• Geomechanics and Engineering
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• 제12권4호
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• pp.579-593
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• 2017

Geosynthetic reinforced soil retaining walls can be employed as railway embankments to carry large static and dynamic train loads, but very few studies can be found in the literature that investigate their dynamic behavior under simulated wheel loading. A large-scale dynamic test on a reinforced soil railway embankment was therefore carried out. The model embankment was 1.65 meter high and designed to have a soilbag facing. It was reinforced with HDPE geogrid layers at a vertical spacing of 0.3 m and a length of 2 m. The dynamic test consisted of 1.2 million cycles of harmonic dynamic loading with three different load levels and four different exciting frequencies. Before the dynamic loading test, a static test was also carried out to understand the general behavior of the embankment behavior. The study indicated the importance of loading frequency on the dynamic response of reinforced soil railway embankment. It also showed that toe resistance played a significant role in the dynamic behavior of the embankment. Some limitations of the test were also discussed.

• Structural Engineering and Mechanics
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• 제77권6호
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• pp.809-817
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• 2021

In this study, the dynamic behavior of a three-span hybrid continuous arch bridge under vehicle loading is investigated. The natural vibration characteristics of the bridge were analyzed through pulsation test. In the dynamic loading test, the vibrations of the bridge under different truck speeds and different pavement conditions were tested, and time histories of deflection and acceleration of the bridge were measured. Based on the dynamic loading test, the impact coefficient was analyzed. The results indicate that the pavement smoothness had more impacts on the vibration of the bridge than the truck's speed. The vertical damping of the bridge under the excitation of the trucks is larger than the transverse damping. Resonance occurs at the side span of the bridge under a truck at 10 km/h.

• Nuclear Engineering and Technology
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• 제38권7호
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• pp.639-656
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• 2006

In order to apply the leak before break (LBB) concept to nuclear piping systems, the dynamic strain aging effect of low carbon steel materials has to be taken into account, in compliance with the requirements of the Korean Standard Review Guide (KSRG) 3.6.3-1. For this goal, J-R tests are needed for a range of various temperatures and loading rates, including dynamic loading conditions. In the dynamic loading J-R test, the unloading compliance method can not be applied to measure the crack growth and direct current potential drop (DCPD) method; this method also has a problem defining the crack initiation point. The normalization method is known as a very useful method to determine the J-R curve under dynamic loading because it does not need additional equipment or complicated loading sequences such as electric current or unloading. This method was accepted by the American Society for Testing and Materials (ASTM) as a standard test method E1820 A15 in 2001. However, it has not yet been clearly verified yet if the normalization method is sufficiently reliable to be applied to LBB. In this study, the basic background of the J-integral, LBB and dynamic loading J-R test are explained, and the current status for dynamic loading J-R test methods are reviewed from the view point of LBB for nuclear piping. In particular, the theoretical and historical background of the normalization method which has received attention recently, is summarized. Recent studies for this method are introduced and future works are suggested that may improve the reliability of LBB for nuclear piping.

• 토지주택연구
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• 제6권3호
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• pp.139-145
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• 2015

말뚝 설계효율(설계지지력/재료강도)을 70%(160톤)에서 80%(190톤)로 개선하기 위해 기존 말뚝재하시험 자료 분석과 정밀 동재하시험 및 국내 최초의 양방향 재하시험을 실시하였다. 기존 동재하시험 데이터를 Davisson 방법으로 분석하면 풍화암 지지층(N치 50/15)에서도 설계지지력 190톤을 만족하였다. 그러나, 이를 CAPWAP으로 해석하면, 타격 에너지 부족으로 목표지지력을 만족하지 못한 말뚝이 전체의 40%가 나타났다. 따라서, 동재하시험 결과에서 목표 지지력을 확인하기 위해서는 6톤 이상의 해머에 의하여 충분한 타격력을 가하는 것이 필수적인 것으로 나타났다. 정적인 양방향 재하시험의 Davisson 분석에 의한 허용지지력은 260.0~335tonf(평균 285.3tonf)를 나타내어 목표지지력을 크게 상회하는 것으로 나타났다. 이 시험결과는 동일 말뚝에 대한 정밀 동재하시험의 허용지지력(평균 202.3tonf) 보다 약 40% 정도 크게 나타났는데, 동재하시험에서 충분하지 않은 타격력, 정적 양방향재하시험 시 주변말뚝에 의한 인터록킹에 의한 지지력 증가 등에 의한 차이로 판단된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.486-493
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• 2006

This paper deals with the procedure and the results on the dynamic loading tests of two large diameter - long drilled shafts (diameter=2.0m, length=75m) which were embedded into weathered rocks through thick soft marine clays and sandy gravels. Prior to the real dynamic loading test, the numerical simulation for the test procedure was performed to check the structural stability of the main pile body using equivalent static elastic analysis and the application of the hammer system using WEAP (Wave Equation Analysis of Pile Driving). Through these preliminary analyses the dynamic loading tests on large diameter - long drilled shafts have been successfully achieved.

• 한국구조물진단유지관리공학회 논문집
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• 제8권2호
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• pp.231-238
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• 2004

R/C교량에서 진행성 균열과 과도한 처짐에 의한 휨 내력의 저하는 차량하중에 의한 동적 반복하중으로부터 발생한다. 이러한 사실은 정적인 단조증가 하중 재하실험으로부터 획득한 자료의 동적 반복하중에서의 확인과 평가의 필요성을 제기한다. 따라서, 본 연구는 CFS로 보강된 R/C보를 단조증가하중 재하실험과 반복하중 재하실험을 동시에 수행하였다. 동적 반복하중 재하실험에 의하여, 단조증가하중 재하실험에 의한 결과의 타당성 및 적합성을 확인하고 반복하중에 의한 모멘트-곡률, 휨 강도의 감소, 균열 및 파괴 특성 등을 평가하였다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권1호
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• pp.50-57
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• 2017

Purpose : This paper is a comparative analysis results of the fatigue test for dental implants and accelerated life test by using a static type loading device commonly used in Korea and a dynamic type loading device (universal-joint) recommended by FDA. Methods : Fatigue tests of dental implant is based on ISO 14801 and classified into static load test and dynamic load test. The tests were carried out on three test specimens by four load stress steps under each loading device. For analysis on failure mode such as crack, fracture and permanent deformation of test specimens, we used X-ray three-dimensional computed tomography on test specimens before and after the fatigue tests. The design of the accelerated life test was based on the analysis results of the fatigue life data obtained from the dynamic load test and the statistical analysis software (Minitab ver.15) was used to analyze the appropriate life distribution. Results : As a result of the fatigue tests and the accelerated life tests at same acceleration condition under each test method, the fatigue life under the dynamic type loading device (universal-joint) was shorter than when static type loading device was applied. Conclusion : This paper can be used as a reference when the universal-joint type loading device for implants fatigue test is applied as ISO 14801.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.1819-1826
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• 2007

This study results of performed field load test in order to estimate the best pile length assessment and allowable bearing capacity of the pile foundation. End of initial driving(EOID) and restrike of pile dynamic loading tests were performed to calculate allowable bearing capacity of the experimental pile side and results were compared with the allowable bearing capacity estimated by theory. The results of allowable bearing capacity by EOID test is $1.08{\sim}1.21$ in the range of compared to the capacity calculated by the Structure Foundation Design Criterion. Allowable bearing Capacity by restrike of pile dynamic loading test is $1.32{\sim}1.48$ in the range of compared to the Structure Foundation Design Criterion. The Foundation Design Criterion underestimated the pile capacity. If the bearing capacity calculated by Structure Foundation Design Criterion is 100, EOID of pile dynamic loading test is 116, restrike of pile dynamic loading test is 138 for 20m pile used in this experimental.

• 한국지반공학회논문집
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• 제34권5호
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• pp.5-17
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• 2018

본 연구에서는 풍화암에 근입된 강관 매입말뚝의 안전율 제안을 위하여 정재하시험과 동재하시험을 수행하였다. 현장재하시험은 직경이 0.508, 0.457m 인 시험말뚝을 제작하여 정재하시험(14회)과 동재하시험(EOID 14회, Restrike 14회)을 실시하였다. 이때, 재하시험은 시험말뚝 시공완료 후 (1)초기동재하시험(EOID)을 수행하였으며, (2)시공완료 28일 후 정재하시험을 시행하였으며, (3)정재하시험 완료 후 15일 후에 재항타동재하시험(Restrike)을 실시하였다. 본 연구 결과 Davisson 판정법의 동재하시험을 이용한 지지력 산정 결과 정재하시험 대비 재항타동재하시험은 약 15% 낮게 나타났다. 정재하시험과 동재하시험의 지지력 분석을 통하여 안전율을 비교하였고, 최종적으로 동재하시험 안전율을 기존 2.0에서 1.75로 수정 제안하였다.

• 한국농공학회논문집
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• 제46권1호
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• pp.61-71
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• 2004

The performance evaluation and deflection of 3 spans concrete simplicity slab bridge analyzed by non-destructive and loading test. Compressive strength of slab and pier appeared in the range of each 353∼366 kgf/$cm^2$ and 152∼215 kgf/$cm^2$ in rebound number test. Also, it appeared that concrete quality of slab was good after performance improvement. The average compressive strength of slab by core picking appeared 229 kg/$cm^2$. In reinforcing bar arrangement test of span and member, it appeared that horizontal and vertical reinforcing bar was arranged to fixed interval. The value of calculation deflection that carried structural analysis with deflection analysis wave in static loading test appeared higher than that of experimental deflection and it appeared that hardness of this bridge was good. Maximum impact factor that estimated from deflection by running speed in dynamic loading test appeared by 0.216 in 10 km/hr running speed.