• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.43-53
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• 2004

The current Korean Concrete Design Code(KCI Code) requires the minimum and maximum content of shear s in order to prevent brittle and noneconomic design. However, the required content of the steel reinforcement In KCI Code is quite different to those of the other design codes such as fib-code, Canadian Code, and Japanese Code. Furthermore, since the evaluation equations of the minimum and maximum shear reinforcement for the current KCI Code were based on the experimental results, the equations can not be used for the RC members beyond the experimental application limits. The concrete tensile strength, shear stress, crack inclination, strain perpendicular to the crack, and shear span ratio are strongly related to the lower and upper limits of shear reinforcement. In this research, an evaluation equation for the minimum content of shear reinforcement is theoretical proposed from the Wavier's three principals of the mechanics of materials.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.2
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• pp.141-150
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• 2004

Recently, it is really concerned about corrosion and aging of reinforced concrete bridges. Corrosional steel reinforcing in concrete affects not only safety of bridges structure but also bending strength of reinforced concrete's member. Rate of corrosion, characteristic of bending strength, and economical evaluation aren't clear in reinforced concrete, considering performance evaluation. The purpose of study is as follows. It studies about ability of resistance's strength and cost of life cycle according to reduction of steel reinforcing's corrosion. Moreover, it shows calculating formula of bending strength with corrosion of current rate and exactly evaluates about the rest life at corrosional reinforced concrete bridges.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.4
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• pp.79-88
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• 2012

The purpose of this study is to evaluate the stiffness of the mechanical sleeve reinforcement splices filling high-strength mortar under monotonic loading. For this objective, we analyzed and compared the previous test data of 189 actual-sized mortar-filled sleeve bar splices specimens, including the reinforcing bar splices prepared and tested by the author. The paper results indicated that the minimum values of compressive strength of mortar($f_g$) multiplied by the ratio of reinforcement development length to bar diameter(L/d) were suggested for holding the stiffness of the mortar-filled sleeve reinforcement splices required in AIJ code.

• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.611-620
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• 2016

In the construction of nuclear power plants, only 420 MPa reinforcing bars are allowed and, therefore, so many large-diameter bars are placed, which results in steel congestion. Consequently, re-bar works are difficult and the quality of RC structures may be deteriorated. To solve the steel congestion, 550 MPa bars are necessary. Among many items for verifying structural performance of reinforced concrete with 550 MPa bars, the 43 mm hooked bars are examined in this study. All specimens failed by side-face blowout and the side cover explosively spalled at maximum loads. The bar force was initially transferred to the concrete primarily by bond along a straight portion. At the one third of maximum load, the bond reached a peak capacity and began to decline, while the hook bearing component rose rapidly. At failure, most load was resisted by the hook bearing. For confined specimens with hoops, the average value of test-to-prediction ratios by KCI code is 1.45. The modification factor of confining reinforcement which was not allowed for larger than 35 mm bars can be applied to 43 mm hooked bars. For specimens with 70 MPa concrete, the average value of test-to-prediction ratios by KCI code is 1.0 which is less than the values of the other specimens. The effects of concrete compressive strength should be reduced. An equation to predict anchorage capacity of hooked bars was developed from regression analysis including the effects of compressive strength of concrete, embedment length, side cover thickness, and transverse reinforcement index.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.570-576
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• 2018

In reinforced concrete structures, the joints of ordinary rebars are usually lap joints, which are bound by binding wires with rebars, and mechanical joints by couplers. In domestic design standards (concrete design code), welded lap joints are restricted for ordinary rebars, but overseas standards allow welded lap joints of ordinary rebars through pre-heating. This study investigated the domestic and international standards/criteria and evaluated the fracture strength by performing the tensile test on the lap welded joint of SD400 grade rebars, which is used the most in the construction sites. The weld length of the specimen for weld lap joints is based on the minimum weld length (8d) given in the KS standard (KS B ISO 17660-1). According to AWS D1.4, the preheating temperature was set to $150^{\circ}C$ for D19 and below, and $260^{\circ}C$ for D22 and above. In the test results, the tensile strength of rebars with welded lap joints exceeded the required strength (125% of the yield strength) according to the concrete design code. To analyze the effect of preheating, the tensile strength of the welded rebars after preheating was not significantly different from that of the welded rebars without preheating. The carbon equivalent content (Ceq) of the rebars used in the test was 0.45% or less. Under AWS D1.4, no preheating is required if the carbon equivalent is less than 0.45%. All specimens with a welded lap length of 8d failed by a bar fracture. The effect of preheating was confirmed to be insignificant due to the low carbon equivalent of the rebar.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.2
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• pp.73-82
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• 2001

본 연구는 실험적 방법과 해석적 방법을 통하여 반복하중을 받는 ├형 철근콘크리트 접합부의 전단특성을 파악함을 목적으로 한다. ├형 접합부는 고강도 재료의 사용으로 인한 체적의 감소 뿐만 아니라, 지진발생 시 반복하중의 작용으로 인한 변동축력 등으로 , 구조적으로 취약한 부분이 될 가능성이 있다. 따라서 본 연구에서는 ├형 접합부의 전단특성을 파악하기 위하여 기동축력, 콘크리트 압축강도, 접합부 전단보강근비를 변수로 한 12개의 실험체를 제작하여 가력실험을 수행하였다. 또한, 유한요소 해석을 수행하여 본 실험결과와의 비교 검토를 통하여 타당성을 검토한 후, 기둥축력과 콘크리트 압축강도의 변화에 대한 변수해석을 통하여 접합부의 전단강도에 미치는 변수는 영향을 파악하였으며, 실험에 의한 실험체의 전단내력을 기존에 제안된 AIJ, ACI 규준 등과 비교 검토하였다. 본 연구의 결로부터 기둥축력과 콘크리트 압축강도가 ├형 철근콘크리트 접합부의 전단강도에 미치는 영향을 확인하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.639-648
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• 1999

레이더법은 건축구조물에 대한 비파괴 검사의 대표적인 방법의 하나이다. 레이더법을 이용하는데 영향을 주는 요인들을 연구하고, 레이더로 측정된 결과들을 분석하기 위해서는 전자기파의 전파에 대한 수치적인 모델링을 통한 이론적인 접근이 필요하다. 콘크리트 시편에 전파되는 전자기파를 모델링 하기 위해 유한차분 시간영역법을 적용하고자 한다. 유한차분 시간영역법은 전자파 해석과 모델링을 통한 시뮬레이션에 매우 유용한 방법이다. 본 연구에서는 유한차분 시간영역법을 이용하여 두께가 다른 4개의 시편과 두께는 100㎜로 동일하고 피복두께가 다른 3개의 시편을 3차원으로 모델링 하였다. 두께 측정 모델링 결과에서는 계산영역의 셀간격과 입사파의 파장/콘크리트 시편의 두께값이 모델링의 정확성에 미치는 영향을 알 수 있었다. 철근이 있는 시편의 모델링에서는 0.08%∼0.5%의 오차로 철근의 위치를 확인할 수 있었다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.1
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• pp.79-88
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• 2023

In this study, a development of the rust formation arising from steel corrosion was modelled to quantify the structural impact in steel reinforced concrete. The interfacial gap, cover depth and diameter of steel rebar were taken for variables in modelling. It was found that the interfacial gap was the most influencing on the structural limit at steel corrosion, followed by steel diameter and cover depth. At 75 mm of cover depth with 20 mm of the steel diameter, the rust amount to reach cracking accounted for 16.95-27.69 ㎛ to 1-10 ㎛ of the interfacial gap. It was found that there was no risk of cracking and structural limit until the rust was formed within the interfacial gap. With a further formation of rust, the concrete section was successively behaved to yielding, cracking and failure. Additionally, the interfacial gap was the most dominant parameter for the rust amount to reach the cracking of concrete at the interfacial zone, whilst the cover depth had a marginal effect on cracking but had a crucial influence on the rust to failure.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.179-190
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• 1998

Shear failure of reinforced concrete (RC) beams is serious problem due to sudden brittle failure and many experimental results proved that size effect in shear strength of RC beams is an important feature of reinforced concrete members. As the sizes of RC beams very large, experiments sometimes become very difficult so that empirical design formula or the experimental data on shear strength of RC beams could not be obtained. Then the numerical analyses for size effect on shear strength of RC beams become very important. In this study, finite-element technique of reinforced concrete is employed of shear analysis of RC beams without web reinforcement and the size effects in shear strength are numerically analyzed. The influencing factors to the size effect in the shear strength of RC beams are extensively analyzed and compared with those by major shear strength equations including several standard specifications.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.4
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• pp.11-17
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• 2008

This study evaluates the seismic performance of post-tensioned flat plate structures with or without slab bottom reinforcement. For this purpose, 3 and 9 story frames were designed only considering gravity loads. This study conducts a nonlinear static pushover analysis. This study was an analytical model that is able to represent punching shear failure and fracture mechanism. The analytical results showed that the seismic performance of a post-tension flat plate is strongly influenced by the existence of slab bottom reinforcement through column. By placing slab bottom reinforcement in a PT flat plate frame, lateral strength and max drift capacity are significantly increased.