• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.223-232
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• 2001

This paper describes Genetic Algorithm-Based Relay Search Method, RS-GA, which is developed in this study to search the multiple design variables in the design space. The RS-GA based on Simple-GA consists of some functions to search many variables from some wide variable space. It repeats a Simple-GA, that is the convergence process of the Simple-GA, which makes many time reiteration itself. From the results of the numerical studies, it was actually found that RS-GA can search all peak-variable from the 2D functions including 5 peaks. Finally, RS-GA applied for design-strengthening problems in composite plate girder bridges using the external prestressing technique is also verified.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.803-808
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• 1998

As carbon fiber is a light-weight materials, high tensile strength and durability compared with rebar, the retrofitting method for RC structures using carbon fiber sheet (CFS) must be use widely. In this paper, the tensile strength test for carbon fiber sheet variable of CF's weight and elastic modulus to evaluate the design tensile strength of carbon fiber sheet which is needed for the strengthening design of CFS and the calculation of strengthening effect. As a result, the design tensile strength of CFS can be calculate using the effect coefficient of strengthening(α) of CFS, the average tensile strength of CFS and the standard deviation of CFS(equation 5)

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.4
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• pp.157-167
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• 2002

In most cases, quantity of reinforcement is determined without regard to the difference of initial strain, and status of damages when calculated the strengthening in flexure at beams. Thus, the purpose of this study is to investigate the flexural strengthening efficiency and behavior of RC beams strengthened with carbon fiber sheets(CFS) considering different status of damages. in this paper, a nonlinear analysis program considering rip-off strength and residual stress of steel bars and concrete in different status of damages is developed to predict the flexural behavior of CFS strengthened beams. Rip-off strength equation is obtained by modifying moment of inertia in the Robert's equation. And conformed developed nonlinear analysis program in variable of strengthening CFS amount and status of damages(initial, case1, case2, case3) and tension reinforcement ratio(0.2~1.0%).

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.579-584
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• 1998

The purpose of this study is to evaluate the flexural strengthening effects of RC beams reinforced with carbon fiber sheets (CFS) in variable of strengthening amount and anchorage length of CFS. This study can be summarized as follows. The CFS shares the tensile stress such as rebar during loading test. Also, as the strengthening amount of CFS is increased, the maximum flexural strength of RC beams reinforced with CFS is increased. Therefore, it is confirmed that the CFS's strengthening method is very effective to improve the flexural strength of RC beams. The maximum flexural strength of RC beams with CFS is determined by bond failure between CFS and concrete surface. So, the evaluation of CFS's strengthening effect can be calculated using the tensile stress of CFS which is peeling. When the anchorage length of CFS. But, in case of same anchorage length of CFS, when the strengthening amount of CFA is increased, the ductility is decreased. Therefore, it is considered that the anchorage of CFS in the end zone is necessary.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.2
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• pp.195-201
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• 1998

The purpose of this study is to evaluate the flexural strengthening effects of RC beams reinforced with carbon fiber sheets (CFS) in variable of strengthening amount and anchorage length of CFS. This study can be summarized as follows ; The CFS shares the tensile stress such as rebar during loading test. Also, as the strengthening amount of CFS is increased, the maximum flexural strength of RC beams reinforced with CFS is increased. Therefore, it is confirmed that the CFS's strengthening method is very effective to improve the flexural strength of RC beams. The maximum flexural strength of RC beams with CFS is determined by bond failure between CFS and concrete surface. So, the evaluation of CFS's strengthening effect can be calculated using the tensile stress of CFS which is peeling. When the anchorage length of CFS is increased, the ductility of RC beams is increased because of delaying the peeling of CFS. But, in case of same anchorage length of CFS, when the strengthening amount of CFS is increased, the ductility is decreased. Therefore, it is considered that the anchorage of CFS in the end zone is necessary.

• Journal of the Korea Concrete Institute
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• v.12 no.5
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• pp.35-46
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• 2000

In this paper, an analytical model is proposed to predict the shear strenth of RC beams strengthened by FRP. This predictional model is composed of two basic models-the upper bound theorem for shear failure (shear tension or shear compression criteria) and a truss model based on the lower bound theorem for diagonal tension creteria. Also, a simple flexural theory based on USD is used to explain flexural failure. The major cause of destruction of RC beams shear strengthened by FRP does not lie in FRP fracture but in the loss of load capacity incurred by rip-off failure of shear strengthening material. Since interfacial shear stree between base concrete and the FRP is a major variable in rip-off failure mode, it is carefully analyzed to derive the shear strengthening effect of FRP. The ultimate shear strength and failure mode of RC beams, using different strengthening methods, estimated in this predictional model is then compared with the result derived from destruction experiment of RC beams shear strengthened using FRP. To verify the accuracy and consistency of the analysis, the estimated results using the predictional model are compared with various other experimental results and data from previous publications. The result of this comparative analysis showed that the estimates from the predictional model are in consistency with the experimental results. Therefore, the proposed shear strength predictional model is found to predict with relative accuracy the shear strength and failure mode of RC beams shear strengthened by FRP regardless of strengthening method variable.

• Journal of the Korean Society for Advanced Composite Structures
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• v.4 no.2
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• pp.1-7
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• 2013

In recent years, fiber reinforced polymer plastic composites are readily available in the construction industry. Fiber reinforced polymer composite has many advantages such as high specific strength and high specific stiffness, high corrosion resistance, light-weight, magnetic transparency, etc. In this paper, we present the result of investigation pertaining to the flexural behavior of flange strengthened I-shape pultruded fiber reinforced polymer plastic (PFRP) member using carbon fiber sheet (CFRP sheet). Test variable is consisted of the number of layers of strengthening CFRP sheet from 0 to 3. From the experimental results, flexural strengthening effect of flange strengthened I-shape PFRP member using CFRP sheet is evaluated and it was found that 2 layers of strengthening CFRP sheet are appropriate considering efficiency and workability.

• Structural Engineering and Mechanics
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• v.46 no.4
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• pp.487-504
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• 2013

In the present work a new friction device, with a set of single or double rotational friction flanges and a link element, is described and tested. The mechanism may be applied for the strengthening of existing r/c or steel buildings as well as in new constructed buildings. The device has selectable variable behavior in different levels of displacement and an interlock mechanism that is provided by the link element. The link element may be designed to lock at preselected level of displacement, offering in this way an extra safety reserve against strong earthquakes. A summary of the existing literature about other similar mechanisms is initially presented in this paper. The proposed mechanism is presented and described in details. Laboratory experiments are presented in detail and the resulted response that proves the efficiency of the mechanism at selectable levels of strength capacity is discussed. Drawings of the mechanism attached to a r/c frame with connection details are also included. Finally a dynamic analysis of two r/c frames, with and without the proposed mechanism attached, is performed and the resulted response is given. The main conclusion is that the proposed mechanism is a cheap and efficient devise for the improvement of the performance of new or existing framed buildings to seismic loads.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.751-756
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• 2001

This paper deals with the experimental evaluation of the performance of R.C beams strengthened with aramid, glass and carbon fiber sheets. To evaluate the effects of FRPs on the flexural strengthening of the beams, strengthening ratio is adopted as a main variable. Seven beams were fabricated and strengthened under same tensile strength based on ultimate strength of FRPs and strengthening length. Deflection, flexural stiffness, strain of FRP, ultimate load and failure load are compared to evaluate the effects of FRPs on structural behavior of retrofitted beams. The results shows that little effects of FRPs on behavior of strengthened beams can be estimated and the fail modes are more influenced on structural behavior than that.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.141-144
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• 2006

The main purpose of this study is to develop a Sprayed FRP repair and strengthening method, which is a new technique for strengthening the existing concrete structures by mixing carbon or glass shot fibers and the epoxy or vinyl ester resins with high-speed compressed air in open air and randomly spraying the mixture onto the concrete surface. At present, the Sprayed FRP repair and strengthening method using the epoxy resin has not been fully discussed. In order to investigate the material property of Sprayed FRP, this study carried out tensile tests of the material specimens which are changed with the combinations of various variables such as the length of shot fiber and mixture ratio of shot fiber and resin. These variables are set to have the material strength equal to one layer of the FRP sheet. As a result, the optimal length of glass and carbon shot fibers were derived into 3.8cm, and the optimal mixture ratio was also deriver into 1:2 from each variable. And also, the thickness of Sprayed FRP to have the strength equal to one layer of FRP sheet was finally calculated.