• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.172-178
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• 1995

보강평판은 평판에 각종 보강재를 용접등의 방법에 의해서 종방향, 횡방향, 경사 또는 임의의 방향으로 부착시켜 굽힘 및 비틀림 강성을 향상시킨 구조요소이다. 이러한 구조요소는 구조적 필요성이나 경량화 설계에 따라 선박의 deck, 철도 차량, 항공기 및 자동차 등의 각종 구조물에서 부하능력 및 경제성을 증대시키기 위하여 널리 사용되고 있고, 또한 자동차용 오일팬, 가전기기의 케이싱과 모터의 케이싱등에도 사용되고 있다. 최근 현장에서는 이러한 구조물의 진동 감소 및 방진 문제가 큰 관심사가 되고 있다. 본 논문은 정사각형 알루미늄 평판에 +자 형태의 Box Beam 보강재를 편면 보강하고 4변 자유단의 경계 조건을 설정하였다. 보강재는 유한요소 정식화 과정을 통하여 평판 요소에 등가시키고, 2차원의 평판 구조로 보강 평판을 모델링하고 구조해석 프로그램인 ANSYS를 이용하여 해석하였다. 실험은 Impact Test에 의해서 주파수 응답 함수(FRF)를 각 시편에 대해서 구하고 이를 해석의 고유진동수와 비교하였다. 그리고 보강재가 임의의 각도로 평판에 부착되었을 때 고유진동수의 변화와 진동 모드(mode shape)를 분석하였다.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.617-626
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• 2011

Seven post-tensioned lightweight concrete (LWC) beam specimens were tested under a symmetrical two-point top loading system. The parameters investigated were the amounts of mild longitudinal reinforcement and effective prestressing. The design compressive strength and dry density of the LWC tested were 30 MPa and 1,770 $kg/m^3$, respectively. Similar to post-tensioned normal weight concrete (NWC) beams, the crack propagation and stress increase of the unbonded tendons were significantly affected by the amounts of mild longitudinal reinforcement and effective prestressing. With the increase in the amounts of mild longitudinal reinforcement and effective prestressing, the serviceability and flexural capacity of the beams were enhanced whereas the stress increase in the unbonded tendons decreased. To control the crack width in post-tensioned LWC beams, a minimum amount of mild longitudinal reinforcement specified in ACI 318-08 provision is required. The flexural behavior of post-tensioned LWC beams and stress increase of the unbonded tendons could be rationally predicted by the proposed non-linear two-dimensional analysis. On the other hand, ACI 318-08 flexure provision was too conservative about the post-tensioned LWC beams.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.421-422
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• 2009

This study investigated the fatigue test of domestic CFRP Tendon and anchorages. Test results revealed that fatigue capacity of anchorages with swage-type and bond-type satisfied the specifications. In domestic CFRP Tendon, fatigue strength of 1 million and 2 million cycle showed 992, 871MPa, respectively.

• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.781-790
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• 2011

This paper contains the experimental results on strengthening effect of RC beams strengthened with NSM CFRP reinforcement and various strengthening details. A total of 14 beams have been tested to analyze strengthening effects of NSMR with various reinforcement details. Variables were cross-sectional shape of CFRP reinforcements, strengthening areas, grooves the number and location etc. Test results revealed that failure modes of NSMR showed two types. One was bond failure at interface between concrete and filler and the other was CFRP rupture. Also, failure mode of specimens with two grooves occurred premature bond failure because of superposition of failure surfaces at concrete around grooves. failure mode of MI specimens considered the equivalent section have changed bond failure to CFRP rupture and CFRP efficiency has improved 83% to 100%.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.171-179
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• 2002

This paper is a part of research series for the verification of the proposed Moon/Lim design equation. An analytical study was performed to examine the relation between the flexural behavior and the unbonded tendon stress of PSC members. The strain compatibility assumption was used in this study since previous studies showed that the stress variations of tendon had a close relation with the member displacements. The proposed equation has been developed with the same assumption of strain compatibility. Therefore the analytical procedure with the strain compatibility assumption was developed to compute the member displacements of previous tests. Then the analytical results were compared with tests results. The comparison showed that the strain compatibility assumption can be properly applicable to the design equation. Based on the analytical results, the relation between the tendon stress and the member flexural behavior at ultimate was examined. A parametric study also carried out with regard to the member displacements. As results, the parameters used for the proposed equation were proven to be proper for the computation of tendon stress.

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.903-910
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• 2005

In recent years, fiber reinforced polymer(FRP) plates have shown a great promise as an alternative to steel plates for reinforced concrete beam rehabilitation. Reinforced concrete beams strengthened with externally bonded FRP sheets to the tension face can exhibit ultimate flexural strengths several times greater than their original strength if their bond strength is enough. Debonding failure, however, may occur before the strengthened beam can achieve its enhanced flexural strength. The purpose of this paper is to investigate the debonding failure strength of FRP-strengthened reinforced concrete beams. An analytical procedure for calculating debonding load between concrete and strengthening FRP is presented. Based on the local bond stress-slip relationship in the previous studies, uniform bond stress is assumed on the effective bond length. The analytical expressions are developed from linear elastic theory and statistical analyses of experimantal results reported in the literature. The proposed method is verified by comparisons with experimental results reported in the previous researches.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.674-684
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• 2002

선박이 물품의 제하 및 적하를 위하여 컨테이너 부두에 접항시 선박의 케이슨과의 충돌에 의한 케이슨의 발생 응력을 파악함으로써 구조 안정성을 검토하였다. 선박이 일정 속도로 항만에 접항시 선박은 케이슨에 부착된 방충재와 충돌하게 된다. 케이슨에 부착된 방충재는 선박의 운동에너지를 흡수하여 케이슨으로 전달되는 전달 에너지를 최소화하여 케이슨의 구조물에 발행하는 응력을 최소화하도록 설계한다. (중략)

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.2083-2099
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• 1991

An experiment has been carried out to investigate the aerodynamic effect of surface roughness on the characteristics of the turbulent separation and reattaching flow downstream of a backward-facing step. The distributions of boundary layer parameters, forward-flow fraction and turbulent stresses in the region near the reattachment point are measured with a split film sensor. It is demonstrated that the streamwise distributions of the forward-flow fraction in the recirculation and reattachment regions are similar, independent of the roughness. The reattachment length is found to be only weakly affected by the roughness. It is also shown that the velocity profile on the rough surface approaches to that of the equilibrium turbulent boundary layer faster than that on the smooth surface in the redeveloping region after reattachment.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.4 s.70
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• pp.335-345
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• 2005

This paper concentrates on the nonlinear analysis of prestressed concrete (PSC) containment structures. Unlike a commercialized program which adopts the perfect bond assumption between concrete and tendon in the analysis of PSC structures, a numerical algorithm to consider the slip effect, simultaneously with the use of commercialized programs such as DIANA and ABAQUS, is introduced in this paper For bonded tendons, the apparent yield stress of an embedded tendon is determined from the bond slip relationship. And for unbonded tendons, Correction for the strength and stiffness of unbonded internal tendons is achieved on the basis of an iteration scheme derived from the slip behavior of tendon along the entire length. Finally, the developed algorithm is applied to two PSC containment structures of PWR and CANDU to verify its efficiency and applicability in simulating the structural behavior of large complex structures, and the obtained result shows that both containment structures represent the ultimate pressure capacity larger than about 3 times of the design pressure.

• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.143-153
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• 2003

New strengthening method based on Near Surface Mounted technique (NSM) is suggested, which can overcome the brittle nature of failure inherent to those reinforced concrete beams strengthened with FRP composite materials. The suggested technique secures ductile failure of reinforced concrete beams by having the strengthening Hybrid FRP rebars unbonded in parts. Experiments were performed in order to compare structural behaviors of strengthened beams with and without unbending along the Hybrid FRP rebars. Test results showed that only those beams strengthened by partially unbonded NSM failed in ductile manner. Theoretical expressions were derived for the minimum unbonded length of Hybrid FRP rebars with which ultimate strength of the reinforced concrete beam with partially unbonded NSM could be reached. The suggested partially unbonded NSM technique is expected to significantly improve the structural behavior of the strengthened beam with FRP composite materials.