• Computers and Concrete
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• 제14권6호
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• pp.675-694
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• 2014

Annular and solid concrete specimens with different aspect ratios and static unconfined compressive strengths were studied for impact loading using SHPB test setup. Numerical simulations in LSDYNA were also carried out and results were validated. The stress-strain curves obtained under dynamic loading were also compared with static compressive tests. The mode of failure of concrete specimen was a typical ductile failure at high strain rates. In general, the dynamic increase factor (DIF) of thin solid specimens was higher than thick samples. In the numerical study, the variation of axial, hydrostatic and radial stresses for solid and annular samples was studied. The core phenomenon due to confinement was observed for solid samples wherein the applied loads were primarily borne by the innermost concrete zone rather than the outer peripheral zone. In the annular samples, especially with large diameter inside hole, the distribution of stresses was relatively uniform along the radial distance. Qualitatively, only a small change in the distribution of stresses for annular samples with different internal diameters studied was observed.

• Journal of the Korean Society of Safety
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• 제12권2호
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• pp.140-145
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• 1997

The main purpose of this study is to establish the reliable method for evaluating fire damage of reinforced concrete building, by using the rational procedure, and to develope the rehabilitation methods of fire damaged concrete structures. Especially, this proposed evaluation method is applied to the fire damaged concrete buildings of domestic, and the rehabilitation methods on the basis of these applied results are proposed and those example are shown. The proposed rational evaluation method for fire damaged concrete building proceeds is estimating the reduction of the mechanical properties of concrete of fire damaged structural members in comparison with the experimental results which are obtained from the compression tests of heated concrete specimens under various temperatures.

• Advances in concrete construction
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• 제6권5호
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• pp.423-463
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• 2018

This paper investigates the behavior of normal and self-compacted steel fiber reinforced concrete (SCC-SFRC) corbels rehabilitated by Basalt Fiber Mesh (BFM) and Basalt Fiber Fabric (BFF) for the first time in literature. The research objective is to study the effectiveness of BFM and BFF in the rehabilitation of damaged reinforced concrete corbels with and without epoxy injection. The experimental program includes two types of concrete: normal concrete, and self-compacted concrete. For normal concrete, 12 corbels were rehabilitated by BFM without injection epoxy in cracks, with two values of compressive strength, three ratios of steel fiber (SF), and two values of shear span. For self-compacted concrete, 48 corbels were rehabilitated with different parameters where 12 corbels were rehabilitated by BFM with and without epoxy injection, 18 heated corbels with three different high-temperature level were rehabilitated by repairing cracks only by epoxy injection, and 18 heated corbels with three different high-temperature level were rehabilitated by repairing cracks by epoxy and wrapping by BFF. All 48 corbels have two values of compressive strength, three values volumetric ratios of SF, and two values of the shear span. Test results indicate that RC corbels rehabilitated by BFM only without injection did not show any increase in the ultimate load capacity. Moreover, For RC corbels that were repaired by epoxy without basalt wrapping, the ultimate load capacities showed an increase depending on the mode of failure of corbels before the rehabilitation. However, the rehabilitation with only crack repairing by epoxy injection is more effective on medium strength corbels as compared to high strength ones. Finally, it can be concluded that use of BFF is an effective and powerful technique for the strengthening of damaged RC corbels.

• Earthquakes and Structures
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• 제15권2호
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• pp.165-178
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• 2018

The aim of this study is to investigate the efficiency of using threaded rods and steel profiles to produce a steel confining system for rehabilitation of damaged concrete corbels for the first time in literature. Some of the specimens were repaired by crack repair epoxy before being confined for further enhancement. A total of 19 two sided damaged corbels were used in the study with different mechanical properties and parameters but similar dimensions. The differences were in rehabilitation style, shear span, fiber percentage, reinforcement steel diameter, and concrete strength. The rehabilitated specimens were loaded with vertical load until failure. Four different configurations were used in the investigation. Test results show that the proposed rehabilitation technique is effective to enhance the load capacity of the corbels and to improve their ductility. Moreover, new formulations were proposed to calculate the load capacity of the rehabilitated corbels. A good fit was observed between numerical and experimental results.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.979-984
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• 2001

The Sang-Jin bridge constructed by the Free Cantilever Method in 1985 is 4-span concrete rahmen bridge with a hinge at midspan. Due to the effect of creep, shrinkage of concrete and relaxation of tendon, the Sang-Jin bridge exposed the excessive displacement at midspan with the passage of time. In order to improve the load-carrying-capacity and durability of the bridge, needs to repair and rehabilitate the structure emerged. New rehabilitation methods were applied such as external prestressing of concrete box, application of pier pre-camber and steel truss jacking. Structural analysis and several tests including static load test, dynamic load test and ambient vibration test were executed to verify the improvement. The test result showed that the displacement of the midspan was improved by 10mm and it was verified that the stiffness of the bridge was increased. Totally, the load-carrying-capacity of Sang-Jin bridge was increased at least 1.56times which was attributed to the new rehabilitation method.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.947-952
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• 2002

Recently, there have been increased much concerns about repair and rehabilitation works for aged concrete structures. In particular, it is known that due to repeated overburden vehicle there are significantly increasing number of aged concrete bridge slabs, which are strongly needed to construct and rehabilitate by innovative construction method. The objective of this research is to develop the new construction method of concrete slab in bridge structure, which can contribute to minimize the traffic congestion during the repair and rehabilitation works of aged concrete slab, and can also sufficiently assure the quality through the minimization of in-situ works at the site. I-beams with punch holes, which are substituted instead of main reinforcing steels in concrete slabs, will be manufactured in accordance with the specification in the factory, and will be preassembled into the panel. After erecting the preassembled panels in the site, concrete will be poured into the slab panel. This research is to investigate physical properties of I-Beam concrete slab through static test.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.493-498
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• 1999

Many concrete pavements closed to the end of service life in out country need to repair. We investigated material and mix designs for thin bonded concrete overlay and applied it to concrete pavement rehabilitation. The concrete with Type III cement showed earlier strength and better durability than the concrete with Type I cement. Designed concrete mixture with TypeIII cement made it possible to open the road earlier against heavy vehicles, increased traffic despite of cold weather in winter. In the field examination after four month, there was no defects like as shrinkage crack, spalling, surface abrasion and scaling, and good traffic condition has been maintained.

• Advances in concrete construction
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• 제15권2호
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• pp.75-84
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• 2023

Currently, polymer matrix nanocomposites (PMCs) are a prominent area of research due to their outstanding mechanical, thermal, and durability properties. The increase in recent studies justifies the possibility of using PMCs in structural retrofitting and reconstruction of damaged infrastructure and serving as new structural material. Using nanotechnology, nanocomposite panels in flooring combine concrete and steel, providing a very high level of performance. In sports flooring, high-performance concrete has become a challenge for reducing sports injuries and refinement in rehabilitation. As a composite material, this type of resistant concrete is one of the most durable and complex multi-phase materials. This article uses polyvinyl alcohol polymer (PVC) and multi-walled carbon nanotubes as concrete matrix fillers. Solution methods have been used for dispersing PVC and carbon nanotubes in concrete. The water-cement ratio, carbon nanotube weight ratio, and heat treatment parameters influenced the concrete nanocomposite's tensile and compressive strength. The dispersion of carbon nanotubes in cement paste and the observation of nano-microcracks in concrete was evaluated by scanning electron microscope (SEM).

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.437-442
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• 2001

Recently, there have been increased much concerns about repair and rehabilitation works for aged concrete structures. In particular, it is known that due to repeated overburden vehicle there are significantly increasing number of aged concrete bridge slabs, which are strongly needed to construct and rehabilitate by innovative construction method. The objective of this research is to develop the new construction method of concrete slab in bridge structure, which can contribute to minimize the traffic congestion during the repair and rehabilitation works of aged concrete slab, and can also sufficiently assure the quality through the minimization of in-situ works at the site. I-beams with punch holes, which are substituted instead of main reinforcing steels in concrete slabs, will be manufactured in accordance with the specification in the factory. and will be preassembled into the Panel. After erecting the preassembled panels in the site, concrete will be poured into the slab panel. This research is to investigate physical properties of I-Beam with punch holes itself through static and fatigue test with rational numerical analysis Finally this research is to suggest reformed I-beam through the numerical analysis.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.593-600
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• 1998

In this study, confinement stress of concrete compression members rehabilitated with C.F.L were analyzed from the test. Test parameters are spacing, thickness and ply of rehabilitation material. Displacement, failure load were measured during test. The failure mode and ultimate load were analyzed from these measured data. In this study, a model equation for calculation of the confining stress with C.F.L was proposed based on the test results investigated here. The proposed equation included the effects of spacing, thickness and ply of rehabilitation material.