• Structural Engineering and Mechanics
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• v.18 no.4
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• pp.475-491
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• 2004

Anchorage devices play an important role in post-tensioned bridge structures since they must sustain heavy loads in order to permit the transfer of the prestressing force to the structure. In external prestressing, the situation is even more critical since the anchorage mechanisms, with the deviators, are the only links between the structure and the tendons throughout the service life of the structure. The behaviour of anchorage devise may be studied by using the finite element method. To do so, each component of the anchorage must be adequately represented in order to approximate the anchor mechanism as accurately as possible. In particular, the modelling of the jaw/tendon device may be carried out using the real geometry of these two components with an appropriate constitutive contact law or by replacing these components by a single equivalent. This paper presents the numerical study of a mono-strand anchorage device. The results of a comparison between two different representations of the jaw/tendon device, either as two distinct components or as a single equivalent, will be examined. In the double-component setup, the influence of the wedge configuration composing the jaw, and the influence of lubrication of the anchor, will be assessed.

• Structural Engineering and Mechanics
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• v.15 no.6
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• pp.609-628
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• 2003

Mechanical anchorage devices are generally tested in the laboratory and may be analyzed using the finite element method. These devices are composed of many components interacting through diverse contact interfaces. Generally, a Coulomb friction law is sufficient to take into account friction between smooth surfaces. However, in the case of mechanical anchorages, a gripping system, named herein the wedge-tendon system, is used to anchor the prestressing tendon. The wedge inner surface is made of a series of triangular notches designed to grip the tendon. In this particular case, the Coulomb law is not adapted to simulate the contact interface. The present paper deals with a new constitutive contact/gripping law to simulate the gripping effect. A parameter identification procedure, based on experimental results as well as on a finite element/neural network approach, is presented. It is demonstrated that all parameters have been selected in a satisfactory way and that the proposed constitutive law is well adapted to simulate the wedge gripping effect taking place in a mechanical anchorage device.

• The korean journal of orthodontics
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• v.52 no.3
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• pp.220-235
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• 2022

Objective: To evaluate the available evidence regarding the clinical effectiveness of different types of anchorage devices. Methods: A comprehensive literature search of different electronic databases was conducted for systematic reviews investigating different anchorage methods published up to April 15, 2021. Any ongoing systematic reviews were searched using PROSPERO, and a grey literature search was undertaken using Google Scholar and OpenGrey. No language restriction was applied. Screening, quality assessment, and data extraction were performed independently by two authors. Information was categorized and narratively synthesized for the key findings from moderate- and high-quality reviews. Results: Fourteen systematic reviews were included (11 were of moderate/high quality). Skeletal anchorage with miniscrews was associated with less anchorage loss (and sometimes with anchorage gain). Similarly, skeletal anchorage was more effective in retracting anterior teeth and intruding incisors and molars, resulting in minor vertical skeletal changes and improvements in the soft tissue profile. However, insufficient evidence was obtained for the preference of any anchorage method in terms of the duration of treatment, number of appointments, quality of treatment, patient perception, or adverse effects. The effectiveness of skeletal anchorage can be enhanced when: directly loaded, used in the mandible rather than the maxilla, used buccally rather than palatally, using dual rather than single miniscrews, used for en-masse retraction, and in adults. Conclusions: The level of evidence regarding anchorage effectiveness is moderate. Nevertheless, compared to conventional anchorage, skeletal anchorage can be used with more anchorage preservation. Further high-quality randomized clinical trials are required to confirm these findings.

• Structural Engineering and Mechanics
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• v.59 no.5
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• pp.867-883
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• 2016

In this paper, the effects of steel-fiber and rebar reinforcements on the ultimate bearing strength of the local anchorage zone were investigated based on experiments and comparisons between test results and design-equation predictions (AASHTO 2012, NCHRP 1994). Eighteen specimens were fabricated using the same anchorage device, which is one of the conventional anchorage devices, and two transverse ribs were used to secure an additional bearing area for a compact anchorage-zone design. Eight of the specimens were reinforced with only steel fiber and are of two concrete strengths, while six were reinforced with only rebars for two concrete strengths. The other four specimens were reinforced with both rebars and steel fiber for one concrete strength. The test and the comparisons between the design-equation predictions and the test results showed that the ultimate bearing strength and the section efficiency are highly affected by the reinforcement details and the concrete strength; moreover, the NCHRP equation can be conservatively applied to various local anchorage zones for the prediction of the ultimate bearing strength, whereby conditions such as the consideration of the rib area and the calibration factor are changed.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.438-441
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• 2004

This paper presents the results of the experimental study on the performances of reinforced concrete beams rehabilitated by external unbonded high tension steel-bar. Design variables for the experiment in this study includes the position of anchorage zone of the high tension steel bar, the anchorage length of the reinforcing steel bar and the types of the shear strengthening measures. 5 specimens were tested with one point monotonically increased loads and structural performances such as strength capacities, ductility capacities and failure modes were analysed. It is found that the structural performance of the rehabilitated beams are strongly depended on the location of anchorage zone of the high tension steel-bars. In the case that anchorage zone is located near the critical shear zone, it is observed that the rehabilitated beam is failed in brittle failure mode and the additional shear strengthening is necessitated. But if anchorage zone is properly located or additional shear strengthening device is provided properly, it is also observed that the strength capacity of the rehabilitated beams could be increased more than $200\%$ by the proposed method.

• Smart Structures and Systems
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• v.22 no.1
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• pp.57-70
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• 2018

For the long-term structural health monitoring of civil structures, the effect of ambient temperature variation has been regarded as one of the critical issues. In this study, a principal component analysis (PCA)-based algorithm is proposed to filter out temperature effects on electromechanical impedance (EMI) monitoring of prestressed tendon anchorages. Firstly, the EMI monitoring via a piezoelectric interface device is described for prestress-loss detection in the tendon anchorage system. Secondly, the PCA-based temperature filtering algorithm tailored to the EMI monitoring of the prestressed tendon anchorage is outlined. The proposed algorithm utilizes the damage-sensitive features obtained from sub-ranges of the EMI data to establish the PCA-based filter model. Finally, the feasibility of the PCA-based algorithm is experimentally evaluated by distinguishing temperature changes from prestress-loss events in a prestressed concrete girder. The accuracy of the prestress-loss detection results is discussed with respect to the EMI features before and after the temperature filtering.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.157-160
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• 2006

Carbon fiber reinforced polymer (CFRP) laminates can be used more efficiently in strengthening applications by applying prestress to the CFRP laminates. A key problem for prestressing with CFRP laminates is anchoring the laminates. These may include fracture to the CFRP laminates due to excessive gripping force or slippage of the CFRP laminates out of the anchorage zone caused by low friction between the anchor device and the lamiantes. The main objective of this study is the development of an applicative wedge-type anchorage system for prestressed CFRP laminates through experimental study. The experimental parameters were the type of anchorage and the effect of elastic modulus of tab. The test results showed that the developed anchor assures 100% CFRP laminate strength.

• 대한치과교정학회:학술대회논문집
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• 2005.11a
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• pp.66.1-66.1
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• 2005

• The Journal of the Korean dental association
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• v.57 no.6
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• pp.333-343
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• 2019

Many orthodontists face difficulties in aligning incisors in an esthetically critical position, because the individual perception of beauty fluctuates with time and trend. Temporary anchorage device (TAD) can aid in attaining this critical incisor position, which determines an attractive smile, the amount of incisor display, and lip contour. Borderline cases can be treated without extraction and the capricious minds of patients can be satisfied with regard to the incisor position through whole dentition distalization using TAD. Mild to moderate bimaxillary protrusion cases can be treated with TAD-driven en masse retraction without premolar extraction. Patients with Angle's Class III malocclusion can be the biggest beneficiaries because both sufficient maxillary incisal display, through intrusion of mandibular incisors, and distalization of the mandibular dentition are successfully achieved. In addition, TAD can be used to correct various other malocclusions, such as canting of the occlusal plane and dental/alveolus asymmetry.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.169-172
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• 2008

Carbon fiber reinforced polymer (CFRP) laminates can be used more efficiently in strengthening applications by applying prestress to the CFRP laminates. A key problem for prestressing with CFRP laminates is anchoring the laminates. These may include fracture to the CFRP laminates due to excessive gripping force or slippage of the CFRP laminates out of the anchorage zone caused by low friction between the anchor device and the lamiantes. The main objective of this study is the development of an applicative mold-type anchorage system for prestressed CFRP laminates through experimental study. The experimental parameters were the type of anchorage detail and the effect of surface treatment. The test results showed that the developed anchor assures 100% CFRP laminate strength.