• Explosives and Blasting
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• v.23 no.2
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• pp.45-56
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• 2005

In this study, fracture formation and fracture volume by blasting demolition of model reinforced concrete pillars were compared with various vertical load and influence of reinforced steel bar. The more vertical load increased, the more tensile cracks and vertical direction cracks produced. In vertical load of 2.0ton, tensile cracks on vertical direction were predominantly produced. Generally, the more vertical load increased, the more bending deformation of concrete steel bar decreased. As a result, vertical load was influenced fracture formation of concrete and bending deformation of reinforced steel bar. Reinforced steel bar was influenced fracture volume of concrete. According to vertical load and influence of reinforce steel bar by blasting demolition of reinforced concrete pillars, drilling and blasting pattern may be modified.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.109-115
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• 2008

As structures are getting super-rise and large-sized, introducing the construction methods such as prefabrication of bar-meshes and complex method are being actively discussed to pursue the high quality of reinforced concrete, the simplification of field works, and the reduction of duration, as well as the study on how to connect reinforcing rods, which occurs while applying the same methods, is in progress Also, the pressure welded joint is a kind of method that heats the ends of reinforced bars locally and joint them, and after the pressure welding, the vulnerable part in the reinforced bar occur. Thus, in the construction field, the throughout quality control is necessary because of the delayed duration and the lowered construct ability. In this study, of the traditional lap splice method and the mechanical splice one, the screw coupler, we tried to look into through experiments the prefabrication method of bar-meshes, a typical joint method usually used for the joint parts for PSC structures applying the reinforced bar with its big diameter, and a newly-developed up-set coupler method. And we also examined the characteristic of tensile.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.183-184
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• 2009

Recently, research is focused on the behavior of ultra high strength fiber reinforced concrete from the high rise building to the span bridge. To verify the characteristics of the behavior of UHSFRC beam, the tension-stiffening model of UHSFRC is adopted as nonlinear analysis.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.50-58
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• 2018

The verification of serviceability of concrete structures requires more informations on the composite behaviors between concrete and reinforcement. Among them, the investigation of crack widths and spacings is based on the tension stiffening effects. In this paper, the tension stiffening effects of high strength concrete members with compressive strength of 80 and 100MPa are investigated experimentally. It was found that the current design code which is based on the tests of normal strength concrete may not describe the tension stiffening effects in high strength concrete correctly. The coefficient that can appropriately reflect the tension stiffening effects in the high strength concrete was proposed. Also, the crack spacing was investigated through the cracking behaviors and the crack width according to the difference of the strains in steel and concrete was estimated. The results of this paper may be used to examine the tension stiffening effects of high strength concrete members.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.275-282
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• 2006

Recently, Fiber Reinforced Polymers(FRP) has been emerged as an alternative material to solve the corrosion of steel reinforcement in reinforced concrete structures. FRP exhibits higher specific strength and lower weight compared to steel reinforcement. Moreover, good resistance to corrosion of the FRP may be useful in aggressive environments causing deterioration such as chloride environment. However, causes for higher initial cost of FRP than that of steel, little information on the long-term behavior of FRP, and brittle failure make the efforts to apply FRP in civil structures slow. Glass fiber among the fibers used to manufacture FRP can be seen as the most beneficial material with regard to initial costs. But its low elastic modulus, which attains barely a quarter of steel, nay thus lead to excessive deflections when used as reinforcement for flexural members. This research was carried out on the tensile properties of hybrid rods made with glass and carbon fibers to improve those of FRP rod made with glass fiber. Parameters were resin type and the arrangement of glass and carbon fibers. The tensile properties of hybrid rods were compared with those of rods manufactured with only glass or carbon fibers. The results indicated that the tensile properties of hybrid rod were good when the carbon fiber was arranged in the core.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.67-73
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• 2011

This study aims to develop an economical precast hollow concrete column with high constructability which consists of only splice sleeve and general reinforcing bar without using PC tendons in order to reduce the construction period and cost. With this purpose, this study performed the finite element analysis and tension test by using some variables such as length of sleeve, diameter of rebar and curing method for suggesting a grouting type splice sleeve which is a new type joint rebar and developing an optimized splice sleeve. As a result, the analysis on the tension performance of splice sleeve did not show any destruction caused by pull-out in reinforcing bar but it only occurred destruction of tension bar or bolt shear rupture from the mechanical defect of sleeve. Therefore, the experiment showed high performance in tension of the suggested splice sleeve and verified the application of precast hollow concrete column.

• Journal of the Korean Geotechnical Society
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• v.24 no.8
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• pp.43-52
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• 2008

In this study, the verification test and creep test for both a single-rebar nail and a multi-rebar nail are carried out to investigate a tensile strength for both nails. The adhesion effects between a rebar and a cement grout, a mobilized frictional force induced by pull-out load, and load transfer characteristics are examined. The results obtained from the field pull-out tests and from the numerical analysis using $FLAC^{2D}$ which is one of the programs developed based on the finite difference method are analyzed and compared for a single-rebar nail and a multi-rebar nail. The field pull-out test results for a multi-rebar nail relative to a single-rebar nail show that a tensile failure load is relatively large and the pull-out loads are well transferred to the ground in deep depth.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.476-483
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• 2023

The present study concerns modelling the structural behaviour for concrete structure into the crack initiation at corrosion of steels. The degradation source included the axial load and steel corrosion. A development of the rust formed on the steel surface was considered with the interfacial gap between steel and concrete. As a result, the tensile damage could occur on the surface of concrete into the cracking with no steel corrosion, which could be further developed by the increasing rust formation, while the cracking at the steel-concrete interface was mainly attributed to the compressive deformation, being restricted within the interfacial zone.

• Journal of the Korea Concrete Institute
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• v.26 no.2
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• pp.159-169
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• 2014

This study generalizes the lateral load-displacement relationship of reinforced concrete shear walls from the section analysis for moment-curvature response to straightforwardly evaluate the flexural capacity and ductility of such members. Moment and curvature at different selected points including the first flexural crack, yielding of tensile reinforcing bar, maximum strength, 80% of the maximum strength at descending branch, and fracture of tensile reinforcing bar are calculated based on the strain compatibility and equilibrium of internal forces. The strain at extreme compressive fiber to determine the curvature at the descending branch is formulated as a function of reduction factor of maximum stress of concrete and volumetric index of lateral reinforcement using the stress-strain model of confined concrete proposed by Razvi and Saatcioglu. The moment prediction models are simply formulated as a function of tensile reinforcement index, vertical reinforcement index, and axial load index from an extensive parametric study. Lateral displacement is calculated by using the moment area method of idealized curvature distribution along the wall height. The generalized lateral load-displacement relationship is in good agreement with test result, even at the descending branch after ultimate strength of shear walls.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.143-150
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• 2008

There is possibility of poor-state concrete filling condition due to segregation of aggregate and paste in reinforced concrete structure. This study was conducted to evaluate the flexural and shear behavior of reinforced concrete beams with different concrete filling conditions. Different concrete filling conditions were intentionally made such that the specimens was soundly cast to obtain the perfect concrete filling condition and cast in such a way that up to the longitudinal tensile reinforcement from the top, good concrete was filled while poor concrete was poured for the bottom part to simulate the poor strength, workability and unsatisfactory compaction. The test results indicate that have no effect of concrete filling conditions on the yielding strength of structures. But, have a great influence on the flexural ductility and shear capacity of structures.