• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.1
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• pp.39-47
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• 2020

Lightly reinforced concrete (RC) moment frames may suffer significant damage during large earthquake events. Most buildings with RC moment frames were designed without considering seismic loads. The load-displacement response of gravity load designed frames could be altered by masonry infill walls. The objective of this study is to investigate the load-displacement response of gravity load designed frames with masonry infill walls. For this purpose, three-story gravity load designed frames with masonry infill walls were considered. The masonry infilled RC frames demonstrated larger lateral strength and stiffness than bare RC frames, whereas their drift capacity was less than that of bare frames. A specimen with a partial-height infill wall showed the least drift capacity and energy dissipation capacity. This specimen failed in shear, whereas other specimens experienced a relatively ductile failure mode (flexure-shear failure).

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.6
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• pp.905-913
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• 2017

To design segment lining, loads such as self weight, vertical load, horizontal load, ground reaction, water pressure, backfill grouting pressure et al. have to be considered. Earth pressure and water pressure are the major factor to design segment lining such as concrete strength, segment thickness and amount of rebar et al. To analysis earth pressure and water pressure acting on segment lining, filed monitoring and back analysis are performed in this study.

• Journal of the Korean GEO-environmental Society
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• v.9 no.4
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• pp.15-21
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• 2008

From the practical point of view, general retaining wall systems, such as gravity wall, cantilever wall and reinforced wall, have several problems. As a countermeasure, precast block type retaining wall systems have been developed and used for the various purposes of construction. The retaining wall systems can be applied not only for mechanical purpose but environmentally friendly aspects by changing the shapes of surface plates and planting on the surface plates. On the other hand, the bulging failure was dominant near the center of wall height. Therefore, an individual block has to be estimated for the stability problem related to turnover and the for design of gravity block type wall. On the basis of this result, the optimum section of the wall has to be determined.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.503-514
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• 2011

In this research, the seismic connection details for two concrete-filled U-shape steel beam-to-H columns were proposed and cyclically tested under a full-scale cruciform configuration. The key connecting components included the U-shape steel section (450 and 550 mm deep for specimens A and B, respectively), a concrete floor slab with a ribbed deck (165 mm deep for both specimens), welded couplers and rebars for negative moment transfer, and shear studs for full composite action and strengthening plates. Considering the unique constructional nature of the proposed connection, the critical limit states, such as the weld fracture, anchorage failure of the welded coupler, local buckling, concrete crushing, and rebar buckling, were carefully addressed in the specimen design. The test results showed that the connection details and design methods proposed in this study can well control the critical limit states mentioned above. Especially, the proposed connection according to the strengthening strategy successfully pushed the plastic hinge to the tip of the strengthened zone, as intended in the design, and was very effective in protecting the more vulnerable beam-to-column welded joint. The maximum story drift capacities of 6.0 and 6.8% radians were achieved in specimens A and B, respectively, thus far exceeding the minimumlimit of 4% radians required of special moment frames. Low-cycle fatigue fracture across the beam bottom flange at a 6% drift level was the final failure mode of specimen A. Specimen B failed through the fracture of the top splice plate of the bolted splice at a very high drift ratio of 8.0% radian.

• Journal of the Korean Geotechnical Society
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• v.38 no.7
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• pp.49-62
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• 2022

The hollow modular concrete block reinforced foundation method is one of the ground reinforcement foundation methods that uses hexagonal honeycomb-shaped concrete blocks with mixed crushed rock to reinforce soft grounds. It then forms an artificial layered ground that increases bearing capacity and reduces settlement. The hollow modular honeycomb-shaped concrete block is a geometrically economical, stable structure that distributes forces in a balanced way. However, the behavioral characteristics of hollow modular concrete block reinforced foundations are not yet fully understood. In this study, a bearing capacity test is performed to analyze the reinforcement effectiveness of the hollow modular concrete block through the laboratory model tests. From the load-settlement curve, punching shear failure occurs under the unfilled sand condition (A-1-N). However, the filled sand condition (A-1-F) shows a linear curve without yielding, confirming the reinforcement effect is three times higher than that of unreinforced ground. The bearing capacity equation is proposed for the parts that have contact pressure under concrete, vertical stress of hollow blocks, and the inner skin friction force from horizontal stress by confining effect based on the schematic diagram of confining effect inside a hollow modular concrete block. As a result of calculating the bearing capacity, the percentage of load distribution for contact force on the area of concrete is about 65%, vertical force on the area of hollow is 16.5% and inner skin friction force of area of the inner wall is about 18.5%. When the surcharge load is applied to the concrete part, the vertical stress occurs on the area of the hollow part by confining effect first. Then, in the filled sand in the hollow where the horizontal direction is constrained, the inner skin friction force occurs by the horizontal stress on the inner wall of the hollow modular concrete block. The inner skin friction force suppresses the punching of the concrete part and reduces contact pressure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.130-137
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• 2017

Due to the economic growth and development of construction technology, a role of foundation to resist heavy loads has been increased. In this present study to improve the structural performance of reinforced concrete pile, the precast HPC pile reinforced with rebar and filling concrete was developed and the strength of pile was predicted based on the limit state design method. The safety of HPC pile strength was evaluated by comparing with the design values. The geometry of HPC pile is a decagon cross section with a maximum width of 500 mm and a minimum width of 475 mm, and the hollow head of pile thickness is 70 mm. The inner area of the hollow head part was made as the square ribbed shape presented in the limit state design code in order to achieve horizontal shear strength between pile concrete and filling concrete. From the shear test results, it was found that the stable shear strength were secured without abrupt failure until maximum load stage despite the shear cracks was found. Shear strength is 135% and 119% higher than that of design value calculated from limit state design code. The driving test results of HPC pile according to the presence of additional reinforcement showed the outstanding crack resistance against impact loads condition. From the bending test results the flexural load between PHC pile and HPC pile was 1.51 times and 1.48 times higher than that of the design flexural load of conventional PHC pile.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.5-16
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• 2002

The pullout behavior of large-diameter steel pipe piles(diameter = 2,500mm, length = 38~40m), which were designed as compression piles but used as reaction piles during a static compression load test on a pile(diameter = 1,000m, length = 40m), was investigated. The steel pipe piles were driven by 20m into a marine deposit and weathered soil layer and then socketed by 10m into underlying weathered and soft rock layers. The sockets and pipe were filled with reinforced concrete. The steel pipe and concrete in the steel pipe zone and concrete and rebars in the socketed zone were fully instrumented to measure strains in each zone. The pullout deformations of the reaction pile heads were measured by LVDTs. Over the course of the study, a maximum uplift deformation of 7mm was measured in the heads of reaction piles when loaded to 10MN, and 1mm of residual uplift deflection was measured. In the reaction piles, about 83% and about 12% of the applied pullout loads were transferred in the weathered rock layer and in the soft rock layer, respectively. Also, at an uplift force of 10MN, shear stresses due to the uplift in the weathered rock layer md soft rock layer were developed as much as 125.3kPa and 61.8kPa, respectively. Thus, the weathered rock layer should be utilized as resisting layer in which frictional farce could be mobilized greatly.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.56-66
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• 2015

This study aims at developing a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were performed on one unreinforced beam-column specimen and two reinforced specimens with U-type precast wall panels. Seismic resistant test of anchored and welded steel plate connections manifested an average of 2.8 times increase in the maximum loading (average 591.8 kN) in comparison to unreinforced beam-column specimen. The maximum drift ratios were also shown between 1.4% and 2.7%. An analytical study was performed while assuming the RC column on the right side and the vertical element of the reinforced PC panel to behave in completely composite manner and the RC column on the left side and PC panel to behave in completely non-composite manner when loading was exerted from upper right end of RC frame of specimen to its left side. It was found with the assumptions that the overall flexural behavior in principle agreed with the experimental result.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.67-78
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• 2004

Soil-steel bridges are made of flexible corrugated steel plates buried in the well-compacted granular soil. One kind of possible collapses of these structures could be initiated by shear or tension failure in the soil cover subjected to vehicle loads. Current design codes provide the requirements for the minimum depth of the soil cover to avoid problems associated with soil cover failures. However, these requirements were developed for short span (less than 7.7 m) structures which are made of unstiffened plates of standard corrugation (150$\times$50 m). Numerical analyses were carried out to investigate the behavior of long span soil steel bridges according to thickness of the soil cover. The span of structures were up to 20 m and deep corrugated plates (381$\times$140 m) were used. The analysis showed that the minimum cover depth of 1.5 m could be sufficient to prevent the soil cover failure in the structures with a span exceeding 10 m. Additional analyses were performed to verify the reinforcement effect of the concrete relieving slab which can be a special feature to reduce the live-load effects. Analyses revealed that the bending moment of the conduit wall with a relieving slab was less than 20% of that without a relieving slab in a case of shallow soil cover conditions.

• Journal of the Korean Society for Railway
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• v.17 no.4
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• pp.251-259
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• 2014

The transition zone between an earthwork and a bridge effect to the vehicle's running stability because support stiffness of the roadbed is suddenly changed. The design criteria for the transition structure on ballast track were not particular in the past. However with the introduction of concrete track is introduced, it requires there is a higher performance level required because of maintenance and running stability. In this present paper, a transition structure reinforced with geosynthetics is suggested to improve the performance of existing bridge-earthwork transition structures. The suggested transition structure, in which there is reinforcing of the approach block using high-tension geosynthetics, has a structure similar to that of earth reinforced abutments. The utilized backfill materials are cement treated soil and gravel. These materials are used to reduce water intrusion into the approach block and to increase the recycling of surplus earth materials. An experiment was performed under the same conditions in order to allow a comparison of this new structure with the existing transition structure. Evaluation items are elastic displacement, cumulative settlement, and earth pressure. As for the results of the real-scale accelerated testing, the suggested transition structure has excellent performance for the reduction of earth pressure and settlement. Above all, it has high resistance the variation of the water content.