• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.2
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• pp.10-18
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• 2012

Most of studies on existing strengthening methods were mainly on increase of stiffness and strength of shear strengthening to rectangular beam. As concrete of beam and slab is poured simultaneously on the characteristics of construction in reinforced concrete beam-slab structure, adjacent slab uniformed after hardening has T-shaped beam cross section which makes the flange of beam, enhances the stiffness of the beam and widens the area supporting compressive strength, but available data of flexural behavior of T-shaped beam are lacking. In this research the T-shaped beams would be made, then the reinforced effects and structural properties can be estimated according to the kinds of reinforced materials and reinforced position. The conclusions are shown as below. To sum up the experimental results, The specimen which was reinforce by CB embedded inside of concrete indicated excellent resistive behavior, internal force and stiffness when it was destroyed. The steel plate reinforced specimen of stiffness and internal force were increase but it expressed lower reinforce effects because of lowering anchored force between concrete. Fiber sheet strengthening showed superior effects but the interfacial delamination was found due to the lack of anchored force in destruction. So the measure is needed now.

• Journal of Bio-Environment Control
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• v.18 no.3
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• pp.192-199
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• 2009

This study was conducted to find proper structural reinforcement methods for the 4.5m-high (eaves height) 1-2W type plastic greenhouse. 3D finite element analysis was used to analyze the steel-tube structure. The 4.5m-high 1-2W type plastic greenhouse was modified by welding 1.5m-long steel-pipes into a 3.0m-tall columns of the standard 1-2W type plastic greenhouse. This remodeling method is widely used in Korea with farmer's discretion to increase the production when they grow paprika. But it is not based on the quantitative structural analysis. The proposed reinforcement methods were proved to stand against the design wind velocity of $40m{\cdot}s^{-1}$ and snow depth of 40cm. It strongly implies that the cross beam between side columns and wind resistance walls, and the lattice type cross beam should be good reinforcements to improve the structural safety of the elevated eaves height plastic greenhouse.

• 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 the Korea Concrete Institute
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• v.19 no.3
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• pp.351-358
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• 2007

Unlike external bonded steel plate or carbon fiber, the external unbonded strengthening using hi-strength bar has some advantages in speed and simplicity of installation. It is not required surface preparations and not affected by environmental conditions. A set of nine laboratory tests on RC beams strengthened using the hi-tension bars are reported. Anchoring pin developed in former research is installed at the end of beam to connect the hish-tension bar to RC beam. The test results strengthened by hi-tension bars are compared with those of non-strengthened specimens. The main test parameters are the cross-sectional area of the high-tension bar, distance of stirrups and condition of supports. Test results show that the beams reinforced are superior to reference specimens, especially for the strength and deformation capacity. Also, shear resisting effect of hi-strength bar can be confirmed in the specimens which have lack of stirrups.

• 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.

• Computational Structural Engineering
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• v.9 no.1
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• pp.33-45
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• 1996

A general stiffener element which includes transverse shear deformation is formulated using the p-version finite element method. Hierarchic C/sup o/-shape functions, derived from Integrals of Legendre polynomials, are used to define the assembled stiffness matrix of the stiffener with respect to the local reference frame is transformed to the plate reference system by applying the appropriate transformation matrices in order to insure compatibility of displacements at the junction of the stiffener and plate. The transformation matrices which account for the orientation and the eccentricity effects of the stiffener with respect to the plate reference axes are used to find local behavior at the junction of the stiffener and the relative contributions of the plate and stiffener to the strength of the composite system. The results obtained by the p-version finite element method are comared with the results in literatures, especially those by the h-version finite element analysis program, MICROFEAP-II.

• Journal of Korean Association for Spatial Structures
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• v.10 no.4
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• pp.49-57
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• 2010

This study is the research appling the representative Displacement-Based Design which is the basic concept of Direct Displacement Based Design proposed by Chopra and Goel to original Reinforced Concrete structure and determining the thickness of retrofit Steel Jacket about the Maximum design ground acceleration, and developing the more improved Algorithm as well as program by the Retrofit Design method and Nonlinear analysis by the Performance design method before and after reinforcement appling the determined retrofit thickness. To predict the target displacement of retrofitted columns, a nonlinear analysis model of reinforced concrete columns has been developed to be based on the nonlinear fiber cross-sectional and segmental analysis model, and the seismic displacement level of retrofitted columns is estimated by two procedures, the direct displacement-based design method and the displacement coefficient method. In examples of seismic retrofit design, the current seismic improved design method gives good results in improvements of displacement levels and displacement ductilities of retrofitted columns.

• Journal of Korean Association for Spatial Structures
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• v.12 no.1
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• pp.69-75
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• 2012

The purpose of this paper is to study comparative analysis of cable dome structures by reinforcement effect with bracing and fabric. Tensegrity systems are stable structures which are reticulated spatial structures composed of compressive straight members, struts, and cables. Tensegrity structures need to be introduced to the initial stress for the self-equilibrated system to have a stable state. In this paper, the effect of reinforcement resisting the in-plan twisting is investigated for the Geiger-type and Zetlin-type models reinforced by bracing and fabric. The effect of initial imperfection is also studied because the structural instabilitity phenomenon of shell-like structures is very sensitive according to the initial condition. We study a more exact analysis concerning the structural instability of tensegrity structures using nonlinear analysis program. Then, two types of tensegrity models will be analysed and compared.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.2
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• pp.83-98
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• 2000

자오방향 및 주변방향으로 피르스트레스트 하중이 작용된 축대칭 쉘 구조물을 기하학적으로 축대칭인 구조물의 특성을 최대한으로 이용할 수 있도록 회전 링요소로 모델화하였다 보강링 요소의 모델은 축대칭 쉘요소를 이용하였으며 본체 구조물과 절점에서 부착되있는 것으로 가정하여 이의 편심을 고려하였다 유체-구조물의 상호관계는 접촉면에서 구조물의 가속도에 비례한 부가질량으로 표현하였으며 부가질량은 유체를 비점성 비압축 및 비회전을 가정하여 유한요소법에 의해 구하였다 이에 대한 수치해석을 통하여 고유진동해석 및 지진하중을 주하중으로 한 동적해석을 실시하였다 프로그램을 통하여 해석한 결과를 프리스트레스 하중 하에서 고유진동수에 대한 정해와 비교한 결과 20개의 요소로 모델링한 경우에서도 정해와 근접한 해를 얻을 수 있었다 또한 내부유체가 있는 경우와 링보강을 한 경우에 대한 고유진동수를 문헌과 비교한 결과 근접한 해를 얻을 수 있었다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.306-309
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• 2010

강철도 플레이트거더교의 경우 일반적으로 레일의 폭보다 거더 사이의 폭이 넓기 때문에 거더에 편심이 작용하게 된다. 이러한 편심 영향으로 거더 내측 상부플랜지에 휨변형이 일어나게 되어, 상부플랜지와 수직보강재 용접이음부에 반복하중에 의한 피로균열이 발생되고 있는 것으로 보고되고 있다. 본 연구에서는 공용중인 강철도 플레이트거더교를 대상교량으로 하여 공용하중에 대한 구조해석을 실시하였다. 대상교량에 대한 현장계측을 기초로 구조모델링을 검증하였고, 검증된 구조모델링을 사용하여 열차하중 하에서의 상부플랜지와 수직보강재 용접연결부에서의 피로균열 보강방안에 대한 구조해석을 실시하였다. 또한 상부플랜지와 수직보강재 용접이음부 상세해석을 통하여 피로균열 발생위치를 확인하고 연결이음부의 적절한 보강방안을 제시하고자 한다.