• Journal of Korean Society of Steel Construction
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• v.28 no.1
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• pp.43-52
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• 2016

A numerical study on required stiffness of the longitudinal stiffener in the webs stiffened with flat plate at one-side of the web was conducted. The longitudinal stiffeners are commonly placed around 0.2D, i.e., 1/5 the web depth due to fabrication convenience although most plate girders for bridges are unsymmetric section. Considering asymmetry of section, aspect ratio of web and the rigidity ratio of longitudinal stiffener(${\gamma}^*$), eigenvalue analysis were performed to evaluate the buckling strength for the webs with a stiffener located at 0.16D~0.24D. Based on the parametric analysis, the required stiffness of the longitudinal stiffener to satisfy the buckling strength specified in AASHTO LRFD specifications was presented.

• Journal of the Korea Concrete Institute
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• v.21 no.2
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• pp.129-138
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• 2009

Recently, for more demands of the economical benefits and environmental conservation, many engineers prefer to choose remodeling. Artificial openings are often unavoidable to make house wider, which will degrade wall strength and stiffness by losing effective wall section that may cause the weakening of system capacity. In these cases the damaged shear walls need to be retrofitted by additional materials or members. In this research, four specimens were tested to investigate the capacity of the damaged wall and the retrofitted wall. The artificially damaged wall was prestressed by tendons to improve the shear capacity of the wall, and the other walls were retrofitted by adding steel plate at the surface for the same purpose. Consequently, these retrofitted walls had improved capacity and stiffness in both shear and flexure. Especially, the wall with steel plate showed ductile behavior after ultimate load and the prestressed wall had greater stiffness than the unstrengthened prototype wall.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.1
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• pp.45-52
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• 2009

The purpose of this study is to evaluate the structural capacities of beam-column specimens retrofitted with CFRP sheet and BRB (Buckling-Restrained Brace) under sustained axial and cyclic lateral loads. Three specimens were made using different retrofitting methods : non-retrofitted, retrofitted with CFRP sheets only, and retrofitted with both CFRP sheet and BRB systems. Lateral load resistant capacities were evaluated based on the load-displacement relations. From the results, the maximum lateral forces of the FRP sheet retrofitted and both the FRP and BRB retrofitted specimens showed approximately 34% and 138% improvement, respectively, compared with the non-retrofitted specimen.

• Land and Housing Review
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• v.6 no.1
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• pp.21-29
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• 2015

Coupling beams posses proper strength, stiffness and ductility capacities to resist efficiently under seismic loads. The strength, stiffness and ductility capacities for special diagonally reinforced concrete coupling beam with a span-to-depth ratio 2.0 or less is higher than those of coupling beam with conventionally reinforced concrete coupling beam. However, diagonally reinforced detailing creates major construction problem. In this study, design alternatives for diagonally reinforced concrete coupling beams were experimentally investigated. The results show that angle reinforced coupling beam(specimen SA) exhibited a better stable behavior in comparison with non-diagonally coupling beams(specimens SB-series) and sustained corresponding drift ratio, peak-to-peak stiffness and cumulative dissipated energy in comparison to diagonally coupling beam(specimen CA).

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.3
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• pp.264-273
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• 1984

초기경향이 있는 보강평판의 비선형 운동 방정식을 Galerkin method에 의하여 유도하였다. Runge Kutta method를 사용하여 step-load를 받고 있는 보강평판의 동적 좌굴문제의 수치해를 구하였다. 정적 좌굴실험에 의하여 좌굴하중을 결정함에 있어 동적 해석법을 응용할 수 있음을 입증하였으며, step-load를 받는 보강평판의 동적 좌굴해석으로 정적좌굴의 초기결함 민감성을 해 석하였다. 보강평판의 초기결함민강성은 평판보다 훨씬 낮으며 보강재의 편심비가 높을수록 민감 성은 둔화된다.

• Computational Structural Engineering
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• v.17 no.1
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• pp.39-42
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• 2004

콘크리트 구조물에 대한 보강공법은 1950년도에 개발된 강판보강공법을 위시로 하여 강연선에 의한 외부프리스트레싱 공법으로 발전하고 있으며, 약 10년전부터는 신소재인 FRP(Fiber Reinforced Polymer)에 의한 보강공법이 본격적으로 개발되어 실용화되고 있다. 강판보강공법은 에폭시 등의 접착제를 이용하여 콘크리트 인장측에 강판을 접착함으로써 강도 및 강성을 증가시키는 공법으로 강판을 보강재로 이용함으로써 공법에 대한 인지도가 높은 장점이 있는 반면, 재료의 가공 및 취급이 어려우며 중량이 커 자중이 증가되는 단점이 있다. 또한, 강재의 부식위험이 상존하고 있어 이에 대한 세심한 배려 및 주기적인 유지관리를 필요로 한다.(중략)

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.227-234
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• 2010

To investigate the flexural behavior of RC beams strengthened with carbon fiber sheets, 1 control beam and 8 strengthened beams(4 NU-beams without U-shaped band and 4 U-beams with U-shaped band) are tested. The variables of experiment are composed of the number of carbon fiber sheets and the existence of U-shaped band, etc. The experimental results showed that the strengthening system with U-shaped band controls the premature debonding and provides a more ductile failure mode than the strengthening system without U-shaped band. It can be found from the load-deflection curves that as the number of fiber sheets is increased, the maximum strength and the flexural rigidity is increased. The experimental results are compared with the analytical results of nonlinear flexural behaviors for strengthened RC beam. The proposed analytical method for strengthened beams is proved to be accurate by an experimental investigation of load-deflection curve, yield load, maximum load, and flexural rigidities in the pre- and post-yielding stages.

• Journal of Korean Society of Steel Construction
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• v.22 no.3
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• pp.219-228
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• 2010

This paper describes an experimental research on the structural behavior and the ultimate strength of longitudinally stiffened plates subjected to local, distortional, or mixed-mode buckling under compression. The stiffened plate undergoes local, distortional, or interactive local-distortional buckling according to the flexural rigidity of the plate's longitudinal stiffeners and the width-thickness ratios of the sub-panels of the stiffened plate. A significant post-buckling strength in the local and distortional modes affects the ultimate strength of the longitudinally stiffened plate. Compression tests were conducted on stiffened plates that were fabricated from 4mm-thick SM400 steel plates with a nominal yield stress of 235MPa. A simple strength formula for the Direct Strength Method based on the test results was proposed. This paper proves that the Direct Strength Method can properly predict the ultimate strength of stiffened plates when the local buckling and distortional buckling occur simultaneously or nearly simultaneously.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.56-63
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• 2018

The present study examined the reversal cyclic flexural behavior of walls with jacket section approach for seismic strengthening through forming the boundary elements at both ends of the wall. The prestressed wire ropes were used for the lateral reinforcement to confine the boundary element of the wall. The main parameter investigated was the height of the jacket section for strengthening. The limit height of the strengthening jacket section was determined by comparing the moment distributions between the existing and strengthened walls. Test results showed that the examined jacket section approach was significantly effective in enhancing the flexural resistance of walls, indicating 46% higher stiffness at peak strength and 210% greater work damage indicator, compared with the flexural performance of the unstrengthened wall. The ductility of the strengthened walls was insignificantly affected by the height of the jacket section when the height is greater than twice the wall length. The flexural capacity of the strengthened walls was 22% higher than the predictions obtained using the equivalent stress block specified in ACI 318-14.

• Geotechnical Engineering
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• v.7 no.4
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• pp.15-24
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• 1991

This paper reports the application study of the concrete bedding reinforcement under a buried conduit with flexible joints subjected to differential settlement via a finite elemen modeling. The reinforcement of concrete bedding helps to minimize the differential settlement between the adjoining conduit segments. Three different field conditions have been considered. The settlement pattern and deformation slope have been evaluated for each boundary condition. The analysis results are compared for both non-reinforced and reinforced cases to measure the effectiveness of concrete bedding reinforcement for restraining deformation of a conduit with flexible joints.