• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.17-18
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• 2009

This research defined slip function using cracking behavior, bond characteristics and numerical analysis of cracking stabilized reinforced concrete member, and proposed a bond stres-slip model.

• Journal of the Korea Institute of Building Construction
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• v.15 no.5
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• pp.465-471
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• 2015

This study proposed V-shaped tie bar method as an alternative of internal cross-tie for reinforced concrete columns in order to enhance the constructability and confinement effectiveness of the lateral tie bars. A total of 35 pull-out specimens were prepared with the parameters of concrete compressive strength and bending angle and embedment length of the V-shaped bar to examine the bond stress-slip relationship of the V-shaped tie bar. The bond strength of the V-shaped tie bars with the bending angle not exceeding $60^{\circ}$ was higher than the predictions obtained from the equations of CEB-FIP provision. Considering the constructability and bond behavior of the V-shpaed tie bar, the bending angle and embedment length of such bar can be optimally recommended as $45^{\circ}$ and 6db, respectively, where db is the diameter of the tie bar.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.1 s.71
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• pp.15-25
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• 2006

The researches on the early-aged concrete hydration process and the techniques for the early-aged concrete crack control mainly have been focused and developed on the massive concretes in both experimental and numerical studies. However, those researches for relatively thin members such as the upper slab of the reinforced concrete rahmen bridge have nearly been attempted. In this study, a designing technique for crack controlling in the thin members of the early-aged reinforced concrete rahmen bridges based on measured temperature history, strength revelation model and sinkage model is proposed. A method of calculating the reinforcing bar area for crack controlling is also proposed and it is found that the distributing bars under the design loads become the main reinforcing bars in the temperature stress analysis of the early-aged reinforced concrete rahmen bridges. It is shown that the proposed analysis technique is able to use the design of crack control for the early-aged reinforced concrete rahmen bridge.

• 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.

• Magazine of the Korea Concrete Institute
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• v.3 no.3
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• pp.141-148
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• 1991

Investigations on the behavior of steel fiber reinforced high strength concrete beams subjected to predominant shear are accomplished to determine their diagonal shear strength including ultimate shear strength. The par¬ameters varied were the fiber volume fraction(Vf) of the steel-fibers and shear span to depth ratio(a/d). The test result show that diagonal shear strength and ultimate shear strength are increased significantly due to crack arrest mechamsm. Predictive equations are suggested for evaluating the diagonal cracking strength and ultimate shear strength of the fiber reinforced high strength concrete beams.

• Magazine of the Korea Concrete Institute
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• v.10 no.3
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• pp.117-124
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• 1998

본 연구는 고성능 철근콘크리트 보의 연성능력에 관한 실험이다. 실험변수로는인장철근비( )와 하중재하형태(1점가력과 2점가력)가 있다. 콘크리트의 실린더 압축강도가 800-900㎏/㎠, 슬럼프 20∼25㎝ 및 슬럼프 플로우가 60∼70㎝인 고성능 철근콘크리트 보의 휨 실험 결과,고성능 콘크리트는 일반강도 콘크리트보다 취성적인 성질을 나타냈으며, 이러한 성질은 고성능 콘크리트의 연성능력을 감소시켰다. 고성능철근콘크리트의 경우 등가응력블록 변수는 MacGregor블록이나 New Zealand 규준을 사용하는 것이 바람직하다. 또한, 극한 곡률을 구할때는 cu= 0.0042값을 사용하는 것이 타당하다고 사료된다. 고성능 철근콘크리트 보의 경우, 현재 ACI 규준의 철근비에서 허용하는 2 및 4 이상의 연성지수 확보는 각각 '/ 0.30 범위에서 정적하중 상태의 경우 철근비가 - '=0.60 b이하에서 가능하고 휨 부재의 모멘트 재분배를 위한 경우는 철근비를 - '=0.33 b이하로 낮추어야 할 것으로 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.391-402
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• 1994

One of the most important design concept for reinforced concrete structures is to achieve a ductile failure mode, and also moment redistribution for economic design is possible in case that adequate ductility is provided. Flexural ductility index is, therefore, used as a reference for possibility of moment redistribution as well as for prediction of flexural behavior of designed R.C. structures. Ductility index equations, however, provide approximate values due to the linear concrete compressive stress assumption at the tension steel yielding state. Theoretically more exact ductility index is calculated by a numerical analysis with the realistic stress-strain curves for concrete and steel to be compared with the result from tire ductility index equations. Variation of ductility index for the selected variables and the reasonable maximum tension steel ratio for doubly reinforced section are investigated. A moment-curvature curve model is also proposed for future research on moment redistribution.

• Magazine of the Korea Concrete Institute
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• v.2 no.4
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• pp.99-107
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• 1990

The transfer of forces across the interface by bond between concrete and steel is of fundamentul importance to many aspects of reinforced concrete behavior. Bond stress-slip relationships were studied using a symmetri¬cal tension test specimen. This type of test is intended to simulate conditions in the tension zone of a concrete beam between primary cracks and below the neutral axis. These relationships between local bond stress and local slip are found to be quite different at different locations along the bar. The bond behavior under cyclic lo¬ading is also studied in the present study, and the increase of bond slip and steel strains is clarified from those tests.

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.993-1000
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• 2005

Various types of FRP materials have been applied for structural strengthening of RC beams in various forms. When CFRP plates are used, a premature failure used to occur before enough strengthening effect appears. This is primarily due to the rip-off of CFRP Plate attached on RC beams. Despite of numerous studies on the rip-off failure of externally strengthened RC beams, its failure mechanism is not definitely clarified yet. Investigations from literatures have shown that the rip-off failure is dependant on the vertical and shear stresses at the level of main reinforcements in RC beams. This study suggests an analytical model to Investigate the rip-off failure load based on the stress states at the level of main reinforcements. The proposed model is relatively simple and produces very comparable results to the test data. It is believed that the proposed model can be successfully used to provide more information on the rip-off failure mechanisms and its prevention.

• 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.