• The Journal of the Korean dental association
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• v.50 no.3
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• pp.126-139
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• 2012

Loss of dentition can lead to not only compromised esthetics and functions of the patient, but also alveolar bone resorption. Bone grafting with prosthetic reconstruction of the gingiva can be selected for the treatment, and it provides many benefits as prosthetic gingival reconstruction does not require a complicated surgical process and is available within a short period of time, with stable clinical results. However, conventional porcelain fused to metal prosthesis has certain limits due to its size, and deformation after several firing procedures. In this clinical report, the author would like to introduce a patient with severe alveolar resorption who was treated with gingiva-shaped zirconia/titanium CAD/CAM implant fixed prosthesis for esthetic and functional rehabilitation. Clinical reports Clinical report 1, 2 : A case of loss of anterior dentition with atrophied alveolar bone. Implant retained zirconia bridge applied with Procera implant bridge system to simulate the gingiva. Upper structure was fabricated with zirconia all ceramic crown. Clinical report 3, 4 : A case of atrophied maxillary alveolus was reconstructed with fixed implant prosthesis, a CAD/CAM designed titanium structure covered wi th resin on its surface. Anterior dentition was reconstructed with zirconia crown. Conclusion and clinical uses. All patients were satisfied with the outcome, and maintained good oral hygiene. Zirconia/titanium implant fixed prosthesis fabricated by CAD/CAM system was highly accurate and showed adequate histological response. No critical failure was seen on the implant fixture and abutment overall. Sites of severe alveolar bone loss can be rehabilitated by implant fixed prosthesis with CAD/CAM system. This type of prosthesis can offer artificial gingival structure and can give more satisfying esthetics and functions, and as a result the patients were able to accept the outcome more fondly, which makes us less than hard to think that it can be a more convenient treatment for the practitioners.

• Journal of the Korean Society for Railway
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• v.11 no.2
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• pp.195-202
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• 2008

The transition area between a bridge and an earthwork is one of the weakest area of track because of the track geometry deterioration caused unequal settlement of backfill of abutment. In case of a ballastless track, the approach slab could be installed to prevent such a phenomenon. But, if there is occurred the inclined displacement on the approach slab by a settlement of the foundation or formation, the track is also under the inclined displacement. And this defect causes reducing the running stability of a vehicle, the riding comfort of passengers, and increasing the track deteriorations by excessive impact force acting on the track. In this study, parametric studies were performed to investigate the displacement limit on the approach slab to avoid such problems. The length and the amount of unequal settlement of approach slab were adopted as parameter for numerical analysis considering vehicle-track interaction. Car body accelerations, variations of wheel force, stresses in rail, and uplift forces induced on fastener clip were investigated. From the result, resonable settlement limit on the end of an approach slab according to slab length was suggested.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.3
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• pp.173-184
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• 2023

Presently, the general seismic fragility evaluation method for a bridge system composed of member elements with different nonlinear behaviors against strong earthquakes has been to evaluate at the element-level. This study aims to develop a system-level seismic fragility evaluation method that represents a structural system. Because the seismic behavior of bridges is generally divided into transverse and longitudinal directions, this study evaluated the system-level seismic fragility in both directions separately. The element-level seismic fragility evaluation in the longitudinal direction was performed for piers, bridge bearings, pounding, abutments, and unseating. Because pounding, abutment, and unseating do not affect the transverse directional damages, the element-level seismic fragility evaluation was limited to piers and bridge bearings. Seismic analysis using nonlinear models of various structural members was performed using the OpenSEES program. System-level seismic fragility was evaluated assuming that damage between element-levels was serially connected. Pier damage was identified to have a dominant effect on system-level seismic fragility than other element-level damages. In other words, the most vulnerable element-level seismic fragility has the most dominant effect on the system-level seismic fragility.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1542-1549
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• 2011

The Transitional zone between bridge abutment and earthwork is one of the representative vulnerable zones in railway where differential settlements may take place due to the different supportive stiffness. Although transitional zones are managed with stricter standards than those of the other earthwork zones either in the design and construction stages, it is very difficult to prevent differential settlement perfectly. A three-dimensional numerical analyses were performed by applying train moving load in this study. The analytical model including abutments and earthwork zones was constituted with rail, sleepers, track concrete layer (TCL), hydraulic stabilized base (HSB), reinforced road bed, and road bed using railway and road base structure. The clamp connecting the rail and sleeper were also modeled as the element with spring coefficient. The train wheel is modeled in the actual size and moved on the rail with 300 km/hr speed. The deformation characteristics at each point of the rail and the ground were considered in detail when moving the train wheel. The analysis results were compared with those from the two-dimensional analysis without considering moving load. The research results show that displacement and stress were greater in the three-dimensional analysis than in other analyses, and the three-dimensional analysis with moving load should be performed to evaluate railway performance.

• Journal of the Korean Geotechnical Society
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• v.21 no.1
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• pp.51-58
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• 2005

The use of geogrid for SRW systems and bridge abutment has increased rapidly over the past 10 years in Korea. The concept of segmental retaining walls and reinforced soil is very old and for example The Ziggurats of Babylonia(i.e. Tower of Babel) were built some 2,500 to 3,000 years ago using soil reinforcing methods very similar to those described in current design. Modern SRW(Semental Retaining Wall) units were introduced in 1960's as concrete crib retaining wall systems. In this paper, the friction properties between segmental concrete units and geogrid are investigated by performing various tests.

• Journal of the Society of Disaster Information
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• v.12 no.1
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• pp.19-31
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• 2016

The purpose of this study was to establish the initial computerized management database which can be applied to a universal project management computer system for managing universal project management and operation. Database construction model presented in this paper suggested the model of organization, activity and operation of bridge construction(two abutment-three-span) based on the organization information classification system of the facility classification, functional component classification, work classification, resource classification. Database model established in this study are considered to be able to take advantage of a very systematic and scientific management for future universal project management and operations.

• Earthquakes and Structures
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• v.17 no.5
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• pp.477-487
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• 2019

Understanding the behavior of skew bridges under the action of earthquakes is quite challenging due to the combined transverse and longitudinal responses even under unidirectional hit. The main goal of this research is to assess the response of skew bridges when subjected to longitudinal and transversal earthquake loading. The effect of skew on the response considering two- and three- span bridges with skew angles varying from 0 to 60 degrees is illustrated. Various pier fixities (and hence stiffness) and cross-section shapes, as well as different abutment's bearing articulations, are also studied. Finite-element models are established for modal and seismic analyses. Around 900 models are analyzed under the action of the code design response spectrum. $Vis-{\grave{a}}-vis$ modal properties, the higher the skew angle, the less the fundamental period. In addition, it is found that bridges with skew angles less than 30 degrees can be treated as straight bridges for the purpose of calculating modal mass participation factors. Other monitored results are bearings' reactions at abutments, shear and torsion demand in piers, as well as deck longitudinal displacement. Unlike straight bridges, it has been typically noted that skew bridges experience non-negligible torsion and bi-directional pier base shears. In a complementary effort to assess the accuracy of the conducted response spectrum analysis, a series of time-history analyses are applied under seven actual earthquake records scaled to match the code design response spectrum and critical comparisons are performed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4845-4852
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• 2012

This research calculated the scour depth of bridge according to inflow and outflow changes of stream's flood discharge and curves by applying scour depth formula for piers and abutments, and by comparing and examining them, evaluated the applicability of scour depth formulas. Overall, if the angles of flood discharge and inflow and outflow increase, the deviation rate of scour depth in bight increased. Especially the deviation rate was 58% at the inflow and outflow angle of $105^{\circ}$ that the bridge plan for this geography need careful examination. Next, as a result of calculating the deviation rate of scour depth at the bight by scour depth formulas, in case of pier, Andru formula showed 58% deviation rate, Laursen formula showed 26% deviation rate, and CSU. formula showed 17% deviation rate. In the case of abutment, Froehlich formula shows 44% deviation rate that when applying above scour depth formulas, scour depth calculation considering repairable characteristics of bight is necessary. Finally, about inflow and outflow angles of $45^{\circ}{\sim}135^{\circ}$ that showed big deviation rate of scour depth, this research performed regression analysis of deviation rates of scour depth due to flood discharge to suggest the regression formula.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.4
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• pp.255-262
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• 2021

In this study, a jointless bridge that integrates the superstructure and abutment without installing an expansion joint was analyzed. An example of a jointless bridge that has been introduced in Korea since 2009. Owing to the short period of use and lack of experience in design, construction, and maintenance, there is insufficient information regarding the long-term behavior of jointless bridges. When analyzing numerous bridges, the numerical analysis model must maintain the numerical values used and ensure the convenience of model construction. In this study, sensitivity analysis was performed to select a numerical model for various types of jointless bridges using commercial finite element programs, MIDAS Civil and ABAQUS 2018. According to a solid element-based model, we analyzed the mean and maximum relative errors between structural models. Consequently, it was found that the beam element-based model exhibits a significantly small relative error in comparison to the shell element, where a relatively large error was recorded. Therefore, the optimal numerical analysis model, a practical model that maintains the similarity and precision of the displacement shape cause by relative error, was judged to be the most suitable for jointless bridges based on the shell element.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.7-14
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• 2011

The numerical analyses were performed to investigate the curling behavior of the post-tensioned prestressed concrete approach slab (PTAS) under environmental loads. A technique to include properly the boundary conditions of one end of PTAS that was connected to the bridge abutment using hinges was proposed for the numerical model. The applicability of a simplified model not having hunches was also investigated. By using the developed models, the curling behavior of PTAS was analyzed when the foundation settlement occurred. The analysis results showed that the maximum tensile stress obtained from the simplified model involving a simplified hinge connection was very closed to that obtained from a rigorous model. When the slab curled up, the maximum tensile stress occurred in the model including no foundation settlement, but when the slab curled down, the maximum stress occurred in the model including partial settlement of the foundation. Therefore, the design of PTAS should be performed considering those maximum tensile stresses.