• 한국해양공학회지
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• 제16권5호
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• pp.49-55
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• 2002

The compression anchor is characterized by decrement of progressive failure, simple site work, economy and durability compared with tension anchor. In this paper, compression anchor is analysed through the laboratory element tests. The formula to be estimate the grout strength in fixed part of compression anchor and the effective reinforcement method for several types of soil were suggested. The following conclusions were made from this study : (1) A formula, which is able to calculate the grout strength in the fixed part of the compression anchor, is suggested. (2) The strength increment ratios( $R_{si}$) are 100％, 132％, 147％, 217％ according to the reinforcement method of grout. The reinforcement method is Non, Outside spiral, Inside-Outside spiral, Steel pipe, respectively. (3) The strength increment ratios( $R_{si}$) by reinforcing can be 8.23 times the strength increment effect according to the reinforcement types and ground confining pressure. (4) The steel pipe reinforcement is most effective in decomposed soil while, in the case of hard rock ground, high confining pressure is exerted on the grout, so there is no need to use reinforcements.

• Earthquakes and Structures
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• 제23권3호
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• pp.221-229
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• 2022

The external post-tension technique is one of the best strengthening methods for reinforcement and improvement of the various steel structures and substructure components such as beams. In the present work, the load carrying capacity of the post-tensioned tapered steel beams with external shape memory alloy (SMA) tendons are studied. 3D nonlinear finite element method with ABAQUS software is used to determine the effects of the increase in the flexural strength, and the improvement of the load carrying capacity. The effect of the different parameters, such as geometrical characteristics and the post-tension force applied to the tendons are also studied in this research. The results reveal that the external post-tension with SMA tendons in comparison with the steel tendons causes a significant improvement of the loading capacity. According to this, using SMA tendon for the reinforcement of the tapered beams causes a decrease in weight of these structures and as a consequence causes economic benefits for their application. This method can be used extensively for steel beams due to low executive costs and simplicity of the operation for post-tension.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.897-902
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• 2001

Recently, structure performance is maximized by using high strength concrete. In design of structure, concrete need combination with reinforcement, but use of common strength reinforcement make member complex bar placement, so high strength concrete members require increased strength reinforcement. If common strength reinforcement replaced by equal tension area of high strength reinforcement, reinforcement ratio increase and brittle failure of member may occur by material change. So, adequate upper limit of strength ratio is required to affirm ductile behavior in application of high strength reinforcement. In this study, ductility behavior was analysed by factor of reinforcement ratio, strength of concrete and reinforcement. The result indicate that ductile failure is shown under 0.35 $\rho_{b}$ in any reinforcement strength of same section and high strength concrete of 800kg/$cm^{2}$ used commonly is compatible with reinforcement of 5500kg/$cm^{2}$.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.197-200
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• 2005

This paper presents an analytical model for evaluation of Tension Stiffening Effect by actual Bond-Slip relationships between the reinforcement and the surrounding concrete. The presence of longitudinal splitting cracks was found to significantly after the tension stiffening. The model is applied to the longitudinal splittings cracks and derived to Tension stiffening model. The predicted values are shown to be in good agreement with the experimentally measured data.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.387-390
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• 2005

Reinforcement corrosion is the principal cause of deterioration of reinforced concrete. It is to be expected that loss of bond between concrete and tension reinforcement would lead to a reduction in shear strength of RC beams designed to fail in shear. This paper presents results of a FE analysis study to evaluate the shear strength of RC beams with exposed reinforcement represented the limiting condition of bond loss.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.81-84
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• 2008

The purposes of this study are to verify a reasonable model of material characteristic and to propose a rational model of reinforcement characteristic considering monotonic and cyclic loading about manufactured reinforcing steel in Korea. Longitudinal reinforcements of the plastic hinge region were behaved tensile deformation and compressional deformation by direction of lateral loading. However Confinement steels were behaved only tensile deformation by lateral loading. Transverse steels were laid the state of tension in the lateral loading of time, and they were laid state that stress is zero when it was removed lateral load. The tests for cyclic tension loading were performed for test variable as yield strength and reinforcement bar sizes. It was estimated that the total strain energy per unit volume was 74 $MJ/m^3$. The modified ultimate concrete compression strain model was proposed based on experimental study of cyclic tension test for manufactured reinforcing steel in Korea.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.879-884
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• 2000

In this study, an experimental work is conducted to evaluate the bond performance between reinforcing bars and surrounding concrete in a lapped splice. The major variable of this test is a transverse reinforcement in lap-spliced tension reinforcing bars. The test results indicate that the bond strength per unit splice length increases with an increase in the transverse reinforcement factor $K_{\alpha}$. The specimens taken less than (c+$K_{tr}$)/$d_b$=3.0 tend to be very brittle at failure. But the specimens taken longer than (c+$K_{tr}$)/$d_b$=3.0 tend to be somewhat ductile at failure.

• 한국구조물진단유지관리공학회 논문집
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• 제25권1호
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• pp.1-6
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• 2021

콘크리트 구조물은 재료의 열화나 초과된 하중 및 환경적 요인에 의해 점차 노후화 되며 그 성능이 감소하여 구조물의 사용성 및 안전성에 영향을 미치게 된다. 노후 교량의 보강 공법 중 외부긴장 공법이 널리 사용 중이지만, 노후도에 따른 보강 효과 및 영향 규명은 미흡한 실정이다. 따라서 이 연구에서는 구조물의 노후도를 콘크리트 압축강도 및 인장철근량의 감소로 가정하고 노후도에 따른 외부긴장 공법의 보강 효과를 확인하기 위해 무보강 및 외부긴장 공법을 적용한 실험체의 4점 재하실험을 수행하여 보강 여부에 따른 거동을 분석하고 보강 효과를 확인하였다. 실험 결과 정착구의 조기 탈락에 따른 극한 상태의 보강량을 확인하기 어려웠으며, 이에 따라 외부긴장 보강 공법의 적용 시 앵커 볼트에 관한 규정 준수가 필요하다. 외부긴장 보강 여부에 따라 균열하중 및 항복하중이 증가하였으나, 균열 이전에는 보강 전, 후의 강성이 유사하여 보강 효과를 확인하긴 어려웠다.

• Structural Engineering and Mechanics
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• 제34권2호
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• pp.189-211
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• 2010

The behaviour of a reinforced concrete tension member is governed by the contribution of concrete between cracks, tension stiffening effect. Under highly repeated loading, this contribution is progressively reduced and the member response approximates that given by the fully cracked member. When focusing on the unloaded state, experiments show deformations larger than those of the naked reinforcement. This has been referred to as negative tension stiffening and is due to the fact that concrete carries compressive stresses along the crack spacing, even thought the tie is subjected to an external tensile force. In this paper a cycle-dependent approach is presented to reproduce the behaviour of the axially loaded tension member, paying attention to the negative tension stiffening contribution. The interaction of cyclic bond degradation and time-dependent effects of concrete is investigated. Finally, some practical diagrams are given to account for the negative tension stiffening effect in reinforced concrete elements.

• 콘크리트학회논문집
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• 제21권4호
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• pp.389-400
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• 2009

현행 기준식에 따르면 초고강도 콘크리트에서는 철근 인장이음길이보다 압축이음길이가 더 길어지는 현상 이 발생된다. 횡보강근의 영향을 반영하면 이러한 경향은 더욱 심화된다. 실제 구조물에서 반드시 존재하는 횡보강근과 철근 지름의 영향을 40, 60 MPa 콘크리트에 대한 압축이음 실험을 통해 강도와 거동 특성을 분석하였다. 지름 22, 29 mm 에 대한 실험 결과 철근 지름의 영향은 없는 것으로 나타났다. 가는 지름의 철근에서는 이음강도의 증진이 기대될 수 있으나, 압축철근에는 주로 큰 지름의 철근이 사용되므로 압축이음에서는 철근 지름의 효과를 고려할 필요가 없을 것 으로 판단된다. 횡보강근이 있는 압축이음강도는 현행 설계기준과 비교할 때 100% 이상 크므로 횡보강근을 고려한 새 로운 설계기준식의 정립이 필요하다. 지압은 이음 단부에 배근된 횡보강근에 의해서만 강도가 향상되며, 이음구간에 배 근된 횡보강근에는 무관하다. 횡보강근량이 많을수록 부착에 의해 발현되는 강도는 거의 선형적으로 증가하며, 이음단 부에만 횡보강근을 배근해도 부착강도가 6% 향상되었다. 횡보강근이 배근된 경우 부착에 의해 발현되는 강도는 인장이 음에 비해 동등하거나 더 낮아지므로, 인장이음에 비해 압축이음의 강도 증진은 단부 지압 효과로만 설명될 수 있다.