• Proceeding of EDISON Challenge
• /
• 2017.03a
• /
• pp.180-186
• /
• 2017

거의 모든 철근콘크리트 구조물의 보강 강재는 분할된 두개 이상의 철근으로 제작되며, 이러한 철근의 분할 부위를 평행한 두개의 철근으로 겹쳐 설치하는 것을 겹이음(Lap splice)이라고 부른다. 일반적으로 겹이음 설계는 무리없이 설계 강도를 만족시킬 뿐만 아니라 충분히 긴 수명을 가진다. 그러나 550MPa 이상의 항복 강도를 갖는 철근이나 인장 부재의 설계, 초고성능 섬유보강 콘크리트의 보강재 설계와 같은 경우, 현행 철근 겹이음 설계만으로는 그 한계가 발생한다. 따라서 현 겹이음 설계는 관련 기준의 추가와 구조적인 측면에서의 개선이 필요할 것으로 보여지며, 이를 위해 적절한 실험과 데이터 분석, 그리고 컴퓨터를 이용한 새로운 설계 모델의 개발 등의 과정이 필요할 것으로 여겨진다. 본 연구는 균질하지 않은 물성의 파괴를 다루는 RBSN(Rigid-Body-Spring Networks)을 통한 컴퓨터 시뮬레이션으로 더 효과적이고 정확한 겹이음 설계가 가능할 것으로 판단하고, 실제 모델링으로 그 가능성을 검증하였다.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.4
• /
• pp.126-132
• /
• 2018

As means to increase the use of concrete with recycled coarse aggregate (RCA), this study aims to evaluate the applicability for flexural strengthening of reinforced concrete beam with high-strength concretes and RCA on which FRP plates, used for repair and strengthening of old and low-durability reinforced concrete structures, is applied. In order to increase the adhesive force of epoxy and FRP plate, FRP plate was installed according to Near-Surface-Mounted (NSM) method. 12 specimens were manufactured using substitution rate of RCA (30%), concrete strengths (40MPa, 60MPa), diameters of deformed bar (D10, D13), and types of FRP plate (AFRP, CFRP) as variables to analyse flexural performance according to FRP plate and substitution rate of recycled aggregate. As a result, in all specimens, specimens strengthened by FRP plate showed a maximum of 17% increase in performance compared to specimens without FRP plate and strengthening performance of CFRP was found to be higher than AFRP. When modulus of rupture was used, the value of cracking moment was similar to that of the reference equation. As bending moment of some specimens strengthened by FRP plate failed to satisfy the criteria of KCI 2012 and ACI 440-2R, additional experiment is deemed as necessary.

• Journal of the Korea Concrete Institute
• /
• v.15 no.6
• /
• pp.811-819
• /
• 2003

The corrosion of steel reinforcing bar(re-bar) has been the major cause of the reinforced concrete deterioration. FRP(Fiber-reinforced polymer) reinforcing bar has emerged as one of the most promising and affordable solutions to the corrosion problems of steel reinforcement in structural concrete. However, FRP re-bar is pone to deteriorate due to other degradation mechanisms than those for steel. The high alkalinity of concrete, for instance, is a possible degradation source. Other potentially FRP re-bar aggressive environments are sea water, acid solution and fresh water/moisture. In this study long-term durability performance of FRP re-bar were evaluated. The mechanical and durability properties of two type of CFRP-, GFRP re-bar and one type of AFRP re-bar were investigated; the FRP re-bars were subjected to alkaline solution acid solution, salt solution and deionized water. The mechanical and durability properties were investigated by performing tensile, compressive and short beam tests. Experimental results confirmed the desirable resistance of FRP re-bar to aggressive chemical environment.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.3
• /
• pp.1-9
• /
• 2014

Improving the earthquake resistance of buildings through seismic retrofitting using steel braces can result in brittle failure at the connection between the brace and the building, as well as buckling failure of the braces. In this study, a non-compression cross-bracing system using the Carbon Fiber Composite Cable (CFCC), which consists of CFCC bracing and bolt connection was proposed to replace the conventional steel bracing. This paper presented the seismic resistance of a reinforced concrete frame strengthened using CFCC X-bracing. Cyclic loading tests were carried out, and the maximum load carrying capacity and ductility were investigated, together with hysteresis of the lateral load-drift relations. Test results revealed that the CFCC X-bracing system installed RC frames enhanced markedly the strength capacity and no buckling failure of the bracing was observed.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.5
• /
• pp.51-58
• /
• 2014

This paper presents a fire exposure test result to evaluate fire resistance capacity of retrofit method using FRP (Fiber Reinforced Polymer) in reinforcement concrete structure. Especially, this paper focused on near-surface-mounted retrofit method; FRP is mounted into the groove after making a groove in concrete. In the test, main parameters are retrofit method and materials for fire proofing. Spray type of perlite and board type of calcium silicate were considered as external fire proof on surface while particle of calcium silicate and polymer mortar as internal one in groove. By increasing the temperature of inside heating furnace, the transfer of temperature from surface of fire proofing material to groove in specimen was measured. As a result, fire proofing using the board of calcium silicate was more effective to delay the heat transfer from outside than spraying with perlite. It was found that the fire proofing could resist outside temperature of $820^{\circ}C$ at maximum to keep the temperature of epoxy below glass transit temperature (GTT).

• 한국방재학회:학술대회논문집
• /
• 2011.02a
• /
• pp.90-90
• /
• 2011

최근 전 세계적으로 지진의 발생 빈도가 증가하며 그 규모도 점차 커지는 경향을 보이고 있다. 대형지진의 발생 시 저층 구조물의 붕괴로 인한 인명 및 사회, 경제적 피해가 두드러짐에 따라 기존 저층 구조물의 내진보강기법에 관한 연구가 활발히 진행 중인 추세이다. 우리나라의 경우 강도증가형 내진보강공법이 주를 이루고 있어 다양한 내진보강기법의 개발 및 적용이 필요한 실정이다. 따라서 본 연구에서는 지진입력하중 저감형 내진보강기법으로서 강재댐퍼시스템을 제안하여 구조적 성능을 파악하고, 이를 적용한 보강 실험체와 비보강 실험체를 제작하여 정적가력실험을 통하여 그 성능을 비교하였다. 제안된 강재댐퍼시스템은 입력에너지를 소산시키는 내부의 슬릿형 댐퍼와 이를 지지하는 기둥 및 외부 프레임으로 구성되며, 내부 댐퍼는 먼저 항복하여 에너지를 소산시키기 위하여 지지기둥 및 프레임에 사용된 강재보다 강성 및 강도가 적게 계획되었다. 강재댐퍼의 성능실험 결과, 비교적 안정적 거동을 하며, 강성과 강도 및 에너지 흡수능력이 우수하게 나타났다. 보강 및 비보강 실험체의 골조는 기존 학교 건축물의 표준도면을 기준으로 하여 골조의 일부를 대상으로 60% 축소율을 적용하여 계획하였으며, 보강 실험체는 미리 제작된 강재댐퍼시스템을 골조 내에 설치하여 에폭시 주입법으로 부착시공 하였다. 보강 및 비보강 골조 실험체의 정적가력 실험결과 비보강 실험체는 기둥의 휨 항복 후 변형의 증가에 따라 휨 및 전단 균열이 증가하면서 최종적으로 기둥이 전단파괴 되었으며, 보강 실험체는 비보강 실험체에 비하여 기둥 및 보의 균열이 적고, 골조에 골고루 분포되어 파괴 규모가 감소하였다. 최대 강도면에서 보강 실험체는 비보강 실험체에 비하여 약 3.4배 우수하였으며, 초기강성은 약 7배 가량 유리한 것으로 평가되어 제안된 강재댐퍼시스템이 강도면에서 우수한 성능을 나타냄을 알 수 있었다. 또한 두 실험체의 기둥 주근 및 띠철근의 변형률을 비교한 결과, 비보강 실험체는 대부분의 철근이 항복하여 큰 변형을 일으킨 반면, 보강실험체에서는 철근의 항복현상이 나타나지 않았고 댐퍼가 항복을 하면서 큰 변형을 일으켰다. 이를 통해 지진하중 입력 시 댐퍼에서 입력 에너지를 흡수하여 큰 하중을 부담하며, 기존의 구조부재에는 입력 에너지가 낮아 손상이 보다 적게 발생함을 확인하였다.

• Journal of the Korea Concrete Institute
• /
• v.24 no.4
• /
• pp.407-414
• /
• 2012

The purpose of this study is to experimentally investigate the shear behavior of reinforced concrete beams embedded with GFRP (glass fiber reinforced polymer) plate with openings. In this study, the parameters include the shape of reinforcement, reinforcement area, and thickness and width of reinforcements. The test was performed on 9 specimens with shear spanto-depth ratio of 2.8. When the reinforcement area was varied, the GFRP plate showed 3.6 times greater shear strength than steel stirrup. The test result showed that shear strength increased as reinforcement area increased. Also, when the shape of a parallelogram GFRP plate was used, it showed higher shear strength than that with rectangular shape. Effect of thickness and width of reinforcement showed that shear capacity increased as width increased. For a comparison study, a calculation of the shear strength of reinforced beams with GFRP plate based on the ACI 318M-08 was compared with the test results. The test results were compared with the maximum shear reinforcement areas required by ACI 318M-08, CSA-04, and EC2-02 provision.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.1
• /
• pp.13-22
• /
• 2015

In this study, a new RCSF (Reinforced Concrete Steel Frame) external connection method is proposed for seismic strengthening of medium-and low-rise reinforced concrete buildings. The RCSF method, proposed in this study, is capable of carrying out the seismic retrofitting construction while residents can live inside structures. The method is one of the strength design approach by retrofit which can easily increase the ultimate lateral load capacity of concrete buildings controlled by shear. The pseudo-dynamic test, designed using a existing school building in Korea, was carried out in order to verify the seismic strengthening effects of the proposed method in terms of the maximum load carrying capacity and ductility. Test results revealed that the proposed RCSF strengthening method installed in RC frame enhanced conspicuously the strength and displacement capacities, and the method can resist markedly under the large scaled earthquake intensity level.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.3
• /
• pp.135-146
• /
• 2008

In this study, the effect of epoxy mortar panel as the shear strengthening material of reinforced concrete beam is investigated by loading test. The main variables are the kind of strengthening material, the amount of reinforcement and the spacing of CFS(Carbon Fiber Sheet) stirrups. The design method to use epoxy mortar panel as shear strengthening of reinforced concrete beam took the shear capacity as the form of the sum of $V_c$, $V_s$, $V_{sheet}$ and $V_p$. By making a comparison between the values calculated by the proposed shear strength prediction formula and those from the loading test results, the mean value was 1.10 and the standard deviation was 8.16%.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.4
• /
• pp.41-49
• /
• 2014

In this study, experimental research was carried out to evaluate the structural performance of the reinforced concrete beam using hybrid retrofitting with two materials (groove and embedding FRP rod, CFRP sheet) in existing reinforced concrete buildings. Seven reinforced concrete beams, retrofitted groove and embedding FRP rod (NER series) and groove and embedding FRP rod with CFRP sheet (NERL series), and standard specimen (NBS) were constructed and tested under monotonic loading. Design parameters of test specimens are the amount of groove and embedding FRP rod and lapping CFRP sheet. Test results showed that the maximum load carrying capacity of specimens with groove and embedding FRP rod and groove and embedding FRP rod with CFRP sheet (NERL series) were increased the by 12~46% and 22~77% respectively in comparison with the standard specimen NBS. Test specimens NER series were failed with the adhesion slip and concrete cover separation. And test specimens NERL series were failed with the adhesion slip due to the confining effect of lapping CFRP sheet.