• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.225-232
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• 1997

철근콘크리트 유공보에 있어서 기존 유공보의 연구는 유공위치를 보춤의 중앙에 위치하여 연구하였으나 철근코크리트 보의 역학적 특성활용과 시공상의 편의성을 위해 사각형 유공의 위치를 보춤 하단에 설치하여 개방형 유공보로 변형하였다. 본 연구에서는 사각형 유공보에 대한 유공크기의 세로길이를 보춤의 0.3배로 하고 가로길이를 세로길의의 1~3배로 변화시켜 보강 및 무보강 상태의 사각형 유공보와 이의 사각형 유공하부 콘크리트를 제외시킨 개방형 유공보에 있어서 총 10개의 시험체를 대상으로 하는 실험을 실시하여 시험체의 최대내력, 유공주위에서의 전단균열과 시험체의 휨인장균열, 주요위치의 변위조사, 주근 및 유공주위의 콘크리트와 보강철근의 변형도조사, 시험체의균열을 조사하여 상호변화를 비교.분석하였다. 이 연구결과로부터 개방형유공보의 유공주위 응력변형상태, 파괴메카니즘, 적절한 개방형 유공크기,설계시 고려사항을 제시하여 차후의 개방형 유공보의 계속적인 연구에 기여하고자 한다.

• Journal of Korean Society of Steel Construction
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• v.13 no.4
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• pp.419-431
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• 2001

This study was to investigate structural behavior of composite structure beams composed of end-RC. center-Steel according to respective reinforcing method for connection zone composed of different materials (SRC) while attaching main bars on steel-flange by welding. The main reinforcing methods are as follows ; non-reinforcing, vertical shear reinforcing (type-stirrup), inclined reinforcing(type-x), horizontal reinforcing(type-web, 0.3L), double horizontal reinforcing (type-web, 0.3L), vertical reinforcing (type-flange, 0.3L). Consequently, It showed little difference in structural properties like ductility and strength according to the attaching method of main bars. For Maximizing the structural properties of composite beam, the most effective methods were vertical reinforcing one and double horizontal reinforcing one.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.6
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• pp.18-28
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• 2015

The purpose of this study is to develop a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were performed on one unreinforced beam-column specimen and two reinforced specimens with U-type precast wall panels. The results were analyzed to find that the specimen with anchored connection experienced shear failure, while the other specimen with steel plate connection principally manifested flexural failure. The ultimate strength of the specimens was determined to be the weaker of the shear strength of top connection and flexural strength at the critical section of precast panel. In this setup of U-type panel specimens, if a push loading is applied to the reinforced concrete column on one side and push the precast concrete panel, a pull loading from upper shear connection is to be applied to the other side of the top shear connection of precast panel. Since the composite flexural behavior of the two members govern the total behavior during the push loading process, the ultimate horizontal resistance of this specimen was not directly influenced by shear strength at the top connection of precast panel. However, the RC column and PC wall panel member mainly exhibited non-composite behavior during the pull loading process. The ultimate horizontal resistance was directly influenced by the shear strength of top connection because the pull loading from the beam applied directly to the upper shear connection. The analytical result for the internal shear resistance at the connection pursuant to the anchor shear design of ACI 318M-11 Appendix-D, agreed with the experimental result based on the elastic analysis of Midas-Zen by using the largest loading from experiment.

• Journal of the Korea Concrete Institute
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• v.18 no.5 s.95
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• pp.603-610
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• 2006

The external unbonded strengthening offers advantages in speed and simplicity of installation over other strengthening techniques. Unlike externally bonded steel plate or carbon fiber sheet, surface preparation of the concrete for installation of high-tension bar is not required and installation is not affected by environmental conditions. Anchoring pin or anchoring plate are installed at the end of beam to connect the high-tension bar to concrete beam. The deviator are used in order that supplementary external bars would follow the curvature of the tested beam. A set often laboratory tests on reinforced concrete beam strengthened using the technique are reported. The main test parameters are the section area of strengthening bar, the depth of deviator and the number of deviators. The paper provides a general description of structural behavior of beams strengthened using the technique. The test result of strengthened beam are compared with those from a reference specimen. It is shown that the reinforcing technique can provide greater strength enhancements to unstrengthened beam and that the provision of deviator enhances efficiency. The ultimate moment of specimen with two deviators was higher than that of specimens with one deviator. It is also shown that the external bars enhance strength of beams in shear.

• Journal of The Korean Digital Architecture Interior Association
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• v.3 no.2
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• pp.47-54
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• 2003

A Steel plate shear wall can be used as one of the lateral force resistant elements in buildings. It have many advantages from a structural point of view such as ductility, energy absorption capacity and initial stiffness etc. In this study to grasp the behavior of steel plate shear wall considering material and geometrical non-linearity, the FEM analyses were carried out using ANSYS(ver. 5.6) program. The analysis results were fully discussed and compared with test results to verify the validity of analysis method. The object of this study is to find out analytically the elasto-plastic behavior of un-stiffened steel plate shear wall.

• Journal of the Korean Geotechnical Society
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• v.21 no.2
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• pp.67-84
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• 2005

This research was conducted to evaluate the effectiveness of reinforcement for nearly saturated soft clay compaction. The effectiveness was investigated by roller compaction test using nearly saturated clay specimens. The nearly saturated condition was obtained by submerging clay in the water for 12 hours. High water content specimens were compacted in plane strain condition by a steel roller. A specimen was compacted by four 5 cm horizontal layers. Specimens were prepared fur both reinforced and unreinforced cases to evaluate the effectiveness of reinforcement. Used reinforcement is a composite consisted of both woven and non-woven geotextile. The composite usually provides drainage and tensile reinforcement to hi인 water-contented clay so that it increases bearing capacity. Therefore, large compaction load can be applied to reinforced clay and it achieves higher density effectively. The reinforcement also increases compaction efficiency because it reduces the ratio between shear and vertical forces during compaction process. The maximum vertical stress on the base of specimen usually decreased with higher compaction thickness. The reinforcement increases soil stiffness under the compaction roller and it initiates stress concentration. As a result, it maintains higher vertical stress level on the base of specimen that provides better compaction characteristics. Based on test results, it can be concluded that the reinforcement is essential to achieve effective compaction on soft clay.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.165-176
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• 2006

This paper deals with the experiment and construction case of concrete beams strengthened with wire rope using the tightening force of bolts. The mechanical bolting of wire rope for prestressing force is adopted, which is very easy for construction. For the flexural strengthening effect of the proposed method, the experiment was proceeded as follows. The main parameters of specimens, concrete strength is 24MPa, are initial prestressing forces of wire rope and the number of saddle. The flexural strengths of strengthened specimens compared with non-strengthened test piece were increased about 160%. Also, as the initial prestressing forces were increased, the crack and ultimate moments were increased. The number of saddle did not play an important role for the moment capacity. This proposed method as a construction example showed a more competitive method than any others.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.1765-1775
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• 2013

The application of FRP wire as a mean of improving strength and ductility capacity of concrete cylinders under axial compressive load through confinement is investigated experimentally in this study. An experimental investigation involves axial compressive test of three confining amounts of FRP wire and three concrete compressive strengths. The effectiveness of FRP wire confinement on the concrete microstructure were examined by evaluating the internal concrete damage using axial, circumferential, and volumetric strains. The axial stress-strain relations of FRP wire confined concrete showed bilinear behavior with transition region. It showed strain-hardening behavior in the post-cracking region. The load carrying capacity was linearly increased with increasing of the amount of FRP wire. The ultimate strength of the 35 MPa specimen confined with 3 layer of FRP wire was increased by 286% compared to control one. When the concrete were effectively confined with FRP wire, horizontal cracks were formed by shearing. It was developed from sudden expansion of the concrete due to confinement ruptures at one side while the FRP wire was still working in hindering expansion of concrete at the other side of the crack. The FRP wire failure strains obtained from FRP wire confined concrete tests were 55~90%, average 69.5%, of the FRP wire ultimate uniaxial tensile strain. It was as high as any other FRP confined method. The magnitude of FRP wire failure strain was related to the FRP wire effectiveness.

• International Journal of Highway Engineering
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• v.6 no.2 s.20
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• pp.37-45
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• 2004

The asphalt concrete pavement takes various advantages of better riding quality, serviceability and easier maintenance. At the same time, it addresses a weak point of the premature failures due to rapid increasement of traffic volume, heavy vehicles and high temperature in summer. It increases the expenditure of maintenance and repair. In order to improve the performance of asphalt pavement avoiding this premature failure, the use reinforcements with geosynthetics have been considered. Geosynthetics are known as an effective reinforcement to restrain fatigue and reflective cracks in asphalt pavements. In this study, a comprehensive parametric study is conducted to capture the efficiency of geosynthetic-reinforcements using viscoelastic properties of the asphalt concrete(AC) layer. The investigated parameters were reinforcement location, AC layer thickness, temperature distribution across the AC layer and modulus of AC and base layer. As a result of observations, that reinforced asphalt concrete could be used effectively for improving resistance against fatigue cracks and permanent deformation. Especially, when a geogrid was placed at the interface between the asphaltic base and the subbase, tensile stress in the horizontal direction was significantly reduced.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.457-464
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• 2006

Fiber-reinforced composite materials due to their high specific strength, high stiffness and light weight are becoming increasingly used in many engineering industry, especially in the aerospace, marin and civil, etc. In this paper, the buckling load and mode shapes of composite laminates with elliptical cross-section including transverse shear deformations are analyzed. For solving this problems, a versatile flat shell element has been developed by combining a membrane element with drilling degree-of-freedom and a plate bending element. Also, an improved shell element has been established by the combined use of the addition of enhanced assumed strain and the substitute shear strain fields. The combined influence of shell geometry and elliptical cross-sectional parameter, fiber angle, and lay-up on the buckling loads of elliptical cylinder is examined. The critical buckling loads and mode shapes analyzed here may serve as a benchmark for future investigations.