• Tunnel and Underground Space
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• 제26권6호
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• pp.493-507
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• 2016

Scaled model tests were performed to investigate the stability of a foundation located above limestone cavities. Cavity shape was assumed to be an ellipse having 1/3 for the ratio of minor to major axis lengths. 12 different test models which have various depths, locations, inclinations, sizes and numbers of cavity were experimented and they were classified into 5 different groups. Crack initiation pressure, maximum pressure, deformation behaviors, failure modes and subsidence profiles of test models were obtained, and then the influences of those parameters on the foundation stability were investigated. No cavity model showed a general shear failure, whereas the models including various cavities showed the complicated three different failure modes which were only punching failure, both punching and shear failures, and double shear failure. The stability of foundation was found to be decreased as the cavity was located at shallower depth, the size and number of cavity were increased. Differential settlements appeared when the cavity was located under the biased part of foundation. Furthermore, subsidence profiles were found to depend on the distribution of underground cavities.

• Journal of Korean Society of Steel Construction
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• 제24권4호
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• pp.371-382
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• 2012

Existing shear wall system may cause ductility fallen to the structure which it is on because relatively weak concrete core would easy to be damaged. In this study, steel hysteresis dampers whose stiffness is higher than existing coupling beam and whose strength is easy to change depending on design load was used in coupling beam. The steel hysteresis damper was proposed for the shape connected in double in series, from this, several static test were conducted to verify structural performance of the damper. FEM analysis was also performed, then design equation were suggested.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.305-308
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• 2008

This paper presents the results of an experimental study carried out Prestressed Concrete Slab System of WAffle Shape(WAS), was perfomed in order to inverstigate it connection shear behavior according to primary paramaters: connection interval, filling matarial. Specimen is produced in Precast Concrete factories and it comprised one WAS panel and two half WAS panels and then it is filled with packing. Within the ranges of the parameters of the connection details used in this test, connections can develop greater shear strength than the nominal shear strength and the design service load for parking structures.

• Journal of the Korea Concrete Institute
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• 제20권6호
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• pp.809-820
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• 2008

A new modified full scale double tee slabs with the length of nib plate - 1,500 mm were suggested, designed, and experimentally evaluated up to the loading of flexural failure. This slabs were composed of the tee section which was same to original PCI double tee and the plate section which was modified in a new shape, and the prestressing force was applied at the bottom of tee section only. This specimens were made from the domestic precast factory. The safety and serviceability of the modified nib plate with the dapped ends were evaluated up to the ultimate flexural strength of tee section. As the experimental loading increased, the flexural crackings developed first in the bottom of the slab and they changed to the increased flexural shear and inclined shear crackings in the nib and dapped portion of the double tees. The suggested modified double tee slabs failed in ductile above the design loading with many evenly distributed flexural crackings. The thickness of nib plate - 250 mm does not show any cracking under the service loading and show several minor flexural cracking up to the ultimate state of tee portion. The proposed specimens were satisfied with the strength and ductility requirements in the design code provisions in the tests. Additional experimental tests are required to reduce the depth and tensile reinforcement of nib plate concrete for the practical use of this system effectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제17권4호
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• pp.400-413
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• 2016

The horizontal shear capacity when the flange of a steel girder is replaced with 80 MPa concrete is important for its structural safety. In this study, 6 specimens with different interface conditions were designed and fabricated based on the Limit State Design Code on Korean Highway Bridges and static tests were performed to measure the horizontal shear capacity. Not only the resistance factors of the stud shear connector, concrete and reinforcement, but also the surface conditions of the casing concrete and spacing of the horizontal shear reinforcements were used as the experimental variables. The experiments showed that the interfaces between the steel girder and the concrete flange have stronger joint performance than those between the concrete flange and deck slab. To ensure the composite action in the plastic zone, the conservative horizontal shear reinforcement is more important than the roughness in the concrete face.

• Journal of the Korean GEO-environmental Society
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• 제4권2호
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• pp.65-76
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• 2003

Stone column is a soil improvement method and can be applicable for loose sand or weak cohesive soil. Since the lack of sand, stone column seems one of the most adaptable approach for poor ground as a soil improvement technique. However, this method was not studied for practical application. In this paper, the bearing capacity of single stone column at the Gaduk, Ulsan and Gwangyang under the bulging and general shear failure mode were compared with those of the suggested formulas. Especially, a test result of single stone column at the Busan area by static load was compared with the bearing capacity of suggested formulas. The analysis results showed that there were not much bearing capacity differences among those suggested bearing capacity formulas. However, the bearing capacity by static load test was almost double of those with suggested formula. The result also showed that the undrained shear strength was the most important parameter for the bearing capacity estimation of stone column.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• 제20권4호
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• pp.455-468
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• 2022

Colloid Formation and Migration (CFM) project is being carried out within the Grimsel Test Site (GTS) Phase Ⅵ. Since 2008, the Korea Atomic Energy Research Institute (KAERI) has joined CFM to investigate the behavior of colloid-facilitated radionuclide transport in a generic Underground Research Laboratory (URL). The CFM project includes a long-term in-situ test (LIT) and an in-rock bentonite erosion test (i-BET) to assess the in-situ colloid-facilitated radionuclide transport through the bentonite erosion in the natural flow field. In the LIT experiment, radionuclide-containing compacted bentonite was equipped with a triple-packer system and then positioned at the borehole in the shear zone. It was observed that colloid transport was limited owing to the low swelling pressure and low hydraulic conductivity. Therefore, a postmortem analysis is being conducted to estimate the partial migration and diffusion of radionuclides. The i-BET experiment, that focuses more on bentonite erosion, was newly designed to assess colloid formation in another flow field. The i-BET experiment started with the placement of compacted bentonite rings in the double-packer system, and the hydraulic parameters and bentonite erosion have been monitored since December 2018.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.791-796
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• 2000

Purpose of this study is to analyze the characteristics and reinforcement effects of restored the RC bridge deck with small precast panel through static load tests and to provide the basic information for the damaged slab decks. In the tests for realizing movement of general RC bridge slabs, 6 samples are prepared and tested. All reinforced samples are restored with 1 or 2-layers precast panels by epoxy mortar. The movement of restored slabs is analyzed and compared with the behavior of non-restored slabs. In result of these tests, tension cracks due to bending moment are show, and after static load test there happens finally a punching shear failure, which is the general type of RC bridge failure. The tests show that restoration of the RC slab results in increasing of loading capacity about 30~50% an restoring panels are stick to slab and moving with slab under loading test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.381-382
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• 2006

The mechanical behaviors of multi-layered foam core sandwich composite were investigated through a 3-point bending test. The sandwich specimens were obtained from sandwich panel consisting of aluminum faces and urethane foam core. Three types of sandwich specimens such as a single structure, a double structure and a triple structure were considered. The span of sandwich specimens were varied from 170mm to 350mm. According to the results, the flexural and shear properties of multi-layered sandwich composite were found to be higher than those of single-layered sandwich composite.

• Journal of Industrial Technology
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• 제20권A호
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• pp.101-111
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• 2000

This research is results of experimental and numerical works on characteristic of strength increase and bearing capacity in dredged and reclaimed soil due to desiccation shrinkage. For a soil sampled from southern coastal area in Korea, basic soil property tests and standard consolidation test with falling head permeability tests were carried out to obtain consolidational characteristics of soil. Double cone penetration test, laboratory vane test and unconfined compression test were also performed to investigate the change of shear strength with degree of desiccation. Model tests were performed in 1G environment and 30G level artificially accelerated condition by using the centrifuge model test facilities to investigate the bearing capacity of desiccated ground. Test results were analyzed by using the theoretical and load-settlement characteristics method proposed by Meyehof & Hanna(1978). On the other hands, the numerical technique, using the finite strain consolidation theory considering the effect of desiccation was used to estimate the appropriate time of using heavy construction equipments in field with respect to strength increase due to desiccation.