• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1490-1495
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• 2005

In this study, Model test of concrete frame structures with various shapes and locations are carried out by means of applying Peck's(1969) settlement method. The results of the model test indicated that important correlations existed between the behavior of frame structure and ground movement. Also, the damage level of frame structure closely influenced by the phase of excavation. Therefore, prediction of damage level at early phase of construction should be very precise. The damage level graph by Cording et al.(2001), the angular distortion provided gradually more serious damage to frame structures for the all cases. But the damage level graph by Burland(1997), was difficult to confirm because of very small amount of deflection ratio.

• Tunnel and Underground Space
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• v.4 no.3
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• pp.287-296
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• 1994

Safety-related structures of power plants have to be protected against the effects of possible hazards and natural phenomena. Earthquakes are considered a major dynamic design loading as a requirement of plant design, but the effects of blast-induced vibratons are not. Due to the difficulties of obtaining construction site for new plants, following ones are inevitably being built in the site adjacent to existing power plants. Therefore considerable thought has been recently given to the dynamic loading generated by blasting works near the plants. In this paper, discussed is applicability of existing vibration standards and industrial codes to the blasting works near safety related structures. Also evaluated are the parameters for the safe vibration limits such as measure of vibration level, frequency consideration, structure response, propagation equation, etc.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.724-729
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• 2003

Installing vibration isolation in structures, such as structures adjacent to subways, may be delicatebecause of the proximity with the vibration source or because of the wave propagation path. This paper discusses on method that install isolation Pads on underground walls as a part of the vibration mitigation system, and also on its efficiency, The proposed method is proven to affect significantly the distribution of acceleration in the neighborhood of the structure and to reduce efficiently the maximum amplitude of the vibration. It is also seen that installing isolating pads until the depth of the foundations and deeper is more efficient than installing such device separately from the structure. This Study being limited to the comparison of installation methods, further Studies considering the thickness, stiffness and other parameters should be required.

• Earthquakes and Structures
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• v.11 no.1
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• pp.1-23
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• 2016

Numerous buildings have been damaged or destroyed in previous earthquakes by developing soft storey. Almost all the seismic codes have provisions to prevent soft storey in structures, most of them have recommended the ratio of stiffness between adjacent storeys, but none of them has proposed the method to calculate the storey stiffness. On the other hand a great number of previous researches on stiffness have been focused on approximate methods and accurate methods by using analytical softwares have been almost neglected. In this study, six accurate methods for calculating the storey stiffness have been studied on 246 two-bay reinforced concrete frames. It is shown with the results of the statistical study and structural analysis that method 3 in which there is no modification of the original model and the forces with triangular distribution similar to seismic forces are applied to the center of mass of all storeys has acceptable accuracy and desirable efficiency for designing and controlling structures.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.113-120
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• 1999

Deep excavation,1 in the urban areas may cause terrible damages to the adjacent structures. Most damages are due to the settlement of ground during excavation work. This article introduces two actual examples of structure damage in subway construction projects. A through of attempts to find out the factors that are affecting to the settlement of ground was made through site investigations and analyses of measurement data. Some suggestions are given to prevent the repeat of trial and error in deep excavation projects. This kind of attempts are eccentrical to the development and improvement of information-oriented construction method.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.561-568
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• 2003

The protection of adjacent structures in urban excavation has been an important issue. But the research on the interaction between ground movements and adjacent structure has been scarce, therefore this study was necessitated. Current design practice for the prediction of excavation-induced ground movements heavily rely on empirical method. In this study, damage levels of brick building are examined closely by means of angular distortion, deflection ratio, horizontal strain. The results of numerical analysis indicated that the movement of actual building was 60∼65% of the ground movement, while angular distortion was 45∼65%. Also numerical analysis for the assessment of brick building can be applied to the building protection at various construction stages.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.425-432
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• 2001

Compaction Grouting System, the method which makes ground compact by injection of low slump mortar, Is widely used for reinforcement of soft ground, restoration of structures happened differential settlement, underpinning and restoration of damaged dam core. The quantitive analysis of ground improvement for this method has not performed yet. So, design parameters about thls method must be studied through performance of CGS in various types of soil to make CGS adaptable widely. In this study PBT, SPT and field density test were performed for analysis of the characteristics of ground improvement and pressuremeter and inclinometer were installed for analysis of the characteristics of compaction in adjacent ground. In this paper, denoted much effects for filled ground that increasing of the bearing capacity, confirming the displacement of adjacent ground and the effective radius of injection.

• Journal of Periodontal and Implant Science
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• v.46 no.2
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• pp.107-115
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• 2016

Purpose: The aim of this study was to evaluate and compare tooth surface characteristics in extracted human molars after cervical enamel projections (CEPs) were removed with the use of three rotating instruments. Methods: We classified 60 extracted molars due to periodontal lesion with CEPs into grade I, II, or III, according to the Masters and Hoskins' criteria. Each group contained 20 specimens. Three rotating instruments were used to remove the CEPs: a piezoelectric ultrasonic scaler, a periodontal bur, and a diamond bur. Tooth surface characteristics before and after removal of the projections were then evaluated with scanning electron microscopy (SEM). We analyzed the characteristics of the tooth surfaces with respect to roughness and whether the enamel projections had been completely removed. Results: In SEM images, surfaces treated with the diamond bur were smoothest, but this instrument caused considerable harm to tooth structures near the CEPs. The piezoelectric ultrasonic scaler group produced the roughest surface but caused less harm to the tooth structure near the furcation. In general, the surfaces treated with the periodontal bur were smoother than those treated with the ultrasonic scaler, and the periodontal bur did not invade adjacent tooth structures. Conclusions: For removal of grade II CEPs, the most effective instrument was the diamond bur. However, in removing grade III projections, the diamond bur can destroy both adjacent tooth structures and the periodontal apparatus. In such cases, careful use of the periodontal bur may be an appropriate substitute.

• Earthquakes and Structures
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• v.6 no.1
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• pp.71-87
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• 2014

Interaction between closely-spaced buildings subject to earthquake induced strong ground motions, termed in the literature as "seismic pounding", occurs commonly during major seismic events in contemporary congested urban environments. Seismic pounding is not taken into account by current codes of practice and is rarely considered in practice at the design stage of new buildings constructed "in contact" with existing ones. Thus far, limited research work has been devoted to quantify the influence of slab-to-slab pounding on the inelastic seismic demands at critical locations of structural members in adjacent structures that are not aligned in series. In this respect, this paper considers a typical case study of a "new" reinforced concrete (R/C) EC8-compliant, torsionally sensitive, 7-story corner building constructed within a block, in bi-lateral contact with two existing R/C 5-story structures with same height floors. A non-linear local plasticity numerical model is developed and a series of non-linear time-history analyses is undertaken considering the corner building "in isolation" from the existing ones (no-pounding case), and in combination with the existing ones (pounding case). Numerical results are reported in terms of averages of ratios of peak inelastic rotation demands at all structural elements (beams, columns, shear walls) at each storey. It is shown that seismic pounding reduces on average the inelastic demands of the structural members at the lower floors of the 7-story building. However, the discrepancy in structural response of the entire block due to torsion-induced, bi-directionally seismic pounding is substantial as a result of the complex nonlinear dynamics of the coupled building block system.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.3
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• pp.207-219
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• 2008

In urban areas, it is very often to excavate ground adjacent to existing structures for the construction of new buildings. Deformation and vibration induced by such construction activities may cause damages to the existing structures and petitions from citizens. To secure safety of the existing structures, particularly of tunnels, establishment of general guidelines on vibration have been crucial concerns, although some institutions have their own guidelines which are not generally accepted. This study aims establishing guidelines for tunnel safety due to blast-induced vibration. Numerical methods are adopted for this study. Blast load equation proposed by International Society of Explosive Engineers (2000) is used to decide detonation pressure. Analysis models were obtained from the construction cases of Seoul Metros. By performing dynamic numerical analysis, vibration velocity of an existing tunnel is evaluated. The numerical results are verified by comparing with the field measurement data obtained in excavation sites adjacent to an existing tunnel. Based on the results vibration safety zone is proposed. Influence circle for vibration velocity is drawn and the area not exceeding the allowable vibration velocity is established.