SPSS를 활용한 플라이애시 혼입 콘크리트의 효율적 배합 제안

조홍범(Cho Hong-Bum),지남용(Jee Nam-Yong) 대한건축학회 2011 大韓建築學會論文集 : 構造系 Vol.27 No.1

For efficient mix design, this paper offers following information: the fly ash (FA) replacement ratio in which strength development is the maximum, the range of FA replacement ratio in which the strength of FA concrete is higher than that of ordinary Portland cement (OPC) concrete, and the binder content per unit strength. For these matters, various statistical analyses were performed based on a wide range of mix proportions and a number of strength test results of ready mixed concretes used in eight construction sites. The strength ratio, the ratio of FA concrete to OPC concrete in compressive strength, was expressed as the function of binder-water ratio and FA replacement ratio by multiple linear regression analysis. This equation suggests the range of FA replacement ratios in which strength ratio of 1 or higher can be obtained when binder content of FA concrete is the same as that of OPC concrete. The strength ratio increases with increasing water-binder ratio. As water-binder ratios decrease, the range of FA replacement ratios also decreases. It is desirable that FA concrete should have FA replacement ratio of about 15% to guarantee required average compressive strength using minimum binder contents. In FA replacement ratio of about 15%, the binder content per unit strength is 10.1∼10.6㎏/㎥/㎫ with respect to water-binder ratio. Because the binder content per unit strength is calculated with respect to water-binder ratio and FA replacement, its concept can be used as a means of determination of the binder content in mix design of FA concrete.

플라이애시의 활성도지수 평가에 관한 기초적 연구

박상준 한국건축시공학회 2008 한국건축시공학회지 Vol.8 No.5

In the evaluation method of KS on the activity factor of fly ash, same amount of cement should be replaced with fly ash. Therefore, contradictory effects on concrete strength exist, i.e. strength decease due to low content of cement and strength increase of strength due to filling-pore-function of fly ash. European Committee for Standardization (CEN) specifies the method 1 to 4, adding fly ash without reducing the content of cement, for the evaluation method on activity factor of fly ash. This study investigates the applicability of the method 2 of CEN to mix design of concrete. The followings are derived ; There is a key ratio of fly ash mixing which enhances the incremental ratio of mixing water to improve fluidity of mortar. The incremental ratio of mixing water is maximized about 11% ratio of fly ash mixing. Compressive strength most slightly increases at that ratio of fly ash mixing. Activity factor of fly ash increases as water-cement ratio becomes low and contents of fly ash becomes high. Moreover, quality of fly ash and condition of mix design affect the applicable amount of fly ash and available range of water-cement ratio. However, this method has some problems for practical purpose because activity factors of fly ash for some cases are over 1.0. Further research should be conducted to develop more useful method of evaluating activity factor of fly ash. In the evaluation method of KS on the activity factor of fly ash, same amount of cement should be replaced with fly ash. Therefore, contradictory effects on concrete strength exist, i.e. strength decease due to low content of cement and strength increase of strength due to filling-pore-function of fly ash. European Committee for Standardization (CEN) specifies the method 1 to 4, adding fly ash without reducing the content of cement, for the evaluation method on activity factor of fly ash. This study investigates the applicability of the method 2 of CEN to mix design of concrete. The followings are derived ; There is a key ratio of fly ash mixing which enhances the incremental ratio of mixing water to improve fluidity of mortar. The incremental ratio of mixing water is maximized about 11% ratio of fly ash mixing. Compressive strength most slightly increases at that ratio of fly ash mixing. Activity factor of fly ash increases as water-cement ratio becomes low and contents of fly ash becomes high. Moreover, quality of fly ash and condition of mix design affect the applicable amount of fly ash and available range of water-cement ratio. However, this method has some problems for practical purpose because activity factors of fly ash for some cases are over 1.0. Further research should be conducted to develop more useful method of evaluating activity factor of fly ash.

재유화형 분말수지 출입 폴리머 시멘트 모르타르의 건조수축 및 강도특성

연규석,주명기,이현종,김성기,이지원,Yeon, Kyu-Seok,Joo, Myung-Ki,Lee, Hyun-Jong,Jin, Xing-Qi,Lee, Chi-Won 한국농공학회 2006 한국농공학회논문집 Vol.48 No.1

This study was conducted to investigate experimentally the drying shrinkage and the strength properties of redispersible SBR and PAE powder-modified mortars. Polymer-cement ratio, content of shrinkage-reducing agent and antifoamer content were manipulated as the experimental variables. The peculiarity of this study is to obtain a high early-age strength by using the portland cement and alumina cement with the ratio of 8 : 2. Until 7 days of age, the drying shrinkage remarkably increased up to $1\~2\times10^{-4}$, while it tended to decrease as the ratio of polymer to cement ratio and the content of shrinkage-reducing agent increased. Polymer-cement ratio was effective in improving the flexural, tensile and adhesive strengths: As the ratio increased, the strengths correspondingly increased. The flexural strength was in the range of $7\~11$ MPa, the tensile strength was $3.5\~5$ MPa and the adhesive strength was $1.2\~3.9$ MPa. On the other hand, the compressive strength tended to decrease as the polymer-cement ratio increased, and it was in the range of $23\~39$ MPa. All strengths, flexural, tensile, adhesive and compressive strengths, decreased as the content of powder shrinkage-reducing agent increased. It turned out that the polymer-cement ratio influenced more on the behavior of drying shrinkage and the properties of strength than the powder shrinkage-reducing agent did.

무릎관절의 동측근력 불균형을 가진 성인여성의 근력운동이 H/Q ratio 및 관절위치감각에 미치는 영향

김재호,정승만 한국웰니스학회 2019 한국웰니스학회지 Vol.14 No.1

The purpose of this study was to investigate the difference in the H/Q ratio and the joint position sen of the knee joint during 12 weeks of exercise in 20 to 30 years old women with H/Q ratio imbalance of the knee joint. Grouping was divided into control group (CG, n = 10) and muscle strength exercise group (MSEG, n = 10) and exercise program was performed with exercise frequency three times a week for 12 weeks. Statistical analysis after the end of the experiment showed that the isokinetic flexors was significantly increased and the H/Q ratio was significantly improved in the MSEG compared to the CG. In addition, the position sense of the knee joint was significantly improved in the MSEG compared to the CG. Therefore, it is concluded that hamstring muscle strengthening exercise can improve H/Q ratio imbalance and sense of joint position, which is a proprioception, for adult women with H/Q ratio imbalance. 이 연구는 무릎관절의 H/Q ratio 불균형을 가진 30~40대 성인여성 20명을 대상으로 12주간 근력운동에 따른 무릎관절의 H/Q ratio와 관절위치감각의 변화 차이를 규명하고자 실시되었다. 집단분류는 통제집단(CG, n=10)과 근력운동집단(MSEG, n=10)으로 구분하였고, 12주간 주3회의 운동빈도로 근력운동 프로그램을 수행하였다. 실험 종료 후 통계분석을 실시한 결과 근력운동집단이 통제집단에 비해 등속성 굴근력이 유의하게 증가하였고, H/Q ratio가 유의하게 개선되었다. 또한 근력운동집단이 통제집단에 비해 무릎관절의 위치감각이 유의하게 향상되었다. 따라서 H/Q ratio 불균형을 가진 성인여성에게 뒤넙다리근(hamstring)의 근력강화 운동은 H/Q ratio 불균형 개선뿐만 아니라 고유수용감각인 관절위치감각 또한 향상시킬 수 있다고 판단된다.

An evolutionary fuzzy modelling approach and comparison of different methods for shear strength prediction of high-strength concrete beams without stirrups

Mohammadhassani, Mohammad,Nezamabadi-pour, Hossein,Suhatril, Meldi,shariati, Mahdi Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.14 No.5

In this paper, an Adaptive nerou-based inference system (ANFIS) is being used for the prediction of shear strength of high strength concrete (HSC) beams without stirrups. The input parameters comprise of tensile reinforcement ratio, concrete compressive strength and shear span to depth ratio. Additionally, 122 experimental datasets were extracted from the literature review on the HSC beams with some comparable cross sectional dimensions and loading conditions. A comparative analysis has been carried out on the predicted shear strength of HSC beams without stirrups via the ANFIS method with those from the CEB-FIP Model Code (1990), AASHTO LRFD 1994 and CSA A23.3 - 94 codes of design. The shear strength prediction with ANFIS is discovered to be superior to CEB-FIP Model Code (1990), AASHTO LRFD 1994 and CSA A23.3 - 94. The predictions obtained from the ANFIS are harmonious with the test results not accounting for the shear span to depth ratio, tensile reinforcement ratio and concrete compressive strength; the data of the average, variance, correlation coefficient and coefficient of variation (CV) of the ratio between the shear strength predicted using the ANFIS method and the real shear strength are 0.995, 0.014, 0.969 and 11.97%, respectively. Taking a look at the CV index, the shear strength prediction shows better in nonlinear iterations such as the ANFIS for shear strength prediction of HSC beams without stirrups.

An evolutionary fuzzy modelling approach and comparison of different methods for shear strength prediction of high-strength concrete beams without stirrups

Mohammad Mohammadhassani,Hossein Nezamabadi-pour,Meldi Suhatril,Mahdi shariati 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.14 No.5

In this paper, an Adaptive nerou-based inference system (ANFIS) is being used for the prediction of shear strength of high strength concrete (HSC) beams without stirrups. The input parameters comprise of tensile reinforcement ratio, concrete compressive strength and shear span to depth ratio. Additionally, 122 experimental datasets were extracted from the literature review on the HSC beams with some comparable cross sectional dimensions and loading conditions. A comparative analysis has been carried out on the predicted shear strength of HSC beams without stirrups via the ANFIS method with those from the CEB-FIP Model Code (1990), AASHTO LRFD 1994 and CSA A23.3 – 94 codes of design. The shear strength prediction with ANFIS is discovered to be superior to CEB-FIP Model Code (1990), AASHTO LRFD 1994 and CSA A23.3 – 94. The predictions obtained from the ANFIS are harmonious with the test results not accounting for the shear span to depth ratio, tensile reinforcement ratio and concrete compressive strength; the data of the average, variance, correlation coefficient and coefficient of variation (CV) of the ratio between the shear strength predicted using the ANFIS method and the real shear strength are 0.995, 0.014, 0.969 and 11.97%, respectively. Taking a look at the CV index, the shear strength prediction shows better in nonlinear iterations such as the ANFIS for shear strength prediction of HSC beams without stirrups.

전단철근비와 보의 단면크기에 따른 철근콘크리트 보의 전단강도 특성 연구

노형진,유인근,이호경,백승민,김우석,곽윤근 대한건축학회 2019 大韓建築學會論文集 : 構造系 Vol.35 No.6

The purpose of this study is to investigate the shear strength of reinforced concrete beam according to beam section size and shearreinforcement ratio. A total of nine specimens were tested and designed concrete compressive strength is 24 MPa. The main variables areshear reinforcement ratio and beam section size fixed with shear span to depth ratio (a/d = 2.5), the tensile reinforcement ratio (ρ = 0.013)and width to depth ratio (h/b = 1.5). The test specimens were divided into three series of S1 (225× 338 mm), S2 (270× 405 mm) and S3(315× 473 mm), respectively. The experimental results show that all specimens represent diagonal tensile failure. For S*-1 specimens (d/s=0),the shear strength decreased by 33% and 46% with increasing the beam effective depth, 26% and 33% for S*-2 specimens (d/s=1.5) and16% and 20% for S*-3 specimens (d/s=2.0) respectively. As the shear reinforcement ratio increases, the decrease range in shear strengthdecreases. In other words, this means that as the shear reinforcement ratio increases, the size effect of concrete decreases. In the S1 series,the shear strength increased by 39% and 41% as the shear reinforcement ratio increased, 54% and 76% in the S2 series and 66% and 100%in the S3 series, respectively. As the effective depth of beam increases, the increase range of shear strength increases. This means that theeffect of shear reinforcement increases as the beam effective depth increases. As a result of comparing experimental values with theoreticalvalues by standard equation and proposed equation, the ratio by Zsutty and Bazant´s equation is 1.30 ~ 1.36 and the ratio by KBC1 andKBC2 is 1.55~.163, respectively. Therefore, Zsutty and Bazant's proposed equation is more likely to reflect the experimental data. The currentstandard for shear reinforcement ratio (i.e.,  max=d/2) is expected to be somewhat relaxed because the ratio of experimental values totheoretical values was found to be 1.01 ~ 1.44 for most specimens. 본 연구에서는 철근콘크리트 보의 크기효과와 전단보강근이 전단강도에 미치는 영향을 분석하기 위해 인장철근비(ρ=0.013), 폭 대 깊이 비(h/b=1.5)와 전단경간비(a/d=2.5)를 일정하게 하였고, 단면의 크기와 전단철근비를 변수로 하여 전단실험을 하였다. 실험결과를 분석하여 다음과 같은 결론을 도출하였다. 1. 초기 균열은 휨 응력에 의해 발생하였고, 하중이 증가함에 따라 전단구간에서 사인장균열이 진행되었다. 사인장균열은 초기에 전단경간의 중립축 부분에서 발생한 후 하중이 증가함에 따라 하부측 지점부분과 상부측 가력부위로 확대되어 진행되었다. 이후 최종파괴형태는 모든 시험체에서 사인장파괴 형태로 관찰되었다. 2. 균열진전에 대해 살펴본 결과 d/s가 0인 시험체들(S1-1, S2-1, S3-1)은 평균 균열간격 176 mm, d/s가 1.5인 시험체들(S1-2, S2-2, S3-2)은 129 mm, d/s가 2.0인 시험체들(S1-3, S2-3, S3-3)은 98 mm로 나타나, 전단철근비가 증가할수록 평균 균열간격이 좁아지는 양상을 나타내었다. 균열폭 역시 동 시리즈 별로 20 mm, 11 mm, 10 mm로 나타나, 전단철근비가 증가할수록 평균 균열폭이 줄어드는 양상을 확인할 수 있었다. 3. 실험결과 전단철근비가 증가하면서 전단강도가 증가하는 경향을 보였다. 그러나 유효깊이가 증가할수록 시험체의 전단강도는 감소하였는데, 이것은 콘크리트 보의 크기효과에 의한 것으로 판단된다. 4. 실험값을 기준식 및 기존 제안식에 의한 이론값과 비교한 결과, Zsutty의 경우 평균 1.36, Bazant의 경우 평균 1.30, KBC1식, KBC2식은 1.55 ~ 1.63으로 나타나, Bazant의 제안식이 좀 더 실험값을 잘 반영한 것으로 판단된다. 5. 전단철근을 배근한 시험체에서 이론값에 대한 실험값의 비가 1.01 ~ 1.44로 나타났다. 특히, CSA 기준에서 요구하는 = 0.7d와 유사한 S=0.67d(d/s=1.5)인 S1-2, S2-2, S3-2 시험체에서는 1.13 ~ 1.39로 나타나 전단철근에 대한 현행기준  = d/2 는 다소 완화시켜도 될 것으로 판단되지만 이를 기준에 반영하기 위해서는 추가적인 연구가 필요하다. 6. d/s가 0인 시험체들(S1-1, S2-1, S3-1)은 유효깊이가 증가할수록 전단강도 값은 33 %, 46 % 감소하였고, d/s가 1.5인 시험체들(S1-2, S2-2, S3-2)은 26 %, 33 %, d/s가 2.0인 시험체들(S1-3, S2-3, S3-3)은 16 %, 20 % 감소하였다. 이를 통해 전단철근비가 증가할수록 전단강도의 감소폭은 줄어드는 것으로 나타났다. 즉, 이것은 전단철근비가 증가할수록 콘크리트의 크기효과는 줄어드는 것을 의미한다. 7. S1시리즈에서는 전단철근비가 증가할수록 전단강도 값은 39 %, 41 % 증가하였고, S2시리즈에서는 54 %, 76 %, S3시리즈에서는 66 %, 100 % 증가하였다. 이를 통해 보의 유효깊이가 증가할수록 전단강도의 증가폭은 늘어나는 것으로 나타났다. 즉, 이것은 보의 유효깊이가 증가할수록 전단철근의 영향이 커진다는 것을 의미한다.

The effects of the H/E ratio of various Cr–N interlayers on the adhesion strength of CrZrN coatings on tungsten carbide substrates

Kim, Hoe-Kun,La, Joung-Hyun,Kim, Kyu-Sung,Lee, Sang-Yul Elsevier 2015 Surface & coatings technology Vol.284 No.-

<P><B>Abstract</B></P> <P>In this work, various Cr–N interlayers were synthesized to improve the adhesion strength of CrZrN coatings on a WC-6wt.% Co substrate. The hardness to elastic modulus ratio (H/E ratio) of the Cr–N interlayers was controlled to obtain the optimum combination of Cr–N interlayer, CrZrN coating, and WC-6wt.% Co substrate. The crystalline phases of the Cr–N interlayers were synthesized using various N<SUB>2</SUB> partial pressures from 0 to 0.28Pa, and the hardness and elastic modulus of the synthesized Cr–N interlayers were measured to be in the ranges of 7 to 28GPa and 335 to 357GPa, respectively. This resulted in H/E ratio variations from 0.021 to 0.079. The results from a scratch test showed that a CrZrN coating with a single phase CrN interlayer exhibited the highest adhesion strength (46N), while the same coating with a Cr interlayer showed the lowest adhesion strength (9N). The improved adhesion strength could be attributed to the H/E ratio of the Cr–N interlayer in that there existed a gradual decrease in the H/E ratio from the CrZrN coating, to the single phase CrN interlayer, and to the WC substrate (0.090, 0.068, and 0.045, respectively). The coating structure with a gradual decrease in H/E ratios induces a smooth transition of stress in the coating under a loading condition. The adhesion strength of the CrZrN coatings could be improved significantly by structuring the coating with an optimal H/E ratio gradient.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CrZrN coatings with various Cr–N interlayers were synthesized on WC substrate. </LI> <LI> H/E ratios of Cr–N interlayers varied from 0.021 to 0.079 due to phase change. </LI> <LI> Single phase CrN interlayer showed a median value of H/E ratio to be 0.068. </LI> <LI> CrZrN coating with CrN interlayer showed the highest critical load (Lc3, 46N). </LI> <LI> Structuring with an optimal gradient of H/E ratio improves adhesion strength. </LI> </UL> </P>

강도한계 이선형 단자유도 시스템의 동적 불안정

한상환,김종보,배문수,문기훈 한국지진공학회 2008 한국지진공학회논문집 Vol.12 No.5

강도한계 이선형 단자유도 시스템의 지진 하중 하에서의 동적 불안정에 대해 연구하였다. 강도한계 이선형 이력 모델은 철골 모멘트 골조의 이력거동을 가장 잘 모사한다. 단자유도 시스템의 동적 불안정을 판단하기 위해 붕괴 강도비를 사용하였고, 이것은 붕괴가 일어날 때의 항복강도 저감계수이다. 단단한 지반에서 측정된 240개의 지진을 이용하고 고유주기, 강성 경화 기울기, 음강성 기울기, 연성 그리고 2{\sim}20%의 감쇠비를 변수로 하여 강도한계 이선형 단자유도 시스템의 붕괴 강도비의 평균과 편차 값들을 구할 수 있도록 통계 분석을 하였다. 비선형 회귀분석을 통해 강도한계 이선형 단자유도 시스템의 붕괴 강도비의 평균과 표준편차를 계산할 수 있는 식을 구하였다. 제안한 식을 이용하여 붕괴 강도비의 확률적 분포를 구하였고, 실제 값과 비교하여 제안한 식의 정확성을 입증하였다. This study investigates the dynamic instability of strength-limited bilinear single degree of freedom (SDF) systems under seismic excitation. The strength-limited bilinear hysteretic model best replicates the hysteretic behavior of the steel moment resisting frames. To estimate the dynamic instability of SDF systems, the collapse strength ratio is used, which is the yield-strength reduction factor when collapse occurs. Statistical studies are carried out to estimate median collapse strength ratios and those dispersions of strength-limited bilinear SDF systems with given natural periods, hardening stiffness ratios, post-capping stiffness ratios, ductility and damping ratios ranging from 2 to 20% subjected to 240 earthquake ground motions recorded on stiff soil sites. Equations to calculate median and standard deviation of collapse strength ratios in strength-limited bilinear SDF systems are obtained through nonlinear regression analysis. By using the proposed equations, this study estimated the probabilistic distribution of collapse strength ratios, and compared this with the exact values from which the accuracy of the proposed equations was verified.

포장용 롤러전압콘크리트의 다짐도와 압축강도의 상관관계 분석

정건우,송시훈,이승우 대한토목학회 2016 대한토목학회논문집 Vol.36 No.6

Roller-Compacted Concrete Pavement (RCCP) is a type of pavement that shares conventional concrete pavement material characteristics and asphalt pavement construction characteristics. Even though RCCP is compacted in the same way and have similar aggregate gradation to asphalt pavements, its materials and structural performance properties are similar to those of conventional concrete pavement. With cement hydration and aggregate interlock, Roller-Compacted Concrete or RCC can provide strength properties equal to those of conventional concrete with low cement content. Therefore, compaction ratio of RCC can highly influence on its strength. In general, 95% of compaction ratio is required for proper strength development. RCC strength can be highly influenced by compaction energy which depends on compaction equipment and compaction method. Therefore, it is necessary to analyze the relationship between compressive strength and compaction ratio of RCC. RCCP specimens were produced at different compaction ratio by using different compaction methods and energies. The compaction ratio was defined by the ratio of the specimen's dry density and its maximum dry density. The maximum dry density was obtained from Modified Proctor test. 28 days compressive strength corresponding to each compaction ratio case was tested. Finally, the relationship between compressive strength and compaction ratio can be analyzed. For application of roller-compacted concrete in domestic construction site, the relationship is important for field compaction management. 롤러전압콘크리트포장 공법은 기존 시멘트 콘크리트 공법의 재료 특성 및 아스팔트 포장의 시공특성을 공유하는 포장 방식이다. 일반 시멘트 콘크리트 포장의 우수한 구조적 성능을 유지하면서, 아스팔트 시공 장비를 사용하여 간소한 시공절차로 경제성을 확보할 수 있다. 롤러전압콘크리트포장 공법은 수화반응과 롤러다짐에 의한 골재 맞물림 효과로 일반 시멘트 콘크리트 포장보다 적은 시멘트량을 사용하여도 충분한 강도를 발현할 수 있다. 또한 일반 시멘트 콘크리트 포장과 동등한 강도 특성을 발휘 할 수 있으며, 본 연구에서는 RCCP의 다짐도와 압축강도의 관계를 정량적으로 도출하고자 한다. 롤러전압콘크리트의 다짐에너지를 변화시키면서 다양한 다짐도를 갖는 시편을 제작하였다. 다짐도는 시편의 건조단위중량과 최대건조단위중량의 비로 정의하였으며, 다양한 다짐도로 성형된 시편의 28일 압축강도를 평가하였고, 다짐도에 따른 강도비의 관계를 도출 하였다. 따라서 롤러전압콘크리트 공법의 국내 현장적용을 위한 다짐도에 따른 강도비의 중요성을 부각하여 현장 다짐도 관리에 적용할 수 있을 것으로 판단된다.