• Journal of the Korea Institute of Building Construction
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• v.18 no.2
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• pp.99-107
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• 2018

The objective of the present study is to propose a reliable shape of supplementary V-ties in the section jacketing approach for seismic strengthening of reinforced concrete columns. A total of 24 pull-out specimens were prepared. The test parameters selected with regard to bond strength of V-ties were the shape of V-ties, embedment length of V-tie legs, and compressive strength of concrete. The measured bond strength of V-ties with different shapes were compared with that of the conventional V-ties and predictions using CEB-FIP equation. Ultimately, V-ties with pressed end-details at their legs could be recommended for the supplementary lateral reinforcement of strengthening columns with jacketing thickness less than the embedment length [= max (75mm, $6d_b$)] of conventional V-ties, where $d_b$ is the diameter of the reinforcing bar used for V-ties.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.253-254
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• 2021

In the field of construction, research on smart construction technology is being actively pursued as a measure to increase productivity and efficiency. The technology that links 3D scanning and BIM of smart construction technology is in the limelight as a technology for checking the state of buildings in the field of architecture. It is thought that these techniques will be of great help in solving problems when the amount of inspection targets is large, such as confirmation of the rebar arrangement intervals, and therefore a large number of human resources are required. Therefore, in this study, we would like to apply 3D scanning to rebar construction to confirm whether the rebar arrangement can be confirmed according to the design drawing. In the study, the wall rebar of the rebar placed at the actual construction site was directly scanned to extract data, and the rebar placing status was confirmed through type analysis. As a result of analyzing the reinforcing bar arrangement state based on the data obtained by 3D scanning, it was found that the technology can be utilized.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.133-142
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• 2013

The shear wall system with coupling beams has been known as an effective means for moderate and high rise buildings up to 40 stories, because this structural system can provide the enhanced lateral stiffness compared to individual shear walls. Typical reinforced concrete coupling beams have difficulties in construction due to complicated reinforcing work on site, and steel coupling beams also have disadvantages in economical point of view because of a large number of stiffeners required for its stability under lateral loading. To overcome these disadvantages in existing coupling beam systems, this study developed the prestressed composite coupling beam with discontinuous webs, which have improved constructability, economic feasibility, and reduced sectional size. The reversed cyclic loading test on two prestressed composite coupling beams with discontinuous webs having different shear reinforcement ratios have been conducted to investigate their structural performances, and test results showed that the proposed composite coupling beams had good seismic performances.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.3
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• pp.186-194
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• 2011

The reinforced concrete beam-column connections are in lack of constructability and are likely to show anchorage failure because of the complex details of joint regions. Under seismic loads, a destruction of the column or the beam-column joint leads to collapse of the whole structures. For this reason, the safety of structures has to be guaranteed by following procedures which are based on the strong column-weak beam design concept: 1) failure of beam by generating plastic hinge in the beam maintained a certain distance from the surface of column, 2) failure of column or beam-column joint. In this study, headed bars were used as longitudinal reinforcements of beam and joint reinforcements in order to improve the strength and constructability of joint and to relocate plastic hinge. The finite element analyses (FEAs) were performed to the reinforced concrete beam-column joints utilizing headed bar reinforcements. To verify the availability of the analysis models, the FEAs for experimental tests performed by previous researchers were conducted and compared with the experimental results. Additional variables are also considered to confirm the excellence of headed bars. Analysis results indicate that the constructability of beam-column connections can be improved by using headed bars for the full anchorage of longitudinal reinforcements of beam under similar structural performance. In addition, the plastic hinge was relocated to the intended place by using headed bars as joint reinforcements. Under cyclic displacement loading, the energy dissipation capacity and ultimate stress were increased and the decrease in stiffness was minimized.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.193-202
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• 2008

Seismic design for bridge columns of the current Korea Highway Bridge Design Specifications which adopt full ductility design concept results in reinforcement congestion problems in construction site. It is due to large amount of confining steel is required even for small ductility demand which is a normal case in low and moderate seismicity regions like Korean peninsular. Therefore a new seismic design method based on limited ductility concept was proposed, which is called ductility demand based design method. It uses the new confining steel design equation considering ductility demand and aspect ratio of the column as well as material strength. The purpose of this study is to verify safety of the ductility demand based design method by the confining steel design equation. Eighty nine circular column test results are selected and investigated in terms of ductility factor and its safety. The safety factor for the circular column test results ranges between 1.11 and 3.98, and the average is 1.90. In this paper, the basic concept and detailed design procedure of the ductility demand based design method are also introduced as well as the investigation of the safety with respect to the major variables in confining steel design.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.122-128
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• 2009

This study is to improve constructability of LB-DECK construction in site such as inconvenience of main and distribution bars in arrangements LB-DECK Panel which is work is applied to many bridges these days as a permanent formwork. So, the constructability is improved by changing the method of allocation of main reinforcing bar and distribution bar which is reviewed for improving efficiency of design and construction process among the suggested methods. The crack shapes, deflections, and strains under static load of the improvement of LB-DECK Panel are compared and analyzed to former LB-DECK Panel. As a result, 13% of strength compared to before the improvement of LB-DECK Panel, and 10% of strength is increased in the case of slab.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.66-71
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• 2019

In this paper, a study was conducted on the method of using GPR data to predict rebar thickness inside a facility. As shown in the cases of poor construction, such as the use of rebars below the domestic standard and the construction of reinforcement, information on rebar thickness can be found to be essential for precision safety diagnosis of structures. For this purpose, the B-scan data of GPR was obtained by gradually increasing the diameter of rebars by making specimen. Because the B-scan data of GPR is less visible, the data was converted into the heatmap image data through migration to increase the intuition of the data. In order to compare the results of application of commonly used B-scan data and heatmap data to CNN, this study extracted areas for rebars from B-scan and heatmap data respectively to build training and validation data, and applied CNN to the deployed data. As a result, better results were obtained for the heatmap data when compared with the B-scan data. This confirms that if GPR heatmap data are used, rebar thickness can be predicted with higher accuracy than when B-scan data is used, and the possibility of predicting rebar thickness inside a facility is verified.

• Journal of the Korea Concrete Institute
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• v.15 no.5
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• pp.705-714
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• 2003

Even though Korean peninsula is located in regions of moderate seismic risks, current seismic design provisions of the roadway bridge design code have adopted the AASHTO code which is based on the requirements for high seismic regions. The objective of this research is to investigate the seismic performance of circular reinforced concrete (RC) bridge piers with limited ductility, which may be desirable in low or moderate seismic regions, such as in Korea. Four test specimens were designed and constructed. The reference specimen was designed with longitudinal steel ratio as 1.01% and the confinement reinforcement ratio as 0.13% without considering earthquake, and three other test specimens were designed in accordance with a limited-ductility concept as 0.3% for the confinement steel ratio. This confinement ratio is 0.32 times of minimum lateral reinforcement specified in current seismic design provisions, and 2.3 times of lateral reinforcement required in nonseismic design provisions. The pseudo-dynamic test was carried out to evaluate the seismic performance of full-scale specimens in size of 1.2m diameter and 4.8m height. Judging from the experiment, the reference specimen was not satisfactory for the demand displacement ductility ${\mu}$=5.0, but three limited-ductility specimens appeared to have the displacement ductility of more than 5.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.171-178
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• 2008

The object of this study is to propose a rate of vibration increase in the analysis of temporary rail non-fixed in the vertical direction and characterize the nonlinear dynamic behavior of temporary rail while considering longitudinal and latitudinal load, vibration and lifting. The rate of vibration increase is proposed through measurement of an actual structure that is largely affected by loading and vibration of the superstructure. Dynamic behavior was additionally characterized by the dynamic response resulting from nonlinear dynamic finite element analysis with vehicle loading, including the rate of vibration increase. As a result, the rate of vibration increase by the vibration of an Auto Bar Machine is determined as 7% and the maximum stress in the analysis of the nonlinear rail is increased 14.5% over that of linear rail, and temporary rail is shown to be very sensitive to the velocity of the superstructure.

• Tunnel and Underground Space
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• v.13 no.2
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• pp.125-137
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• 2003

Field measurements were carried out in this study to investigate the behavior of cut and cover tunnel such as the distribution and the magnitude of the earth pressure during back fill process. Three kinds of measuring instruments, such as the earth pressure load cell, the concrete strain gauge and the reinforcing bar meter of embedded type in concrete structure were installed and measured. Earth pressure load cells measured the outside forces acting on the tunnel lining with radial directions. Three load cells were installed at the crown, the right and the left shoulder of the tunnel, respectively. Three sets of reinforcing bar meter were installed in the double reinforcements of the tunnel lining and their locations were the same with the position of the earth pressure load cells. Concrete strain gauge was installed only one site of the upper compressive part at the tunnel crown. Based on the measurements, the deformation and the earth pressure acting on the tunnel lining were investigated with the back fill process. Considerations on the validity of the field measurements were paid.