• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.136-139
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• 2003

The re-bar work in the construction of nuclear power plants is difficult, due to the large diameter and the congestion of reinforcements. The mechanical anchorage offers a potential solution for this problem. However, the requirements or the standards for the shape of anchor plate of mechanical anchor has not been clearly established up to now. In this paper, the required performance of the mechanical anchorage for large diameter reinforcements in nuclear power plants are proposed, and the anchor plates are designed through nonlinear finite element analysis. The diameters of anchor plate are determined to be $\sqrt{5}$ times of reinforcement diameter for longitudinal reinforcements and $\sqrt{10}$ for shear reinforcements. The thickness of anchor plates is optimized as 0.3-0.35 times of reinforcement diameter for longitudinal reinforcements and 0.5~0.56 times for shear reinforcements.

• 한국도로학회논문집
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• 제8권2호
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• pp.37-47
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• 2006

The structural response and performance of a flexible pavement can be improved through the use of geogrids as base course reinforcement. Current ongoing research at the University of illinois has focused on the development of a geogrid base reinforcement mechanistic model for the analysis of reinforced pavements. This model is based on the finite element methodology and considers not only the nonlinear stress-dependent pavement foundation but also the isotropic and anisotropic behavior of base/subbase aggregates for predicting pavement critical responses. An axisymmetric finite element model was developed to employ a three-noded axisymmetric membrane element for modeling geogrid reinforcement. The soil/aggregate-geogrid interface was modeled by the three-noded membrane element and the neighboring six-noded no thickness interface elements. To validate the developed mechanistic model, the commercial finite element program $ABAQUS^{TM}$ was used to generate pavement responses as analysis results for simple cases with similar linear elastic material input properties. More sophisticated cases were then analyzed using the mechanistic model considering the nonlinear and anisotropic modulus property inputs in the base/subbase granular layers. This paper will describe the details of the developed mechanistic model and the effectiveness of geogrid reinforcement when used in different quality unbound aggregate base/subbase layers.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.475-483
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• 2008

It is necessary to develop a national design method for surface reinforcement of very soft ground because most current design works rely on crude empirical correlations. In this paper, the mechanical behavior of very soft ground that is surficially reinforced was investigated with the aid of a sents of numerical analysis. Several material properties of each dredged soft ground, reinforcement and backfill sand mat have been exercised the numerical analysis in order to compare the result of numerical analysis with those of the laboratory model test. Through the matching process between the numerical and experimental result, it is possible to find the appropriate material properties of the dredged soft ground, reinforcements and backfill sand mat. These verified material properties permit to show the effect of the stiffness of reinforcement and the thickness of sand mat on the overall deformation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.859-862
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• 2008

본 연구는 GFRP 보강근의 정착길이 산정식을 제안하는 것이다. 정착길이 산정식을 제안하기 위해 인발실험을 실시하였다. 실험변수는 묻힘길이, 피복두께, 보강근 직경, 보강근 종류이다. 묻힘길이는 15d$_b$, 30d$_b$, 45d$_b$로 하고, 순 피복두께는 0.5d$_b$, 1.0d$_b$, 1.5d$_b$, 및 2.0d$_b$로 계획하였다. 사용된 보강근은 모두 3종류(국내 2종, 국외 1종)이고 보강근 크기는 D10, D13, D16이다. 실험은 겹침이음된 GFRP 보강근 양 단부를 동시에 인발하여 최종파괴에 도달될 때까지 GFRP 보강근에 하중을 가력하였다. 인발실험을 통해 얻은 결과를 토대로 각 변수에 따른 GFRP 보강근의 부착특성 및 평균부착응력을 산정하였으며, 실험체중 쪼갬파괴된 실험체만을 선택하여 회귀분석을 통해 정착길이 산정식은 제안하였고 ACI 440.1R-06에 제안하고 있는 식과 비교하였다. 본 연구를 통해 제안된 회귀분석에 의한 제안식을 근거로 겹침이음된 GFRP 보강근을 이용한 휨 설계가 가능할 것으로 판단된다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.198-202
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• 2004

An analytical model using expanded bridging model was proposed to predict the elastic properties and behaviors of stitched multi-axial warp knitted (MWK) fabric composites, The characteristics of MWK fabric composites are the assemblage of multi-layers of fiber bundles for in-plane reinforcement and stitch yams for the through-the-thickness reinforcement. In the analysis, a representative volume of the MWK fabric composite was identified, The geometric limitations, effects of stitching yams and design parameters of MWK fabric composites were considered in the model. Then, the elastic properties and behaviors of MWK fabric composites were predicted, Finally, the results of proposed model of the composites were verified through the experiments, The predicted results were in fair agreement with the experimental results

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 추계 학술논문 발표대회
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• pp.30-31
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• 2014

Since consists of regression equation by penetration depth prediction calculated by existing NDRC formula mainly considers properties of projectile, impact velocity, compressive strength as parameter, it is difficult to apply it to fire reinforced concrete. In this study, scabbing limit thickness was predict considering fiber reinforcement effect by local fracture of concrete was evaluated through high-velocity impact test. As a result of applying fracture reduction coefficient to NDRC, it was possible to predict scabbing limit thickness of fiber reinforced concrete similarly with actual measurement.

• Steel and Composite Structures
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• 제39권3호
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• pp.275-290
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• 2021

The main purpose of this research work is to investigate the critical buckling load of functionally graded (FG) porous plates with graphene platelets (GPLs) reinforcement using generalized differential quadrature (GDQ) method at thermal condition. It is supposed that the GPL nanofillers and the porosity coefficient vary continuously along the plate thickness direction. Generally, the thermal distribution is considered to be nonlinear and the temperature changing continuously through the thickness of the nanocomposite plates according to the power-law distribution. To model closed cell FG porous material reinforced with GPLs, Halpin-Tsai micromechanical modeling in conjunction with Gaussian-Random field scheme are used, through which mechanical properties of the structures can be extracted. Based on the third order shear deformation theory (TSDT) and the Hamilton's principle, the equations of motion are established and solved for various boundary conditions (B.Cs). The fast rate of convergence and accuracy of the method are investigated through the different solved examples and validity of the present study is evaluated by comparing its numerical results with those available in the literature. A special attention is drawn to the role of GPLs weight fraction, GPLs patterns through the thickness, porosity coefficient and distribution of porosity on critical buckling load. Results reveal that the importance of thermal condition on of the critical load of FGP-GPL reinforced nanocomposite plates.

• 대한기계학회논문집
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• 제6권3호
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• pp.232-238
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• 1982

The behavior of corner crack propagation by unidirectional plane bending fatigue was investigated in the butt welded joints of SS41 and SM50 steel plates including an edge through-thickness notch. The properties of fatigue crack propagation were inspected in the weld metal, heat-affected zone, and base metal of the welded joints. Main results obtained are as follows; (1) When a plate with an edge through-thickness notch is loaded by plane bending fatigue in indirection, the 2 variant corner cracks on the upper and lower edge of the plate are initiated and propagated respectively from the notch. (2) In case of a specimen containing a corner crack, it is more reasonable to estimate the crack propagation rate by area of fracture surface than by crack surface length. (3) The rate of fatigue crack propagation becomes faster in the following order; weld metal, heat-affected zone, and base metal. (4) The specimen including reinforcement shape is rapidly failed throughout bond due to effect of its shape when the repeated load exceeds a certain cycle.

• Advances in concrete construction
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• 제1권1호
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• pp.103-119
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• 2013

The applicability of limit analysis methods in design and assessment of concrete structures generally requires a certain plastic deformation capacity. The latter is primarily provided by the ductility of the reinforcement, being additionally affected by the bond properties between reinforcing steel and concrete since they provoke strain localization in the reinforcement at cracks. The bond strength of reinforcing bars is not only governed by concrete quality, but also by construction details such as bar ribbing, bar spacing or concrete cover thickness. For new concrete structures, a potentially unfavorable impact on bond strength can easily be anticipated through appropriate code rules on construction details. In existing structures, these requirements may not be necessarily satisfied, consequently requiring additional considerations. This two-part paper investigates in a theoretical study the impacts of the most frequently encountered construction details which may not satisfy design code requirements on bond strength, steel strain localization and plastic deformation capacity of cracked structural concrete. The first part introduces basic considerations on bond, strain localization and plastic deformation capacity as well as the fundamentals of the Tension Chord Model underlying the further investigations. It also analyzes the impacts of the hardening behavior of reinforcing steel and concrete quality. The second part discusses the impacts of construction details (bar ribbing, bar spacing, and concrete cover thickness) and of additional structure-specific features such as bar diameter and crack spacing.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.676-679
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• 1997

The present paper is concerned with the optimal deslgn that the static spring rate of the fiber-reinforcement composite spring is fitted to that of the steel leaf spring. The thickness and w~dth of springs were selected as deslgn variables. And object functions of the regression model were obtained through the analysis with a common analytic program. After regression coefficients were calculated to get functions of the regression model, optimal solutions were calculated with DOT. E-GlassIEpoxy and CarbonIEpoxy were used as fiber reinforcement materials in the design, which were compared and analyzed with the steel leaf spring. It was found that the static spring rate of the optimal model was almost similar to that of the existing spring.