• 한국안전학회지
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• 제18권1호
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• pp.81-88
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• 2003

Recently, pile foundations were constructed in rough or soft ground than ground of well condition thus it is important that prediction of ultimate bearing capacity and calculation of proper safety factor applied pile foundation design. This study were performed to dynamic loading tests for the thirty two piles at four different construction sites and selected pile at three site were performed to static loading tests and then compare with measured value and value of static and dynamic loading tests. The load-settlement curve form the dynamic loading tests by CAPWAP was very similar to the results obtained from the static load tests. Based on dynamic and static loading tests, the reliability of pile-driving formula were analyzed and then suggested with proper safety factor for prediction of allowable bearing capacity in this paper.

• Smart Structures and Systems
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• 제34권1호
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• pp.63-72
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• 2024

In-situ penetration tests using dynamic penetrometers are widely used for estimating soil resistance. Additionally, these dynamic penetrometers have been instrumented to improve tests accuracy. This paper introduces smart instrumented dynamic penetrometers and discusses experimental studies for various cases. An energy monitoring module was developed to enhance the dynamic penetration tests. The standard penetration test (SPT) and instrumented dynamic cone penetrometer (IDCP) tests were conducted using the energy monitoring module. Dynamic responses obtained by the energy monitoring module were used to calculate the transferred energies into the rod head and tip to correct the evaluation of ground strength. In addition, a crosshole-type dynamic penetrometer (CDP) was developed to measure the penetration index and shear wave velocity simultaneously to estimate the strength and stiffness of ground. The results of this study indicate that smart instrumented dynamic penetrometers may be effectively used to characterize the strength and stiffness of ground.

• 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.

• Geomechanics and Engineering
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• 제17권3호
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• pp.253-259
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• 2019

Concrete-to-concrete bedding planes (CCBP) are observed from time to time due to the multistep hardening process of the concrete materials. In this paper, a series of direct/cyclic shear tests are performed on CCBP under static and dynamic normal load conditions to study the frictional behavior effect by the shear velocities, normal impact frequencies, horizontal shear frequencies, normal impact force amplitudes, horizontal shear displacement amplitudes and normal load levels. According to the experimental results, apparent friction coefficient k ($k=F_{Shear}/F_{Normal}$) shows different patterns under static and dynamic load conditions at the stable shear stage. k is nearly constant in direct shear tests under constant normal load conditions (DCNL), while it is cyclically changing with nearly constant peak value and valley value for the direct shear tests under dynamic normal load conditions (DDNL), where k increases with decreasing normal force and decreases with increasing normal force. Shear velocity has little influence on peak values of k for the DCNL tests, but increasing shear velocity leads to increasing valley values of k for DDNL tests. It is also found that, the valley values of k ascend with decreasing impact normal force amplitude in DDNL tests. The changing pattern of k for the cyclic shear tests under constant and dynamic normal load conditions (CCNL and CDNL tests) are similar, but the peak value of k is smaller in CDNL tests than that in CCNL tests. Normal load levels, shear displacement amplitudes, vertical impact frequencies, horizontal shear frequencies and normal impact force amplitudes have little influence on the changing pattern of k for the cyclic shear tests. The tests of this study provide useful data in understanding the frictional behavior of the CCBP under distinct loadings, and these findings are very important for analyzing the stability of the jointed geotechnical structures under complicated in situ stress conditions.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.291-298
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• 2001

It is very difficult to accomplish load tests of piles with large diameter constructed on the offshore area, because of requirement for large scaled loading equipment and bad testing conditions. Therefore, so far in many cases pile driving dynamic formulas have applied to quality control, and recently dynamic load test method is widely used for confirming bearing capacities of such piles. However, in cases of piles with very large diameter about 2,500mm, it is nearly impossible for regular type load test methods of piles such as static and dynamic to apply owing to very large design load. This is case studies of load tests such as modified static and dynamic load tests of piles and point load tests of rock samples for estimating rational allowable bearing capacity of very large diameter piles constructed on the marine area.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.46-50
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• 2002

In other to evaluate the static and dynamic stiffness of machine tool structure, the accuracy and error from experimental methods are studied in this paper. The F.E.M., impulse tests and exciter tests are performed for the general simple structure whose exact solution can be obtained. So that the parameter and dynamic compliance can be got. From the result, the variation of natural frequency can be verified from the static preload. Further more the relationship of identify and difference for compliance and direction is presented in the exciting direction and measurement direction.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.877-883
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• 2009

Shaking table tests are performed to evaluate the dynamic group pile effect in fine sand. Single pile tests and $2{\times}4$ group pile tests are performed on 3D pile spacing. Dynamic p-y backbone curves are obtained to evaluate dynamic group pile effect by using dynamic p-y curve of single pile. And dynamic group pile p-multiplier is estimated by dynamic p-y backbone curve. Dynamic p-multiplier can be calculated by using subground reaction ratio of dynamic p-y backbone curve which is the same displacement of p-y curve peak point As the result, dynamic group pile effects are evaluated in terms of a shaking frequency, a shaking acceleration, and a relative density. Dynamic group pile p-multiplier is the largest at lead pile, and the value decrease at middle pile and trail pile. p multiplier increases as increasing input acceleration and decreasing relative density. This results coincide with NCHRP's research which suggest p multiplier increases as increasing pile cap displacement.

• Steel and Composite Structures
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• 제31권5호
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• pp.437-452
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• 2019

In this study, in-situ static and dynamic tests of four pre-stressed concrete (PC) track beams with different span lengths and curvatures in a straddle monorail transit system were reported. In the static load tests, the strain and deflection at critical sections of the PC track beams were measured to determine the load bearing capacity and stiffness. The dynamic responses of strain, deflection, acceleration, and displacement at key positions of the PC track beams were measured under different train speeds and train loads to systematically study the dynamic behaviors of the PC track beams. A three-dimensional finite element model of the track beam-vehicle coupled vibration system was established to help understand the dynamic behavior of the system, and the model was verified using the test results. The research results show that the curvature, span length, train speed, and train loads have significant influence on the dynamic responses of the PC track beams. The dynamic performance of the PC track beams in the curve section is susceptible to dynamic loads. Appropriate train loads can effectively reduce the impact of the train on the PC track beam. The PC track beams allow good riding comfort.

• Geomechanics and Engineering
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• 제38권5호
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• pp.487-495
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• 2024

In this study, a series of shaking table model tests were performed to evaluate the dynamic earth pressure acting on pile foundation during liquefaction. The dynamic earth pressure acting on piles were evaluated with depth and pile diameters comparing with excess pore water pressure, it means that the kinematic load effect plays a substantial role in dynamic pile behavior during liquefaction. The dynamic earth pressure acting on pile foundations with mass exhibited significant similarity to those without upper mass. Analyzing the non-fluctuating and fluctuating components of both excess pore water pressure and dynamic earth pressure revealed that the non-fluctuating component has a dominant influence. In case of non-fluctuating component, dynamic earth pressure is larger than excess porewater pressure at same depth, and the difference increased with depth and pile diameter. However, in the case of the fluctuating component, the earth pressure tended to be smaller than the excess pore water pressure as the depth increased. Based on the results of a series of studies, it can be concluded that the dynamic earth pressure acting on the pile foundation during liquefaction is applied up to 1.5 times the excess pore water pressure for the non-fluctuating component and 0.75 times the excess pore water pressure for the fluctuating component.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 지반공학 공동 학술발표회
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• pp.306-313
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• 2005

For seismic response analysis of rockfill dam, dynamic material properties, by field test, are needed. Density and elastic wave profiles have to be known to get an information of the material properties of structure. In this study, various field tests are applied to the example of rockfill dam to get an information of dynamic material properties and seismic safety is evaluated by seismic response analysis with the result of field tests.