• 콘크리트학회논문집
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• 제18권3호
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• pp.379-388
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• 2006

본 연구의 목적은 휨과 전단에 지배 받는 철근콘크리트 보에서 아치작용에 의한 전단기여분을 평가하는 모델을 개발하는 것이다. 전단력은 휨모멘트의 변화률이라는 관계식을 기초로, 분산트러스 이상화 기법을 이용하여 횡단면에서 베르누이(Bernoulli) 휨 평면으로부터 전단변형적합조건을 새롭게 유도하였다. MCFT와 분산트러스 이상화를 통해 전단흐름에 의한 복부전단요소의 전단곡률을 일치시키는 전단변형적합조건을 수립하였다. 전단변형적합조건을 이용하면, 보 전단거동은 타이드아치작용과 보 작용의 두 성분으로 수치적 분해 될 수 있다. 그리고 두 기본 작용의 분해가 가능하기 때문에 전단에 지배받는 보의 내력을 예측할 수 있다. 제안 모델의 유효성은 기존 문헌에 수록된 활용 가능한 실험 자료를 통해 검증하였고, 수행 결과는 예측치와 실험치 사이에서 실질적으로 일치하는 결과를 얻었다. 결과의 정확성으로부터 제안 모델의 합리성을 확신할 수 있었다.

• 콘크리트학회논문집
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• 제29권4호
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• pp.371-378
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• 2017

본 연구에서는 철근콘크리트 아치 데크의 정적재하실험을 통해 휨 거동을 평가하였다. 휨 실험은 길이 2.5 m, 폭 1.2 m, 중심단면 두께 100 mm, 단부단면 두께 160 mm의 실제 크기 프리캐스트 철근콘크리트 아치 데크의 정적재하 실험을 실시하였다. 실험결과는 극한설계강도에 비하여 약 1.74배 높은 하중을 견디는 것으로 관찰되었다. 반면, 실험체에는 구간에 따라 각각 다른 거동이 관찰되었다. 이러한 거동은 아치 데크와 이를 지지하는 반력대 사이에 일체거동이 이뤄지지 않은 이유로 인한 것으로 판단되었다. 그러므로 추후 연구에서는 반력대를 제외한 아치 데크의 정적재하 실험을 통해 정밀한 거동을 확인해야 할 것으로 사료된다. 실험결과를 종합하여 보면, 철근콘크리트 아치 데크는 일반형태의 바닥판에 비하여 우수한 구조적 이점을 통해 설계기준보다 높은 구조성능을 나타내었다. 이를 통해, 향후에는 장지간 바닥판으로써의 활용이 가능할 것으로 사료된다.

• Advances in concrete construction
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• 제7권1호
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• pp.11-22
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• 2019

A comprehensive assessing approach for durability of reinforced concrete structures dealing with the corrosion process of rebar subjected to the attack of aggressive agent from environment was proposed in this paper. Corrosion of rebar was suggested in the form of combination of global corrosion and pitting. Firstly, for the purposed of considering the influence of rebar's radius, a type of Plane Corrosion Model (PCM) based on uniform corrosion of rebar was introduced. By means of FE simulation approach, global corrosion process of rebar regarding PCM and LCM (Linear Corrosion Model) was regressed and compared according to the data from Laboratoire $Mat{\acute{e}}riaux$ et $Durabilit{\acute{e}}$ des Constructions (LMDC). Secondly, pitting factor model of rebar in general descend law with corrosion degree was introduced in terms of existing experimental data. Finally, with the comprehensive numerical simulation, the durability of an existing arch bridge was studied in depth in deterministic way, including diffusion process and sectional strength of typical cross section of arch, crossbeam and deck slab. Evolution of structural capacity considering life-cycle rehabilitation strategy indicated the degradation law of durability of reinforced arch bridges.

• Computers and Concrete
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• 제31권6호
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• pp.469-484
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• 2023

The response mechanism of simply supported two-way reinforced concrete (RC) slabs under fire was numerically studied from the view of stress redistribution using the finite element software ABAQUS. Results show that: (1) Simply supported two-way RC slabs undergo intense stress redistribution, and their responses show four stages, namely elastic, elastic-plastic, plastic and tensile membrane stages. There is no cracking in the fire area of the slabs until the tensile membrane stage. (2) The inverted arch effect and tensile membrane effect improve the fire resistance of the two-way slabs. When the deflection is L/20, the slab is in an inverted arch effect state, and the slab still has a good deflection reserve. The deformation rate of the slab in the tensile membrane stage is smaller than that in the elastic-plastic and plastic stages. (3) Fire resistance of square slabs is better than that of rectangular slabs. Besides, increasing the reinforcement ratio or slab thickness improves the fire resistance of the slabs. However, an increase of cover thickness has little effect on the fire resistance of two-way slabs. (4) Compared with one-way slabs, the time for two-way slabs to enter the plastic and tensile cracking stage is postponed, and the deformation rate in the plastic and tensile cracking stage is also slowed down. (5) The simply supported two-way RC slabs can satisfy with the requirements of a class I fire resistance rating of 90 min without additional fire protection.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.878-883
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• 2003

To modify some problems of ACI shear provisions, ultimate shear strength equation considering size effect and arch action to compute shear strength in high-strength concrete beams without stirrups is presented in this research. Three basic equations, namely size reduction factor, rho factor, and arch action factor, are derived from crack band model of fracture mechanics, analysis of previous some shear equations for longitudinal reinforcement ratio, and concrete strut described as linear function in deep beams. Constants of basic equations are determined using statistical analysis of previous shear testing data. To verify proposed shear equation for each variable, namely d, , ρ, f/sub c/' and aid, about 250 experimental data are used and proposed shear equation is compared with ACI 318-99 code, CEB-FIP Model code, Kim & Park's equation and Zsutty's equation. While proposed shear equation is simpler than other shear equations, it is shown to be economical predictions and reasonable safety margin. Hence proposed shear strength equation is expected to be applied to practice shear design.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.1091-1096
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• 2003

Pullout tests of single headed bars using plain concrete blocks indicate that the embedment depth of $10d_b$ is in general required for the headed bars to develop pullout strength equivalent to 125% of bar yield strength. In this experimental study, test results of multiple headed bars installed in reinforced concrete column sections are presented. Test variables included embedment depth, column main reinforcement ratio, and spacing of column ties. 2D29 bars were pulled out at one time from normal strength concrete. Test results indicated that the embedment depths, column tie spacings, and column main reinforcement ratios all influenced the pullout strengths of the headed bars. When the embedment depth was not sufficient, narrow tie spacings especially resulted in increased pullout strengths of the headed bars. Test results also indicated that the embedment depth of 15㏈ was sufficient for the closely spaced two headed bars (head-to-head spacing =$6d_b$) to develop pullout strength equivalent to 125% of the bar yield strength.

• International Journal of Concrete Structures and Materials
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• 제5권1호
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• pp.19-28
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• 2011

This paper documents an experimental study of dynamic response of reinforced concrete beams following instantaneous removal of a bearing column. Four half-scale specimens representing two-span beam bridging across the removed column were tested. The test boundary conditions simulated rotational and longitudinal restraints imposed on a frame beam by the neighboring structural components. The gravity loads were simulated by attaching mass blocks on the beams at three locations. Dynamic loading effects due to sudden removal of a column were simulated by quickly releasing the supporting force at the middle of the specimens. The experimental study investigated the load-carrying capacity of beams restrained longitudinally at the boundaries and dynamic impact on forces. The tests confirmed the extra flexural strength provided by compressive arch action under dynamic loading. The tests also indicated that the dynamic amplification effects on forces were much lower than that assumed in the current design guideline for progressive collapse.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.365-368
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• 2004

This paper deals with the verification of the new truss model that has been conceptually derived and formulated in preceding research. Since the model includes the arch $coefficient-\alpha$, the characteristics of this coefficient are examined, and it appears that the $coefficient-\alpha$ is a function of a/d, $\rho$ and $\rho_v$. The arch $coefficient-\alpha$ is applied to the test specimens available in literatures, and the predicted values are shown to be in excellent agreement with the experimental results.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.213-216
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• 2008

강관의 내부에 콘크리트를 충전한 구조인 콘크리트 충전 강관 구조(Concrete Filled Steel Tubular Structure, CFT 구조)는 강재와 콘크리트의 단점을 상호 보완하고 장점을 극대화 할 수 있다는 이점이 있다. 이와 같은 CFT 거더의 장점을 살리면서 CFT 거더보다 더 뛰어난 경제적, 구조적 효율성을 얻기 위해 기존의 CFT 구조에 아치 형식과 프리스트레스를 도입한 신형식 거더인 CFTA(Concrete-Filled and Tied Tubular Arch) 거더에 대한 연구가 현재 진행 중이다. CFTA 거더의 가장 큰 특징은 아치형상과 외부로 노출되어 있는 텐던인데 현재 연구과정에서 지적되고 있는 문제점 중의 하나는 외부로 노출된 텐던의 안전성에 관한 문제이다. 따라서 본 논문에서는 외부로 노출되어 있는 텐던에 대한 안전성 평가를 수행하였다. 또한, collision numerical simulation을 사용하여 동적 충돌에 대한 해석도 수행하였다. 모델의 해석을 위해 유한요소 해석 결과의 신뢰성이 높고, 타 연구에서도 많이 사용되고 있는 ABAQUS 6.5-1을 이용하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 추계 학술논문 발표대회
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• pp.115-116
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• 2011

TNowadays, the global warming is the most serious problem in the world and the cement industry is one of the factors which are responsible for it. Therefore, the development of new binders with enhanced environment and durability performance is needed. In this regard, the geopolymer technology is one of the breakthrough developments as an alternative to the portland cement. This paper shows some points of view on the development of geopolymers by reviewing previous researches including historical background, constituents of geopolymers, process of geopolymerization and several applications of geopolymer. Hence, the author proposes two research trends which are finding the best combination between the source materials and alkali liquid then, evaluating the corrosion for the metal bars.