• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.2
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• pp.58-67
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• 2003

Over the last decade fiber-reinforced polymer (FRP) reinforcement consisting of glass, carbon, or aramid fibers embedded in a resin such as vinyl ester, epoxy, or polyester has emerged as one of the most promising and affordable solutions to the corrosion problems of steel reinforcement in structural concrete. But reinforcing rebar for concrete made of FRP rebar has linear elastic behavior up to tensile failure. For safety a certain plastic strain and an elongation greater than 3% at maximum load is usually required for steel reinforcement in concrete structures. The same should be required for FRP rebar. Thus, the main object of this study was to develop new type of hybrid FRP rebar Also, this study was evaluated to the mechanical properties of Hybrid FRP rebar. The Manufacture of the hybrid FRP rebar was achieved by pultrusion, and braiding and filament winding techniques. Tensile and interlaminar shear test results of Hybrid FRP rebar can provide its excellent tensile strength-strain behavior and interlaminar stress-strain behavior.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1156-1161
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• 2004

The factors affecting the long-term design strength of geogrid for railroad reinforcement can be classified into factors on creep deformation, installation damage, temperature, chemical degradation, biological degradation. Especially, creep deformation and installation damage are considered as main factors to determine the long-term design strength of geogrid. This paper describes the results of a series of experimental study, which are carried out to assess the combined effect of installation damage and creep deformation for the long-term design strength of geogrid reinforcement. In this study, a series of field tests are carried out to assess installation damage of a various geogrids according to different fill materials, and then creep tests are conducted to assess the creep properties of both undamaged and damaged geogrids.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.271-274
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• 2005

In this research, 13 RC slabs connected by hinged joints were tested. the new slab was connected to the existing slab by hinge joint injecting dowel bars between two slabs. Main parameters of the slabs were the spacing of the dowel bars (150mm, 300mm, and 450mm) and the locations of the longitudinal reinforcement of the old slab. The test results indicated that the joint strength of the RC test slabs having various types of dowel bars was about twice that calculated by the ACI 318-02 code. The locations of the longitudinal reinforcement of the old slab slightly increased the strength of the slabs connected by hinged joints.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.31-34
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• 2005

An experimental investigation was conducted to examine the hysteric behavior of Ultra-High strength concrete columns for the requirement of ACI provision. Seven 1/3 scaled columns were fabricated to simulate an 1/2 story of actual structural members with the cross section $300\times300mm$ and the shear span ratio 4. The main variables are axial load ratio, configuration and volumetric ratio of transverse reinforcement. It has been found that the behavior of columns was affected by axial load ratio rather than the amount and the configuration of transverse reinforcement. Consequently, to secure the ductile behavior of 100MPa Ultra-High strength concrete columns, ACI provision for the requirement of transverse steel may considered axial level and the detail of transverse reinforcement.

• Tunnel and Underground Space
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• v.15 no.6 s.59
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• pp.425-431
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• 2005

A series of geotechnical surveys and in-situ tests were carried out to evaluate the stability of underground mine cave in an abandoned coal mine. After the closure of the mine, the underground mine drifts have been utilized for a tourist route since 1999. The dimension of the main cave is 5m width, 3m height and 230m length. The surrounding rock mass of the cave is consist of black shale, coal and limestone. Also, the main cave is intersected by two fault zone. Detailed field investigations including Rock Mass Rating(RMR), Geological Strength Index(GSI) and Q classification were performed to evaluate the stability of the main cave and to examine the necessity of reinforcement. Based on the results of rock mass classification and numerical analysis, suitable support design was recommended for the main cave. RMR and Q values of the rock masses were classified in the range of fair to good. According to the support categories proposed by Grimstad & Barton(1993), these classes fall in the reinforcement category of the Type 3 to Type 1. A Type 3 reinforcement category signifies systematic bolting and no support is necessary for the Type 1 case. From the result of numerical analysis, it was inferred that additional support on the several unstable blocks is required to ensure stability of the cave.

• The Journal of Korea Robotics Society
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• v.15 no.2
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• pp.197-204
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• 2020

In this paper, we present a learning platform for robotic grasping in real world, in which actor-critic deep reinforcement learning is employed to directly learn the grasping skill from raw image pixels and rarely observed rewards. This is a challenging task because existing algorithms based on deep reinforcement learning require an extensive number of training data or massive computational cost so that they cannot be affordable in real world settings. To address this problems, the proposed learning platform basically consists of two training phases; a learning phase in simulator and subsequent learning in real world. Here, main processing blocks in the platform are extraction of latent vector based on state representation learning and disentanglement of a raw image, generation of adapted synthetic image using generative adversarial networks, and object detection and arm segmentation for the disentanglement. We demonstrate the effectiveness of this approach in a real environment.

• Smart Structures and Systems
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• v.13 no.6
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• pp.943-957
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• 2014

When subjected to fatigue loading, the main failure mode of partially prestressed concrete (PPC) structure is the fatigue fracture of tensile reinforcement. Therefore, monitoring and evaluation of the steel stresses/strains in the structure are essential issues for structural design and healthy assessment. The current study experimentally investigates the possibility of using fiber Bragg grating (FBG) sensors to measure the steel strains in PPC beams in the process of fatigue loading. Six full-scale post-tensioned PPC beams were exposed to fatigue loading. Within the beams, the FBG and resistance strain gauge (RSG) sensors were independently bonded onto the surface of tensile reinforcements. A good agreement was found between the recorded results from the two different sensors. Moreover, FBG sensors show relatively good resistance to fatigue loading compared with RSG sensors, indicating that FBG sensors possess the capability for long-term health monitoring of the tensile reinforcement in PPC structures. Apart from the above findings, it can also be found that during the fatigue loading, there is stress redistribution between prestressed and non-prestressed reinforcements, and the residual strain emerges in the non-prestressed reinforcement. This phenomenon can bring about an increase of the steel stress in the non-prestressed reinforcement.

• Structural Engineering and Mechanics
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• v.27 no.6
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• pp.741-771
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• 2007

Tests were conducted on two partially pre-stressed concrete solid beams subjected to combined loading of bending, shear and torsion. The beams were designed using the Direct Design Method which is based on the Lower Bound Theorem of the Theory of Plasticity. Both beams were of $300{\times}300mm$ cross-section and 3.8 m length. The two main variables studied were the ratio of the maximum shear stress due to the twisting moment, to the shear stress arising from the shear force, which was varied between 0.69 and 3.04, and the ratio of the maximum twisting moment to the maximum bending moment which was varied between 0.26 and 1.19. The required reinforcement from the Direct Design Method was compared with requirements from the ACI and the BSI codes. It was found that, in the case of bending dominance, the required longitudinal reinforcements from all methods were close to each other while the BSI required much larger transverse reinforcement. In the case of torsion dominance, the BSI method required much larger longitudinal and transverse reinforcement than the both the ACI and the DDM methods. The difference in the transverse reinforcement is more pronounce. Experimental investigation showed good agreement between design and experimental failure loads of the beams designed using the Direct Design Method. Both beams failed within an acceptable range of the design loads and underwent ductile behaviour up to failure. The results indicate that the Direct Design Method can be successfully used to design partially prestressed concrete solid beams which cater for the combined effect of bending, shear and torsion loads.

• Architectural research
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• v.19 no.4
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• pp.117-124
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• 2017

In this research, we carried out finite element analysis depends on the variations such as the strength of the main bar, concrete, shear-span ratio(a/d) and existence of shear reinforcing bar. Throughout the results of FEM analysis, we were able to figure out how each variation can effect on shear performance. As the strength of concrete increased, the maximum shear force enhancement effect of each specimen was evaluated. As a result, the shear strengthening effect was 51~97% for shear reinforced specimens, and 26~44% for non-shear reinforced specimens. As the yield strength of reinforcing bars increases, the shear reinforcement effect of the specimen the specimens without shear reinforcement were 3%~6% higher than those with shear reinforcement. Theoretical and analytical values were compared using the design equations obtained from the CEB code. Theoretical and analytical values were compared using the design equations obtained from the CEB code. As a result, the error rate was the highest at 3.64 in the S1.0-C0 series and the lowest at 1.46 in the S1.7-C1 series. Therefore, the design equation of the CEB code is estimated to underestimate the actual shear strength of deep beams that are not subjected to shear reinforcement.

• Journal of Korean Academy of Nursing
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• v.17 no.3
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• pp.177-183
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• 1987

This study investigated and evaluated a method effectively promote a communication function in families with a schizophrenic patient and the patients' interaction, by a family approach using reinforcement of functional communication between patients and their parents. The subjects of the study were patients receiving treatment in Won Gwang University Mental Hospital from July 1985 to July 1986, and their families. In the experimental group, a family approach using reinforcement of functional communication twice a week was taught. Each of the six sessions took sixty minutes, during which the interviews and questionaires were carried out. The total number of patients receiving treatment in the hospital at that time, 42, were divided by a systematic method into 20families in an experimental group and 22 in a control group. The results from testing the hypotheses established in this study, to analyse the effects of family approach through reinforcement of functional communication, are as follows; The results of the test of the first hypothesis are shown in Table 1. “patients and their parents in an experimental group receiving group training in reinforcement of functional communication will show a greater degree of interaction than those of the control group” was supported. Significant differences included Main Effects p＜.001, Interactions p＜.001 and Explained p＜.001 in the interactions of patients, and mothers. Scores were higher for the experimental group after the treatment as well as higher than the control group.