• 제목/요약/키워드: Falling weight test

검색결과 79건 처리시간 0.023초

크로스홀 형태의 동적 콘 관입기를 이용한 노반의 강성특성 평가 (Stiffness Characterization of Subgrade using Crosshole-Type Dynamic Cone Penetrometer)

  • 홍원택;최찬용;임유진;이종섭
    • 한국지반공학회논문집
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    • 제34권2호
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    • pp.55-63
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    • 2018
  • 열차의 하중을 적절한 강성으로 지지하기 위하여 다짐시공된 노반의 효과적인 강성특성 평가 기법에 대한 연구가 요구된다. 본 연구에서는 상부노반에 대하여 크로스홀 형태의 동적 콘 관입기(CDCP)를 적용함으로써 심도에 따른 강성특성을 평가하고자 하였다. CDCP의 적용을 위하여 세 단면의 다짐시공 완료된 상부노반이 대상 현장으로 선택되었으며, 각각의 개소에 대하여 CDCP 관입실험 및 들밀도시험, 동평판재하시험(LFWD)이 수행되었다. CDCP 관입실험 결과, 심도에 따른 탄성파 발신시간 및 전단파 수신시간을 획득하였으며, 이를 이용하여 노반의 전단파속도 주상도를 획득하였다. 또한, 동일 개소에서 들밀도시험으로부터 획득한 노반의 밀도 및 전단파속도 주상도를 이용하여 심도에 따른 최대전단강성계수($G_{max}$)를 평가할 수 있었다. CDCP 관입실험 및 들밀도시험으로부터 평가된 최대전단강성계수와 LFWD시험으로부터 획득한 동탄성계수($E_{vd}$)를 상호비교한 결과 매우 우수한 선형관계를 보이므로, CDCP 관입실험으로부터 유효한 강성특성을 평가할 수 있을 것이라 판단되었다. 또한, CDCP 관입실험으로부터 도출되는 결과는 일정 심도에 대한 대표 강성특성이 아닌 심도에 따른 연속적인 강성특성 이므로 노반의 강성특성 평가에 효과적으로 이용될 수 있을 것이라 기대된다.

현장 도로평가장비를 이용한 입상재료층의 비선형 재료상수 추정에 관한 연구 (Evaluation of the Nonlinearity Parameter in Unbound Material for Asphalt Concrete Pavement using Field-NDT Equipment)

  • 서주원;최준성;김수일
    • 대한토목학회논문집
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    • 제28권2D호
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    • pp.227-234
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    • 2008
  • 국내의 경우 도로포장설계시 외국의 설계법을 단순히 도입하여 사용하고 있지만 건설재료, 기후 및 교통조건 등이 외국과 상이하기 때문에 근본적인 제한성이 있다. 특히, 국내 포장구조해석에서 아스팔트층 거동특성만을 중요시하는 해석은 포장구조체가 각 층의 영향을 받는 종합적인 거동특성을 보인다는 포장구조체 시스템적인 특성을 고려한다면 많은 문제점을 내포하고 있다. 따라서, 도로포장 설계시 합리적이고 경제적인 설계를 할 수 있도록 포장구조체의 해석시스템을 구축하여야 한다. 본 연구에서는 포장하부의 다층구조로서의 역학적 거동을 정확히 해석하기 위하여 비파괴 시험장비인 FWD(Falling Weight Deflectometer) 를 이용하여 층 재료 자체의 성질을 대변하는 모델 중 포장하부를 구성하는 재료에 대한 비선형 탄성모델의 적용성을 검토하고, 복잡한 실험을 통해 얻게되는 비선형탄성모델의 구성인자인 재료상수를 FWD 시험자료로부터 직접 추정하는 체계를 제안하였다. 먼저, FWD 시험의 비선형성을 고찰하고, 실내 $M_R$ 시험을 통해 결정되는 재료상수를 현장에서 수집된 FWD 자료로부터 추정하는 체계를 제안하였다. 제안된 체계로부터 추정된 재료상수는 실내시험을 통해 제안된 국내 보조기층의 재료상수 범위 내에 있음을 알 수 있었다. FWD 를 이용한 비선형모델 적용의 신뢰성을 검증하기 위하여 깊이별 처짐 측정장비인 MDD(Multi-Depth Deflectometer) 현장시험자료를 이용하였다. 검증결과, 본 연구에서 제안한 비선형탄성모델을 적용한 방법이 기존의 선형탄성모델보다 실제 MDD 실측값에 더 가까운 결과를 나타냄을 알 수 있었다.

FWD 처짐량 기반 도로 공동 및 함몰 위험도 평가 기초 연구 (Preliminary Evaluation of Subsurface Cavity and Road Cave-in Potentials Based on FWD Deflections)

  • 김태우;윤진성;이창민;백종은;최연우
    • 한국도로학회논문집
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    • 제19권5호
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    • pp.59-68
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    • 2017
  • PURPOSES : The objective of this study is to evaluate the potential risk level of road cave-ins due to subsurface cavities based on the deflection basin measured with falling weight deflectometer (FWD) tests. METHODS: Ground penetrating radar (GPR) tests were conducted to detect road cavities. Then FWD tests were conducted on 13 pavement test sections with and without a cavity. FWD deflections and a deflection ratio was used to evaluate the effect of geometry of the cavity and pavement for road cave-in potentials. RESULTS : FWD deflection of cavity sections measured at 60 cm or a closer offset distance to a loading center were 50% greater than more robust sections. The average deflection ratio of the cavity sections to robust sections were 1.78 for high risk level cavities, 1.51 for medium risk level cavities, and 1.16 for low risk level cavities. The relative remaining service life of pavement with a cavity evaluated with an surface curvature index (SCI) was 8.1% for the high level, 21.8% for the medium level, and 89.8% compared to pavement without a cavity. CONCLUSIONS : FWD tests can be applied to detect a subsurface cavity by comparing FWD deflections with and without a cavity measured at 60 cm or a closer offset distance to loading center. In addition, the relative remaining service life of cavity sections based on the SCI can used to evaluate road cave-in potentials.

A Feasibility Study of Wood-plastic Composite Paver Block for Basic Rest Areas

  • Yang, Sungchul
    • Journal of the Korean Wood Science and Technology
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    • 제47권1호
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    • pp.51-65
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    • 2019
  • A wood-plastic composite (WPC) paver block was manufactured using wood chips waste through an extrusion process, and it was intended to be used for paving in basic rest areas. The first stage in this study covered preliminary tests in terms of flexural strength and dimensional swelling to determine the optimal WPC compounding mix condition, by variation of the WPC ingredients. Next, three different paver blocks including the WPC block, a non-porous cement block, and a porous cement block were tested in terms of various material properties in the laboratory. Finally, two outdoor test sections of the proposed paver blocks were prepared to simulate a basic rest area. Test results indicated that the flexural strength of the WPC paver blocks was about 1.6 times greater than that of the tested cement paver blocks. The WPC block pavement was unaffected by water buoyance as well as volume expansion due to swelling. Results from the impact absorbance test and light falling weight deflectometer (LFWD) test clearly showed that the WPC block paving system marginally satisfied the comfortable and safe hardness range from the pedestrians' perspective, while the results demonstrated that it is structurally sound for application as a road paving block.

도로하부 매설관의 매설심도 및 되메우기 재료가 포장체에 미치는 영향 평가 (Evaluation on the Effect of Depth Buried Pipeline and Refilling Materials on Pavement Performance)

  • 백철민;김영민;권수안;황성도;김진만
    • 한국도로학회논문집
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    • 제15권2호
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    • pp.105-112
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    • 2013
  • PURPOSES : Compared to the criteria from advanced countries, Korea has conservative criteria for the buried depth of pipeline (about 30~70cm deeper) causing the waste of cost and time. Therefore, this research investigated the effect of various buried depths of pipeline on pavement performance in order to modify the criteria to be safe but economical. In addition, a recycled aggregate which is effective in economical and environmental aspect was evaluated to be used as a refilling material. METHODS : In this study, total 10 pilot sections which are composed with various combinations of pavement structure, buried depth of pipeline, and refilling material were constructed and the telecom cable was utilized as a buried pipeline. During construction, LFWD (Light Falling Weight Deflectometer) tests were conducted on each layer to measure the structural capacity of underlying layers. After the construction is completed, FWD (Falling Weight Deflectometer) tests and moving load tests were performed on top of the asphalt pavement surface. RESULTS : It was found from the LFWD and FWD test results that as the buried depth decrease, the deflections in subbase and surface layer were increased by 30% and 5~10%, respectively, but the deflection in base layer remained the same. In the moving load test, the longitudinal maximum strain was increased by 30% for 120mm of buried depth case and 5% for 100mm of buried depth case. Regarding the effect of refilling material, it was observed that the deflections in subbase and surface layer were 10% lager in recycled aggregate compared to the sand material. CONCLUSIONS : Based on the testing results, it was found that the change in buried depth and refiliing material would not significantly affect the pavement performance. However, it is noted that the final conclusion should be made based on an intensive structural analysis for the pavement under realistic conditions (i.e., repeated loading and environmental loading) along with the field test results.

기능적 전기자극 치료가 편마비 환자의 균형에 미치는 영향 (Effects of Functional Electrical Stimulation on the Balance of Hemiplegic Patients)

  • 김용철;이석민;송창호
    • The Journal of Korean Physical Therapy
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    • 제16권3호
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    • pp.97-111
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    • 2004
  • This study, adopting the pretest-post test experimental study, is designed to find out how the functional electrical stimulation makes effect on the balance of a patient with spasticity of the ankle plantarflexor muscle caused by hemiplegic after stroke. The 46 subjects for this study were randomly sampled out of the patients who were hospitalized from September 1, 2003 to November 30, 2003 in H sanitarium in Yangpyung. The patients were with spasticity of the ankle plantarflexor muscle caused by hemiplegic after stroke and able to walk without supporting implements. The purpose of the study is firstly to analyze the change of ROM, FRTof a patient with spasticity of the ankle plantarflexor muscle when the functional electrical stimulation is applied and secondly to find out how the sex, age, height, weight, part of the diagnosis, duration of pain, experience of relapse and getting hurt from a fall of a patient make effect on the change. The experimental group for the study is divided into two to compare the differences of the effect. The exercising treatment only was performed for the conrtol group, and the functional electrical stimulation to the ankle dorsiflexor muscle as well as the exercising treatment was applied to the experimental group. The ROM test was performed to check the range of motion of the ankle with a double armed universal goniometer. The test was done 3 times to take an average. FRT were performed to check the balance. The statistical test was conducted using the SPSS 10.0/PC program by means of the following methods: χ2-test and t-test for testing homogeneity between the groups; paired t-test, independent sample t-test, F-test, and two-way ANOVA for analyzing the changes before and after the treatment. The levels of statistical significance of all the data were maintained at p<.05. According to the test, ROM has more decreased in experimental group than in control group when the functional electrical stimulation was applied only to the experimental group. However, the significant statistic difference was not shown (p=.059). FRT showed remarkable differences in the experimental group compared to the control group, showing the significant statistic difference (p=.000). On the one hand, the change of ROM, FRT related with the sex, age, height, weight, part of the diagnosis, and experience relapse was a meaningless minimum value. The change of ROM related to the duration of pain and the experience of falling down was also meaningless. However, FRT showed significant statistic difference (p<.05). According to the test above, the application of functional electrical stimulation to a patient with spasticity of the ankle dorsiflexor muscle caused by hemiplegic after stroke makes significant effect on the balance of a patient, but the result has nothing with the sex, age, height, weight, part of the diagnosis, duration of pain, experience of relapse and getting hurt from a fall of a patient. However, it is regarded to give contribution to the balance improvement of a patient. Therefore, this study expects to be a valuable clinical material for a patient with spasticity.

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굴 패각 분말을 충전재로 활용한 폴리머 콘크리트의 강도 및 내구 특성 (Strength and Durability Properties of Polymer Concrete Utilizing Oyster Shell Powder as a Filler)

  • 성찬용;김영익
    • 한국농공학회논문집
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    • 제52권6호
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    • pp.125-134
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    • 2010
  • This study was performed to evaluate the workability, strengths and durability of polymer concrete using oyster shell that are reclaimed at public shore illegally or leaved on the surroundings of shore to prevent the environmental pollution. We investigated the effect of oyster shell powder (OSP) and $CaCO_3$. on the slump, compressive strength, flexural strength, acid sulfuric and freezing and thawing resistance as a filler of polymer concrete. Modified OSP obtained by crushing oyster shell (less than 0.15 mm size) consists of 60.47 wt% of $SiO_2$ and 39.5 wt% of $CaCO_3$. As a result of slump test by OSP and $CaCO_3$. contents, it is found that slump of specimen used OSP is lower than that used $CaCO_3$. and the more OSP contents are, its slump is increased. Compressive and flexural strength of polymer concrete using OSP are similar or slightly lower than that using $CaCO_3$. In acid sulfuric test for 5 % $H_2SO_4$ and freezing thawing test, regardless of kinds of fillers and contents are not found fatal defects in weight change, falling-off in surface and durability factor.

지오셀을 이용한 투수성 포장의 지지력 평가 (Evaluation of Bearing Capacity for Permeable Pavement using Geocell)

  • 이수형;유인균;이대영
    • 한국지반신소재학회논문집
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    • 제11권3호
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    • pp.11-17
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    • 2012
  • 본 논문에서는 하부층 연약지반 보강공법으로 사용되고 있는 지오셀을 이용한 투수성 도로포장의 지지력 거동 특성을 다루었다. 현장시험을 통해 지오셀 포장의 지지력 변화를 일반쇄석 포장과 비교하여 분석하기위해 FWD를 이용하여 지지력 특성을 평가하였다. 실험결과 1.5mm 두께의 지오셀의 경우 보강효과가 나타나는 것으로 측정되었으며 재하하중이 증가함에 따라 보강효과도 큰 것으로 평가 되었다.

비 마약성 진통제 DA-5018의 신체의존성 (Physical Dependence on DA-5018, a Non-narcotic Analgesic Agent)

  • 강경구;김동환;백남기;김원배;양중익
    • Biomolecules & Therapeutics
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    • 제4권3호
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    • pp.232-238
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    • 1996
  • The physical dependence potency of DA-5018, a non-narcotic analgesic agent, was tested in mice dosed with 0.5 and 4 mg/kg/day for 2 months and daily increasing doses of 1, 2, 4, 6, 8 and 10 mg/kg over 10 days. Physical dependence was assessed taking natural withdrawal induced morphine-type abstinence (jumping, falling, biting or backward locomotion, rearing etc.) as well as barbiturates-type abstinence (body weight reduction, convulsion, ataxia etc.) into consideration. The results were compared with those after the same daily increasing doses of morphine. DA-5018 did not show evidence of physical dependence liability or abuse potential as measured by morphine-type or barbiturate-type abstinence signs following daily increasing or 2-month repeated administration. On the other hand, daily increasing doses of morphine produced physical dependence and the dependent state disappeared about 6 hours after the start of withdrawal signs. In the single dose suppression test, a single dose of morphine completely suppressed natural withdrawal signs that appeared in morphine-dependent animals. Therefore, these results indicate that DA-5018 does not have abuse potential and physical dependence liability.

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노인의 악력과 보행 가변성 간의 연관성: 예비연구 (Association between Hand Grip Strength and Gait Variability in Elderly: Pilot Study)

  • 이도연;이윤곤;신성훈
    • PNF and Movement
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    • 제20권1호
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    • pp.125-134
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    • 2022
  • Purpose: The aim of this study was to establish an association between grip strength and gait variability in the elderly. Methods: The participants in this experiment (n = 20) were aged 65 or older. Power grip and lateral pinch forces were obtained in grip strength tests, and spatiotemporal gait parameters were collected from IMU sensors during 6 min actual walking to test the gait of participants. The collected gait parameters were converted to coefficient of variation (CV) values. To confirm the association between grip strength and gait variability, a partial correlation analysis was conducted in which height, weight, and gait speed were input as controlling variables. Results: Grip power showed a significant negative correlation with the stride length CV (r = -0.52), and the lateral pinch force showed a significant negative correlation with the stance CV (r = -0.65) and swing CV (r = -0.63). Conclusion: This study reveals that gait variability decreases as grip strength increases, although height, weight, and gait speed were controlled. Thus, grip strength testing, a simple aging evaluation method, can help identify unstable gait in older adults at risk of falling, and grip strength can be utilized as a non-invasive measurement method for frailty management and prevention.