• Advances in concrete construction
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• 제8권2호
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• pp.101-117
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• 2019

Structural strengthening of reinforced concrete (RC) beams is becoming essential to meet the up-gradation of existing structures due to the infrastructure development. Strengthening is also essential for damaged structural element due to the adverse environmental condition and other distressing factors. This article reviews the state of the field on repair, retrofitting and rehabilitation techniques for the strengthening of RC beams. Strengthening of RC beams using various promising techniques such as externally bonded steel plates, concrete jacketing, fibre reinforced laminates or sheets, external prestressing/external bar reinforcement technique and ultra-high performance concrete overlay have been extensively investigated for the past four decades. The primary objective of this article is to discuss investigations on various strengthening techniques over the years. Various parameters that have been discussed include the flexural capacity, shear strength, failure modes of various strengthening techniques and advances in techniques over the years. Firstly, background information on strengthening, including repair, retrofitting, and rehabilitation of RC beams is provided. Secondly, the existing strengthening techniques for reinforced concrete beams are discussed. Finally, the relative comparisons and limitations in the existing techniques are presented.

• 한국구조물진단유지관리공학회 논문집
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• 제22권6호
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• pp.30-36
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• 2018

기존 콘크리트 구조물의 노후화 또는 지진과 같은 외부 하중에 의하여 구조물의 구조 성능이 저하되기 때문에, 기존 건물의 보수 및 보강 연구는 중요하다. 외부부착 탄소섬유 보강 공법과 같은 효율적인 보수 공법을 사용하면 경제적으로 콘크리트 구조물의 구조 성능을 높일 수 있다. 따라서 외부부착 탄소섬유를 사용한 콘크리트 부재의 실험 연구는 많이 진행되었다. 특히, 콘크리트 보를 사용한 전단 보강에 관한 연구는 탄소섬유의 양, 부착 각도, 스트립의 폭, 그리고 재료간의 상호작용에 관한 것이었다. 하지만 선행된 연구에 비하여 탄소섬유의 이 방향 레이아웃에 관한 다양한 변수 연구는 부족한 상황이다. 따라서 이 연구에서는 이 방향 레이아웃 외부부착 탄소섬유 공법을 사용하여 콘크리트 보의 전단보강 효과를 검증하였다. 이 방향 레이아웃의 보강 효과는 스터럽과의 전단 기여도, 실험체의 전단 거동과 보강 시점에 따른 최대 내력의 비교를 통하여 이루어졌다.

• Structural Engineering and Mechanics
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• 제75권2호
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• pp.271-282
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• 2020

The preservation of historic masonry-arch railway bridges is of paramount importance due to their economic benefits. These bridges which belong to past centuries may nowadays be expected to carry loads higher than those for which they were designed. Such an increase in loads may be because of increase in transportation speed or in the capacity of freight-wagons. Anyway, adequate increase in their load-carrying-capacity through structural-strengthening is required. Moreover, the increasing costs of material/construction urge engineers to optimize their designs to obtain the minimum-cost one. This paper proposes a novel numerical optimization method to minimize the costs associated with strengthening of masonry-arch railway bridges. To do so, the stress/displacement responses of Sahand-Goltappeh bridge are assessed under ordinary train pass as a case study. For this aim, 3D-Finite-Element-Model is created and calibrated using experimental test results. Then, it is strengthened such that following goals are achieved simultaneously: (1) the load-carrying-capacity of the bridge is increased; (2) the structural response of the bridge is reduced to a certain limit; and, (3) the costs needed for such strengthening are minimized as far as possible. The results of the case study demonstrate the applicability/superiority of the proposed approach. Some economic measures are also recommended to further reduce the total strengthening cost.

• Steel and Composite Structures
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• 제23권4호
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• pp.385-397
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• 2017

Currently, CFRP (Carbon Fiber Reinforced Polymer) plate bonding is used quite extensively as a strengthening method. In this technique, a composite CFRP plate or sheet of relatively small thickness is bonded with an adhesion material to steel or concrete structure in order to improve its structural behavior and strength. The sheets or plates do not require much space and give a composite action between the adherents. In this study, the rotation capacity of CFRP-strengthened cold-formed steel (CFS) beams has been evaluated through numerical investigation. Studies on different structural levels have been performed. At the beam level, C-section has been adopted with different values of profile thickness, web height, and flange width. At the connection level, a web bolted moment resistant type of connection using through plate has been adopted. In web-bolted connections without CFRP strengthening, premature web buckling results in early loss of strength. Hence, CFRP sheets and plates with different mechanical properties and geometric configurations have been examined to delay web and flange buckling and to produce relatively high moment strength and rotation capacity. The numerical results reveal that CFRP strengthening may increase strength, initial stiffness, and rotation capacity when compared with the case without strengthening.

• 한국구조물진단유지관리공학회 논문집
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• 제2권3호
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• pp.212-222
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• 1998

In several structural problems, the low concrete strength of compression members has the severest influence on the structural safety. However, the repairing and strengthening techniques for compression members are not established and evaluated. This study aimed to develop and evaluate the rehabilitation techniques to obtain proper structural strength of wall with low concrete strength. The specimens with low strength of concrete were retrofitted with commonly using section increase method and epoxy bonded glass fiber techniques. The tests were executed to failure under concentric and eccentric loads. In this paper, the structural behavior and failure modes were investigated to evaluate the strengthening effects of walls subjected to compression and out-of-plane bending.

• 한국구조물진단유지관리공학회 논문집
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• 제4권3호
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• pp.169-176
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• 2000

In the strengthening of the existed reinforced concrete(RC) structures, it is required that the more rational strengthening method and the amounts of strengthening materials would be decided under the consideration of the present state of RC structures. Therefore, this study examined the strengthening effects of concrete cylinders strengthened with carbon fiber sheet(CFS). In this studying we modeled the reduction of internal forces and the initial strains of concrete cylinders as the load history over the elastic limit. From the results, it revealed that the strengthening of two layer CFS was more effective on the concrete cylinders under the action of load history such as cyclic and cracking load.

• 한국구조물진단유지관리공학회 논문집
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• 제12권6호
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• pp.225-232
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• 2008

본 논문에서는 FRP 보강재의 부착방식에 따른 RC보의 휨보강 성능평가에 대하여 연구하였다. 기존의 FRP 휨보강공법은 보강재의 형태에 따라 크게 FRP 쉬트 보강공법과 FRP 플레이트 보강공법으로 분류될 수 있으며, 각 공법은 에폭시의 양생기간동안 쉬트의 들뜸이 발생하지 않도록 주의해야하거나, 앵커설치 등 시공이 복잡하며, 인력이 많이 소요되는 단점이 있다. 이러한 문제점을 개선하기 위하여 본 논문에서는 Velcro형 고정재를 사용하여 FRP 플레이트를 임시 고정하는 보강공법을 제안하였고, 이에 대한 휨보강 성능평가 실험을 실시하였다. 실험은 FRP보강재의 부착방식을 변수로 하여 총 4개 실험체에 대하여 수행하였다. 실험결과 벨크로형 FRP판 보강공법은 타 공법에 비하여 우수한 시공성을 가짐과 동시에 휨내력이나 연성도 면에서도 우수한 보강성능을 확보하고 있는 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제4권4호
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• pp.121-128
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• 2000

When RC beams are strengthening in flexure with steel plate, they have initial strain due to dead load. Strain of steel used in strengthening member is zero. The effect of strengthening in flexure at member changes in accordance with the quantity of initial strain. But in most cases, Quantity of reinforcement is determined without regard to the difference of initial strain when there are calculated the strengthening in flexure at beams. Such method is possible to suggest inadequate quantity of reinforcement. Thus, the object of the study is to suggest practical design equation and reinforcement proposal using comparison and analysis reinforcement efficiency about fexural strength in case with regard and without regard to the initial strain when Re beams are strengthening in flexure with steel plate.

• Structural Engineering and Mechanics
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• 제74권2호
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• pp.243-254
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• 2020

Devastating RC structural failures in the past have identified that the behavior of beam-column joints is more critical and significantly governs the global structural response under seismic loading. The congestion of reinforcement at the beam-column joints with other constructional difficulties has escalated the attention required for strengthening RC beam-column joints. In this context, numerous studies have been carried out in the past, which mainly focused on jacketing the joints with different materials. However, there is no comparative study of different approaches used to strengthen RC beam-column joints, from efficiency and cost perspective. This paper presents a detailed investigation carried out to study the various strengthening schemes of exterior RC beam-column joints, viz., steel fiber reinforcement, carbon fiber reinforced polymer (CFRP) strengthening, steel haunch strengthening, and confining joint reinforcement. The effectiveness of each scheme was evaluated experimentally. These specimens were tested under horizontal loading that produced opening moments on the joints and their behavior was studied with emphasis on strength, displacement ductility, stiffness, and failure mechanism. Special attention was given to the study of crack-width.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 봄 학술발표회 논문집
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• pp.117-124
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• 1998

Static load tests were performed to propose the appropriate strengthening method of R/C deep beam using Carbon Fiber Sheets and compared to those of nonlinear structural analysis. Fiber direction and anchorage method on the deep beam specimen were chosen as experimental variables, which lead to the following conclusions that initial shear cracks are independent of strengthening method and fiber directions perpendicular to the expected fracture mode, which was given by the nonlinear structural analysis, show better performance compared to those of horizontal and vertical fiber directions.