• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.5
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• pp.74-82
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• 2017

Localized corrosions damages in their structural sections can be occurred affected by installed environment conditions with high temperature as near the coastline and humidity or their poor maintenance situation. In bearing supports of steel bridges, especially, lower web and vertical stiffener in end girder support can be easily corroded because of relatively higher humidity due to the narrow space in the end of girder and the wetted accumulated sediments affected by rain water or antifreezing admixture leaked from expansion joint. It can be related to change in their structural performance. In this study, thus, bearing strength test specimens were fabricated considering corrosion damage in the web and vertical stiffeners and the change in their bearing strengths were experimentally evaluated. From the test results, localized corrosion damage of structural members in the end girder affected the bearing strength of end girder support, especially, localized corrosion damage of the vertical stiffener relatively highly affected their bearing strengths.

• Tunnel and Underground Space
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• v.8 no.2
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• pp.146-156
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• 1998

Nemerical algorithms were developed to analyze the behavior of the double lining as well as ground mass separately or simultaneously. A lining interface element was especially developed, verified and applied to the study on the coupled interaction of shotcrete and the concrete lining. It could be known fro parameter studys on double lining support systems that as the contact surface between shotcrete and concrete lining was rougher, the more decreased bearing capacity against the cracking of the system. If the thickness of the shotcrete increased, the bearing capacity of the double lining also increased linearly with the thickness. If the thickness of the concrete lining increased, the bearing capacity of the double lining had the relationship of the characteristic S-shape of a sigmoid function with the thickness. When the thickness increased over a given value, it was not useful to increase more the thickness because bearing capacity had no remarkable change. It could be concluded that the behavior of the shotcrete and concrete lining was generally reversed before and after the ratio of horizontal to vertical earth preassure of 1.0 and 0.5 respectively. Therefore, we could guess that the movement which two shotcrete and concrete lining deflect toward each other around the crown caused a friction between two linings and thus this disadvantageous effect could contribute to reducing the bearing capacity against the cracking.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.225-232
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• 1999

Construction case of PRD (Percussion Rotary Drill) pipe pile and matters to be attended in construction of PRD pile were reviewed. The compressive and uplifting static pile load tests for PRD piles were performed and, also, analysis by Pile Driving Analyzer was done. Based on these results, bearing components in each resisting part (that is: steel toe, external skin, and internal skin) were measured separately. The measured resisting force was compared to the value calculated by the estimated formula. The pile capacity was mobilized in steel toe area and the external skin friction and the internal friction were not produced. Thus, it could be considered that toe of PRD pile should be supported in hard bearing stratum (for example, the fresh soft rock).

• Geomechanics and Engineering
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• v.18 no.3
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• pp.315-328
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• 2019

This paper presents an investigation on bearing capacity, load-settlement behavior and safety factor of rock-soil slopes reinforced using geogrid-box method (GBM). To this end, small-scale laboratory studies were carried out to study the load-settlement response of a circular footing resting on unreinforced and reinforced rock-soil slopes. Several parameters including unit weight of rock-soil materials (loose- and dense-packing modes), slope height, location of footing relative to the slope crest, and geogrid tensile strength were studied. A series of finite element analysis were conducted using ABAQUS software to predict the bearing capacity behavior of slopes. Limit equilibrium and finite element analysis were also performed using commercially available software SLIDE and ABAQUS, respectively to calculate the safety factor. It was found that stabilization of rock-soil slopes using GBM significantly improves the bearing capacity and settlement behavior of slopes. It was established that, the displacement contours in the dense-packing mode distribute in a broader and deeper area as compared with the loose-packing mode, which results in higher ultimate bearing load. Moreover, it was found that in the loose-packing mode an increase in the vertical pressure load is accompanied with an increase in the soil settlement, while in the dense-packing mode the load-settlement curves show a pronounced peak. Comparison of bearing capacity ratios for the dense- and loose-packing modes demonstrated that the maximum benefit of GBM is achieved for rock-soil slopes in loose-packing mode. It was also found that by increasing the slope height, both the initial stiffness and the bearing load decreases. The results indicated a significant increase in the ultimate bearing load as the distance of the footing to the slope crest increases. For all the cases, a good agreement between the laboratory and numerical results was observed.

• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.417-424
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• 2003

A bearing failure in RCS(Reinforced Concrete Column and Steel Beam) system is recognized as one of the distinct joint failure modes for the composite frames. Vertical and transverse reinforcement in addition to concrete are effective for better transfer of vortical forces through concrete bearing. To examine the effect of the vertical bars, tie bars, a U-type detail developed in this study and concrete confinement, local bearing tests were conducted using 22 small-scale concrete block specimens. Test results show that vertical reinforcement and tie bars mainly contribute to the bearing capacity. However larger amounts of tie reinforcement are required than those recommend from ASCE guidelines, to apply the nominal concrete strength as 2 $f_{ck}$ over the bearing area. Cross ties are proved to be highly effective for resisting the vertical forces. Maximum bearing strength can be increased upto 2.5 $f_{ck}$ . An accurate prediction model for bearing strength is proposed for better design of the composite Joint.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.481-488
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• 1998

Elastomeric bearing is used as one of the most useful way for isolation structures, because the horizontal stiffness is much lower than the vertical stiffness. In the design criteria of Elastomeric bearing, the stability of the bearings is evaluated by shear strain due to compression, lateral displacement, and rotation. The question how soft rubber can sustain heavy structure is now able to be solved by Ultimate capacity test of Laminated Elastomeric Bearings, which results 1,200kg/$\textrm{cm}^2$ of the max. compressive stress and this shows what a sufficient safety factor Elastomeric bearing has !

• Geomechanics and Engineering
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• v.14 no.4
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• pp.345-354
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• 2018

Currently, layered geogrid method (LGM) is the commonly practiced technique for reinforcement of slopes. In this paper the geogrid-box method (GBM) is introduced as a new approach for reinforcement of rock-soil slopes. To achieve the objectives of this study, a laboratory setup was designed and the slopes without reinforcements and reinforced with LGM and GBM were tested under the loading of a circular footing. The effect of vertical spacing between geogrid layers and box thickness on normalized bearing capacity and failure mechanism of slopes was investigated. A series of 3D finite element analysis were also performed using ABAQUS software to supplement the results of the model tests. The results indicated that the load-settlement behavior and the ultimate bearing capacity of footing can be significantly improved by the inclusion of reinforcing geogrid in the soil. It was found that for the slopes reinforced with GBM, the displacement contours are widely distributed in the rock-soil mass underneath the footing in greater width and depth than that in the reinforced slope with LGM, which in turn results in higher bearing capacity. It was also established that by reducing the thickness of geogrid-boxes, the distribution and depth of displacement contours increases and a longer failure surface is developed, which suggests the enhanced bearing capacity of the slope. Based on the studied designs, the ultimate bearing capacity of the GBM-reinforced slope was found to be 11.16% higher than that of the slope reinforced with LGM. The results also indicated that, reinforcement of rock-soil slopes using GBM causes an improvement in the ultimate bearing capacity as high as 24.8 times more than that of the unreinforced slope.

• Geotechnical Engineering
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• v.13 no.1
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• pp.75-84
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• 1997

This paper presents a bearing capacity determination method for spread footings subjected to vertical central loading and located above underground cavities. For the development of the method, a parametric study on bearing capacity of a spread footing located above an underground cavity was performed by using a threetimensional elasto-plastic finite element computer program. From the results of the finite element analysis, bearing capacity values for the conditions analyzed were determined and used as a data base from which semiempirical equation to for the bearing capacity determination method were formulated by means of a regression analysis. The effectiveness of this method was illustrated by comparing the bearing capacity values computed from this method with those of available model footing tests as well as finite element analysis data. It was concluded that the method presented in this paper can be effectively used for practical applications at least within the conditions investigated.

• Geomechanics and Engineering
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• v.21 no.6
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• pp.565-570
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• 2020

Large tonnage pile foundation load test system is designed in this paper by using pre-stressed technique to optimize the design of anchor pile reaction beam system, in which project pile can be successfully taken as anchor pile. The test results show that the cracks and excessive deformations of the prestressed anti-force device designed in this study have not occurred, and the prestressed tendons of the anchor pile ensure that the anchor pile will not be pulled and fractured, and the prestressed tendons can be reused, thus ensuring the safety and reliability of the test. This test method can directly test bearing capacity of long rock-socketed piles, and analysis bearing behaviors from test results of sensors which embedded in the pile. Through test studied, authors summarized the vertical bearing characteristics of long rock-socketed piles and the main problems that should be paid attention to during design and construction, and provided reliable solutions.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.165-180
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• 1999

Static load tests were performed for open-ended piles, closed-ended piles, piles with grouted toe, and base-grouted piles by using calibration chamber. Then vertical bearing capacities determined from load tests were compared with each other. The stability of base-grouted pile during a simulated seaquake was investigated by changing the penetration depth. Also, static load tests and seaquake tests for 2-piles and 4-piles group were performed. The bearing capacity of the pile grouted inside the toe was 11.2~30.8% less than that of open-ended pile because of reduction of base resistance due to disturbance of base soil under pile toe. The bearing capacity of a base-grouted pile was 23.8~33.9% more than that of an open-ended pile and was similar to that of a closed-ended pile. The bearing capacity of base-grouted group pile was increased ; the bearing capacity of base-grouted 2-piles group increased 14.6~31.8% compared to that of open-ended 2-piles group, and that of base-grouted 4-piles group increased 15.3~22.4% compared to that of open-ended 4-piles group. During the simulated seaquake in deep sea, stability of base-grouted pile was found to be dependent on the pile penetration depth. During seaquake motion, single long base-grouted pile longer than 20m was stable and short base-grouted pile shorter than 12m failed. But relatively long base-grouted pile longer than 12m kept mobility state. Bearing capacity of base-grouted group pile with penetration depth less than 7m was degraded a little bit ; so, base-grouted group pile could maintain mobility condition.