• Journal of the Korean Geotechnical Society
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• v.26 no.7
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• pp.161-170
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• 2010

For the development of load and resistance factor design, reliability analysis is required to calibrate resistance factors in the framework of reliability theory. The distribution of measured-to-predicted pile resistance ratio was obrained based on only the results of load tests conducted to failure for the assessment of uncertainty regarding pile resistance and used in the conventional reliability analysis. In other words, successful pile load test (piles resisted twice their design loads without failure) results were discarded, and therefore, were not reflected in the reliability analysis. In this paper, a new systematic method based on Bayesian theory is used to update reliability indices of driven steel pipe piles by adding more proof pile load test results, even not conducted to failure, to the prior distribution of pile resistance ratio. Fifty seven static pile load tests performed to failure in Korea were compiled for the construction of prior distribution of pile resistance ratio. The empirical method proposed by Meyerhof is used to calculate the predicted pile resistance. Reliability analyses were performed using the updated distribution of pile resistance ratio. The challenge of this study is that the distribution updates of pile resistance ratio are possible using the load test results even not conducted to failure, and that Bayesian updates are most effective when limited data are available for reliability analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.641-652
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• 2007

In this paper, a half-scaled substructure test was performed to evaluate the buckling and structural safety of an existing transmission tower subjected to wind load. A loading scheme was devised to reproduce the dead and wind loads of a prototype transmission tower, which uses a triangular jig that is mounted on the reduced model to which the similarity law of a half length was applied. As a result of the preliminary numerical analysis carried out to evaluate the stability of a specimen for the design load, is was confirmed that the calculated axial forces of tower leg members were distributed to $80{\sim}90%$ of an admissible buckling load. When the substructured transmission tower was loaded by 270% of its maximum admissible buckling load, it was failed due to the local buckling that is occurred in joints with weak constraints for out-of-plane behavior of leg members. By inspection of load-displacement curves, displacements and strains of members, it is considered that this local buckling was due to additional eccentric force by unbalanced deformation because the time that is reached to yielding stress due to the bending moment is different at each point of a same section.

• Journal of the Korean Geotechnical Society
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• v.33 no.1
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• pp.67-77
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• 2017

In the present study, uplift load carrying behavior of micropiles with installation angle and pile spacing was investigated based on uplift load tests using single and group micropiles. In addition, evaluation methods of uplift load carrying capacity of group micropiles were proposed based on FHWA (2005) and Madhav (1987) and they were compared with test results to confirm the validity of proposed methods. From the test results, uplift load carrying capacities of single and group micropiles increased with the increase of the installation angle up to $30^{\circ}$, whose values also increased slightly with increasing pile spacing. For the proposed method based on FHWA (2005), the estimated values were similar to measured values up to $15^{\circ}$ of installation angle and 5D of pile spacing. For the proposed method based on Madhav (1987), on the other hand, it was observed that the estimated values were in good agreement with measured values in all installation conditions.

• KCI Concrete Journal
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• v.12 no.2
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• pp.23-30
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• 2000

This paper presents behavior of concrete pavement at transverse joint subject to static test load. The test was conducted on 1/10 scale model in the laboratory. Load transfer across the crack is developed either by the interlocking action of the aggregate particles at the faces of the joint or by a combination of aggregate interlock and mechanical devices such as dowel bars. In this study, significant three variables considered to the performance of joints were selected. : (a)diameter of dowel bars(2.5mm, 3.0mm, 4.0mm), (b)presence or absence of dowel bars, (c)aggregate types(crushed stone, round stone). Experimental results were analyzed to find relationships among displacement of discontinuous plane at jointed slab, load transfer efficiency and joint opening, etc. Displacement of discontinuous plane at joint was decreased according to the increase of dowel bar diameter. In addition, it is found that model slabs made using crushed stone had better load transfer characteristics by aggregate interlock than model slabs made using similarly graded round stone. Displacement of discontinuous plane was increased according to the increase of loading. In addition, it was decreased as dowel diameter(2.5mm, 3.0mm, 4.0mm) was increased. In the case of slab without dowel bars, displacement of discontinuous plane was greatly increased and load transfer effciency of slab applied crushed stone was shown 30 percent greater than round stone. In addition, load transfer efficiency of slabs, which were made using crushed and round stone without dowel bars, was decreased to 20 percent and 30 percent, respectively as it was compared with slabs made us-ing dowel bars.

• The Journal of Korean Physical Therapy
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• v.17 no.3
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• pp.429-440
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• 2005

The purpose of this study was to compare the effects of knee joint position sense following local and general load protocols in 25 healthy male subjects. Proprioception of the knee joint was evaluated by measuring absolute angular errors at matching angles before, after and between 2 different types of load protocols. Proprioception tests(on the dominant knee) were performed in which proprioception of the passivepassive reproduced and active-active reproduced knee position was measured. Local load was provided with maximum isokinetic knee extension-flexion on the isokinetic dynamometer(Cybex), and general load was 10 minutes running on a treadmill. Peak torque(knee extension and flexion) and heart rate(beats per minute) was evaluated as an indicator of local and general fatigue during load protocols. The results were as follows: 1. For pasive-pasive reproduced knee position test, significant difference in absolute angular errors after general load protocol was detected compared with that before general load protocol(P<.05), significant difference in absolute angular errors after local load protocol was detected compared with that before local load protocol(P<.05). However, no significant difference in absolute angular errors of general load protocol was detected compared with that of local load protocol (P>.05), no significant difference in absolute angular errors of local load protocol was detected compared with that of general load protocol(P>.05). 2. For active-active reproduced knee position test, significant difference in absolute angular errors after general load protocol was detected compared with that before general load protocol(P<.05), significant difference in absolute angular errors after local load protocol was detected compared with that before local load protocol (P<.05). Also, significant difference in absolute angular errors of general load protocol was detected compared with that of local load protocol(P<.05), significant difference in absolute angular errors of local load protocol was detected compared with that of general load protocol(P<.05). 3. A significant decrease of peak torque of knee extensors and flexors was seen after local load, although heart rate was significantly increased(P<.05). No significant change of peak torque of knee extensors and flexors was seen after general load(P>.05), although heart rate was also significantly increased(P<.05). The previous study revealed that knee proprioception is significantly altered when the muscle mechanoreceptors are dysfunctional due to muscle fatigue, although the joint mechanoreceptors have no significantly effect on knee proprioception when the presence of knee muscle fatigue. However, the results of this study are different from those of the previous study in that muscle weakness of the knee could not be seen after general load. This study shows that general load may diminish motor control by the central nervous system. Proprioceptional decline without muscle weakness of knee after general load suggests a change in the proprioceptional pathway without influence from muscle mechanoreceptors.

• Journal of Industrial Technology
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• v.15
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• pp.187-193
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• 1995

In this paper, a short-term load forecasting expert system considering the load variation due to the change in temperature is presented. The change in temperature is an important load variation factor that varies the normal load pattern. The conventional load forecasting methods by artificial neural networks have used the technique where the temperature variables were included in the input neurons of artificial neural networks. However, simply adding the input units of temperature data may make the forecasting accuracy worse, since the accuracy of the load forecasting in this method depends on the accuracy of weather forecasting. In this paper, the fuzzy expert system that modifies the forecasted load using fuzzy rules representing the relations of load and temperature is presented and compared with a conventional load forecasting technique. In the test case of 1991, the proposed model provided a more accurate forecast than the conventional technique.

• Land and Housing Review
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• v.8 no.4
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• pp.233-247
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• 2017

In Europe and the USA, the use of limit state design method has been established, and the Korea Ministry of Land, Transport and Maritime Affairs has implemented the bridge substructure design standard based on the critical state. But Korean piling methods and ground conditions are different from Europe and USA, the limit state design method can not be used immediately. In this study, the resistance coefficient was proposed by comparing and analyzing the results of the static load test(9 times) and dynamic load tests(9 times of EOID and 9 times of Restrike) with the bearing capacity calculated by Meyerhof(LH design standard, Road bridge design standard) method and surcharge load method(using Terzaghi's bearing capacity coefficient and Hansen & Vesic's bearing capacity coefficient). The previous LHI study showed the resistance coefficient of the LH design standard was 0.36 ~ 0.44, and this research result showed the resistance coefficient was 0.39 ~ 0.48 which is about 8% higher than the previous study. In this study, we tried to obtain the resistance coefficient mainly from the static load test and the resistance coefficient was 0.57 ~ 0.69(Meyhof method : LH design standard) based on the ultimate bearing capacity and the resistance coefficient was 0.49 ~ 0.60(Meyhof method : LH design standard) based on the Davissons bearing capacity. The difference of the resistance coefficient between the static and dynamic load test was greater than that we expected, we proposed the resistance coefficient(0.52 ~ 0.62 : Meyerhof method: LH design standard) using the modified bearing capacity of the dynamic load test. Summarizing the result, the coefficient of resistance obtained from the static and dynamic load tests was 0.35 ~ 0.76, which is greater than 0.3 suggested by the Road bridge design standard, so the economical design might be possible using the coefficient of resistance proposed by this study.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.173-182
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• 2000

To find axial and lateral responses of impact-driven H piles in embankment(SM), the H piles are instrumented with electric strain gages, dynamic load test is performed during driving, and then the damage of strain gages is checked simultaneously. Axially and laterally static load tests are performed on the same piles after one to nine days as well. Then load-settlement behavior is measured. Furthermore, to find the set-up effect in H pile, No. 4, 16, 26, and R6 piles are restriked about 1, 2, and 14 days after driving. As results, ram height and pile capacity obtained from impact driving control method become 80cm and 210.3∼242.3ton, respectively. At 15 days after driving, allowable bearing capacity by CAPWAP analysis, which 2.5 of the factor of safety is applied for ultimate bearing capacity, increases 10.8%. Ultimate bearing capacity obtained from axially static load test is 306∼338ton. This capacity is 68.5∼75.7% at yield force of pile material and is 4∼4.5 times of design load. Allowable bearing capacity using 2 of the factor of safety is 153∼169ton. Initial stiffness response of the pile is 27.5ton/mm. As the lateral load increases, the horizontal load-settlement behaves linearly to which the lateral load reaches up to 17ton. This reason is filled with sand in the cavity formed between flange and web during pile driving. As the result of reading with electric strain gages, flange material of pile is yielded at 19ton in horizontal load. Thus allowable load of this pile material is 9.5ton when the factor of safety is 2.0. Allowable lateral displacement of this pile corresponding to this load is 23∼36mm in embankment.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.1
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• pp.89-97
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• 2007

This paper describes a load simulator with power recovery capability, which is based on the voltage source converter-inverter set. The load simulator can save the electric energy that should be consumed to test the operation and performance of the power quality compensator and the power equipment. The load simulator consists of a converter-inverter set with a DSP controller for system control and PWM pulse generation. The converter operates as a universal load to model the linear load and the non-linear load, while the inverter feed the energy back to the power source with harmonic compensation. the performance of proposed load simulator was analyzed with scaled-model experiment, interconnected with the active power filter. The experimental results confirms that the proposed load simulator can be utilized to test the performance of active power filter.

• Journal of the Korean Geotechnical Society
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• v.36 no.8
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• pp.61-72
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• 2020

It is generally considered that differences of axial stiffness between exiting pile and reinforcing pile affect the load distribution ratio during vertical extension remodeling. But there are few cases to verify the effect of stiffness by field load test on load distribution ratio in Korea. In this paper, a series of load tests for micropiles were carried out to evaluate the effect of axial stiffness on the load distribution ratio. First, different types of micropiles were constructed so that conventional micropiles simulated existing piles and waveform micropiles simulated reinforcing piles. Secondly, load tests were performed to evaluate the stiffness of each piles. After then, the raft was installed to make a piled raft system and load tests were applied on foundation to verify the effect of axial stiffness on the load distribution ratio. The experimental results show that the stiffness of waveform micropiles were 2.5 times larger than that of conventional micropiles, and the load distribution ratio between existing and reinforcing piles was increased according to axial stiffness of piles.