• Earthquakes and Structures
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• v.19 no.6
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• pp.471-484
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• 2020

Previous earthquakes show that, structural safety evaluations should include the evaluation of nonstructural components. Failure of nonstructural components can affect the operational capacity of critical facilities, such as hospitals and fire stations, which can cause an increase in number of deaths. Additionally, failure of nonstructural components may result in economic, architectural, and historical losses of community. Accelerations and random vibrations must be under the predefined limitations in structures with high technological equipment, data centers in this case. Failure of server equipment and anchored server racks are investigated in this study. A probabilistic study is completed for a low-rise rigid sample structure. The structure is investigated in two versions, (i) conventional fixed-based structure and (ii) with a base isolation system. Seismic hazard assessment is completed for the selected site. Monte Carlo simulations are generated with selected parameters. Uncertainties in both structural parameters and mechanical properties of isolation system are included in simulations. Anchorage failure and vibration failures are investigated. Different methods to generate fragility curves are used. The site-specific annual hazard curve is used to generate risk curves for two different structures. A risk matrix is proposed for the design of data centers. Results show that base isolation systems reduce the failure probability significantly in higher floors. It was also understood that, base isolation systems are highly sensitive to earthquake characteristics rather than variability in structural and mechanical properties, in terms of accelerations. Another outcome is that code-provided anchorage failure limitations are more vulnerable than the random vibration failure limitations of server equipment.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.2
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• pp.1-8
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• 2008

Friction pendulum system is developed to prevent the damage of transformer, which is the most important among the electric power facilities, due to the earthquake and its seismic capacity is verified through the shaking table test. The applicability of friction pendulum system is confirmed as test results of compressive capacity test and friction test. Especially, as a result of shaking table test with a large scale transformer model, friction pendulum system gives to the reduction of maximum response acceleration by 30% at anchorage of transformer and 59% at the top of porcelain bushing comparing with the existing anchorage type. In addition to the reduction of maximum response acceleration, natural frequency of transformer is shifted to long period due to the friction pendulum system. In case that friction pendulum system is applied to the transformer, the damage of transformer can be prevented effectively under the earthquake.

• The Journal of the Korean bone and joint tumor society
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• v.6 no.4
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• pp.152-162
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• 2000

Purpose : To verify radiological changes of limb salvage operation using tumor prosthesis. Materials and Methods : Sixty-nine cases which used tumor prosthesis were reviewed. They have been followed up for average four years and nine months. We evaluated radiographs by ISOLS(International Symposium On Limb Salvage) radiological implants evaluation system immediate postoperatively, at postoperative 1 year and last follow-up. After converting 'excellent, good, fair, poor' to '4, 3, 2, 1' for stastical analysis, data were analyzed according to the use of cement, anatomical sites, diagnosis implant designs and age (<20 year vs. ${\geq}$20 year) using t-test and ANOVA. Results : The outcomes of cemented type prostheses were superior in remodelling and interface but inferior in anchorage. The scores of proximal femur and distal tibia were worse in bone remodelling. Osteosarcoma group had lower scores in anchorage and implant articular problem. There were no significant differences according to four different implant designs and age. Conclusion : In the intermediate term follow-up radiological evaluation, cemented type prosthesis were better in the aspects of bony resorption and osteolysis, and cementless one in anchorage. Distal femur and proximal tibia have higher scores in bony resorption, and osteosarcoma was worse tumor entity in anchorage and articular problem, and chemotherapy may be the cause.

• Computers and Concrete
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• v.22 no.4
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• pp.395-405
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• 2018

In this paper, the performance of post-installed adhesive bonded anchor embedded in concrete is assessed using numerical simulations. This study aims at studying the influence of parameters on the performance of a chemically bonded anchorage system. Non-linear finite element modelling and simulations are carried out by properly using the material properties and phenomenon. Materials parameters such as characteristic length, fracture energy, damage criteria, tension retention and crack width of concrete and interface characteristics are carefully assigned so as to obtain a most realistic behaviour of the chemical anchor system. The peak strength of two different anchor systems obtained from present numerical studies is validated against experimental results. Furthermore, validated numerical models are used to study the load transferring mechanism and damage progression characteristics of various anchors systems where strength of concrete, strength of epoxy, and geometry and disposition of anchors are the parameters. The process of development of strain in concrete adjacent to the anchor and energy dissipated during the course of damage progression are analysed. Results show that the performance of the considered anchorage system is, though a combined effect of material and geometric parameters, but a clear distinction could be made on the parameters to achieve a desired performance based on strength, slip, strain development or dissipated energy. Inspite the increase in anchor capacity with increase in concrete strength, it brings some undesirable performance as well. Furthermore, the pullout capacity of the chemical anchor system increases with a decrease in disparity among the strength of concrete and epoxy.

• Journal of Korean Society for Geospatial Information Science
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• v.18 no.3
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• pp.21-27
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• 2010

When the capacity of underground caverns' structures is measured, a general surveying is difficult to decide an accurate section of irregular shape and a photographic surveying has problems on picture acquisition due to underground dusts, noise and lighting conditions, etc. The laser scanner system is being much used for 3-dimensional modeling such as topography, planimetric features and structures, etc. without a target by measuring arriving time of a laser pulse reflected after scanning the laser pulse and calculating space coordinates of the reflection position. Accordingly, the present research carried out section and earthwork volume measurement of a tunnel by using a laser scanner in underground anchorage excavation work that a bridge construction is being executed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.8 s.227
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• pp.1237-1244
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• 2004

The orthodontic surgery including lingual orthodontics has recently attracted a person's attention due to its functional and esthetic appreciation. The skeletal anchorage with the miniscrew is newly adopted in the lingual orthodontics to assist the upholding ability. The appliciation needs to understand the mechanism of the orthodontic appliance and its related orthodontic correction for optimal orthodontic treatment. There is, however, few information about the qualitative and quantitative effect of the orthodontic appliance with the miniscrew has not been well identified. In this paper, three dimensional finite element analysis is introduced to the lingual orthodontics in order to investigate the effect of the anterior retraction force on the miniscrew and transpalatal arch wire. The analysis determines the adequate location of the miniscrew and the point of force application of the anchorage system in the lingual orthodontics. The analysis results demonstrate the effect of the position of the miniscrew and the transpalatal arch wire on the lingual orthodontics.

• Journal of Korean Port Research
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• v.15 no.1
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• pp.75-85
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• 2001

Accuracy of dredging processes depends on the types of equipment used, the sediments encountered, whether the work to be performed is new or maintenance dredging, pre- and post-hydrographic surveying and so forth. Among those, position surveying accuracy which is directly determined by the control of the dredge's position and depth surveying accuracy being surveyed at the dredging point during dredging work are important factors. The purpose of this study is to develop 'Dredge Management System'for Grab dredge which is composed of 4 sub-system using LADGPS for dredge position determining system and dredging point determining system, tide gauge system and optical sensor for depth determining system and GIS and ENC for total management system. This system is installed on the grab dredge 'EUNJIN G-18'and applied to anchorage dredging work. at Pohang Harbor. The results revealed that this system is easy to operate, achieves good accuracy with only 45cm unevenness, reduces working period by 22 percent and saves cost 16.6 percent.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.507-514
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• 2015

This study focused on the investigating of the improving measure of marine traffic system around Pyung-Taek Pilotage area. First, we analyzed the marine traffic environment on the study area based on the expert point of view of pilot and shipmasters. Then suggested the following countermeasures to improve the traffic safety according to the analytic results of the hazardous items on the Jangan-Seo and Ippa pilot embarking/disembarking area. We suggested to establish Mokdeok-do TSS and TSS in Ando area, and to adjust the width of Jangan-seo TSS to improve the congestion on the TSSs. Also suggest to put lightbuoys along the outer limit of the TSS. In addition, recommend to establish traffic safety specific area on the Jangan-seo/Ippa-do water, and to suggest expand the anchorage area of Ippa and Jangan-seo anchorage. It is anticipated to improve the traffic safety on the study area through the marine traffic system improvements.

• International Journal of Highway Engineering
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• v.9 no.3
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• pp.135-143
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• 2007

The pavement system constructed by tieing a number of precast concrete slabs employing prestressing techniques is called the precast prestressed concrete pavement. The behavior of this type of pavement system under post-tensioning was analyzed using a finite element model. First, the optimal number of anchors was determined by investigating the distribution of compressive stresses in the pavement system due to post-tensioning. Then, the effects of the parameters such as the horizontal resistance of underlying layers, the pavement length, the slab thickness, and the bearing area of the anchorage on the distribution of compressive stresses were analyzed. The horizontal resistance of underlying layers induced the loss of compressive stresses, and the loss increased in the middle of the pavement. As the pavement length increased or the slab thickness decreased, the stress loss due to the horizontal resistance of underlying layers became larger. However, the bearing area of the anchorage where the compressive forces were applied did not much affect the distribution of compressive stresses.

• Journal of Korean Society of Steel Construction
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• v.26 no.1
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• pp.1-10
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• 2014

In this study, out-of-plane flexural test was performed to analyze behavior properties for a beam specimen which imitated a structure with connection member between reinforced concrete and steel plate concrete part. Tie bars between a upper and a lower steel plate, and tie wide flange shapes between upper and lower ribs were designed to prevent the steel plate or the ribs from breakaway in the connection of the specimen. As a result of the test, ductile failure behavior of the specimen and the functionality of the tie members were conformed as originally intended. Also, tension tests were performed to evaluate the design appropriateness of two specimens produced to anchor and connect mechanically #14 bars. The two test results showed that the anchorage connection system behaves in elastic limit during the main bars yielded, and the integrity of the designed system was verified.