• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.2
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• pp.121-127
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• 2010

An experimental study of composite beam with perforated fiber reinforced polymer(FRP) plank as a permanent formwork and the tensile reinforcement was performed. A combined formwork and reinforcement system can facilitate rapid construction of concrete members since no conventional formwork is needed, which requires time consuming assembly and dismantling. In order for a smooth FRP plank to act compositely with the concrete, the surface of the FRP needs to be treated to increase its bond properties. Aggregates were bonded to the FRP plank using a commercially available epoxy and perforated web of plank. No additional flexural or shear reinforcement was provided in the beams. For comparison, two control specimens were tested. One control had no perforated hole in the web of FRP plank and the other had internal steel reinforcing bars instead of the FRP plank. The beams were loaded by central patch load to their ultimate capacity. This study demonstrates that the perforated FRP plank has the potential to serve as a permanent formwork and reinforcing for concrete beam.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1999.11a
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• pp.216-221
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• 1999

A mental task combined with noise background is an effective model of laboratory stress for study of psychophysiology of the autonomic nervous system (ANS). The intensity of the background noise significantly affects both a subjective evaluation of experienced stress level during test and the physiological responses associated with mental load in noisy environments. Providing tests of similar difficulties we manipulated the background noise intensity as a main factor influencing a psychophysiological outcome and the analyzed reactivity along withe the noise intensity dimension. The goal of this study was to identify the patterns of ANS responses and the relevant subjective stress scores during performance of word recognition tasks on the background of white noise (WN) of the different intensities (55, 70 and 85 dB). Subjects were 27 college students (19-24 years old). BIOPAC, Grass Neurodata System and AcqKnowlwdge 3.5 software were used to record ECG, PPG, SCL, skin temperature, and respiration. Experimental manipulations were effective in producing subjective and physiological responses usually associated with stress. The results suggested that the following potential autonomic mechanisms might be involved in the mediation of the observed physiological responses: A sympathetic activation with parasympathetic withdrawal during mild 55 and 70dB noise (featured by similar profiles) and simultaneous activation of sympathetic and parasympathetic systems during intense 85dB WN. The parasympathetic activation in this case might be a compensatory effect directed to prevent sympathetic domination and to maintain optimal arousal state for the successful performance on mental stress task. It should be mentioned that obtained results partially support Gellhorn's (1960; 1970) "tuning phenomenon" as a possible mechanism underlying stress response.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.3
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• pp.100-106
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• 2013

In this paper, in order to analyze lightning impulse response characteristics in combined installations of SPDs and RCDs, surge protection coordination between SPDs and RCDs are experimentally investigated by using the combination wave generator. Six different types of single-phase residual current operated circuit-breakers with integral overcurrent protection for household and similar uses(RCBOs) being present on the domestic market are tested according to KS C IEC 61009-1 standard. As a result, when a class I SPD is located on the source side of an RCBO, all kinds of specimens are able to provide the proper coordination between the SPD and RCBOs without nuisance tripping, unintended operation or damage due to test impulse currents. However, in the case that the class II SPD is located on the load side of RCBOs, a lot of L-N mode injected currents is split into the RCBO, and a few RCBOs are damaged. Coordination between SPDs and RCDs is not valid and a role of SPDs is of no use. When combining SPDs with RCDs, it is necessary to select SPDs and RCDs in consideration of the protection voltage level of metal oxide varistor embedded in RCDs.

• Journal of Korean Society of Steel Construction
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• v.15 no.6 s.67
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• pp.661-672
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• 2003

The advanced analysis and optimal design of semi-rigid frame were presented. Advanced analysis can predict the combined nonlinear effects of connection, geometry, and material on the behavior and strength of semi-rigid frames. The Kishi-Chen power model was used to describe the nonlinear behavior of semi-rigid connections. Geometric nonlinearity was determined using stability functions. On the other hand, material nonlinearity was determined using the Column Research Council (CRC) tangent modulus and parabolic function. The direct search method proposed by Choi and Kim was used as optimization technique. The member with the largest unit value evaluated using the LRFD interaction equation was replaced one by one with an adjacent larger member selected from the database. The objective function was assumed as the weight of steel frame, with the constraint functions accounting for load-carrying capacities, deflections. inter-story drifts, and ductility requirement. Member sizes determined by the proposed method were compared with those derived using the conventional LRFD method.

• Archives of Plastic Surgery
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• v.36 no.5
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• pp.543-547
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• 2009

Purpose: Adhesion is the most common and troublesome complication after repair of flexor tendon injury. Recently, use of sodium hyaluronate derivatives for adhesion prevention is increasing. A commercial product, Guardix$^{(R)}$, sodium hyaluronate(NaHe) combined with carboxymethylcellulose(CMC) has been newly developed as a preventive material for adhesion. We have investigated its effect in rabbits. Methods: Twenty seven male New Zealand white rabbits were operated under ketamine anesthesia. After tendon repair in zone II of the hind paw, Guardix$^{(R)}$(experimental group) or normal saline(control group) was administered. Biomechanical tests were performed to estimate adhesion formation at 2, 4, 8, and 12 weeks after the operation. Maximum tensile load to flex the distal interphalangeal joint 50 degree from its resting state(MTL50) was measured, depicting the amount of adhesion formed. Subsequently, breaking strength was assessed. Results: There were no postoperative complications such as infection, wound dehiscence, or hematoma. MTL50 was significantly lower in the experimental group than in the control group at 4, 8, 12 weeks (p<0.05). Mean value of MTL50 was 6.64N in the experimental group and 28.53N in the control group at 12 weeks after surgery. There were no significant differences in breaking strength. Conclusion: Our results indicate that Guardix$^{(R)}$ is helpful in reducing adhesion formation and does not interfere with normal healing processes of the tendon.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.31-37
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• 2002

Recently a simplified design procedure as well as load transfer model for seismic steel moment connections with welded straight haunch have been proposed by Lee and Uang. Cyclic seismic testing was conducted to verify the proposed design procedure and to develop the details that will prevent the cracking at the haunch tip, where stress concentration was the highest. All the specimens thus designed effectively pushed plastic hinging away from the haunch tip and were able to develop satisfactory plastic rotation capacity of 0.04 radian with no fracture. A sloped edge combined with drilling a hole near the haunch tip or a pair of stiffeners(partially or fully) extended from the beam web successfully prevented the crack initiation at the haunch tip. The strut action of the haunch web, which had been predicted from the previous analytical study, was also experimentally identified through the strain gage readings.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.527-534
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• 2006

A real-time hybrid method, in which the experimental implementation and the numerical computation of a structure are simultaneously carried out in real-time and combined on-line, has been used as a dynamic testing technique of structure to investigate its dynamic behaviors. In this paper, an experimental hybrid method, which implements the earthquake response control of a building structure with a TLD by using only a TLD as an experimental part, is proposed and is experimentally verified through a shaking table test. In the proposed methodology, the whole building structure with a TLD is divided into the upper TLD and the lower structural parts as experimental and numerical substructures, respectively. At the moment, the control force acting between their interface is measured from the experimental TLD with shear-type load-cell which is mounted on shaking table. Shaking table vibrates the upper experimental TLD with the response calculated from the numerical substructure, which is subjected to the excitations of the measured interface control force at its top story and an earthquake input at its base. The experimental results show that the conventional method, in which both a TLD and a building model are physically manufactured and are tested, can be replaced by the proposed methodology with a simple experimental installation and a good accuracy for evaluating the control performance of a TLD.

• Advances in concrete construction
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• v.8 no.3
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• pp.173-185
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• 2019

This article presents a comparative study of the effect of steel layouts on the seismic behavior of transition steel-concrete composite connections, both experimental and analytical investigations of concrete filled steel tube-reinforced concrete (CFST-RC) and steel reinforecd concrete-reinforced concrete (SRC-RC) structures were conducted. The steel-concrete composite connections were subjected to combined constant axial load and lateral cyclic displacements. Tests were carried out on four full-scale connections extracted from a real project engineering with different levels of axial force. The effect of steel layouts on the mechanical behavior of the transition connections was evaluated by failure modes, hysteretic behavior, backbone curves, displacement ductility, energy dissipation capacity and stiffness degradation. Test results showed that different steel layouts led to significantly different failure modes. For CFST-RC transition specimens, the circular cracks of the concrete at the RC column base was followed by steel yielding at the bottom of the CFST column. While uncoordinated deformation could be observed between SRC and RC columns in SRC-RC transition specimens, the crushing and peeling damage of unconfined concrete at the SRC column base was more serious. The existences of I-shape steel and steel tube avoided the pinching phenomenon on the hysteresis curve, which was different from the hysteresis curve of the general reinforced concrete column. The hysteresis loops were spindle-shaped, indicating excellent seismic performance for these transition composite connections. The average values of equivalent viscous damping coefficients of the four specimens are 0.123, 0.186 and 0.304 corresponding to the yielding point, peak point and ultimate point, respectively. Those values demonstrate that the transition steel-concrete composite connections have great energy dissipating capacity. Based on the experimental research, a high-fidelity ABAQUS model was established to further study the influence of concrete strength, steel grade and longitudinal reinforcement ratio on the mechanical behavior of transition composite connections.

• Structural Monitoring and Maintenance
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• v.2 no.3
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• pp.253-267
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• 2015

Corrosion has significant adverse effects on the durability of reinforced concrete (RC) structures, especially those exposed to a marine environment and subjected to mechanical stress, such as bridges, jetties, piers and wharfs. Previous studies have been carried out to investigate the corrosion behaviour of steel rebar in various concrete structures, however, few studies have focused on the corrosion monitoring of RC structures that are subjected to both mechanical stress and environmental effects. This paper presents an exploratory study on the development of corrosion monitoring and detection techniques for RC structures under the combined effects of external loadings and corrosive media. Four RC beams were tested in 3% NaCl solutions under different levels of point loads. Corrosion processes occurring on steel bars under different loads and under alternative wetting - drying cycle conditions were monitored. Electrochemical and microscopic methods were utilised to measure corrosion potentials of steel bars; to monitor galvanic currents flowing between different steel bars in each beam; and to observe corrosion patterns, respectively. The results indicated that steel corrosion in RC beams was affected by local stress. The point load caused the increase of galvanic currents, corrosion rates and corrosion areas. Pitting corrosion was found to be the main form of corrosion on the surface of the steel bars for most of the beams, probably due to the local concentration of chloride ions. In addition, visual observation of the samples confirmed that the localities of corrosion were related to the locations of steel bars in beams. It was also demonstrated that electrochemical devices are useful for the detection of RC beam corrosion.

• Steel and Composite Structures
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• v.9 no.4
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• pp.381-395
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• 2009

This paper presents the details of an advanced Finite Element (FE) analysis of a plane steel portal frame with semi-rigid beam-to-column connections subjected cyclic loading. In spite of several component models on cyclic behaviour of connections presented in the literature, works on numerical investigations on cyclic behaviour of full scale frames are rather scarce. This paper presents the evolution of an FE model which deals comprehensively with the issues related to cyclic behaviour of full scale steel frames using ABAQUS software. In the material modeling, combined kinematic/isotropic hardening model and isotropic hardening model along with Von Mises criteria are used. Connection non-linearity is also considered in the analysis. The bolt slip which happens in friction grip connection is modeled. The bolt load variation during loading, which is a pivotal issue in reality, has been taken care in the present model. This aspect, according to the knowledge of the authors, has been first time reported in the literature. The numerically predicted results using the methodology evolved in the present study, for the cyclic behaviour of a cantilever beam and a rigid frame, are validated with experimental results available in the literature. The moment-rotation and deflection responses of the evolved model, match well with experimental results. This proves that the methodology for evolving the steel frame and connection model presented in this paper is closer to real frame behaviour as evident from the good comparison and hence paves the way for further parametric studies on cyclic behaviour of flexibly connected frames.