• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.733-738
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• 2000

It is difficult to obtain accurate fracture toughness values by RILEM committees proposed three point bend test(TPB) because the shape of load-deflection curve is irregular and final crack propagation occurs after some slow stable cracking. However, for disk test, fracture toughness is easily obtained from crack initial load. We examined the cracked high strength concrete disk and the experimental results were compared with the results by finite element analysis(FEA). Also we compared experimental fracture locus with theoretical fracture locus.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.862-867
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• 2004

In this paper, the crack properties of steel fiber reinforced concrete (SFHC) beams by experimental method are discussed. The major role played by the steel fiber occurs in the post-cracking zone, in which the fibers bridge across the cracked matrix. Because of its improved ability to break crack, SFRC has better crack properties than that of reinforced concrete (RC). Crack properties are influenced by longitudinal reinforcement ratio, volume and type of steel fiber, strength of concrete and the stress level. Crack width and crack number in the SFRC beams havebeen evaluated from experimental test data at various levels in the beams.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.407-410
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• 2005

This paper describes an evaluation of reinforcement tension in RC beams using the variable truss models. The models were examined with the beam test results by Kim, Kim and White. Consequently, a fixed inclination $\theta$ at the support un-explains global state of internal force flow in cracked reinforced concrete beams subjected to shear and bending. Accordingly, we must introduce the arch factor for development of consistent model in reinforced concrete beams subjected to shear and bending

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.401-404
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• 2008

Crack is a penetration path of harmful material such as chloride ion, and causes a serious deterioration in durability. So, the characteristics of chloride penetration are investigated for the cracked flexural concrete members using high-durable materials. For these, the flexural crack of beam specimen is introduced by transverse loading. And, Rapid Chloride Penetration Test (RCPT) and Long-term chloride penetration test are carried out to compare the chloride penetration depth. From test results when crack is happened, the chloride penetration resistance of the durable member was superior than that of the normal member. Blast furnace slag concrete member has a excellent chloride penetration resistance in long-term chloride penetration test.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4252-4265
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• 2023

In the case of nuclear power plants near end of their design life, a reassessment of the performance of safetyrelated equipment may be necessary to determine whether to shut down or extend the operation of the power plant. Therefore, it is necessary to evaluate the level of performance decline due to degradation. Electrical cabinets, including MCC and switchgear, are representative safety-related equipment. Several studies have assessed the degradation and seismic performance of nuclear power plant equipment. Most of those researches are limited to individual components due to the size of safety-related equipment and test equipment. However, only a few studies assessed the degradation performance of electrical cabinets. The equipment of various nuclear power plants is anchored to concrete foundations, and crack in concrete foundations is one of the most representative of degradation that could be visually confirmed. However, it is difficult to find a study for analysis through testing the effect of cracks in concrete foundations on the response of electrical cabinet internal equipment fixed by anchors. In this study, using a simple cabinet model considering cast-in-place anchor in uncracked and cracked concretes, a tri-axial shaking table tests were performed and the seismic behavior were observed.

• Journal of the Korea Concrete Institute
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• v.27 no.3
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• pp.299-309
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• 2015

Ultra High Performance Fiber Reinforced Concrete (UHPFRC) is distinguished from the normal concrete by outstanding compressive and tensile strength. Cracked normal concrete resists shear by aggregate interlocking while clamped by transverse reinforcement, which is called as shear friction theory. Cracked UHPFRC is expected to have a different shear transfer mechanism due to rather smooth crack face and post-cracking behavior under tensile force. Twenty-four push-off specimens with transverse reinforcement are tested for four different fiber volume ratio and three different ratio of reinforcement along the shear plane. The shear friction strength for monolithic concrete are suggested by limit analysis of plasticity and verified by test results. Plastic analysis gives a conservative, but reasonable estimate. The suggested shear friction factor and effectiveness factor of UHPFRC can be applied for interface shear transfer design of high-strength concrete and fiber reinforced concrete with post-cracking tensile strength.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.300-307
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• 2005

Steel Reinforced Concrete (SRC) composite column has several advantage such as excellent durability, rapid construction, reduction of column section. Due to these aspect, applications of SRC columns to bridge piers are continuously increasing. For the design of relatively large SRC columns for bridge piers, it is necessary to check the current design provisions which were based on small section having higher steel ratio. In this study, seven concrete encased composite columns were fabricated and static tests were performed. Embedded steel members were a H-shape rolled beam and a partially filled steel tube. Based on the test results, the ultimate strength according to section details and local behavior were estimated. For the analysis of inelastic behavior of the SRC column, the cracked section stiffness of the columns was evaluated and compared with calculations. The stiffness of the cracked section showed that 25% of the initial value and this stiffness reduction occurred at 85% of the ultimate load in the experiments.

• Journal of the Korea Concrete Institute
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• v.25 no.6
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• pp.621-630
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• 2013

Several techniques for steel corrosion detection are proposed and HCP (half cell potential) technique is widely adopted for field investigation. If concrete has cracks on surface, steel corrosion is rapidly accelerated due to additional intrusion of chloride and carbon dioxide ions. This study is for an evaluation of HCP in cracked concrete exposed chloride attack. For this work, RC (reinforced concrete) beams are prepared considering 3 w/c ratios (0.35, 0.55, and 0.70) and several cover depths (10~60 mm) and various crack widths of 0.0~1.0 mm are induced. For 35 days, SST (salt spraying test) is performed for corrosion acceleration, and HCP and corrosion length of rebar are evaluated. With increasing crack width, w/c ratios, and decreasing cover depth, HCP measurements increase. HCP evaluation technique is proposed considering the effects of w/c ratios, crack width, and cover depth. Furthermore anti-corrosive cover depths are obtained through Life365 program and the results are compared with those from this study. The results shows relatively big difference in cracked concrete, however provide similar anti-corrosive conditions in sound concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.23-30
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• 2012

For cracked concrete, it is obvious that cracks should be preferential channel for the penetration of aggressive substances such as chloride ions according to the previous researches. In order to extend the lifetime of cracked concrete, critical issues in the performance of the concrete is the risk of chloride-induced corrosion. Even though crack width can be reduced due to the high reinforcement ratio, the question is to which extend these cracks may jeopardize the durability of cracked concrete. If the size of crack is small, surface treatment system can be considered as one of the best options to extend the service life of concrete structures exposed to marine environment simply in terms of cost effectiveness versus durability performance. Thus, it should be decided to undertake an experimental study on the effect of surface coating system, which can be able to seal the concrete and the cracks to aggressive substances-induced corrosion in particular. In this study, it is excuted to examine the effect of surfaced treated systems on chloride penetration and carbonation through compressive stress induced cracks. Experimental results have showed conclusively that critical stress linked with deterioration, should be existed in compressive stress ratio 50 ~ 70% for chloride penetration and 70 ~ 80% for carbonation, respectively. When the critical stress is exceeded in concrete, a comparatively large deterioration was measured where the critical stress in concrete, the increase in the mass transportation is marginal in spite of the large increase in micro-cracks. As for the effect of surface coating system on crack-sealing, it can be seen conclusively that cracks can be healed.

• Structural Engineering and Mechanics
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• v.38 no.4
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• pp.503-516
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• 2011

Uncertainty in concrete properties, including concrete modulus of elasticity and modulus of rupture, are predicted by developing a microstructural homogenization model. The homogenization model is developed by analyzing a concrete representative volume element (RVE) using the finite element (FE) method. The concrete RVE considers concrete as a three phase composite material including: cement paste, aggregate and interfacial transition zone (ITZ). The homogenization model allows for considering two sources of variability in concrete, randomly dispersed aggregates in the concrete matrix and uncertain mechanical properties of composite phases of concrete. Using the proposed homogenization technique, the uncertainty in concrete modulus of elasticity and modulus of rupture (described by numerical cumulative probability density function) are determined. Deflection uncertainty of reinforced concrete (RC) beams, propagated from uncertainties in concrete properties, is quantified using Monte Carlo (MC) simulation. Cracked plane frame analysis is used to account for tension stiffening in concrete. Concrete homogenization enables a unique opportunity to bridge the gap between concrete materials and structural modeling, which is necessary for realistic serviceability prediction.