• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 춘계학술대회 논문집
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• pp.437-439
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• 2007

This paper was analyzed the resistivity change characteristic of mortar model block and concrete that was made earth electrode that's used concrete or basic concrete of building for 1 year. The early resistivity measurement value of concrete model block is higher than mortar model block. But after 1 year the resistivity measurement value of mortar model block is significantly higher than concrete model block. Because depends on time elapsed complete dryness factor of mortar model block that has not gravel is higher than concrete model block. And absorptance and function of mortar mode block was by far outstanding than concrete model block in the data for verification of the amount of contained water and the amount of dryness of mortar model block and concrete model block.

• International Journal of Concrete Structures and Materials
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• 제18권1E호
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• pp.11-16
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• 2006

The use of the current ACI 318 stress block parameters has been reported to provide unconservative estimations of the moment capacities for high-strength concrete columns. Accordingly, several concrete stress block parameters have been recently proposed. This paper discusses various concrete stress block parameters for high-strength concrete and their influences on the code provisions. In order to adopt the proposed stress block parameters to the design code, it is necessary to understand the impact of the change of the stress block parameters on various aspects of the code provisions. For this purpose, the influence of using of different stress block parameters on the location of the neutral axis and the tensile strain in extreme tension steel as well as the axial and moment capacities are investigated. In addition, the influence on the prestressed concrete members is also elucididated.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.300-305
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• 1996

Reinforced concrete column is an effective structural element to take advantage of high strength concrete. This paper presents an experimental and analytical strength of high strength concrete rectangular tied column sections under eccentric loading. The test variables are concrete strength, steel ratios, slenderness and eccentricity. The analytical results of the ACI's rectangular stress block, Zia's modified rectangular stress block, and a trapezoid block are compared with experimentally obtained data. It may be concluded that the trapezoid stress block provided the most reasonable column section capacities for high strength concrete columns.

• Advances in concrete construction
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• 제7권1호
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• pp.1-9
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• 2019

The conventional ACI rectangular stress block is developed on the basis of normal-strength concrete column tests and it is still being used for the design of high-strength concrete members. Many research papers found in the literature indicate that the nominal strength of high-strength concrete members appears to be over-predicted by the ACI rectangular stress block. This is especially true for HSC columns. The general shape of the stress-strain curve of high-strength concrete becomes more likely as a triangle. A triangular stress block is, therefore, introduced in this paper. The proposed stress block is verified using a database which consists of 52 tested singly reinforced high-strength concrete beams having concrete strength above 55 MPa (8,000 psi). In addition, the proposed model is compared with models of various design codes and proposals of researchers found in the literature. The nominal flexural strengths computed using the proposed stress block are in a good agreement with the tested data as well as with that obtained from design codes models and proposals of researchers.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.261-264
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• 2002

This study is intended to develop the new concrete block for planting through investigating weight and basic physical properties, varying the shapes of concrete block for planting. According to the results, unit weight, void ratio and absorption water ratio of concrete block show 1625kg/$m^3M$ 30%, and 7.7% respectively, and pH is small, compared with non neutralization and pH is below 8.5 after 7 days elapses. The compressive strength of concrete block for planting shows 38kgf/$cm^2$ at the age of 7 days, and 50kgf/$cm^2$ at the age of 28 days respectively. As the number of the hole is many and the area of hollow is large, weight of developed concrete block for planting grow light. Weight of optimum scheme with 2 hollow is reduced by 25%.

• 콘크리트학회논문집
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• 제11권3호
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• pp.59-67
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• 1999

The mass concrete structures are generally constructed in an incremental manner by deviding the whole structures by a series of many blocks. The temperature and stress distributions of any specific block are continuously affected by the blocks placed before and after the specific block. For an accurate analysis of mass concrete structures, the sequence of all the blocks must be accordingly considered including the change of material properties with time for those blocks considered. The purpose of this study is to propose a realistic analysis method which can take into account not only the influence of the sequence, time interval and size of concrete block placement on the temperatures and stresses, but also the change of material properties with time. It is seen from this study that the conventional simplified analysis, which neglects material property changes of some blocks with time and does not consider the effect of adjacent blocks in the analysis, may yield large discrepancies in the temperature and stress distributions of mass concrete structures. This study gives a method to choose the minimum number of blocks required to obtain reasonably accurate results in analysis. The study provides a realistic method which can determine the appropriate size and time interval of block placement, and can be efficiently used in the design and construction of mass concrete structures.

• Structural Engineering and Mechanics
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• 제90권5호
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• pp.505-515
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• 2024

In this study, obtaining theoretical stress-strain curves and determining the parameters defining the equivalent rectangular stress block were aimed for 3 and 4-layered rectangular Reinforced Concrete (RC) cross-sections subjected to flexure. For these aims, the analytical stress-strain model proposed by Hognestad was chosen for the concrete grades (20 MPa≤fck≤60 MPa) used in this study. The tensile strength of the concrete was neglected and the thickness of the concrete layers in the compression zone of the concrete cross-section was taken as equal. In addition, while concrete strength was kept constant within each layer, concrete strengths belonging to separate layers were increased from the neutral axis towards the outer face of the compression zone of the concrete cross-section. After the equivalent rectangular stress block parameters were determined by numerical iterations, variations of these parameters depending on concrete strength in layers and layer numbers were obtained. Finally, some analytical equations have been proposed to predict the equivalent stress block parameters for the 3 and 4-layered RC cross-sections and validities of these proposed equations were shown by different metrics in this study.

• International Journal of Concrete Structures and Materials
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• 제9권1호
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• pp.21-33
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• 2015

This study aimed to present a reinforced concrete block system that reduces the flange thickness of the existing form block used in new buildings and optimizes the web form, and can thus capable of being used in the seismic retrofit of new and existing buildings. By conducting a compression test and finite element analysis based on the block and grouted concrete strength, it attempted to determine the compression capacity of the form block that can be used in new construction and seismic retrofit. As a result, the comparison of the strength equation from Architectural Institute of Japan to the prism compression test showed that the mortar coefficient of 0.55 was suitable instead of 0.75 recommended in the equation. The stress-strain relation of the block was proposed as a bi-linear model based on the compression test result of the single form block. Using the proposed model, finite element analysis was conducted on the prism specimens, and it was shown that the proposed model predicted the compression behavior of the form block appropriately.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.743-748
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• 1997

In this paper, a new type of precast perforated concrete block is presented to be used in the construction of a step seawall. The overtopping rate of the perforated step seawall is lower than that of the traditional non-perforated step seawall. In construction stage, the cost of total construction of the perforated block is cheaper than that of traditional block. The new type of perforated block may be used as an alternative for shore protection facility.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.993-996
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• 2008

콘크리트 구조물 설계에 사용되는 콘크리트 압축 응력블럭은 실제 응력분포를 등가의 삼각형, 직사각형, 사다리꼴 또는 포물선-직선 등 여러 형태로 나타낸 것이다. 이러한 콘크리트의 압축 응력블럭은 주요 선진국의 설계기준마다 그 형태가 조금씩 다르며, 각 나라 콘크리트의 재료적 특성을 반영하여 적용하고 있다. 현재, 우리나라 콘크리트 설계기준에 적용하고 있는 직사각형 압축 응력블럭은 ACI 설계기준과 동일한 형태이고, 이는 고강도 콘크리트의 재료적 특성을 반영하지 못하여 비합리적 이라는 여러 연구결과가 발표되어왔다. 본 연구는 주요 선진국의 설계기준에 적용되는 콘크리트 압축 응력블럭에 대해 검토하였으며, 우리나라 콘크리트의 재료적 특성을 알기 위해 콘크리트 압축 응력블럭 실험을 실시하였다. 실험을 통해 하중 및 변형률을 얻었으며, 실험 결과에 의한 응력블럭계수를 도출하였다. 실험에 의한 응력블럭계수와 주요 선진국의 설계기준에 적용하는 응력블럭계수 값들을 비교.분석하였다. 또한, 주요 설계기준의 응력블럭에 따른 공칭 축력-모멘트 상관도를 비교 분석하였다.