• 콘크리트학회논문집
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• 제12권5호
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• pp.121-130
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• 2000

Currently, in evaluating a flexural strength of a concrete member, the effect of specimen depth has not been systematically studied, even though its effect on ultimate strength of a section is very important. For all types of loading conditions, the trend is that the strength of a member tends to decrease when the member depth increases. In this study, the influence of specimen depth on flexural compressive strength of concrete member was examined experimentally. A series of C-shaped specimens subjected to axial compressive force and bending moment were tested using three geometrically similar specimens with different length-to depth ratios (h/c = 1, 2 and 4) which have compressive strength of 55 MPa. The results indicate that the flexural compressive strength decreased as the specimen depth increased. A model equation was derived based on regression analyses of the experimental data. Also, the results show that ultimate strain decreases as the specimen depth increases. Finally, a general model equation for the depth effect is proposed.

• International Journal of Concrete Structures and Materials
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• 제10권4호
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• pp.451-460
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• 2016

An anchorage system is necessary in most reinforced concrete structures for connecting attachments. It is very important to predict the strength of the anchor to safely maintain the attachments to the structures. However, according to experimental results, the existing design codes are not appropriate for large anchors because they offer prediction equations only for small size anchors with diameters under 50 mm. In this paper, a new prediction model for breakout shear strength is suggested from experimental results considering the characteristics of large anchors, such as the prying effect and size effect. The proposed equations by regression analysis of the derived model equations based on the prying effect and size effect can reasonably be used to predict the breakout shear strength of not only ordinary small size anchors but also large size anchors.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 가을 학술발표회 논문집
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• pp.83-87
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• 1990

The effect of concrete strength on shear cracking strength in reinforced concrete beams is investigated analytically. The quantitative response of reinforced concrete beam-end-part with varing concrete stiffness, which is a function of concrete compressive strength, is examined utilizing a finite element mothod. The result indicates that the severer shear stress localization/concentration takes place in the beam having higher concrete strength. Thus the increase ratio of shear cracking strength with respect to concrete compressive strength decreases as the concrete strength becoms higher.

• 대한조선학회논문집
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• 제55권3호
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• pp.205-214
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• 2018

This paper deals with the experimental study on the hygrothermal ageing effect to the strength of Carbon Fiber Reinforced Plastics (CFRP) materials for marine leisure boat manufactured by vacuum assisted resin infusion method. The experiments performed consist of tensile, flexural and shear tests according to American Society for Testing and Materials (ASTM) and Korean Industrial Standards (KS) test methods. Test coupons are varied from uni-directional(UD, $0^{\circ}$, $90^{\circ}$), Bi-Directional (BD), and Double-Bias (DB) carbon fiber fabrics in conjunction with epoxy resin. The results of tensile test show that tensile strength reduces significantly while not the same degree of reduction is observed for elasticity modulus with respect to the existence of hygrothermal ageing effect. This implies that the tensile strain induced from external load holds steady values but ultimate strength values change widely under hygrothermal ageing effect. In case of the flexural test, $0^{\circ}$ UD shows more strength reduction than $90^{\circ}$ UD while BD has reduced values in both flexural strength and elasticity modulus under hygrothermal ageing effect. It is learned that the bending strain induced from external load and ultimate strength values are reduced with respect to hygrothermal ageing effect. Shear test performed only on DB materials, and the results show marginal reduction in ultimate strength and moderate reduction in elasticity modulus. This means that the shear strain varies more than ultimate shear strength with respect to hygrothermal ageing effect. The experiment conducted in this paper clearly demonstrates the differences in material properties of the CFRP for the consideration of hygrothermal ageing effect. Findings obtained from this experimental study can serve as a fundamental input data for the realistic structural responses of marine leisure boat built in CFRP materials.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2010년도 정기 학술발표대회
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• pp.42-42
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• 2010

In order to assure the quality of concrete structure in construction process, the odor strength measured by using odor sensor was used to evaluate curing effect. Then, the compressive strength and odor strength in ordinary concrete N were shown in water curing(=standard curing), indoor and outdoor atmospheric curing condition. The difference between odor strength in the standard curing and that in each curing condition was defined as the difference in the odor strength. And the difference in odor strength in slag powder concrete BP cured in water curing(=standard curing) for different period before exposing in outdoor atmosphere in winter season were evaluated at the age of 14 days. A necessity to prolong the moisture curing for the slag powder concrete BP compared with the ordinary concrete N to obtain a required curing effect was shown by measuring the odor strength and long term compressive strength.

• Journal of the Korean Wood Science and Technology
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• 제42권2호
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• pp.112-118
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• 2014

The depth effect on bending strength of Japanese larch structural lumber was investigated by using the published data of two different depth lumbers with the same length. Depth effect parameters were derived from Weibull's weakest link theory and compared to the results from other researches. Depth effect on bending strength was significant for No.1 and No.3 lumber, but not insignificant for No.2 lumber. Calculated value of the depth effect adjustment factors was 0.21, 0.11 and 0.22 by lumber grade, respectively. These results were similar to those results from previous researches and supported depth effect on bending strength of lumber. An apparent depth adjustment factor has been proposed to 0.2 in the literatures. Based on this study, depth adjustment factor was considered to 0.2 as a conservative optimum design value that should be incorporated in domestic building code (KBC) for structural lumber.

• 한국생활과학회지
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• 제19권4호
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• pp.641-653
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• 2010

This study invesitgated the mediation effect of self-resilience on the relationship between perceived family strength and adolescents' level of adjustment at school. Participants were 479 elementary and middle school students from Daejeon. Data were analysed by SPSS 12.0 and Structural Equation Modeling with AMOS 5.0. Results were as follows: Firstly, family strength gives a direct effect on adolescent's school adjustment. Secondly, family strength is mediated by self-resilience on adolescent's school adjustment. Thirdly, significant differences in the path coefficients of the two groups were not found. These results indicate that we should expand the subjects of family and juvenile welfare, including general adolescents and general families, in order to improve family strength. In addition, programs such as the personal relationship and confidence elevation programs should be enacted to support elementary students' self-resilience.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2008년도 춘계학술대회
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• pp.290-307
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• 2008

The aim of this study was to estimate adverse effect on compression strength of corrugated fiberboard containers due to vibration during distribution process. Distribution environment such as road conditions and compression strength of corrugated fiberboard containers for selected agricultural products were studied. We found that increasing humidity does not effect significantly on natural frequencies of boxes, but results in accelerative effect to decrease compression strength of boxes. Box structures and product types also effect on loss of compression strength greatly.

• 콘크리트학회지
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• 제11권2호
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• pp.95-103
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• 1999

콘크리트 원주형 공시체의 크기에 따른 압축강도의 감소현상은 많은 관심을 받아 왔으나, 지금까지도 이에 대해 제시된 모델식이 드문 실정이다. 기존의 연구결과에 의하면 콘크리트의 강도는 부재의 크기가 증가할수록 감소하며 그 파괴거동을 규명하기 위해서는 비선형 파괴역학 이론을 적용해야 함을 알 수 있다. 표준형 및 비표준형 공시체의 크기에 따른 압축강도의 변화를 파괴역학 이론에 따라 연구하고 실용적인 예측 모델식이 제시된 바 있지만 콘크리트의 강도수준에 따른 파괴메카니즘의 차이를 고려한 관계식은 전무한 상황이다. 따라서, 본 논문에서는 공시체의 크기와 h/d의 영향 및 콘크리트 압축강도수준을 고려하여 보다 일반화된 압축강도 예측 모델식을 제시한다.

• Computers and Concrete
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• 제23권6호
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• pp.409-419
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• 2019

In the present study, effect of size and placement of cubic specimens on compressive strength of self-compacting lightweight concrete (SCLC) were considered. To do so, 81 specimens of different sizes (50 mm, 75 mm, 100 mm, and 150 mm) were prepared by using three different mixes of SCLC. Results of the cured specimens were then used in regression analyses to find predictive equations with regard to both the placement direction and the size. Test results showed that the strength ratio in cases in which the direction of loading and placement were parallel, were higher than those specimens, whose configurations were normal between loading and placement. In addition, strength ratios in SCLC mixes were slightly higher than those are for self-compacting normal weight concrete. In order to analyze the effect of size on compressive strength the conventional size effect law as well as the modified size effect law (MSEL) were used. Besides, the convergence criterion of nonlinear regression process of size effect study has been discussed. Analyses of the results showed that the unconstraint nonlinear regression in size effect study of SCLC mixes could lead to erroneous results.