• 대한토목학회논문집
• /
• 제28권6A호
• /
• pp.809-817
• /
• 2008

최근 사용되고 있은 구조물의 보강 방법 중 내력 및 사용성 향상효과가 타 공법에 비해 월등한 외부 긴장공법이 많이 사용되고 있다. 그러나 외부 긴장재로 보강된 구조물에 대하여 반복하중에 의한 피로 성능에 대한 평가가 부족하고 이에 대한 연구도 매우 부족한 실정이다. 따라서 본 연구에서는 FRP 긴장재로 외부 보강된 철근콘크리트 보의 반복하중에 따른 피로거동 특성을 분석함으로써 외부 긴장공법의 안전성 및 타당성을 평가하고자 하였다. 본 실험연구에서는 비교 변수로 외부 긴장재의 종류(FRP 긴장재, Steel 긴장재)와 하중범위를 채택하여 실험을 실시하였다. 하중은 FRP 보강 시험체의 항복강도를 기준으로 최소하중을 50%로 삼고 최대하중을 70~85%로 변경하여 4점 재하방식으로 sine파를 이용하여 3Hz의 주기로 실험을 실시하였다. FRP 긴장재로 외부 보강된 철근콘크리트 보에 대한 피로 실험연구 결과로부터 FRP 외부 긴장 공법은 FRP 긴장재, deviator에서의 절곡부, 정착장치 등에서 피로에 대한 충분한 안전성이 확인되었다.

• Structural Engineering and Mechanics
• /
• 제4권2호
• /
• pp.177-190
• /
• 1996

A method to numerically evaluate the behaviour of single span beams, prestressed with external tendons and symmetrically loaded is presented. This algorithm, based on the Finite Difference Method, includes second order effects and large displacements in an attempt to more fully understand the behaviour of the beam up to collapse. The numerical technique discussed is particularly appropriate for the analysis of R.C. and P.C. beams rehabilitated or strengthened by means of external prestressing but it is reliable for the analysis of new beams as well.

• 콘크리트학회논문집
• /
• 제11권6호
• /
• pp.13-24
• /
• 1999

The external, unbonded prestressed concrete(PSC) members exhibit very different structural behavior from that of internal bonded PSC members because of eccentricity change and slip occurrence during loading process. The purpose of the present study is to propose the ultimate failure stresses of prestressing (PS) steels for those external unbonded PSC members. To this end, a comprehensive analysis has been made using the nonlinear finite element analysis program developed recently for external unbonded PSC members by authors. A series of major influencing variables have been included in the analysis. It was found that the span-depth ratio, neutral axis depth-effective depth ratio, load geometry, amount of ordinary steel, and prestressing steel ration have great influence for the ultimate failue stress of PS steel is preposed and is compared with experimental dat as well as existing formulas for internal unbonded members. The Comparison indicates that the proposed equation agrees relatively well with experimental data and that existing formulas including ACI and AASHTO equations show some discrepancies from experimental ones. The present study allows more realistic analysis and design of prestressed concrete structures with external unbonded tendons.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
• /
• pp.457-462
• /
• 2002

Generally speaking, durability, load carrying capacity and the life of structure becomes to be shortened in all structures as time passed. Also, we have to repair and reinforce because of tile decrease of the traffic volume and overloaded vehicles in the bridge. External prestressing method is most popular and effective strengthening method which can be used for the prestressed concrete-girders. When strengthening with external prestressing method, there are many ways to install anchorage system. But, These methods have many faults. For example, the achorage force is so small or an anchorage system installation damages an existing structure. So, this paper suggested a new anchorage system to strengthen without any damage to the structure and then confirm the increase of durability and the properties of behavior with experimentation.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
• /
• pp.411-416
• /
• 2002

With a rapid industrialization, repair and strengthening methods for a damaged bridges are raised a head in face of safety and reduction of physical distribution costs of bridges. Above all, external prestressing method has the high adaptability for concrete structures and the reliable effect of strengthening. Innovative ideas for bridges strengthening were considered along with established methods. That methods are identified, described. However there is not a systematic and categorized manual for external prestressing method. This study will provide a systematic and reliable manual with investigating the arrangement shape of cable and characteristics of brackets. And the key result of this study is an extensive compilation, which can be used by practicing engineers, of the most effective techniques for strengthening existing bridges.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
• /
• pp.721-726
• /
• 1999

Diverse strengthening methods for reinforced concrete are applied to real structures with a variety of materials. On the other hand, only external prestressing is used for strengthening damaged prestressed concrete girders. But the end brackets for external prestressing are hard to design and to manufacture, the magnitude of prestressing is limited when applied to real structures. The current end brackets are not clearly understood in load transmitting mechanisms and they may damage the original girder by drilling during construction. And also the designed welding area of the current bracket is insufficient to support the high load. The problems of current end bracket are solved in this study. And a new and improved end bracket is proposed and tested. The tested end bracket is similar to the end bearing bracket, but many supportting plates are addded to increase its welding length of the weakest point of the bracket. The increased welding length finally increases its load carrying capacity significantly.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
• /
• pp.461-464
• /
• 2004

External prestressing method is the most papular method to strengthen concrete structures. The key parts of external prestressing method is an anchoring device which holds the prestressing cables. The most popular anchoring devices is an end bearing type, which has to be welded at site to assamble the anchor. The welding at site has a significant Quality problem. In this paper, new anchoring system has been developed, which needs no site welding. A design method for the new anchor has been proposed and developed to optimize the anchoring system. The developed anchors are very efficient, small, and compact, which have two types, one for abutment section and the other one for pier section. The anchors are expected to be used very widely, because of its convinience.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
• /
• pp.1003-1006
• /
• 2003

In recent years, FRP plates have been studied for flexural reinforcement of RC structures due to easy installation and good Quality control. This study presents experimental field test results for the effectiveness of flexural reinforcement of the RC slab using external prestressing with thin CFRP strips made by the pultrusion process. It was demonstrated that flexural strength was considerably increased with relatively easy installation when compared to the other methods used for the composite reinforcement.

• 한국강구조학회 논문집
• /
• 제18권6호
• /
• pp.717-726
• /
• 2006

교량의 보강공법으로 주로 사용되는 외부강봉을 이용한 후인장공법은 적용범위가 넓고 교량의 극한 및 항복에 대한 강성을 증가시켜 휨 보강 효과가 뛰어나지만, 모재접합부의 응력집중, 비효율적인 하중분배, 고정앵커부설치, 유지관리의 어려움 등의 단점이 있다. 본 연구는 기존의 외부강봉을 이용한 후인장공법이 가지는 단점을 보완하고 강판접합공법의 장점을 접목한 새로운 개념의 보강공법으로 커버플레이트의 열변형 특성을 이용한 다단계 프리스트레싱 보강공법을 제안하고자 한다. 커버플레이트의 열변형 특성을 이용한 다단계 프리스트레싱 보강공법은 커버플레이트를 다단계로 가열하여 가열단계별로 거더의 하부플랜지에 고장력볼트로 접합한 뒤, 열원을 제거하여 발생하는 다단계 수축력을 보강에 필요한 프리스트레싱력으로 이용하는 보강공법이다. 커버플레이트의 다단계 프리스트레싱에 의한 보강효과는 커버플레이트의 온도분포와 가열구간에 따라 결정되므로 본 연구에서는 커버플레이트의 열전달 모형실험 및 강거더 모형 실험을 통하여 커버플레이트의 열전달해석과 프리스트레스 도입효과를 분석하였으며, 단경간 강거더 교량을 대상으로 제안된 보강공법의 효율성 및 적용성을 검토하였다.

• 한국강구조학회 논문집
• /
• 제14권1호
• /
• pp.79-85
• /
• 2002

본 연구에서는 기존에 사용된 H-Beam 교량을 편향부와 외부 긴장력을 도입하여 보강효과에 의하여 지간을 증가시킬 수 있고 단면을 축소할 수 있다는 근거를 제시하였고, 유연도법을 이용하여 편향부의 효과에 의한 추가 긴장량을 산정하였다. 또한, 실험변수(긴장량, Tendon의 개수, 편향부의 유 무)에 의해서 표준실험체(기존 H-Beam)와 외부 긴장된 H-Beam 등 5개의 실험체를 제작하여 휨 실험을 실시하여 외부 긴장된 H-Beam의 역학적 거동을 연구하였다. 특히, 보강효과 및 편향부의 효과를 실험적으로 검증하였다.