• Steel and Composite Structures
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• 제3권6호
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• pp.421-438
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• 2003

Aging and deterioration of existing steel structures necessitate the development of simple and efficient rehabilitation techniques. The current study investigates a methodology to enhance the flexural capacity of steel beams by bonding Glass Fibre Reinforced Plastic (GFRP) sheets to their flanges. A heavy duty adhesive, tested in a previous study is used to bond the steel and the GFRP sheet. In addition to its ease of application, the GFRP sheet provides a protective layer that prevents future corrosion of the steel section. The study reports the results of bending tests conducted on a W-shaped steel beam before and after rehabilitation using GFRP sheets. Enhancement in the moment capacity of the beam due to bonding GFRP sheet is determined from the test results. A closed form analytical model that can predict the yield moment as well as the stresses induced in the adhesive and the GFRP sheets of rehabilitated steel beam is developed. A detailed finite element analysis for the tested specimens is also conducted in this paper. The steel web and flanges as well as the GFRP sheets are simulated using three-dimensional brick elements. The shear and peel stiffness of the adhesive are modeled as equivalent linear spring systems. The analytical and experimental results indicate that a significant enhancement in the ultimate capacity of the steel beam is achieved using the proposed technique. The finite element analysis is employed to describe in detail the profile of stresses and strains that develop in the rehabilitated steel beam.

• Earthquakes and Structures
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• 제15권2호
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• pp.113-122
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• 2018

This study presents a new beam-column model comprising material nonlinearity and joint flexibility to predict the nonlinear response of reinforced concrete structures. The nonlinear behavior of connections has an outstanding role on the nonlinear response of reinforced concrete structures. In presented research, the joint flexibility is considered applying a rotational spring at each end of the member. To derive the moment-rotation behavior of beam-column connections, the relative rotations produced by the relative slip of flexural reinforcement in the joint and the flexural cracking of the beam end are taken into consideration. Furthermore, the considered spread plasticity model, unlike the previous models that have been developed based on the linear moment distribution subjected to lateral loads includes both lateral and gravity load effects, simultaneously. To confirm the accuracy of the proposed methodology, a simply-supported test beam and three reinforced concrete frames are considered. Pushover and nonlinear dynamic analysis of three numerical examples are performed. In these examples the nonlinear behavior of connections and the material nonlinearity using the proposed methodology and also linear flexibility model with different number of elements for each member and fiber based distributed plasticity model with different number of integration points are simulated. Comparing the results of the proposed methodology with those of the aforementioned models describes that suggested model that only uses one element for each member can appropriately estimate the nonlinear behavior of reinforced concrete structures.

• 한국해양공학회지
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• 제34권6호
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• pp.481-488
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• 2020

Composite materialsuch as glass-fiber reinforced plastic and carbon-fiber reinforced plastic (CFRP) shows anisotropic property and have been widely used for structural members and outfitings of ships. The structural safety of composite structures has been generally evaluated via finite element analysis. This paper presents a technique for updating the finite element model of anisotropic beams or plates via natural frequencies. The finite element model updates involved a compensation process of anisotropic material properties, such as the elastic and shear moduli of orthotropic structural members. The technique adopted was based on a discrete genetic algorithm, which is an optimization technique. The cost function was adopted to assess the optimization problem, which consisted of the calculated and referenced low-order natural frequencies for the target structure. The optimization process was implemented with MATLAB, which includes the finite element updates and the corresponding natural frequency calculations with MSC/NASTRAN. Material properties of a virtual cantilevered orthotropic beam were estimated to verify the presented method and the results obtained were compared with the reference values. Furthermore, the technique was applied to a cantilevered CFRP beam to successfully estimate the unknown material properties.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.531-536
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• 2003

It is generally known that RC flexural members strengthened by GFRP(Glass Fiber Reinforced Polymers) tend to be failed by premature bond failure near the flexural-shear cracks happened at the mid-span of beams. It is therefore strongly recommended that premature bond failure must be avoided to insure the intended strengthening effects sufficiently. The various methodologies such as increasing bonded length of GFRP and bonding details including U-shape wrappings and epoxy shear-keys are examined in this study. The bonded length of GFRP are calculated based on the assumed bond strengths of epoxy saturating resin. Total six half scale RC beam specimens were constructed and tested to investigate the effectiveness of each methodologies to prevent the bond failure of GFRP. Test results of each specimens are discussed in this paper.

• Structural Engineering and Mechanics
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• 제54권4호
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• pp.711-723
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• 2015

This study investigates the identification of added mass and its location in the glass fiber reinforced polymer (GFRP) beam structures. The main emphasis of this paper is to ascertain the importance of inclusion of rotational degrees of freedom (dofs) in the introduction of added mass or damage identification. Two identification indices that include the rotational dofs have been introduced in this paper: the modal force index (MFI) and the modal rotational curvature index (MRCI). The MFI amplifies damage signature using undamaged numerical stiffness matrix which is related to changes in the altered mode shapes from the original mode shapes. The MRCI is obtained by using a higher derivative of rotational mode shapes. Experimental and numerical results are compared with the existing methods leading to a conclusion that the contributions of the rotational modes play a key role in the identification of added mass. The authors believe that the similar results are likely in the case of damage identification also.

• 한국전산구조공학회논문집
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• 제21권5호
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• pp.483-491
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• 2008

철근콘크리트 보에 대한 섬유-강판 복합플레이트의 보강효과를 연구하였다. 합계 12개 철근콘크리트 보 중, 7개는 탄소 섬유-강판 복합플레이트(CSP)로 보강되었으며, 4개는 유리섬유-강판 복합플레이트(GSP)로 보강되었고, 나머지 1개는 비교를 목적으로 보강되지 않았다. 보강보 실험결과, 새로 개발된 섬유-강판 복합플레이트 보강시스템은 보강재의 조기탈락을 제어하여 연성파괴를 유도하는 것으로 나타났다. 본 연구에 사용된 CSP 보강보의 연성지수는 $3.01\sim3.81$, GSP 보강보의 연성지수는 $3.55\sim4.95$로 측정되었다. ESP 보강보 및 GSP 보강보의 최대하중은 보강하지 않은 기준보에 비해 각각 115%, 107% 향상된 것으로 측정되었다. 또한, 보강보 실험과 해석 결과들은 잘 일치하는 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제63권5호
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• pp.575-583
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• 2017

The study covers the behavior of reinforced concrete deep beams loaded under 4-point bending, failed by shear and repaired using bonding glass fiber reinforced plastics fabrics (GFRP) patches. Two rehabilitation methods have been used to highlight the influence of the composite on the ultimate strength of the beams and their failure modes. In the first series of trials the work has been focused on the reinforcement/rehabilitation of the beam by following the continuous configuration of the FRP fabric. The patch with a U-shape did not provide satisfactory results because this reinforcement strategy does not allow to increase the ultimate strength or to avoid the abrupt shear failure mode. A second methodology of rehabilitation/reinforcement has been developed in the form of SCR (Strips of Critical Region), in which the composite materials reinforcements are positioned to band the inclined cracks (shear) caused by the shear force. The results obtained by using this method lead a superior out come in terms of ultimate strength and change of the failure mode from abrupt shearing to ductile bending.

• Advances in materials Research
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• 제8권4호
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• pp.337-359
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• 2019

Shape Memory Polymer Composites (SMPC) have gained popularity over the last few decades due to its flexible shape memory behaviour over wide range of strains and temperatures. In this paper, non-linear bending analysis has been carried out for SMPC beam under the application of uniformly distributed transverse load (UDL). Simplified C⁰ continuity Finite Element Method (FEM) based on Higher Order Shear Deformation Theory (HSDT) has been adopted for flexural analysis of SMPC. The numerical solutions are obtained by iterative Newton Raphson method. Material properties of SMPC with Shape Memory Polymer (SMP) as matrix and carbon fibre as reinforcements, have been calculated by theory of volume averaging. Effect of temperature on SMPC has been evaluated for numerous parameters for instance number of layers, aspect ratio, boundary conditions, volume fraction of carbon fiber and laminate stacking orientation. Moreover, deflection profile over unit length and behavior of stresses across thickness are also presented to elaborate the effect of glass transition temperature (T_g). Present study provides detailed explanation on effect of different parameters on the bending of SMPC beam for large strain over a broad span of temperature from 273-373K, which encompasses glass transition region of SMPC.

• 한국재난정보학회 논문집
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• 제9권3호
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• pp.315-323
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• 2013

최근 건설 산업에서 FRP는 재료적 장점으로 RC 구조물의 보강 재료로서 많이 사용되어지고 있다. FRP 외부부착보강은 중량에 비하여 높은 강도 및 강성, 우수한 내구성과 시공성등 여러 가지 장점을 가지는 공법이다. 그러나 외부부착보강은 구조물이 투수성이 낮은 보강재로 밀폐되고 수분이 외부로 배출되지 못함으로 인하여, 장기적인 구조물의 손상을 발생시키는 문제점이 있다. 본 연구에서는 기존의 FRP (Fiber Reinforced Polymer)와 재료적성질은 동등하면서, 투수성을 지녀 콘크리트 구조물의 모체와 부착성 및 내구성능 및 내구성이 우수한 유리섬유 패널(Glass Fiber Composite Pannel )에 대해서 휨 실험을 수행하여 복합소재 스트립의 섬유함량의 변화에 따른 실험변수별 내력증진 및 연성 증진 효과를 비교 분석하였다.

• Computers and Concrete
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• 제21권2호
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• pp.127-137
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• 2018

In this study, the behavior of the number of anchorage bolts on the glass-fiber reinforced polymer (GFRP) plates adhered to the surfaces of reinforcing concrete (RC) T-beams was investigated analytically. The analytical results were compared to the test results in term of shear strength, and midpoint displacement of the beam. The modelling of the beams was conducted in ABAQUS/CAE finite element software. The Concrete Damaged Plasticity (CDP) model was used for concrete material modeling, and Classical Metal Plasticity (CMP) model was used for reinforcement material modelling. Model-1 was the reference specimen with enough sufficient shear reinforcement, and Model-2 was the reference specimen having low shear reinforcement. Model-3, Model-4 and Model-5 were the specimens with lower shear reinforcement. These models consist of a single variable which was the number of anchorage bolts implemented to the GFRP plates. The anchorage bolts of 2, 3, and 4 were mutually mounted on each GFRP plates through the beam surfaces for Model-3, Model-4, and Model-5, respectively. It was found that Model-1, Model-3, Model-4 and Model-5 provided results approximately equal to the test results. The results show that the shear strength of the beams increased with increasing of anchorage numbers. While close results were obtained for Model-1, Model-3, Model-4 and Model-5, in Model-2, the rate of increase of displacement was higher than the increase of load rate. It was seen, finite element based ABAQUS program is inadequate in the modeling of the reinforced concrete specimens under shear force.