• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.1 s.47
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• pp.41-49
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• 2006

Through the 1982 Urahawa-ohi and the 1995 Kobe earthquakes, a number of bridge columns were observed to develop a flexural-shear failure due to the bond slip as a consequence of premature termination of the column longitudinal reinforcement. Because the seismic behavior of RC bridge piers is largely dependent on the performance of the plastic hinge legion of RC bridge piers, it is desirable that the seismic capacity of RC bridge pier is to evaluate as a curvature ductility. The provision for the lap splice of longitudinal steel was not specified in KHBDS(Korea Highway Bridge Design Specification) before the implementation of 1992 seismic design code, but the lap splice of not more than 50%, longitudinal reinforcement was newly allowed in the 2005 version of the KHBDS. The objective of this research is to investigate the distribution and ductility of the curvature of RC bridge column with the lap splice of longitudinal reinforcement in the plastic hinge legion. Six (6) specimens were made in 600 mm diameter with an aspect ratio of 2.5 or 3.5. These piers were cyclically subjected to the quasi-static loads with the uniform axial load of $P=0.1f_{ck}A_g$. According to the slip failure of longitudinal steels of the lap spliced specimen by cyclic loads, the curvatures of the lower and upper parts of the lap spliced region were bigger and smaller than the corresponding paris of the specimen without a lap splice, respectively. Therefore, the damage of the lap spliced test column was concentrated almost on the lower part of the lap spliced region, that appeared io be failed in flexure.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.6
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• pp.1-12
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• 2008

As internal and external seismic experiment results, the seismic performance of RC bridge piers is largely dependent on the ratio of lap-spliced bars to all longitudinal reinforcing bars in plastic hinge regions, and confining effects of transverse reinforcements. Capacity and displacement ductility of non-seismically designed existing RC piers are reduced by lap splices in plastic hinge regions. The provision for the lap splice of longitudinal reinforcing bars was not specified in KBDS (Korean Bridge Design Specifications) before the implementation of 1992 seismic design code, but the ratio of lap-spliced bars to all longitudinal reinforcing bars in plastic hinge regions is restricted to 50% in the 2005 version of KBDS. This paper presents a seismic assessment of RC piers at lap-splicing ratios of 0%, 50%, and 100%. Through a comparison of experimental and analytic results of RC piers, we introduce an appropriate ultimate strain of confined concrete in plastic hinge regions with lap-splices, and propose a method for estimating displacement ductility ratios of non-seismically designed existing RC piers using fiber element analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.3
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• pp.31-38
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• 2003

Lap splices were located in the plastic hinge region of most bridge piers that were constructed before the adoption of the seismic design provision of Korea Highway Design Specification on 1992. But sudden brittle failure of lap splices may occur under inelastic cyclic loading. The purpose of this study is to analytically predict nonlinear hysteretic behavior and ductility capacity of reinforced concrete bridge piers with lap splices under cyclic loading. For this purpose, a nonlinear analysis program, RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology) is used. Lap spliced bar element is developed to predict behaviors of lap spliced bar. Maximum bar stress and slip of lap spliced bar is also considered, The proposed numerical method for seismic performance evaluation of reinforced concrete bridge piers with lap splices is verified by comparison with reliable experimental results.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.685-692
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• 2020

In this study, the experimental and analytical study were performed on the location of longitudinal cracks in the middle of underground box structures. The location where the longitudinal cracking occurred was investigated that the overlapping joint of the rebar and the section of maximum tensile stress generated. Using the finite element analysis, the strength reduction ratio of the rebar was estimated by lack of overlap joint length. As the result of adequacy investigation for the length of the overlap joint presented in the design criteria, it was analytically proved that the lack of the overlap joint length could be cause the decreasing cross-sectional force and concrete cracking. As the result of this study, the adequacy of the overlapping criterion in the current design criteria was confirmed based on the finite element analysis and actual field case. In the case of overlapping joints installed in inappropriate position, it was considered that a long term crack control would be need to ensure the sufficient safety factor for the designed cross-sectional force.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.111-120
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• 2012

This paper is a report about lap splice performance of rebar embedded in the strain-hardening cement-based composites (SHCCs) under monotonic and repeated tension loading. Ten mix proportions of cement-based composites such as SHCCs and normal concrete were investigated. The study parameters are comprised of (1) types of reinforcing fibers (polyethylene and steel fiber), (2) replacement levels of expansive admixture (EXA, 0% and 10%), and (3) compressive strength (30 and 100 MPa) of cement-based composites. Lap splice lengths (ld) of rebars in SHCC materials and normal concrete were 60% and 100% of splice length calculated by code requirements for structural concrete, respectively. Test results indicated that SHCCs materials can lead to enhancements in the lap splice performance of embedded rebar. All of the fiber reinforcement conditions (PE-SHCC and PESF-SHCC) considered in this study produced considerable improvements in the tensile strength, cracking behavior, and bond strength of lap-spliced rebar. Furthermore, adding EXA to SHCC matrix improved the tensile lap splice performance of rebar in SHCC materials. However, for controlling crack behavior, the performance of PE-SHCC was better than that of PESF-SHCC due to its mechanical properties. This study demonstrated an effective approach for reducing required development length of lap spliced rebar by using SHCC materials.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.59-67
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• 2014

In tension lap splices of straight deformed bars, KCI Code (KCI2012) and ACI Code (ACI318-11) requires that the lap lengths for class B splice are 1.3 times as development length. KCI2012 contains development length provisions for the use of headed deformed bars in tension and does not allow their tension lap splices. The purpose of this experimental study is to evaluate that KCI2012 equation for the development length, $l_{dt}$, of headed bars can be used to calculate the lap length, $l_s$, of headed deformed bars in grade SD400 and SD500, having specified yield strength of 400 and 500 MPa. Test results showed that specimens with $l_s$ equal to $1.3l_{dt}$ had maximum flexural strengths as 1.16~1.31 times as the nominal flexural strengths, flexural failure mode, and ductility. These observations indicate that $1.3l_{dt}$ is suitable to the tensile lap length of headed deformed bars in grade SD400 and SD500.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.3
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• pp.287-295
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• 2023

The collapse of bridges due to earthquakes results in many casualties and property damages. Thus, accurate prediction and preparation are required for the behavior of bridges during earthquakes. In particular, columns play an important role in the seismic behavior of bridges. The risk of collapse due to an earthquake increases when there is a problem of the insufficient lap splice in the column. In this study, to analyze the characteristics of the lap splice in the column, a numerical model was defined for the insufficient lap-spliced columns and verified using experimental data. The developed column model was applied to a commonly used RC slab bridge. Nonlinear static analysis for the column was performed to evaluate the change in the performance of the column according to the lap-spliced length. In addition, this study assessed the effect of the lap-spliced length on the seismic fragility analysis.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.247-255
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• 2022

In this paper, a bending test was conducted on beams with two lap splice details when the effective depth of tensile high strength headed bars overlapped is the same and different. Through bending test, the lap splice performance of the high-strength headed bars was evaluated, and the applicability of the KDS-2021 design formula was evaluated. In the LS specimens with lap splice details where the high strength bars had the same effective depth, all specimens with 1.3 times or more of the development length of the KDS-2021 equation and 1 times or more of the ACI318-19 had the flexural failure mode after the ductile behavior to ensure sufficient lap splice performance. For specimens with details of lap joints between headed bars with different effective depth, when lap splice length is calculated by the KDS-2021 formula, the flexural stress may be transmitted so that the flexural strength at the cross section with the large effective depth and the cross section with the small effective depth becomes similar.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.10a
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• pp.833-835
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• 2018

최근 돼지의 상태 및 행동을 분석하기 위하여 카메라를 이용한 돈사 내 돼지에 대한 감시 시스템에 관한 연구가 활발히 진행되고 있다. 특히, 대부분의 국내 돈사는 돼지를 밀집 사육하는 방식이기 때문에 돼지의 겹침이 빈번하게 발생한다. 돼지들 간 겹침이 발생하게 되면 한 마리의 돼지로 인식하는 문제가 있기 때문에 개별 돼지의 탐지 및 추적이 불가능하다. 본 논문에서는 깊이 정보 영상을 이용하여 겹침 돼지를 탐지하고 개별 돼지로 특정 하는 방법을 제안한다. 즉, 임계 값을 설정하여 돼지와 배경을 분리함으로써 돼지들의 영역을 탐지하고, 탐지된 돼지들의 영역 크기를 비교하여 겹침 돼지를 탐지한다. 이후 탐지된 겹침 돼지의 깊이 정보를 이용하여 겹침 돼지를 두 마리의 돼지로 특정한다. 실험 결과, 겹침 돼지를 탐지하였고 탐지된 겹침 돼지에 대하여 각각 서 있는 돼지와 누워 있는 돼지로 특정 하였다.

• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.687-696
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• 2004

It has been known that practically unavoidable lap splices of longitudinal reinforcement in the plastic hinge region have a bad effect on the seismic performance of reinforced concrete bridge columns. Lap splices were usually located in the plastic hinge region of most bridge columns designed before the implementation of the new seismic design provisions of 1992 Korea Bridge Design specification. The objective of this research is to evaluate the seismic performance of full-sized reinforced concrete bridge piers with lap splice of longitudinal reinforcement in the plastic hinge region, and to develop an appropriate lateral confinement concept of RC bridge columns with lap-spliced longitudinal steels in low or moderate seismicity region. Eight test specimens in the aspect ratio of 4.0 were made with three types of lap splicing, two levels of confinement steel ratios and two types of tie configurations. It was confirmed from the Quasi-Static test that displacement ductility ratios were significantly reduced for nonseismic test columns with lap spliced longitudinal steels but were satisfied the seismic requirement for limited ductile design specimens. As a conclusion, pertinent lateral confinement content was proposed for the seismic. performance of RC bridge piers with $50\%$ lap-spliced longitudinal reinforcing steels in low or moderate seismicity region.