• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.774-781
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• 2002

Shear behaviors of eight dapped ends of four full-scale domestic single-tee slabs were evaluated. The dapped ends with 10cm topping concrete were designed based on live load requirements for the domestic parking lot of m 500kgf/㎡ and for the large market of 1,200 kgf/㎡. All specimens were designed by the ACI 318-99 design. The variations of the experiment were the shape of hanger reinforcements as followings: 1) general PCI design method(currently used in domestic), 2) 90 degree bent-up, 3) 60 degree bent-up. All experiments were conducted with 1.2 m shear span. The results obtained in this study were 1) all specimens fully complied with the shear strength requirements as specified by ACI 318-99 except for one strand bond slip specimen, 2)a specimen with the 60 degree bent up hanger reinforcing detail showed the best shear behaviors under full service and ultimate load, and 3)a specimen with the 90 degree bent up hanger reinforcing detail resulted in the worst shear behaviors.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.750-758
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• 2002

Concrete is deformed by load and subjected to micro damage under allowable deformation because of non-homogeneous property. When micro damage is accumulated, it is cracked and finally fractured. Characterization of AE can be demonstrated the micro damage which it is not discovered from visual observation, and it become known to an advantage that was clearly discriminated from the existing NDT method. This study was carried out the analysis and evaluation of concrete damage by acoustic emission technique. As a results of damage analysis, it was found out that the more concrete strength has increased, the more concrete has subjected to micro damage at lower stress ratio for chylinder specimen, and this is possible only AE method which could be described the brittle properties. Also it was revealed that the kaiser effect and felicity effect were existed in reinforced concrete bending specimens and it is found out that the onset of interface debonding between concrete and steel could be conformed in comparison with felicity ratio, AE activity and load history. From the results of this study, it was conformed that the deteriorative degree of reinforced concrete structure should be evaluated using felicity ratios.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.180-189
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• 2002

The objective of this experimental research is to assess the seismic performance of circular RC bridge pier specimens retrofitted with fibers which were designed as a prototype of Hagal bridge in the city of Suwon, Korea. Pseudo dynamic test has been done for four(4) test specimens which were nonseismically or seismically designed by the related provisions of the Korea roadway bridge design specification, and four nonseisemic test specimens retrofitted with fibers in the plastic hinge region. Glass and carbon fiber sheets were used for the seismic capacity enhancement of circular test specimens. Important test parameters were confinement steel ratio, load pattern, and retrofitting. The seismic behavior has been analyzed through the displacement ductility, energy analysis, and capacity spectrum. Approximate 7.7 ∼8.7 displacement ductility was observed for nonseismic test specimens retrofitted with fibers subjected to Korea Highway Cooperation artificial earthquake motions. It is concluded that these retrofitted test specimens could have sufficient seismic capacity in the region of moderate seismic zone.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.1
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• pp.43-50
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• 2010

To address the problems caused by the corrosion of steel rebar, active research has recently been carried out on members where fiber-reinforced polymer (FRP) is used in place of rebar. As FRP bar is highly brittle and has a low modulus of elasticity, further research is needed on the evaluation of serviceability, in other words on the deflection of flexural concrete members reinforced with FRP rebars. Taking the reinforcement ratio as a variable, this paper analyzes the flexural capacity of concrete beams reinforced with CFRP rebar. The test results of specimens reinforced with CFRP rebar show an increase in stiffness and resisting force along with an increase in the reinforcement ratio. A reinforcement ratio of about 1.3 is needed for the member reinforced with CFRP rebar to show same section property of a steel member. Through a comparison for the value of an effective moment of inertia, the equation suggested by Bischoff & Scanlon predicted values closest to the actual results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.100-108
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• 2010

The axial strength of existing RC columns were experimentally investigated in this paper to understand the strength characteristics of existing structural members and to get a appropriate data in strengthening design of RC members in a remodelling construction. Ten RC columns were prepared by being cut and extracted directly from the demolition site of the apartment housings. Each column was tested under uniaxial loadings with different eccentricities in order to evaluate the axial strength of existing RC columns. From the test results, it was found that axial strength of all the specimens were at least 75% higher than those of the theoretical values required by current code. But member displacement ductility ratio were relatively low ranging from 2.12~5.86.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.111-118
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• 2010

Reinforced steel corrosion due to concrete carbonation is one of main factors on the durability of RC structure. The carbonation velocity have an effect on carbon dioxide density, concrete quality and structural shape. Specially, these problems have increased in urban area. This study investigates the carbonation status of the bridges and quantifies the effect of carbonation based on various domestic field data. The failure probability of durability is evaluated on the basis of reliability concept. According to experimental results of the carbonation depth, the carbonation depth increased with structural age and carbonation velocity decreased with high strength of concrete. In most cases, the failure probability of durability by carbonation was more than 10%. Also, The results requires the minimum cover thickness of 70-80mm for target safety index(${\beta}$=1.3) proposed by Korean concrete specification.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.185-193
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• 2012

In this study, an estimation equation was proposed to predict the shear strength of RC interior beam-column connections. The proposed equation considered the effect of both truss and arch mechanisms, while the existing equations in the ACI and AIJ design codes consider only arch mechanism. In addition, the proposed equation estimates the shear strength of RC joints by considering the contribution of the vertical and horizontal steel bars on the effective compressive strength of concrete. The shear strength of RC joints calculated by the proposed equation was compared with the test results of 54 RC joints, which failed in shear before plastic hinges developed at the end of the adjacent beams. The comparison study showed that the proposed equation estimated the strength of the 54 specimens with a mean value of 1.14 and the coefficient of variation of 20%. The proposed equation provides improved prediction compared to those obtained from the equations in the ACI and AIJ design codes.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.24-32
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• 2002

The modified compression field theory is already applied in shear problem at some code(AASHTO-1998) partly. Nominal shear strength of concrete beam is sum of the concrete shcar strength and the steel shear strength in the current design code. But Torsional moment strength of concrete is neglected in the calculation of the nominal torsional moment strength of concrete beam In the current revised code. Tensile stress of concrete strut between cracks is still in effect due to tension stiffening effect. But The tensile stresses of concrete after cracking are neglected in bending and torsion In design. The torsional behavior is similar to the shear behavior in mechanics. Therefore the torsional moment strength of concrete should be concluded in the nominal torsional moment strength of reinforced concrete beam. This paper shows that the torsional moment strength of concrete is caused by the average principal tensile stress of concrete. To verify the validity of the proposed model, the nominal torsional moment strengths according to two ACI codes (89, 99) and proposed model are compared to experimental torsional moment strengths of 55 test specimens found in literature. The nominal torsional moment strengths by the proposed model show the best results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.201-208
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• 2010

Information on the distribution characteristics of construction errors is very important to determine the member factors, which are to be introduced in a new Korean design code for reinforced concrete structures. The new design code, which is under development for reinforced concrete structures, is based on the performance design concept. The construction errors of reinforced concrete members are mainly caused by the firmness and dimensional accuracy of forms, the arranging condition of reinforcing bars, the pouring and compaction methods of concrete, the skills of field workers, and the experience of supervisors. To find out the construction errors of reinforced concrete structures already built in Korea, a field survey for cover thickness, effective depth of reinforcement, the thickness of slabs and walls, and the dimension of beams and columns has been performed. Based on the survey, which is the first time in Korea, the analysis results are presented. The measuring methods for the construction errors, which have been established through the laboratory tests, are also presented. In addition, the measured construction errors from the survey are compared with the allowable tolerances in the current domestic and foreign specifications.

• Journal of KIBIM
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• v.14 no.3
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• pp.13-21
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• 2024

This study aims to simplify the rebar quantity estimation process during the detailed design stage of buildings by addressing identified issues in the existing rebar quantity estimation process and establishing a BIM-based simplification method. To validate the applicability of the proposed method, it was applied to a case study of 'K' High School, with the results compared to rebar quantities from shop drawings to assess usability in real projects. It showed an error rate of 1.4% for SHD22S and 2.63% for HD10 among the types of rebar used in the case model. SHD22S, used as the main rebar in the columns, exhibited this error due to differences in the calculation method for splice and anchorage lengths. HD10, used as stirrup rebar in the columns, showed errors due to the omission of hook length considerations in the simplified estimation formula. Although these discrepancies resulted in cumulative errors of 10 to 20 meters, the error rates of 1.4% and 2.63% respectively fall within the generally accepted rebar overage rate of 5%, suggesting that this method is sufficiently accurate for quantity estimation during the detailed design stage. This study presents a method for efficiently estimating rebar quantities based on BIM during the detailed design stage. While traditional 2D quantity estimation and BIM-based methods often suffer from inefficiencies due to repetitive tasks and high modeling complexity, the proposed method assumes BIM models at LOD200, which are less complex and automate most of the structural information required for rebar quantity estimation, thereby reducing repetitive tasks. However, to further minimize errors, especially those related to hook and anchorage length calculations, additional research is needed to refine the estimation process and expand its applicability to the entire building's rebar quantity estimation.