pile as sheet piles are needed in field for a cutoff wall and are limited to use because of driveability in the ground condition of having a larger strength than a weathered rock. Extensive 101 cases of numerical approach were conducted to investigate the behavior of sheet pile retaining wall reinforced with H-pile, changing installing members of two types of sheet pile and three types of H-pile, the embedded depth of sheet pile and H-pile, the horizontal space between H-piles and excavation conditions. As the results of numerical analysis, combined use of the sheet pile SP-IIIA with H-Pile H250 and the sheet pile SP-IV with H-Pile H350 among precast products was found to be efficient since two members tended to reach allowable stresses simultaneously or have similar stress concentration ratios. Increased stiffness in reinforced sheet pile showed reduction of lateral displacement of wall. Embedded depth of sheet pile did not affect stability of wall significantly so that driving the penetrable depth of sheet pile should be enough to maintain stability of wall and satisfy purposes of cutoff and stiffness increase of wall.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.46 no.1
• /
• pp.57-65
• /
• 2020

To prevent loss of hair protein during hair washing process by water through, a shield coating the pathway of water molecules was studied. Hydrophobic virgin hair, hydrophilic hair, which was damaged only methyleicosanoic acid (18-MEA) on the surface, and a repaired hair re-bound 18-MEA, were prepared and water mass changes by as heat were measured. Results showed that hydrophobic hairs followed bi-exponential function of 39 s and 151 s and other two hairs exhibited fast- and mono-exponential decay with 83 s, reflecting the extraction of water molecules without any resistance at the hydrophobic surface. On the assumption that hydrophobic surface resists an extraction of protein in water during the wash, the protein concentrations were compared from the hair of hydrophobic and hydrophilic surface. The extracted hair proteins were 179 and 148 ㎍/mL from the hair coated with hydrophilic polyethylene glycol (PEG) and hydrophobic polydimethylsiloxane (PDMS), respectively. This study suggested that hydrophobic coating on the hair surface could be used to prevent protein loss in wash, represented by LFM. In conclusion, this research provides some useful information to contribute to the development of hair washing products that can prevent protein loss in the cleaning process by granting hydrophobic coatings.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.2
• /
• pp.84-91
• /
• 2022

This study investigated the behavior of out-of-plane skewed moment connections that were designed as IMFs, as per the Korean standards. A total of 14 finite element models were constructed with the consideration of two types (single- and double-sided connections) and four levels of skew angle (0°, 10°, 20°, and 30°). The results indicated that the skewed connections considered in this study met the acceptance criteria for IMFs given by the codes. However, the load-carrying capacities of skewed connections were decreased as the skew angle increased. For the connection with a skew angle of 30°, the peak load was noted to be 13% less and the energy dissipation capacity could be 26% less than that of non-skewed connection. In addition, because of the skewed nature, the stress distribution in the skewed beam flange near the connection was asymmetric and the stresses were concentrated on the beam inner flange. Column twisting induced by the skewed configuration was very small and negligible in the beam and column combination considered in this study.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.43 no.3
• /
• pp.277-285
• /
• 2023

Recently, as the magnitude and frequency of earthquakes increases, research is needed to increase the ductility of the columns in order to prevent the collapse of structures. In this study, to evaluate the performance of columns reinforced with continuous transverse reinforcing bars, the FE model for the dynamic analysis of structures reinforced with continuous transverse reinforcing bars for circular and rectangular columns is to be verified using the results of uniaxial compression experiments in the previous study. As a result, the experimental value of the column reinforced with continuous transverse reinforcement and the result value related to the dynamic analysis showed similar behavior, and the reliability was high. As a result of the analysis, the usability of the rectangular column reinforced with continuous lateral reinforcing bars was confirmed because the dissipated energy performance of the columns reinforced with spiral reinforcing bars was higher than that of the columns reinforced with band reinforcing bars.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.6
• /
• pp.70-78
• /
• 2023

The ordinary concentrically braced frame has an advantage of having simple design procedure. For this reason, it has been widely used for the small-sized frame structures subject to moderate or lower magnitude earthquake, even though its seismic performance against the earthquake load is not much effective compared to that of other frame systems. To enhance seismic performance of the ordinary concentrically braced frame where the bracing has a weakness for compressive behavior under lateral earthquake, seismic retrofitting by viscous damper has been commonly introduced. However, the viscous damper, itself, generally does not have stiffness for restoring the structure to the original position. This may cause residual displacement to the structure. In this paper, a self-centering viscous damper system in which upper and lower beams having flexural rigidity play a role as a nonlinear-elastic spring, restoring the spring-damper system subject to external displacement history to its original location, is developed. The numerical analysis for a simplified frame structure shows how including the developed self-centering viscous damper system leads to an enhanced seismic performance of the frame structure through energy dissipation during earthquake excitation.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.6
• /
• pp.22-29
• /
• 2023

In the evaluation of seismic performance for structural materials and components, the loading rate and axial force can have a significant impact. Due to time-delay effects between input and output displacements, It is difficult to apply high-rate displacement in cyclic tests and hybrid simulations. Additionally, the difficulty of maintaining a consistent vertical load in the presence of lateral displacement has limited fast and real-time tests performed while maintaining a constant vertical load. In this study, slow, fast cyclic tests and real-time hybrid simulations were conducted to investigate the rate dependency and the influence of vertical loads of Isolation Bearing. In the experiment, the FLB System including an Adaptive Time Series (ATS) compensation and a state estimator was constructed for real-time control of displacement and vertical load. It was found that the vertical load from the superstructure and loading rate can have a significant impact on the strength of the seismic isolation bearing and its behavior during an earthquake. When conducting experiments for seismic performance evaluation, they must be implemented to be similar to reality. This study demonstrates the excellent performance of the system built and used for seismic performance evaluation and enables accurate and efficient seismic performance evaluation.

• Journal of Dental Anesthesia and Pain Medicine
• /
• v.24 no.2
• /
• pp.109-117
• /
• 2024

Background: Dental fear and anxiety are significant challenges in managing behavior in children. Oral administration of sucrose or sweet-tasting solutions has shown effectiveness in reducing procedural pain in infants and neonates. This study aimed to investigate whether pre-application of sucrose solution had an effect on minimizing pain perception during injection and to assess the potential impact of the child's age and sweet preference. Methods: A randomized control clinical trial was conducted on 60 children aged 3-9 years requiring buccal infiltration injections. Following parental consent, demographic data of the children were recorded. Sweet preferences was assessed using a modified forced-choice test. Children were equally and randomly allocated into study (sucrose) and control groups using a lottery method. Sucrose solution or distilled water, respectively, was applied to the lateral surface of the tongue for 2 min. Topical anesthetic was applied at the site of injection, followed by local anesthesia administration. The children rinsed their mouths thrice with water immediately after anesthetic injection. A video was recorded during injection which was then scored by three blinded examiners on the Sound Eye Motor (SEM) scale. The children also self-evaluated using Wong-Baker Faces Pain Rating Scale (WBFPS). Results: The mean SEM scores and WBFPS scores were analyzed using the Kruskall-Wallis test. The mean SEM score in the study group was 1.37 ± 0.61, compared to 3.17 ± 0.87 in the control group, showing a statistically significant difference (P < 0.001). Mean pain scores assessed by WBFPS in the study group were 0.60 ± 1.4, while in the control group, they were 6.27 ± 2.33, also showing a statistically significant difference (P < 0.001). Children with a sweet preference demonstrated a subjective reduction in pain perception. Conclusion: Application of sucrose before dental injections in children helps to minimize pain upon injection across all age groups.

• Clinical and Experimental Pediatrics
• /
• v.50 no.1
• /
• pp.79-84
• /
• 2007

Purpose : Tibial internal torsion is prevalent in East Asian countries such as Korea and Japan, where sitting on the floor is common behavior. Tibial internal torsion or excessive lateral tibial torsion may cause esthetical, functional, or psychological problems and also may induce degenerative arthritis in older age. The aim of this study is to evaluate the therapeutic effect of Tibial Counter Rotator (TCR) in patients with tibial internal torsion. Method : One hundred forty nine children (274 limbs) with tibial internal torsion participated in this study. Transmalleolar angle were measured with gravity goniometer. When tibial internal torsion was detected, TCR was applied at least for 3 hours a day during sleep. The patient's progress was followed monthly and transmalleolar angle was reevaluated by the same examiner. Results : Transmalleolar angle was significantly increased in patients with tibial internal torsion during TCR application (P<0.001). Conclusion : TCR can be one of the effective methods for correcting tibial internal torsion in children under 12 years old of age.