• Journal of the Korea Institute of Building Construction
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• v.23 no.5
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• pp.519-526
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• 2023

This research endeavors to explore the nuances in apparent resistivity readings in concrete specimens due to the proximity of embedded reinforcement. To systematically gauge this, concrete samples incorporating singular and paired rebars were meticulously crafted. These rebars were strategically positioned at intervals of 0.03m, 0.04m, and 0.05m from each specimen's midpoint. Subsequent resistivity assessments were conducted at 0.01m increments up to the predetermined rebar location for each sample. A consistent observation was the nadir in apparent resistivity manifesting at the rebar's epicenter. Notably, dual-rebar configurations registered lower resistivity values at this central juncture compared to their single-rebar counterparts. This metric underscores the palpable impact of surrounding reinforcement on resistivity readings. Further, as the spatial separation between rebars increased, the distinctness in their locational identification via resistivity became increasingly pronounced.

• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.685-692
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• 2007

When the shear force governs the response of an RC element, as in the case of a low-rise shear wall, the effect of shear on the element's response is thought to be responsible for the 'pinching effect' in the hysteretic loops. However, it was recently shown that this undesirable pinching effect can be eliminated in the hysteretic load-deformation curves of a shear-dominant element if the steel grid orientation is properly aligned in the direction of the applied principal stresses. In this paper, the presence and absence of the pinching mechanism in the hysteretic loops of the shear stress-strain curves of RC elements was explained rationally using a compatibility aided truss model. The analytical results indicate that the pinching effect of the RC elements is strongly related to the direction of the steel arrangement. The area of the energy dissertation does not increase proportionally to the difference between the direction of the principal compressive stress and the direction of the steel arrangement.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.165-173
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• 2008

One of the most important requirements for reinforced concrete constructions is the bond behavior between concrete and reinforcement. For practical application, it is very important to study bond behavior of reinforcing bars in recycled aggregate concrete (RAC). Thirty six pull-out tests were carried out in order to investigate the bond behaviour between recycled coarse aggregate concrete (RCAC) and deformed bars. RCA replacement ratios (i.e., 0%, 30%, 60% and 100%) and positions of deformed bar (i.e., vertical and horizontal position) were considered as variables in this paper. Each specimen was in the form of a cube, with edges of 150 mm in length and for the pull-out tests, a deformed bar, 13 mm in diameter, was embedded in the center of each specimen. Based on the test results, the bond strength between the RCAC and deformed bars were influenced by both RCA replacement ratios and positions of deformed bars. It was found that under the equivalent mix proportion (i.e., the mix proportions are the same, except for different RCA replacement ratios), the bond strength between the RCAC and the ribbed bar has no obvious relation with the RCA replacement ratio, whereas the positions of deformed bars have a significant effect on the bond behavior between the RCAC and deformed bars. Under the condition of same RCA replacement ratio, the specimen of horizontal reinforcement at upper position (HU type) appear considerably low bond stress.

• Journal of the Korea Institute of Building Construction
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• v.23 no.2
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• pp.209-220
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• 2023

Ensuring accuracy within tolerance is crucial for a marking robot; however, rebar displacement frequently occurs during the structural work process, necessitating corrections to layout lines or rebar locations. To guarantee precision and automation, the marking robot must be capable of measuring rebar error and determining appropriate adjustments for marking lines and rebar placement. Consequently, this study proposes a method for measuring rebar location error using a LiDAR sensor and implementing a layout assessment process based on the measurement results. The rebar recognition experiment using the LiDAR sensor yielded an average error of 5mm, demonstrating a reliable level of accuracy for wall rebars. Additionally, this research proposed a process that enables the robot to evaluate rebar and marking corrections based on the error range. The findings of this study can contribute to the automated operation of marking robots while accounting for construction errors, potentially leading to improvements in structural quality.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1179-1185
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• 2007

The study of girder-to-column joints under experiment and numerical analysis was carried out to evaluate change of the flexural capacity of the joints with the 2-layer upper reinforcement of girder within rectangular section and the single-layered upper reinforcement at the girder flange. According to the analysis results using the flange width, the flange thickness and the location of reinforcements in the upper flange as variables, in the models with a same effective width, the increasing rate of capacity has nothing to do with the flange width with a same effective width. However, the capacity of the models with the upper reinforcements arranged close to the rectangular beam section is larger than that of the models with the upper reinforcements arranged remotely from the rectangular section. If the range of arrangement fur reinforcement exceeds the effective width, despite of increasing the flange thickness, the capacity is not increased.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1093-1096
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• 2008

This study investigated the bond behavior between recycled coarse aggregate (RCA) concrete and deformed reinforcing bars. The position (i.e., vertical, horizontal) and the location (i.e., 375mm, 225mm and 75 mm) of deformed bar were considered as a main test parameter in this paper. From the test results, it was found that maximum bond strength of top reinforcement was decreased compared with that of bottom reinforcement. Also bar embedded horizontally 225mm above from base could not satisfy bond strength requirement provided in CEB-FIP code. It was caused by the fact that bonded area at the bottom of horizontal reinforcement was significantly reduced by the poring water and laitance. In this specimen, the bond strength provided by bearing stress and wedging action of concrete was not fully observed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1349-1360
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• 2013

The post-tensioned anchorage zones of normal concrete have larger cross sections because of congested reinforcements to resist high bearing and bursting stresses. The high compressive and tensile strength of newly developed UHPC (Ultra High Performance Concrete) may reduce the cross sectional dimensions and simplify the reinforcement details, if used for post-tensioned members. The Finite Element Analysis was performed to evaluate the mechanical behavior of post-tensioned anchorage zones using UHPC without anchorage plates and confining reinforcements. The results show that the maximum bursting stresses are less than the values given in current design code without failure due to vertical cracks. The location of maximum bursting stresses were at 0.2 times of width of the models. The bursting force from FEA is less than that is obtained using simplified formular in Korean Bridge Design Code.

• Computational Structural Engineering
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• v.8 no.2
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• pp.73-84
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• 1995

The study summarized in this paper is concerned with the buckling of longitudinal bars in reinforced concrete columns with numerical analysis method. The objectives of this study are (1) to investigate the stress transfer mechanism between concrete and reinforcement and (2) to propose a modeling equation. The results give an acceptable agreement between the proposed modeling equation and published computer packages as follows; (1) the proposed equation is a possible of strain softening of concrete and buckling of reinforcement. (2) the buckling of longitudinal bar is mainly influenced by spacing of hoop and location of the bar

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.556-565
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• 2009

In this paper, we propose a CAD software framework to automatically generate a shop drawing. Shop drawing is to draw the geometric figures representing an arrangement of steel bars for a concrete building on its structural design, based on its construction specifications and the design rules, and its well-formed process lead to be automated. A key point of the design automation is to minimize the user interactions by automatically recognizing the design specifications and to finally generate the shape of the geometric figures. The graphic pipeline of the proposed framework consists of four stages; a specification DB, specification extraction, binding, and rendering. To effectively extract all specifications only for a figure from the DB and bind them to its shape, we use a hierarchical approach; the specifications are classified into three common, structural, and figure classes, and each attribute is extracted in design phases. Based on our framework, we implemented a specialized CAD for shop drawing using AutoCAD and could easily update it according to user's demands.

• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.123-130
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• 2010

In this study, mixed recycled coarse aggregate (RCA) was produced by mixing RCA from waste concrete in order to evaluate a new method of RCA production. Bond strength between reinforcing bars and RCA concrete was qualitatively evaluated as a part of continuous studies to establish design code of reinforced concrete structural members using recycled aggregate. For practical application, specimens were manufactured with the ready mix RCA concrete. Parameters investigated include: concrete compressive strength (i.e 21, 27 and 40 MPa), replacement levels (i.e 0, 30, 60 and 100%), bar position (i.e vertical and horizontal) and bar location (75 and 225 mm). For the pull-out test, each specimen was in the form of a cube, with each side of 150 mm in length and a deformed bar, 16 mm in diameter, was embedded in the center of each specimen. From the test results, the most of HT type specimen with compressive strength of 21 and 27 MPa showed lower bond strength than the ones provided in CEB-FIP and considered in reinforcement location factor ($\alpha\;=\;1.3$). It was reasoned that bonded area of top bar specimen was reduced at the soffit of reinforcement because of bleed water of fresh concrete. Therefore the reinforcement location factor in current KCI design code should be reviewed and modified.