• Journal of the Korean Society for Railway
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• v.13 no.2
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• pp.186-193
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• 2010

Track system and periodic live load are characteristics of railway bridges. In the design and construction of railway bridge, periodic live load increases the importance of dynamic behavior. And It is well known that behavior of railway bridge may be affected by track system in real bridge. Through experimental study, static and dynamic behaviors were investigated. Deflection and stress due to bending moment were measured, the location of neutral axis of each section, natural frequency, damping ratio were analyzed for each three track systems - girder only, installed ballast track system and installed concrete slab track system. According to measured values for the each type of track system, concrete track system increases the stiffness of bridge by 50%, and ballast system does by 7%, dynamic responses of structure change linearly with the magnitude of load and location of neutral axis of each sections varies with each track system. Damping ratio is almost equal without and with track. Therefore, the effects of track system on the integral behaviors of railway bridge can not be ignored in the design of bridge, especially in the case of concrete slab track system. So study of the quantitative analysis method for effects of track system must be performed.

• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.149-160
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• 1999

This paper is a part of a research aimed at the verification of basic design rules of high-strength concrete columns. A total of 32 column specimens were tested to investigate structural behavior and strength of eccentrically loaded reinforced concrete tied columns. Main variables included in this test program were concrete compressive strength. steel amount, eccentricity, and slenderness ratio. The concrete compressive strength varied from 356 kg/$cm^2$ to 951 kg/$cm^2$ and the longitudinal steel ratios were between 1.13 % and 5.51 %. Test results of column sectional strength are compared with the results of analyses by ACI rectangular stress block, trapezoidal stress block, and modified rectangular stress block. Axial force-moment-curvature analysis is also performed for predicting axial load-moment strength and compared with the test results. The ACI rectangular stress block provides over-estimated column strengths for the lightly reinforced high strength column specimens. The calculated strengths by moment-curvature analyses are highly affected by $k_3$ values of the concrete stress-strain curve. Observed failure mode. concrete ultimate strain, and stress block parameters are discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.6
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• pp.1109-1116
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• 2016

There are various test methods for evaluating the reflective cracking resistance of asphalt concrete pavement. Repeated direct tensile test is cheap and simple compared to the other traditional experimental methods. Determination of failure criteria is needed to apply a repeated direct tensile test. Various methods were used to determine the number of failure of repeated direct tensile test. The number of failure was defined as the time to reach 10% of the initial load, this method can be satisfied with specified tolerance of 10%. When the thickness of specimen is increased to 50 mm from 30 mm, the failure number is increased by 13.6 times. Thus, this result shows that the thickness of pavement is a big influence on the reflective cracking resistance. Reflective cracking resistance of asphalt concrete is decreased according to the increase in opening displacement. The repeated direct tensile test can be used as a reflective cracking resistance factor in pavement design, because it can evaluate the reflective cracking resistance according to the pavement thickness, opening displacement, material properties etc.

• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.127-140
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• 2004

Conventional methods for the assessment of liquefaction potential were primarily for areas of severe earthquake zones (M=7.5) such as North America and Japan. Detailed earthquake related researches in Korea started in 1997, including development of the seismic design standards for port and harbour structures, which was later completed in 1999. Because most contents in the guidelines were quoted through literature reviews from North America and Japan, which are located in strong earthquake region, those are not proper in Korea, a moderate earthquake region. This requires further improvement of the present guidelines. Considering earthquake hazard data in Korea, use of laboratory tests based on irregular earthquake motion appears to be effective to reflect the dynamic characteristics of soil more realistically than those using simplified regular loading. In this study, cyclic triaxial tests using irregular earthquake motions are performed with different earthquake magnitudes, relative densities, and fines contents. Assessment of liquefaction potential in moderate earthquake regions is discussed based on various laboratory test results. Effects of these components on dynamic behavior of soils are discussed as well. From the test results, screening limits and magnitude scaling factors to determine the soil liquefaction resistance strength in seismic design were re-investigated and proposed using normalized maximum stress ratios under real irregular earthquake motions.

• 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.

• Journal of the Korean Geosynthetics Society
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• v.19 no.1
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• pp.83-91
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• 2020

In this study, the characteristics of support behavior according to the change of ground condition of the cast-in-place pile and the large Caisson foundation, which are increasingly used as foundations of large structures and bridges. the allowable bearing capacity calculated using the yield load analysis method was analyzed to calculate similar allowable bearing capacity for each method. In addition, the allowable bearing capacity calculated by the ultimate load analysis method was found to have a large difference in bearing capacity for each method. Through this point, it can be usefully used as an empirical formula for evaluating the settlement characteristics of piles in future design and construction. In addition, as a result of examining the ground force distribution during sedimentation of large caissons, the section of the weathered rock layer showed almost constant ground force distribution as ground forces decreased after yield occurred at the base corner. And in the bed rock layer section, the foundation's center was transformed into a ground force in the form of a convex downward due to an increase in the ground resistance of the central part. Using these results, the theory previously presented by Fang (1991) and Kőgler (1936) was proved.

• Composites Research
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• v.16 no.3
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• pp.32-40
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• 2003

In recent years, the investigation on the development of fiber reinforced plastic(FRP) Re-Bar has been greatly increased due to the attractive physical and mechanical properties of FRP. The primary reason of such a tendency is in the fact that it does not ordinarily cause durability problems such as those associated with steel reinforcement corrosion. This study is an experimental investigation on the flexural behavior of one-way concrete slabs, which can be used to construct bridge deck, reinforced with GFRP Re-Bar bundle. The tensile tests of GFRP Re-Bar produced by domestic industry and third point bending tests of one-way slab specimens reinforced with GFRP Re-Bar bundle are peformed. For all slab specimens, load-deflection relations are predicted by using the ACI committee 440 and the results are compared with experimental ones. In order to establish the design criteria or guidelines of concrete flexural member reinforced with FRP Re-Bar, it is needed to evaluate the serviceability limit state as well as the strength limit state.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.263-272
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• 2019

This paper describes the results of bearing capacity using field loading test of pile, in order to extend the applicability of drilled shaft with mid-size, and the results were compared with the prediction results of design bearing capacity by empirical formular. The static load test result showed that the allowable bearing capacity of high pile strength was about 2.4 times higher than that of low pile strength. The dynamic load test result showed that the allowable bearing capacity of high pile strength was about 1.4 times~1.5 times higher than that of low pile strength. The comparison result of allowable bearing capacity between static and dynamic load test showed that the difference of allowable load ranged from 3% to 6% under the same settlement conditions. As a result of comparing the ultimate bearing capacity by load test and design bearing capacity, it was found that the FHWA proposed equation could be more reasonable than the other proposed equation in load sharing ratios of end bearing and skin friction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.2125-2133
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• 2013

Recently, an interest on joint behavior between adjacent concrete slab tracks has increasing due to large application of such track system. Dowel bars are widely used to improve load transfer capacity across the joints. Dowel bars reduce the deflections and stresses by transferring the load between the slabs. This study proposes the lumped shear spring model to efficiently model dowel joints of adjacent slabs. This model includes bearing stiffness between dowel bar and concrete as well as dowel gap. Strength of the proposed spring model is evaluated based on Concrete Capacity Design method under the assumption of shear failure mode in the joints. Experiments are also performed up to failure to evaluate the accuracy of the proposed model. It has been observed that the proposed model is able to predict initial nonlinearity due to dowel gap, and capture material nonlinearity of the test slabs. Thus, it is recommended that the proposed model can be effectively applied to the dowel joints of concrete slab track.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.1
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• pp.411-417
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• 2013

The moment responses of electric pole foundations for a railroad were investigated using real-scale load tests. Large overturning moments were applied to two square rigid piles with a 1.1 m width and a 2.2 m embedded depth. Two different installation methods-with and without a form-were applied to evaluate the influence of the form work on the moment capacities of the foundations. The reduction of ground strength caused by the excavation without a form is more pronounce than the decrease of frictional strength due to the smooth concrete surface with a form. From the test results, it is found that the current design method which applies a proportional coefficient to consider the effect of a form work is not appropriate. When the normal and frictional stressed is considered separately, the effect of a form work can be estimated reasonably by reducing the friction angle between soil and foundation by 20%.