급속 동결 융해에 대한 콘크리트의 저항 시험방법(KS F 2456)에 전단파 적용을 위한 실험적 연구

안지환,전성일,권수안 한국도로학회 2012 한국도로학회논문집 Vol.14 No.5

PURPOSES : It is important to consider the long-term performance of concrete pavement, because concrete pavement is more exposed to the various environmental conditions than any other concrete structures. One of the several methods to evaluate the long-term performance of concrete during winter is KS F 2456. Relative dynamic modulus of elasticity shows the resistance to freezing and thawing. METHODS : To measure relative dynamic modulus of elasticity, ultra sonic is generally used. But in this study, to measure the relative dynamic modulus of elasticity, both ultra sonic and shear wave were used and then compared each other. RESULTS : The results from the measurement by ultrasonic wave and shear wave were divided into three types. Type 1 : Specimens are good and relative dynamic modulus of elasticity did not decrease until 300 cycle. Type 2 : The relative dynamic modulus of elasticity decreased from the late cycle.(about 150 cycle later) Type 3 : The relative dynamic modulus of elasticity consistently decreased from the beginning. As a result of ANOVA, there is no difference according to measuring method, in type 2 and 3. But there is a difference according to measuring method, in type 1's relative dynamic modulus of elasticity. CONCLUSIONS : It is proved that shear wave can be used to understand the damage tendency of relative freezing and thawing and to measure the relative dynamic modulus of elasticity.

평판재하시험, 흙강성측정기 및 동적콘관입시험기를 이용한 노상토의 탄성계수 비교

김규선 한국지반공학회 2015 한국지반공학회논문집 Vol.31 No.3

This paper describes the correlation and relationship between elastic moduli measured by three stiffness measurementmethods with different mechanical characteristics to evaluate the compaction characteristics of subgrade soils. The SoilStiffness Gauge (SSG) with very small strain (≈ 0.001%) ranges, static Plate Loading Test (PLT) with mid-level strain(≈ 0.01~0.1%) ranges, and Dynamic Cone Penetrometer (DCP) using penetration resistance were implemented tomeasure the elastic modulus. To use the elastic modulus measured by different measurement methods with a wide rangeof strain in practice, it is required to identify the correlation and relationship of measured values in advance. Thecomparison results of the measured elastic moduli (ESSG, EPLT, EDCP) using the three measurement methods for domesticand overseas subgrade soils under various conditions indicate that the evaluated elastic modulus relies on the types ofsoils and the level of stress condition. The correlation analysis of the measured elastic moduli except the data of cementtreated soils indicates that the static elastic modulus (EPLT) is evaluated as about 60 to 80% of the dynamic elasticmodulus (ESSG). Unusual soils such as cement treated soils are required to be corrected by the stress correction duringthe correlation analysis with typical soils, because these types of soils are sensitive to the stress condition when measuringthe static elastic modulus (EPLT) of soils. In addition, when considering the use of DCP data for the evaluation of theelastic modulus (EDCP), the measured data of the elastic modulus less than 200 MPa show more reliable correlation.

암종별 P파 속도, 정탄성계수 및 동탄성계수의 상관관계 분석 연구

문성우,김형신,윤현석,서용석 대한지질공학회 2019 지질공학 Vol.29 No.3

The relationship between the P wave velocity, static elastic modulus, and dynamic elastic modulus of different rock types was investigated to identify the distributive characteristics of the dynamic elastic modulus. Laboratory and in situ test results from 1,646 rock specimens, which are obtained for design and construction of structure, were analyzed, and grouped into three key rock types: gneiss, granite, and sandstone. These relationships were verified by comparing them with the results from previous studies. The gneiss samples exhibit a linear P wave velocity-static elastic modulus relationship, whereas the granite and sandstone samples exhibit exponential relationships. Their coefficient of determination (R2) values are all in the 0.491-0.642 range, and are similar to those obtained in previous studies. The relationship between the static and dynamic elastic modulus exhibits a linear relationship for all rock types, yielding a coefficient of determination in the 0.543-0.676 range. The relationship between the P wave velocity and static elastic modulus follows an exponential regression for all rock types, with a high coefficient of determination that is in the 0.875-0.940 range. 국내 40개 구조물 설계 시 수행된 1,646개의 실내 및 현장시험 결과를 활용하여 국내 암종에 따른 동탄성계수의 분포특성을 파악하기 위하여 암종별 P파 속도, 정탄성계수, 동탄성계수 간의 상관식을 도출하고 기존 연구사례와 비교하여 검증하였다. P파 속도와 정탄성계수의 관계를 살펴보면 편마암에서는 선형, 화강암과 사암에서는 지수 함수의 관계를 보인다. 결정계수(R2)는 0.491~0.642로 높지 않지만, 결정계수를 0.836~0.990로 제시하고 있는 기존의 연구사례와 유사한 분포범위를 보인다. 정탄성계수와 동탄성계수의 상관식은 모든 암종에서 선형적인 관계를 보이며, 결정계수는 0.543~0.676이다. P파 속도와동탄성계수의 상관식은 지수함수의 관계를 보이며, 결정계수는 0.875~0.940으로 높게 나타난다.

충격반향기법을 이용한 화해를 입은 고강도 콘크리트의 탄성파 특성

이준철,이창준,김화중,이지희 한국화재소방학회 2015 한국화재소방학회논문지 Vol.29 No.1

본 연구에서는 충격반향기법을 이용하여 화해를 입은 고강도 콘크리트의 화재손상정도를 평가하였다. 100 MPa급의 고강도 콘크리트 시편을 제조하여 100~800 oC의 고온에 2시간 동안 노출한 후 충격반향기법의 응답스펙트럼을 이용하여시편의 탄성파 속도를 측정하였으며, 이를 이용하여 동탄성계수를 산출하였다. 이후 직접 압축강도 실험을 통해 시편의잔존압축강도와 정탄성계수를 측정하였다. 실험결과, 노출되는 온도가 높을수록 탄성파의 속도, 동탄성계수, 잔존압축강도, 정탄성계수가 저하되는 경향을 나타냈으며, 탄성파 속도와 압축강도, 동탄성계수와 정탄성계수는 선형적인 상관관계를 나타냈다. 따라서 충격반향기법을 이용하여 화해를 입은 고강도 콘크리트의 화재손상정도를 평가하는 것이 가능하다고 판단된다. In this study, the damages of high strength concrete exposed to high temperature have been evaluated by the impactecho method. Elastic wave velocity and dynamic modulus of elasticity were measured by the impact echo method, and thecompressive strength and the static modulus of elasticity were measured by the compression testing method after exposureto high temperature. The results showed that elastic wave velocity has a linear correlation with the compressivestrength and dynamic modulus of elasticity has a linear correlation with static modulus of elasticity. Based on results, it isconcluded that the impact echo method can be effectively applied to evaluate the mechanical properties of fire damagedhigh strength concrete.

동적 초미소 경도법에 의한 심도별 대전화강암 내 광물들의 역학적 특성

최정해(Junghae Choi),신주호(Juho Shin),장형두(Hyongdoo Jang),강성승(Seong-Seung Kang) 한국암반공학회 2017 터널과지하공간 Vol.27 No.3

동적 초미소 경도법의 압입시험, 하중-비하중 시험, 그리고 반복시험을 이용하여 심도별 대전화강암 내 광물들의 경도와 역학적 특성을 살펴보았다. 시험 결과 세 개 구간(Group-1, -2, -3)으로 광물 집단의 분류가 가능하였다. Martens 경도값은 세 가지 시험법 모두에서 41 m와 223 m 심도에 따른 차이가 크지 않았다. 그럼에도 불구하고, 그 크기는 반복시험<하중-비하중 시험<압입시험 순으로 나타났다. 광물 집단별 평균 Martens 경도, 탄성계수, indentation work 등을 고려해 볼때, 그들의 경계는 비교적 뚜렷하게 나타났다. 결론적으로 동적 초미소경도법의 세 가지 형태 시험법을 이용함으로써 광물들에 대한 비교적 정확한 경도값을 얻을 수 있었다. 또한 하중-비하중 시험과 반복시험으로부터는 광물들의 탄성계수와 광물들의 탄성적-소성적 성질 특성 파악도 가능하였다. The hardness and mechanical properties of the minerals in the Daejeon granite according to depths were investigated by indentation test, load-unload test, and cycle test of dynamic ultra-micro hardness. As a result of the tests, it was possible to classify into three mineral groups (Group-1, -2, -3). The Martens hardness was not significantly different between 41 m and 223 m depths in three mode tests. Nevertheless, they showed in the order of a cycle test<load-unload test <indentation test. Considering the average Martens hardness, elastic modulus, and indentation work for each mineral group, their boundaries were relatively clear. In conclusion, A relatively accurate hardness of minerals can be obtained by three mode tests of dynamic ultra-micro hardness. In addtion, it was possible to characterize the elastic modulus and the elastic-plastic properties of the minerals from the load-unload and cycle tests.

방진마운트 개발을 위한 와이어 메쉬 탄성계수 추출

김태연(T. Y. Kim),신윤호(Y. H. Shin),문석준(S. J. Moon),정병창(B. C. Jung),이태진(T. J. Lee) 한국소음진동공학회 2016 한국소음진동공학회 논문집 Vol.26 No.7

To alleviate the vibration problem or to satisfy the required criteria for manifesting the guaranteed performance of precise equipment, various vibration isolation materials or apparatus, such as viscoelastic material, air and coil spring, have been developed and applied. Among them, a wire mesh material is regarded as one of the good candidate for reducing the vibration in terms of moderate material price, easy shape machining and long life cycle without the property deterioration induced by the aging or environmental effects. In this paper, prior to wire mesh isolator design, the static and dynamic elastic modulus of wire mesh materials are extracted from the experiment by the simple shaped cylindrical specimens and their characteristics for applying to vibration isolator design are examined. The simple shaped specimens were made as considering the design parameters of a wire mesh mount; i.e. the density, wire diameter and wire mesh slope, and the sensitivity analysis were also performed from a view point of the extracted elastic modulus.

진동제어 콘크리트 개발에 관한 실험적 연구(I)

정영수,이대형,최우성 한국콘크리트학회 1996 콘크리트학회지 Vol.8 No.5

최근의 각종 사회시설의 확충에 따른 건설공사 및 교통시설 등은 많은 진동을 유발하여 사회적인 문제를 야기하고 있는 실정이다. 본 연구는 각종 제진재료를 이용하여 진동을 억제할 수 있는 콘크리트를 개발하여 각종 건설공사에서 흔히 발생할 수 있는 진동공해문제를 억제하고자 하며 아울러 폐기물의 재활용차원에서 폐자재를 이용하여 유용한 제진콘크리트를 개발하고자 하는데 그 목적이 있다. 우선, 제진재료를 이용한 압축강도 200kg/$\textrm{cm}^2$ 이상의 콘크리트 배합비를 찾기 위하여 Pilot실험을 수행하였으며, 선정된 적정배합비에 다른 진동시험제를 제작하여 재료의 동적특성 즉, 1차공명진동수, 동탄성계수 및 감쇠비를 측정하여 제진효과를 조사하였다. 제진재료로서는 Foam, Latex, Rubber Powder 그리고 Plastic Resin 등을 사용하였으며 진동의 감쇠효과가 있는 것으로 나타났다. 실험방법으로는 KS F 2437 규정과 진동파의 속도법을 사용하였으며, 감쇠비 측정은 Frequency Response Spectrum 곡선에 대한 Polynomial Curvefitting방법과 기하학적 해석방법을 이용하여 각각의 결과를 비교.분석하였다. Recently, the construction of infrastructures has been booming and accelerating to keep up with rapid economic growth. Construction activities and operation of transportation facilities cause unfavorable effects such as civil petitions associated with vibration-induced damages or nuisances. Accordingly, the objective of this study is to develop vibration-controlled concrete using various vibration-controlled mixtures, and also to recycle obsolete materials in part. As the first step to achieve this research, preliminary mix designs have been carried out to obtain an appropriate mix proportion above 200kg/$\textrm{cm}^2$ in uniaxial compressive strength. Test specimen based on the mix proportion selected have been actuated by the impact hammer to investigate their dynamic characteristics. Vibration-controlled mixtures are foam, latex, rubber powder and plastic resin, which have been determined to reduce a vibration by and large. KS F2437 and travel time method have been used to figure out 1st natural frequency and dynamic elastic moduli. Damping ratios have been computed by adopting the polynomial curvefitting method and the geometric analysis method on the frequency response spectrum curve. of which results have been compared and analyzed hereon.

Bottom Ash를 잔골재로 치환한 콘크리트의 압축강도에 관한 연구

김형무,김영수 대한건축학회지회연합회 2005 대한건축학회지회연합회 학술발표대회논문집 Vol.1 No.1

The purpose of this study is to analyze the strength development of concrete containing bottom ash as a part of fine aggregate. The experimental program included the measurement of concrete for compressive strength, splitting tensile strength, permeability, dynamic elastic modulus. The results of the experimentation are as follow. The compressive strength of concrete using bottom ash decreased according to increase of the replacement rate of bottom ash. The highest compressive strength showed at the replacement ratio of 30% bottom ash and 10% fly ash. The concrete containing CSA, CaSO4 as activator was effective on the compressive strength development. But the concrete using NaOH as activator showed a poor characteristic. In the case of using bottom ash, fly ash as fine aggregate, the concrete is waterproofed concrete than ordinary concrete by the pozzolanic effect.

그라우트 주입율 변화에 따른 사질토의 동적계수 특성

안광국(Ahn Kwangkuk),박준영(Park Junyoung),오종근(Oh Jonggeun),이준대(Lee Jundae),한기환(Han Kihwan) 한국지반환경공학회 2011 한국지반환경공학회논문집 Vol.12 No.5

전단탄성계수와 감쇠비와 같은 동적지반계수는 반복하중과 동적하중을 받는 지반구조물 설계에서 중요한 요소이다. 선형한계변형률 내에서 미소변형률에 관한 전단탄성계수와 감쇠비는 변형률과 관계없이 일정하다. 전단탄성계수는 최대전단탄성계수로 감쇠비는 최소 감쇠비로 고려하였다. 동적변형특성 범주내의 최대선형탄성계수에 관련된 많은 시험들이 수행됨과 동시에 간극비, 과압밀비, 구속압, 지질이력, PI 그리고 하중주기수에 관련된 많은 인자들이 동적지반특성에 영향을 미친다. 그러나 그라우팅에 의해 향상된 지반동적특성에 관한 연구는 지하연속벽시공, 심층혼합처리공법, 강관다단그라우팅과 같이 미비한 실정이다. 본 논문에서는 그라우팅에 의해 향상된 동적지반특성을 연구하기 위하여 함수비(20%, 25%, 30%), 그라우트 주입율(5%, 10%, 15%),양생기간(7일, 28일)을 변화시키면서 공진주시험을 실시하였다. 그 결과, 밀크 그라우트의 주입율과 재령, 함수비에 따라 동적계수인 전단탄성계수와 감쇠비가 영향을 받는 것으로 나타났다. Ground dynamic parameter such as shear elastic modulus and damping ratio is a very important variable in design of ground-structure with repeated load and dynamic load. Shear elastic modulus and damping ratio on small strain below linear limit strain is constant regardless of strain. Shear elastic modulus as the maximum shear elastic modulus and damping ratio as the minimum damping ratio were considered. As a lot of experiment related to the maximum shear elastic modulus, which is in dynamic deformation characteristics, have been conducted, many factors including voiding ratio, over consolidation ratio(OCR), confining pressure, geology time, PI, and the number of load cycle affect to dynamic soil characteristic. However, the research of ground dynamic characteristic improved with grout is absent such as underground continuous wall construction, deep mixing method, umbrella arch method. In order to investigate the dynamic soil characteristics improved with grout, in this study, resonant column tests were performed with changing water content(20%, 25%, 30%) and injection ratio of grout(5%, 10%, 15%), cure time(7th day, 28th day) As a result, shear elastic modulus and damping ratio, which are ground dynamic parameter, are affected by the injection ratio of milk grout, cure time and water content.

Effect of Freeze-Thaw Cycles on Dynamic Characteristics of Undisturbed Silty Clay

Gao Hang Cui,Zhuo Cheng,Daili Zhang,Shuxian Ma,Zhiqiang Liu 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.9

We conducted dynamic triaxial tests of undisturbed soil samples under different control parameters using the Global Digital Systems (GDS) dynamic triaxial instrument. We investigated the dynamic and engineering characteristics of undisturbed soil under a freeze–thaw cycle. When the dynamic load amplitude and the number of freeze–thaw cycles were adjusted, we explored the cumulative plastic strain, dynamic elastic modulus, and dynamic strength of undisturbed soil, and we then proposed appropriate fitting formulae to compute the cumulative plastic strain, dynamic elastic modulus, and dynamic strength. The findings revealed that as the number of freeze–thaw cycles increased, the cumulative plastic strain grew, the dynamic strength progressively fell, and the dynamic elastic modulus dropped first, but then increased. The critical physical and dynamic features of soil changed dramatically during one to six freeze–thaw cycles. This study’s suggested formula for the average growth ratio can directly reflect the cumulative plastic strain fluctuation of soil throughout freeze–thaw cycles. The formula has a good fitting effect on undisturbed soil, according to the test findings, and the accumulative plastic strain, dynamic elastic modulus, and dynamic strength may be computed within a specified range. The findings of this study contribute to a better understanding of the effect of the freeze–thaw cycle on the dynamic characteristics of undisturbed silty clay, as well as a theoretical foundation for the design and construction of silty clay highway subgrade in seasonally frozen regions as well as the dynamic analysis of vehicle simulation in seasonally frozen regions.