• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.6
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• pp.353-360
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• 2018

This paper is to investigate the micro-behavior of the double-span beams with WUF-W seismic connection under combined axial tension and moment and to propose the rational rotational capacity of it for progressive collapse-resistant analysis and design addressing the stress and strain transfer mechanism. To this end, the behavior of the double-span beams under the column missing event is first investigated using the advanced nonlinear finite element analysis. The characteristics of fracture indices of double-span beams with WUF-W connection under combined axial tension and flexural moment are addressed and then proposed the rational rotational capacity as the basic datum for the progressive collapse-resistant design and analysis. The distribution of fracture indices related to stress and strain for the double-span beams is investigated based on a material and geometric nonlinear finite element analysis. Furthermore, the micro-behavior for earthquake and progressive collapse is explicitly different.

• The Journal of the Korean dental association
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• v.44 no.11 s.450
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• pp.739-747
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• 2006

Objectives. The standardization of connection between fixture and abutment has not been defined. The success of dental implants was not always depends on connection. However, the connection mechanism is one of the most important things for dental implant treatment success. Most implant systems are very comparable in their design and engineering. They share many common characteristics and have similar strengths and weaknesses. Their significant weaknesses are connection, microgap and the resulting micromovement allowing bacterial contamination and bone loss. In the present study, we investigated the clinical performance of Ankylos implant (conical connection implant) Patients and Methods. The clinical performance of conical connection implant was studied under well-controlled clinical conditions. A total of 133 conical connection implants were placed in 50 patients from April 2005 to March 2006. The mean follow-up loading period of implants which was considered successful was 220$\pm$29 days. We recorded the age, sex, installation site, reason of edentulous region, bone density of installation site, diameter and length of dental implants and periods from installation to uncovering surgery using patients medical chart. Results Four Ankylos implants were lost during pre-loading period. 129 implants provided excellent clinical performance during 220$\pm$29 days on an average. The short-term success rate of this conical connection implant system was 96.99%.

• Steel and Composite Structures
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• v.37 no.6
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• pp.649-662
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• 2020

Although several types of rigid shear connectors have been developed particularly to increase load-carrying capacity, application is limited due to the complicated details of such connection. In this study, push-out tests were performed for specimens with hybrid shear connectors using headed studs and shear plates to identify the effects of each parameter on the structural performance of such shear connection. The test parameters included steel ratios of headed stud to shear plate, connection length, and embedded depth of shear plates. The peak strength and residual strength were estimated using various shear transfer mechanisms such as stud shear, concrete bearing, and shear friction. The hybrid shear connectors using shear plates and headed studs showed large load-carrying capacity and deformation capacity. The peak strength was predicted by the concrete bearing strength of the shear plates. The residual strength was sufficiently predicted by the stud shear strength of headed studs or by shear friction strength of dowel reinforcing bars. Further, the finite element analysis was performed to verify the shear transfer mechanism of the connection with hybrid shear connector.

• Steel and Composite Structures
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• v.5 no.1
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• pp.49-70
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• 2005

This paper reports on finite element analysis techniques that may be applied to the study of circular hollow structural sections and related bearing connection geometries. Specifically, a connection detail involving curved steel saddle bearings and a Structural Tee (ST) connected directly to a large-diameter Hollow Structural Section (HSS) truss chord, near its open end, is considered. The modeling is carried out using experimentally verified techniques. It is determined that the primary mechanism of failure involves a flexural collapse of the HSS chord through plastification of the chord wall into a well-defined yield line mechanism; a limit state for which a shell-based finite element model is well-suited to capture. It is also found that classical metal plasticity material models may be somewhat limited in their applicability to steels in fabricated tubular members.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.136-139
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• 2000

Epoxy materials are used as insulation material for electric power cables. In the case of a flow of excess current due to the temperature difference which occurs between the heat of the conductor and the atmosphere, heat degrades connection point of the cables. Also, the mechanical stress, which occurs due to the thermal expansion coefficient of cable connection electrode system and epoxy insulation materials along with the gap between thermal conduction based on the extra high voltage of transmitted voltage, increases possibility of cracks to occur. The relationship between mechanical stress and electrical breakdown mechanism is verified for the epoxy materials such as high toughness epoxy materials, which comes to be used contemporarily, and for the breakdown mechanism of epoxy materials on the multi-stresses (mechanical and electrical) due to the variation of the temperature.

• Journal of Korea Multimedia Society
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• v.11 no.8
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• pp.1101-1110
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• 2008

Nespot provides a convenient wireless internet connection service. The existing IEEE 802.1X EAP-MD5 authentication mechanism can be achieved based on ID/password information for a wireless connection. The Nespot system offers an advanced accounting and authorization procedure for providing wireless user authentication mechanism. However, many problems were found on the existing Nespot EAP-MD5 mechanism such as a ill value exposure, a leakage of personal information on wireless authentication procedure and a weakness on Nespot mutual authentication mechanism. Therefore, we analyzed the limitation of the existing IEEE 802.1X EAP-MD5 certification system, and suggested a one-time session key based authentication mechanism. And then we offered a simplified encryption function on the Nespot certification process for providing secure mutual authentication process.

• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.163-174
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• 2004

A number of experiments were performed to investigate the punching shear strength of flat plate-column connections. According to the experiments, the punching shear strength varies significantly with design parameters such as the column size of the connection, reinforcement ratio, and boundary condition. However, current design methods do not properly address the effects of such design parameters. In the present study, a theoratical approach using Rankine's failure cirterion was attempted to define the failure mechanism of the punching shear According to the study, the failure mechanism can be classified into the compression-controlled and the tension-controlled, depending on the amount of bottom re-bars placed at the connection, and the punching shear strength is also significantly affected by the flexural damage of slab. Based on the finding, a new strength model of punching shear was developed, and verified by the comparisons with existing experiments and nonlinear finite element analyses. The comparisons show that the proposed strength model addressing the effects of various design parameters can predict accurately the punching shear strength, compared to the existing strength models.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.1 s.71
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• pp.73-83
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• 2006

The failure mechanism of a hollow bridge deck which is made of fiber reinforced polymer (FRP) to improve its durability and life time significantly is investigated using both experiments and analyses. While the Load-displacement behavior of the deck in the longitudinal direction is almost linear just before the failure, the behavior in the transverse direction shows a strong nonlinearity even in its initial response with relatively small magnitude of loads. We found that the nonlinearity is due to the imperfection of the connection between the flange and the web; a plastic deformation can t라e place in the connection. The argument is demonstrated using a simple structural model in which a rigid plastic hinge is introduced to the connection. We also checked the contribution of the delamination mechanism to the failure. But the delamination is not the main mechanism which initiates and causes the failure of the bridge deck. In order to improved the structural behavior of the deck in the transverse direction, we suggested that the empty space of the bridge deck is filled with a foam and confirmed the improved behavior by a numerical analysis.

• Steel and Composite Structures
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• v.39 no.4
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• pp.383-399
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• 2021

In the study, three 1:3-scale unequal span steel-concrete composite substructures with top-seat angle and double web angle connection were designed and identified as specimens GTSDWA-0.6, GTSDWA-1.0, and GTSDWA-1.4. Pseudo-static tests and refined numerical model analysis were conducted to examine the anti-progressive collapse performance of a semi-rigid steel-concrete composite substructure. The results indicated that the failure modes of the three specimens revealed that the fracture occurred in the root of the long leg of the top/seat angle in tension at the connection. With increases in the span ratio of the left and right composite beams, the bearing capacities of the composite substructures decreased, and the corresponding displacement increased. With respect to GTSDWA-0.6 and GTSDWA-1.4, the resistance due to the short composite beam corresponded to 62% and 60%, respectively, and the total resistance provided by the short composite beam exceeded that of the long composite beam. With respect to GTSDWA-1.0, the resistance due to the left and right composite beams was similar. All three specimens underwent the flexure mechanism and flexure-axial mixed mechanism stages. They resisted the external load mainly via the flexure mechanism. Moreover, the addition of stiffeners on both sides of the top and seat angles is advantageous in terms of improving the collapse resistance and ductility of unequal span composite substructures.

• KIPS Transactions on Computer and Communication Systems
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• v.9 no.3
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• pp.67-76
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• 2020

With the fast development in wireless communications and vehicular technologies, vehicular ad hoc networks (VANETs) have enabled to deliver data between vehicles. Recently, VANETs introduce a Vehicular Cloud (VC) model for collaborating to share and use resources of vehicles to create value-added services. To construct a VC, a vehicle should search vehicles that intend to provide their own resource. The single-hop search cannot search enough provider vehicles due to a small coverage and non-line-of-sights of communications. On the other hand, the multi-hop search causes very high traffics for large coverage searching and frequent connection breakages. Recently, many Roadside Units (RSUs) have been deployed on roads to collect the information of vehicles in their own coverages and to connect them to Internet. Thus, we propose a RSU-aided vehicular resource search and cloud construction mechanism in VANETS. In the proposed mechanism, a RSU collects the information of location and mobility of vehicles and selects provider vehicles enabled to provide resources needed for constructing a VC of a requester vehicle based on the collected information. In the proposed mechanism, the criteria for determining provider vehicles to provide resources are the connection duration between each candidate vehicle and the requester vehicle, the resource size of each candidate vehicle, and its connection starting time to the requester vehicle. Simulation results verify that the proposed mechanism achieves better performance than the existing mechanism.