• Transactions of the KSME C: Technology and Education
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• v.3 no.3
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• pp.165-173
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• 2015

This paper presents numerical results of static structural stability analysis in development of a vertical transfer device of a PRT(Personal Rapid Transit) vehicle. The vertical transfer of a fully occupied vehicle operating on a road network is the first attempt, which is expected to contribute to overcome the limitations of conventional 2-dimensional operation mode. In particular, the vertical transfer apparatus designed based on vertical circulating conveyors is capable of continuous transfer without time delay so that it enables to accommodate a high traffic density. This system has been frequently used in a logistics field; however, it is essential to assess a structural integrity because an external force by a vehicle weight is exerted on the conveyors in the form of a concentrated load unlike a conventional logistic transport. In this study, prior to the production process, the structural performance of the pilot design in an early stage is numerically evaluated using the commercial finite element method (FEM) solver (i.e., $Ansys^{(R)}$).

• Wind and Structures
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• v.31 no.2
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• pp.143-152
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• 2020

The wind design of buildings is typically based on strength provisions under ultimate loads. This is unlike the ductility-based approach used in seismic design, which allows inelastic actions to take place in the structure under extreme seismic events. This research investigates the application of a similar concept in wind engineering. In seismic design, the elastic forces resulting from an extreme event of high return period are reduced by a load reduction factor chosen by the designer and accordingly a certain ductility capacity needs to be achieved by the structure. Two reasons have triggered the investigation of this ductility-based concept under wind loads. Firstly, there is a trend in the design codes to increase the return period used in wind design approaching the large return period used in seismic design. Secondly, the structure always possesses a certain level of ductility that the wind design does not benefit from. Many technical issues arise when applying a ductility-based approach under wind loads. The use of reduced design loads will lead to the design of a more flexible structure with larger natural periods. While this might be beneficial for seismic response, it is not necessarily the case for the wind response, where increasing the flexibility is expected to increase the fluctuating response. This particular issue is examined by considering a case study of a sixty-five-story high-rise building previously tested at the Boundary Layer Wind Tunnel Laboratory at the University of Western Ontario using a pressure model. A three-dimensional finite element model is developed for the building. The wind pressures from the tested rigid model are applied to the finite element model and a time history dynamic analysis is conducted. The time history variation of the straining actions on various structure elements of the building are evaluated and decomposed into mean, background and fluctuating components. A reduction factor is applied to the fluctuating components and a modified time history response of the straining actions is calculated. The building components are redesigned under this set of reduced straining actions and its fundamental period is then evaluated. A new set of loads is calculated based on the modified period and is compared to the set of loads associated with the original structure. This is followed by non-linear static pushover analysis conducted individually on each shear wall module after redesigning these walls. The ductility demand of shear walls with reduced cross sections is assessed to justify the application of the load reduction factor "R".

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.6
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• pp.455-462
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• 2013

The effects of earthquakes can be devastating especially to existing structures that are not based on earthquake resistant design. This study proposes a steel grid shear wall that can provide a sufficient lateral resistance and can be used as a seismic retrofit method. The pushover analysis was performed on RC structure with and without the proposed steel grid shear wall. Obtain the performance point that the target structure for seismic loads applied to evaluate the response and performance levels. The capacity spectrum at performance point is nearly elastic range, so satisfied the performance objectives(LS level). And response modification factor(R factor) were calculated from the pushover analysis. The R factor approach is currently implemented to reflect inelastic ductile behavior of the structures and to reduce elastic spectral demands from earthquakes to the design level. The R factor increases from 2.17 to 3.25 was higher than the design criteria. As a result, according to reinforcement by steel grid shear wall, strength, stiffness, and ductility of the low-rise RC structure has been appropriately improved.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.609-616
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• 2010

FRP-concrete composite deck, an innovative system, is composed of concrete in the top and FRP panel in the bottom. Bottom FRP panel can reduce self weight and improve workability. This system requires strong connection between FRP and concrete. Therefore coarse sand coating was previously applied on FRP to improve the bonding. In this study, concrete wedge method is newly introduced to enhance both vertical bond and fatigue performance. Three FRP-concrete composite deck specimens with the concrete wedges were manufactured, and static and fatigue tests were carried out. The results showed that the new FRP-concrete composite deck satisfied deflection and crack width limits set by the design codes. And the fatigue test showed that the composite deck was capable of two million load cycles under 50% of its static strength. Based on the results, it can be concluded that that this new system has outstanding mechanical and durability performance, and therefore, satisfactorily be used in designing FRP-concrete composite deck.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.9-14
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• 2017

In the present work, a mechanical performances under cyclic loading in RC (Reinforced Concrete) beams with normal steel and FRPH (Fiber Reinforced Plastic Hybrid) bar are investigated. For the work, RC beam members with $200{\times}200{\times}2175mm$ of geometry and 24 Mpa of design strength are prepared, and 4-point-bending tests are performed for evaluation of cracking, yielding, and ultimate loads. Through static loading test, 48.9kN and 36.0 kN of yielding loads are measured for normal RC and FRPH beam, respectively. They have almost same ultimate load of 50.0 kN. Typical tension hardening behavior is observed in FRPH beam, which is caused by the behavior of FRPH bar with tension hardening. In cyclic loading conditions, FRPH beam has more smaller crack width and scattered crack pattern, and it shows more elastic recovery than normal RC beam. The energy dissipation ratio in FRPH beam is 0.83, which is greater than 0.62 in normal RC beam and it shows more effective resistance to cyclic loadings.

• Composites Research
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• v.28 no.4
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• pp.219-225
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• 2015

Air spoiler, which can reduce the drag during operation, can be considered as a possible means to reduce carbon dioxide emission and to increase fuel efficiency. In this study, a composite air spoiler was designed and tested by static and repeated loads. The Green Water Pressure of 0.1 MPa a ship experiences during operation was perpendicularly applied to the air spoiler. Air spoiler was manufactured with sandwich panel which has glass fabric face and balsa core. Multiple sandwich panels were assembled to steel frame by bolt joint. The joint was designed to have bearing failure and examined by static and fatigue tests. Tests showed that the designed joint has enough margin of safety to endure joint failure. The developed sandwich panel to air spoiler is planned to be applied to a large scale commercial ship.

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.23-32
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• 2017

The joints between precast PSC slabs of the intermediate road slab in double deck tunnel are inevitably generated in the road traffic vehicle traveling direction. Therefore, it is important to make the behavior of parts on the joint in one piece. The imtermediate road slab system of double deck tunnel in great depth proposed in this study will be constructed with precast PSC slab in order to minimize the construction period. And the joint connection between the precast slab has been developed in two methods: the 'Transverse tendon reinforcement method' and 'High strength bolts connection method'. Also, the experiments were performed for the full scale model in order to evaluate the performance of the intermediate road deck slab with two type joints systems, the structural stability was verified through the F.E.M analsysis. The results of static loading test and F.E.M analysis investigated a very stable behavior of intermediate road deck slab in double deck tunnel applying the joint methods developed in this study, in the cracks and deflections to satisfy the design standards of Highway Roads Bridges (2011), it was determined that there is no problem even servicebility.

• Korean Journal of Applied Biomechanics
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• v.26 no.4
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• pp.397-405
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• 2016

Objective: Pilates is a low/mid-intensity exercise that can be easily performed by elderly individuals as it is an individual body-oriented exercise. It is also a cardio workout that can be performed anywhere to develop strength and flexibility. Therefore, we investigated the effects of 8 week Pilates program on the balancing ability of elderly individuals. Method: The research participants were selected from elderly residents in B city. Ten individuals voluntarily signed an agreement to undergo free measurements as well as to participate in the workout program. (Height: $157.1{\pm}11.9cm$, Weight: $61.7{\pm}8.0kg$). The Pilates exercise was performed 60 minutes a day, three times a week for a total of eight weeks. The measurement variables used to test balance were the vestibular test, 5 m habitual and maximum walk test and 3 m tandem walk test. A series of paired t-test were conducted using IBM SPSS Statistics 23.0 to analyze all the research data collected in order to determine the balance ability of the participants before and after the Pilates program. Additionally, the statistically significant level for all analysis was set to ${\alpha}=.05$. Results: In the vestibular test, some meaningful changes were observed in the length envelope area (ENV) while standing on one foot, but there were no significant differences in the ENV, rectangle(REC), root mean square, and total length. Results also revealed that statistically significant differences existed in the 5 m habitual and maximum walk test, as well as the 3 m tandem walk test. Conclusion: To summarize the findings, the 8 week Pilates program employed in this study significantly improved the dynamic balance of the elderly participants. Thus, elderly individuals that frequent perform Pilates are expected to enjoy positive benefits such as increased balance and fewer falling accidents.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.40-47
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• 2021

In this study, the structural behavior by the details of the lap region with the headed bar was estimated through finite element analysis. To solve the finite element analysis of the anchorage region with complex contact conditions and nonlinear behavior, a quasi-static analysis technique by explicit dynamic analysis was performed. The accuracy of the finite element model was verified by comparing the experimental results with the finite element analysis results. It was confirmed that the quasi-static analysis technique well reflected the behavior of enlarged headed bar connection. As a result of performing numerical analysis using 21 finite element models with various development lengths and transverse reinforcement indexes, it was confirmed that the increase of development length and transverse reinforcement index improved the maximum strength and ductility. However, to satisfy the structural performance, it should be confirmed that both design variables(development length and transverse reinforcement index) must be enough at the design criteria. In the recently revised design standard(KDS 14 20 52 :2021), a design formula of headed bar that considers both the development length and the transverse reinforcing bar index is presented. Also the results of this study confirmed that not only the development length but also transverse reinforcing bars have a very important effect.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.5
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• pp.81-88
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• 2021

Structural health monitoring (SHM) systems have attracted considerable interest owing to the frequent earthquakes over the last decade. Smart concrete is a technology that can analyze the state of structures based on their electro-mechanical behavior. On the other hand, most research on the self-sensing response of smart concrete generally investigated the electro-mechanical behavior of smart concrete under a static loading rate, even though the loading rate under an earthquake would be much faster than the static rate. Thus, this study evaluated the electro-mechanical behavior of smart ultra-high-performance concrete (S-UHPC) at three different loading rates (1, 4, and 8 mm/min) using a Universal Testing Machine (UTM). The stress-sensitive coefficient (SC) at the maximum compressive strength of S-UHPC was -0.140 %/MPa based on a loading rate of 1 mm/min but decreased by 42.8% and 72.7% as the loading rate was increased to 4 and 8 mm/min, respectively. Although the sensing capability of S-UHPC decreased with increased load speed due to the reduced deformation of conductive materials and increased microcrack, it was available for SHM systems for earthquake detection in structures.