• Computers and Concrete
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• 제27권4호
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• pp.343-353
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• 2021

In this study, in order to improve the seismic performance of existing reinforced concrete (RC) framed structures, various external attachment of corner steel frame configurations was considered as a user-friendly retrofitting method. The external steel frame is designed to contribute to the lateral stiffness and load carrying capacity of the existing RC structure. A six-story building was taken into account. Four different external corner steel frame configurations were suggested in order to strengthen the building. The 3D models of the building with suggested retrofitting steel frames were developed within ABAQUS environment using solid finite elements and analyzed under horizontal loadings nonlinearly. Horizontal top displacement vs loading curves were obtained to determine the overall performance of the building. Contributions of steel and RC frames to the carried loads were computed individually. Load/capacity ratios for the ground floor columns were presented. In the study, 3D rendered images of the building with the suggested retrofits are created to better visualize the real effect of the retrofit on the final appearance of the façade of the building. The analysis results have shown that the proposed external steel frame retrofit configurations increased the lateral load carrying capacity and lateral stiffness and can be used to improve the seismic performance of RC framed buildings.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.1096-1101
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• 2004

Generally, the buckling of thin-walled structures has studied for rectangular sections or circular sections. Rectangular sections have small stiffness and circular sections have large stiffness when they are compared with rectangular sections for local buckling. But both of them have similar stiffness to column buckling. Therefore in this paper, we are going to analyze the local buckling for the box section with rounded comer and compare with rectangular section. Also we confirm that the rounded comer section has larger local buckling strength than rectangular section.

• 한국도로학회논문집
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• 제15권1호
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• pp.95-102
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• 2013

PURPOSES: The existing method evaluating the existence of the hollows in concrete pavement does not consider the stiffness of pavement. In addition, the method uses unreasonable logic judging the hollow existence by the deflection caused by zero loading. In this study, the deflection of slab corner due to heavy weight deflectometer (HWD) was measured in concrete pavement sections where underground structures are located causing the hollows around them. METHODS: The modulus of subgrade reaction obtained by comparing the actual deflection of slab to the result of finite element analysis was calibrated into the composite modulus of subgrade reaction. The radius of relative stiffness was calculated, and the relationship between the ratio of HWD load to the radius of relative stiffness and the slab deflection was expressed as the curve of secondary degree. RESULTS: The trends of the model coefficients showing width and maximum value of the curve of secondary degree were analyzed by categorizing the pavement sections into three groups : hollows exist, additional investigation is necessary, and hollows do not exist. CONCLUSIONS: The results analyzed by the method developed in this study was compared to the results analyzed by existing method. The model developed in this study will be verified by analyzing the data obtained in other sections with different pavement structure and materials.

• Steel and Composite Structures
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• 제48권5호
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• pp.485-498
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• 2023

The need for carbon neutrality in the world strives the construction industry to reduce the use of construction materials. Aiming to this, recycled aggregate concrete (RAC) could be used as it reduces the carbon dioxide emissions. Currently, RAC is mainly used in non-structural members of civil constructions, seldom used in structural members. To broaden its structural use, a new type of composite column, i.e., the square and rectangular RAC filled FRP tubes (CFFTs), has been concerned in this study. The investigation on their axial compressive behavior through physical test and numerical analysis demonstrated that the load-carrying capacity of such column is reduced with the increase of replacement ratio of recycled aggregate and aspect ratio of section but can be improved by the increase of FRP confining stiffness and corner radius, said capacity can be equivalent to their steel reinforced concrete counterparts. At failure, the hoop strain at corner of tube is unexpectedly smaller than that at flat side of the tube although the FRP tube ruptured at its corner first, revealing a premature failure. Besides, a design-oriented stress-strain model of concrete and an analysis-oriented finite element model are proposed to predict the load-strain response of square and rectangular CFFT columns, which facilitates the engineering use of RAC in load-carrying structural members.

• 한국구조물진단유지관리공학회 논문집
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• 제26권6호
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• pp.128-138
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• 2022

본 연구에서는 원심성형으로 제작된 100MPa이상의 초고강도 콘크리트 각형보를 피암터널의 상부구조로 적용하기 위해 원심성형 보를 부모멘트 영역인 하부구조와 일체화시킨 우각부 단면에 대한 구조적인 안전성을 검증하는 것을 목적으로 실물크기의 시험체를 제작하고 하중재하시험 및 해석연구를 수행하였다. 피암터널 표준모델에 대해 시방규정에 의한 하중조합으로 설계하였을 때 상부슬래브 단부의 우각부에 최대 모멘트가 발생하는 것과 같은 효과를 기대하기 위하여 수정된 캔틸레버 형식의 구조모형 시험체를 제작하여 우각부 고정연결방법에 대한 성능과 최적연결시공법을 도출하기 위한 연구가 수행되었다. 실험결과, 개발된 고정연결장치는 형상과 연결방식에 상관없이 모두 안정적인 휨 거동을 나타내었다. 또한, 시험체는 파괴시까지 고정연결장치에 의해 연결된 원심성형 PSC 각형보와 상부슬래브가 일체 거동을 하는 것으로 나타나 고정연결장치의 성능이 매우 우수한 것으로 확인되었다. FEM 해석에 따른 우각부 해석모델의 거동은 재하실험과 비교하여 강성이 미소하게 나타났으나 전체적인 거동이 거의 유사하게 나타났다. 따라서, 본 연구에서 개발한 원심성형 각형보와 벽체간의 우각부 연결부를 시공함에 있어 구조적으로 문제가 없을 것으로 판단된다.

• 국제초고층학회논문집
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• 제3권1호
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• pp.1-8
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• 2014

When seismic isolation system is applied to high aspect-ratio (height/wide-ratio) steel structures, there are several problems to be taken into consideration. One is lifting up tensile force on the isolation bearing by overturning moment caused by earthquake. Another is securing building stiffness to produce seismic isolation effects. Under these conditions, this paper reports the structural design of high-rise research building in the campus of Tokyo Institute of Technology. With the stepping-up system for the corner bearings, the narrow sides of single span framework are designed to concentrate the dead load as counter-weight for the tensile reaction under earthquake. Also we adopted concrete in-filled steel column and Mega-Bracing system covering four layers on north & south framework to secure the horizontal stiffness of the building.

• Interaction and multiscale mechanics
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• 제5권3호
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• pp.267-284
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• 2012

In most of the design offices, analysis of the frame is carried out without considering the effect of the rigidity of mat. The analysis of the superstructure without modelling the foundation properly and conversely analysing the foundation system without considering the stiffness of the superstructure may mislead the estimation of the forces. This paper examines the parameters, which affect the interaction and they are grouped into relative stiffness factors ${\kappa}_{rs}$ and ${\kappa}_{sb}$. An interaction analysis is performed for the five storeyed space frame of 3 bays ${\times}$ 5 bays, using ANSYS finite element code. The soil was treated as an isotropic, homogenous and elastic half space medium and the following conclusions were drawn from the analyses. The differential settlement is reduced due to interaction and the performance of the mat depends on ${\kappa}_{sb}$ values. The moments $M_x$ and $M_y$ in the corner column at all the storey levels are higher in the case of the interaction analysis than in the conventional analysis. The axial forces in the peripheral columns increased and to that extent, the inner column axial loads are reduced. In the beam, more variation is seen in the support moments than in the span moments.

• Earthquakes and Structures
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• 제11권4호
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• pp.665-680
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• 2016

This paper focuses on the study of seismic behavior of steel reinforced concrete special-shaped column-beam joints. Six specimens, which are designed according to the principle of strong-member and weak-joint core, are tested under low cyclic reversed load. Key parameters include the steel form in column section and the ratio of column limb height to thickness. The failure mode, load-displacement curves, ductility, stiffness degradations, energy dissipation capacity and shear deformation of joint core of the test subassemblies are analyzed. The results indicate that SRC special-shaped column-beam joints have good seismic behavior. All specimens failed due to the shear failure of the joint core, and the failure degree between the two sides of joint core is similar for the exterior joint but different for the corner joint. Compared to the joints with channel steel truss, the joints with solid web steel skeleton illustrate better ductility and energy dissipation capacity, but the loading capacity and stiffness are roughly close. With the increasing of the ratio of column limb height to thickness, the joints illustrate higher loading capacity and stiffness, better energy dissipation capacity, but worse ductility.

• Steel and Composite Structures
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• 제16권5호
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• pp.455-480
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• 2014

Sixteen concrete filled square CFRP-steel tubular (S-CFRP-CFST) stub columns under axial compression were experimentally investigated. The experimental results showed that the failure mode of the specimens is strength loss of the materials, and the confined concrete has good plasticity due to confinement of the CFRP-steel composite tube. The steel tube and CFRP can work concurrently. The load versus longitudinal strain curves of the specimens can be divided into 3 stages, i.e., elastic stage, elasto-plastic stage and softening stage. Analysis based on finite element method showed that the longitudinal stress of the steel tube keeps almost constant along axial direction, and the transverse stress at the corner of the concrete is the maximum. The confinement effect of the outer tube to the concrete is mainly focused on the corner. The confinements along the side of the cross-section and the height of the specimen are both non-uniform. The adhesive strength has little effect both on the load versus longitudinal strain curves and on the confinement force versus longitudinal strain curves. With the increasing of the initial stress in the steel tube, the load carrying capacity, the stiffness and the peak value of the average confinement force are all reduced. Equation for calculating the load carrying capacity of the composite stub columns is presented, and the estimated results agree well with the experimental results.

• 한국구조물진단유지관리공학회 논문집
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• 제9권2호
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• pp.225-235
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• 2005

본 논문에서는 새로운 흙막이 지보재인 IPS(Innovative Prestressed wale System) 띠장의 기본 개념과 미캐니즘에 대하여 설명하고 도심지 굴착 현장에 적용된 IPS 띠장의 거동 및 안정성에 대하여 논하였다. IPS 띠장은 강선, H-beam 받침대, 띠장으로 구성되어 있으며 IPS 띠장에 강선의 인장력을 도입하여 흙막이 벽체에 선행 하중을 가하고 지반 굴착으로 인한 토압을 IPS 띠장의 휨강성을 활용하여 버팀보에 전달하는 새로운 개념의 흙막이 지보재이다. 휨강성이 큰 IPS 띠장을 활용하면 흙막이 벽체를 지지하는 버팀보의 설치 간격을 획기적으로 넓힐 수 있으며 굴착시에 넓은 작업 공간을 제공받는다. 그리고 굴착 공사에 사용되는 강재의 물량을 줄일 수 있다. 그러므로 굴착 공사에서 IPS 띠장을 활용하면 경제성과 시공성을 확보할 수 있다. 또한 굴착으로 인한 흙막이 벽체의 변형을 억제하여 흙막이 구조물의 안정성을 높일 수 있다. 본 논문에서는 IPS 띠장의 기본 개념과 미캐니즘에 대하여 언급하고 도심지 굴착 현장에 적용된 IPS 띠장의 현장 적용성을 확인하였다. IPS 띠장의 현장 계측 결과를 분석하여 IPS 띠장의 거동과 안정성을 확인하고 IPS 띠장이 적용된 벽체의 거동을 알아보았다. 또한 IPS 띠장에 작용하는 토압을 지지하는 코너 스트럴의 거동을 알아보았다.