최근 국내 구조물들의 노후화가 진행됨에 따라 구조물 보강과 관련된 연구에 대한 관심이 높아지고 있다. FRP보강은 노후화가 진행되어 성능이 저하된 구조물을 보강하는데 사용되며 주로 유리섬유를 사용한다. 그러나 이 유리섬유는 환경적 재 활용의 문제점이 대두되고 있다. 따라서 본 연구에서는 친환경적이고 내열성이 우수한 현무암 섬유를 활용한 휨 보강 플레이트 적용방법과 기존 FRP 외부부착의 문제점을 해소하기 위하여 연성 코팅용 보강페인트를 활용한 휨 보강 페인팅 적용방법을 통하여 각각의 경우에 대한 3점 휨 시험을 통하여 보강성능을 평가, 비교하였다. 그 결과 BFRP 보강의 경우 무보강 시험체에 비하여 약 1.2배 높은 강성 값을 나타내었고 콘크리트-BFRP 계면 부착력에 의한 연성효과도 나타났다. 반면 연성 코팅 보강페인팅 적용을 통한 휨 보강의 경우, 무보강 시험체에 비하여 약간의 개선효과는 나타났으나 실험체 제작의 오차 등을 고려할 때 실질적인 보강효과는 크게 나타나지 않았다. 따라서 연성 코팅페인팅을 활용한 보강방법의 경우, 향후 다양한 시공조건에 따른 추가연구가 필요할 것으로 판단된다.

In this study, we will develop a hybrid cross-sectional shape of steel inserted type glued-laminated timber that can improve the strength of structural glued-laminated timber and maximize the ductility by using steel plate with excellent tensile and deformation ability. A total of three specimens were fabricated and the flexural performance test was carried out to evaluate the structural performance of the steel inserted type glued-laminated timber. In order to compare the effect of steel inserted glued-laminated timber, one structural glued-laminated timber test specimen composed of pure wood was manufactured. In addition, in order to evaluate the adhesion performance of the steel inserted, one each of a screw joint test specimen and a polyurethane joint test specimen was prepared. As a result, all the specimens showed the initial crack in the finger joint near the force point. This has been shown to be a cause of crack diffusion and strength degradation. The use of finger joints in the maximum moment section is considered to affect the strength and ductility of the glued-laminated timber beam. Polyurethane-adhesive steel inserted glued-laminated timber showed fully-composite behavior with little horizontal separation between the steel plate and glued-laminated timber until the maximum load was reached. This method has been shown to exhibit sufficient retention bending performance.

FRP 시트(Sheet)를 활용한 보강 공법은 제작 과정에서의 간편함과 시공의 용이성으로 현장에서 다수 적용되고 있으며, 기존 연구자들은 FRP 시트로 보강한 철근콘크리트의 휨강도를 예측하기 위한 연구를 진행하였다. 그러나 이는 주로 탄소 섬유와 유리 섬유에 한정되어 있었다. 이 연구에서는 바잘트 섬유시트의 역학적 성질을 파악하기 위하여 물성 시험을 수행하였으며, 바잘트 섬유시트로 보강한 철근콘크리트 보의 휨실험을 수행하였다. 휨실험 결과 보강량이 증가할수록 실험체의 내력이 증가하였다. 또한 휨파괴 및 시트 파단, 시트 부착 탈락, 시트 박리가 발생하였다.

직물섬유 보강 콘크리트(textile reinforced concrete, TRC)는 콘크리트 매트릭스를 직물섬유로 보강한 복합재료로 높은 강도 및 우수한 연성을 발휘한다. 본 논문에서는 TRC로 보강된 구조 부재의 성능 평가를 위해 그 유효물성치를 멀티스케일에 기반한 해석적 방법을 통해 평가하였다. 유효물성치 산정을 위해 감소차수모델(reduced order model)에 기반한 3차원 유닛셀 유 한요소해석법을 이용하였다. 계산된 유효물성치를 TRC 보강 휨 부재의 유한요소해석에 활용하여 하중-변위 그래프를 도출하였 다. 계산된 유효물성치를 TRC 보강 휨 부재의 유한요소해석에 활용하여 하중-변위 그래프를 도출하였으며, 이의 정확성을 평가 하기 위해 TRC 복합패널의 4점 휨실험을 수행하고 그 결과를 유한요소 해석결과와 비교 및 분석하였다.

본 연구에서는 내진성능향상을 목표로 CNT-복합소재로 보강된 콘크리트 구조물의 휨 인장 거동을 다루었다. 다양한 CNT 함유량에 따른 복합소재의 재료적 물성은 수정된 Halpin-Tasi 모델을 적용하여 멀티스케일해석 이론으로부터 도출하였다. 휨인장 시험은 복합소재의 종류, CNT 함유비율, 도포제의 유무, 그리고 보강 방법에 따라서 수행하였다. 변수 실험 결과는 CNT-복합재로 보강된 콘크리트 구조의 향상된 휨인장 거동에 대하여 CNT 함유량과 적절한 도포제의 적용 (부착)의 중요성을 보여주었다.

현대 섬유 기술의 발전으로 박리에 의한 복합체 파괴 가능성을 줄일 수 있고, 복합체의 전단강도를 향상시킬 수 있는 있는 3차원 직물섬유를 제작할 수 있게 되었다. 본 연구에서는 3D 직물섬유의 시멘트 기반 복합체 적용 가능성을 살펴보기 위해 3D 직물섬유의 종류, 매트릭스의 종류, 보 부재 높이를 변수로 한 3D 직물섬유 보강 모르타르 보 시험체를 제작하고 휨실험을 수행하였다. 휨실험 결과, 3D 직물섬유 보강 모르타르 부재는 전형적인 직물섬유 보강 콘크리트의 휨거동과 유사한 결과를 나타내었다. 3D 직물섬유 보강을 통해 보 부재의 휨강성 및 휨인성이 향상되었고, 6mm 스페이서를 가진 직물섬유 보강 시험체가 4mm 스페이서를 가진 직물섬유 보강 시험체 보다 더 높은 휨강도 및 휨인성을 보였다. 3D 직물섬유 보강 모르타르의 휨강도 및 휨인성을 보다 향상시키기 위해서는 높은 인장강도와 탄성계수를 가지는 섬유의 적용, 섬유량의 증가, 인장단에 가까운 섬유의 배치가 필요하다.

Synthetic wood has been widely used in place of wood such as the building exterior materials and/or the floor plate of moving path. However, it has many disadvantages such as relatively low strength, low durability, and heavy weight, etc. In this study, the synthetic wood deck combined with an aluminum profile was suggested to overcome these disadvantages. The flexural strength of the aluminum-synthetic wood deck was obtained through the theoretical equations under three-point bending conditions. In addition, the finite element analyses were also conducted to evaluate the flexural strength of the aluminum-synthetic wood deck.

In this paper, four point bending tests were carried out to analyse flexural strengthening effect by CFRP (Carbon Fiber Reinforced Polymer) layers for I shape PFRP (Pultruded Fiber Reinforced polymer) flexural member retrofitted with CFRP sheet. Comparing load-displacement relation and sectional stress distribution, the flexural strengthening effect by the number of CFRP layers was founded.

Numerical analysis was performed to evaluate for reinforcing performance of RC beams in flexure strengthened with Textile Reinforced Mortar (TRM) in this study. New bond strength model for TRM based on the model proposed by Teng et al. was suggested to predict the flexural behavior of RC beams and effective stress in accordance with debonding of TRM. And reduce factor of 0.729 was suggested by investigation of results on the bending test of RC beams strengthened with TRM. Reliability of proposed bond strength model was verified through the comparisons between collected test results and predicted results about the ultimate load of RC beams occurred by debonding of TRM. The ratios of predicted results on the total experimental results, the average and coefficient of variation were 1.00 and 0.094, respectively. Also, nonlinear analysis method proposed by Cho et al. was used to predict the displacement at the cross-section of mid-span for RC beams in flexure strengthened with TRM. At the three state of the RC beams such as occurrence of initial flexural crack in tensile concrete, yield of tensile rebar, and ultimate in accordance with debonding of TRM. Displacements of beams were calculated at the three state and load-displacement curves by predicted results were compared to the collected test results.

Most of the cultural assets in Korea are wooden structures. Due to the material characteristics of wood, the preservation of traditional wooden structure is impossible by simple maintenance. Damaged member is replaced with new member or completely dissolve and restore them. But member has a cultural value, so that it is impossible to arbitrarily replace each member. Although the preservation treatment method using synthetic resin is emphasized, there is no exact standard for proper reinforcement ratio. This paper is experimental study for reinforcement ratio of wooden flexural member with synthetic resins, Reinforced ratio on section area of flexural member. As a result, synthetic resin reinforcement are selected as experimental variables by proper ratio enhanced flexural capacity of reinforced wooden member than new wooden member.

Flexural capacity of a Textile Reinforced Mortar(TRM) was investigated by an experimental study. The test program was accomplished on reinforced concrete(RC) slabs consisted of concrete(average compressive strength of 22.23 MPa) and rebar(strength class of SD400). RC slab had 450 mm and 150 mm in size and 2,600 mm in clear span. Strengthening was accomplished by applying carbon-fiber mesh in layers of mortar. Control slab(unstrengthened) and six slabs strengthened with TRM were fabricated to confirm the reinforcing performance in this study. Test variables considered amount of reinforcement and use of anchorage. As a results, it was validated that the flexural capacity of slabs strengthened with TRM increased from 159.9% to 285.2% according to the amount of TRM compared with unstrengthened slab. Experimental results indicated that there are increase in ductility as well as load carrying and deformation capacities when using multiple layers of textile.

철근콘크리트 슬라브의 휨강도 보강을 위해 제안된 섬유보강폴리머(Fiber Reinforced Polymer, FRP)와 초 고거동 콘크리트(Ultra High Performance Concrete, UHPC)의 합성구조의 파괴 시 거동을 살펴 본 결과, 과다한 휨 보강으로 인한 전단파괴와 보강된 FRP의 탈착에 의한 파괴가 발생하였다. 전단강도와 휨 강도의 크기를 고려한 설계 기준을 제시하여 휨 보강 한도를 제한하고, 전단 철근을 추가하여 탈착에 의한 파괴를 보강하였다. 휨 강도의 보강을 제한 하고 부착 철근이 보강된 슬라브의 실험 결과, 휨에 의한 연성파괴가 유도되었다.

Molding trouble in injection-molded parts is caused by change of complexed molding product and molding process condition, etc. Warpage, which is one of the molding trouble, acts as possible factor which results in defect in assembly. In this study, a mold was designed to produce specimens with rib parallel to flow direction, specimens with rib perpendicular to flow direction and specimens without rib. This work researched change of warpage according to injection molding condition such as packing pressure, packing time, resin temperature in crystalline polymers(PP). Flat shape with ribs showed higher warpage than flat shape without ribs. The Specimens with ribs that are located perpendicular to the flow direction.

So far, square concrete filled tubular(CFT) columns have been used in a limited width thickness ratio. The reason is that local buckling occurs in steel tube easily. Once the local buckling occurs, the confinement effect of steel tube on concrete disappears. In this study, we developed welded built-up square steel tube with reinforcement which are placed at the center of the tube width acts as an anchor. 3 specimens of slender welded built-up square CFT columns and 3 specimens of slender welded built-up square steel tube columns were manufactured with parameters of width(B) of steel tube, width thickness ratio(B/t). we conducted a experimental test on the 6 specimens under eccentric load, and evaluated the structural resistance and behavior of 6 specimens.

For the last decade many bridges and buildings have experienced flexural strengthening with the fiber reinforced polymer(FRP) bonding system, demands for increasing heavy traffic loads and the changing of the code application. Of the many strengthening systems, NSM(near surface mounted) system with FRP has become attractive and popular way of strengthening for the existed RC structures and many studies and applications of this technique have significantly increased all over the world. Meanwhile, polymer mortar that contains much of the same ingredients as cement but includes the addition of certain polymer resins for enhancing desired physical properties, has been used as an alternative adhesive. This paper focuses on flexural behaviour of CFRP-bar NSM system with variables such as kinds of adhesive, anchorage, sectional aspect ratio. Based on the test results and test-to -predicted ratio, this paper provides researchers and practical engineers a fundamental knowledge and intuition.

The purpose of this study is intended to determine the validity of shear reinforcement by evaluating flexural performance in the hollow slab. The hollow slab is relatively light and second moment of inertia is large. Due to these characteristics, it can be used to slab system efficiently. Therefore the prediction of the structural behaviors is very important because of decrease of shear and flexural strength which is caused by hollow section of slab interior. In this study, the flexural test were performed to analyze the flexural capacity of the hollow slab w/ or w/o shear reinforcement. A total of six full scale specimens were tested. These specimens have three cases of reinforcing bar ratio, 0.009, 0.018 and 0.024. To verify the flexural behavior such as ultimate load, load-deflection and crack pattern, the flexural experiment were tested by using loading frame. Experimental results have shown that the flexural behavior are depend on the reinforcing bar ratio. Also the hollow slab with shear reinforcement have shown flexural behavior. Therefore, it is appropriate that the hollow slab is reinforced by shear reinforcement to improve the flexural performance of the hollow slab.

The bond strength is not enough due to the delaminate of epoxy between FRP and steel. However, the adhesion reinforcement method can improve the bond strength between steel plate and FRP plate. In this study, a bolt tighting and FRP sheet wrapping methods were used to improve bond strength between steel plate and FRP plate. Also, flexural test were performed according to the attachment pattern for AFRP plate strengthened steel beams.