• Journal of the Korean Society for Railway
• /
• v.13 no.2
• /
• pp.186-193
• /
• 2010

Track system and periodic live load are characteristics of railway bridges. In the design and construction of railway bridge, periodic live load increases the importance of dynamic behavior. And It is well known that behavior of railway bridge may be affected by track system in real bridge. Through experimental study, static and dynamic behaviors were investigated. Deflection and stress due to bending moment were measured, the location of neutral axis of each section, natural frequency, damping ratio were analyzed for each three track systems - girder only, installed ballast track system and installed concrete slab track system. According to measured values for the each type of track system, concrete track system increases the stiffness of bridge by 50%, and ballast system does by 7%, dynamic responses of structure change linearly with the magnitude of load and location of neutral axis of each sections varies with each track system. Damping ratio is almost equal without and with track. Therefore, the effects of track system on the integral behaviors of railway bridge can not be ignored in the design of bridge, especially in the case of concrete slab track system. So study of the quantitative analysis method for effects of track system must be performed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.3
• /
• pp.543-552
• /
• 1994

A series of drained plane strain compression tests was performed on dried samples of dense Toyoura sand and Silver Leighton Buzzard sand prepared by air-pluviation method to find out the deformation and strength characteristics on the value of confining pressure ${\sigma}{_3}^{\prime}({\sigma}{_3}^{\prime}=0.05{\sim}4.0kgf/cm^2)$. The axial and lateral strains measured in this apparatus ranged from $10^{-6}$ up to the failure of the specimen. So the stress-strain characteristics would be investigated from very small to very large strain levels. It was found that the change of the angle of internal friction ${\phi}^{\prime}{_{max}}=arcsin\{({\sigma}{_1}^{\prime}-{\sigma}{_3}^{\prime})/({\sigma}{_1}^{\prime}+{\sigma}{_3}^{\prime})\}_{max}$ with the change of ${\sigma}{_3}^{\prime}$ is very small when ${\sigma}{_3}^{\prime}$ is lower than higher. Furthermore, the effect of confining pressure on stiffness of sands was evaluated. It was also found that for the range of shear strain ${\gamma}$ from $10^{-6}$ to those at peak, the Rowe's stress-dilatancy relation seems to be a good approximation for air-dried Toyoura sand and Silver Leighton Buzzard sand, irrespective of the change of ${\sigma}{_3}^{\prime}$.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.11
• /
• pp.1335-1343
• /
• 2012

In this study, the lightweight modular design of hybrid railway carbody structures made of sandwich composites and aluminum extrusions was investigated by using topology and size optimization techniques. The topology optimum design was used to select the best material for parts of the carbody structure at the initial design stage, and then, the size optimum design was used to find the optimal design parameters of hybrid carbody structures using first-order and sub-problem methods. Through the topology optimization analysis, it was found that aluminum extrusions were suitable for primary members such as the underframe and lower side panel module to improve the stiffness and manufacturability of the carbody structures, and sandwich composites were appropriate for secondary members such as the roof and middle side panel module to minimize its weight. Furthermore, the results obtained by size optimization analysis showed that the weight of hybrid carbody structures composed of aluminum extrusions and sandwich composites could be reduced by a maximum of approximately 17.7% in comparison with carbody structures made of only sandwich composites.

• The Journal of Engineering Geology
• /
• v.15 no.2 s.42
• /
• pp.155-168
• /
• 2005

The behavior of earth retention wall installed in a cut slope is different from the behavior of retention wall applied in an urban excavation. In order to establish the design method of anchored retention wall in the cut slope, the behavior of anchored retention wall needs to be investigated and checked in detail. In this study, the behavior of anchored retention wall was investigated by the instrumentation installed in the cut slope, where was stabilized by a row of piles in an apartment construction site. The horizontal displacement of anchored retention wall was larger than the displacement of slope soil behind the wall at the early stage of excavation. As the excavation depth became deeper, the horizontal displacement of slope soil was larger than the displacement of anchored retention wall. It means that the horizontal displacement of anchored retention wall due to excavation is restrained by soldier pile stiffness and jacking force of anchor at the early stage of excavation. lacking force of anchor was mainly influenced on the horizontal displacement of anchored retention wall. The displacements of anchored retention wall and slope soil were affected mainly by rainfall infiltrated from the ground surface. Meanwhile, the horizontal displacement of anchored retention wall with a sloped backside was about $2\~6$ times larger than the displacement of anchored retention wall with a horizontal backside of excavation.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.6
• /
• pp.13-20
• /
• 2017

High-rise building shapes are changing from orthogonal to irregular form and the current trend is to arrange members in geometric grid-patterns at the perimeter of buildings. This study proposes a simple model for the preliminary design of a hexagrid high-rise building. The size of the cross section is set to be different at each module and hexagrid unit, which is different from the previous studies in which all hexagrid members were the same. To examine the effect of hexagrid size on structural performance, 60-story hexagrid buildings with 1-, 2- and 4-story high modules are designed and analyzed. Maximum lateral displacement, steel tonnage, load carrying percentage of perimeter frame and combined strength ratio are compared for 15 buildings. As the lateral load carrying capacity of hexagrid structure was inferior to a diagrid structural system, proper lateral stiffness should be allocated to the core frame in a hexagrid structure. The best ratio of flexural to shear deformation was 4 and larger unit size was better in considering constructional cost and structural efficiency. As the maximum lateral displacements of the buildings were within 84%~108% of the limit, the proposed method seems to be applicable to preliminary design of hexagrid buildings.

• Journal of Biomedical Engineering Research
• /
• v.38 no.1
• /
• pp.43-48
• /
• 2017

Chemotherapy, radiation therapy, and surgery are major methods to treat cancer. However, current cancer treatments report severe side effects and high recurrences. Recent studies about engineering nanoparticles as a drug carrier suggest possibilities in terms of specific targeting and spatiotemporal release of drugs. While many nanoparticles demonstrate lower toxicity and better targeting results than free drugs, they still need to improve their performance dramatically in terms of targeting accuracy, immune responses, and non-specific accumulation at organs. One possible way to overcome the challenges is to make precisely controlled nanoparticles with respect to size, shape, surface properties, and mechanical stiffness. Here, we demonstrate $500{\times}200nm$ discoidal polymeric nanoconstructs (DPNs) as a drug delivery carrier. DPNs were prepared by using a top-down fabrication method that we previously reported to control shape as well as size. Moreover, DPNs have multiple payloads, poly lactic-co-glycolic acid (PLGA), polyethylene glycol (PEG), lipid-Rhodamine B dye (RhB) and Salinomycin. In this study, we demonstrated a potential of DPNs as a drug carrier to treat cancer.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.11
• /
• pp.747-754
• /
• 2017

The Concrete-Filled Tube (CFT) system was developed for its excellent structural performance, such as its good stiffness, stress and ductility, which is derived from the mechanical advantages of its composite structure. However, it is known that the flat type of reinforcing plates need stiffeners placed at a certain distance from each other to avoid buckling failure, which increases the cost accordingly. This paper investigates the contribution of the rib elements placed inside the steel tube for the purpose of increasing the bond strength between the steel and concrete and fire performance with no additional protection. The test results also demonstrate the effectiveness of the corrugated rib's shape against fire. The results of this study showed that the buckling prevention and fire resistance performance criteria were satisfied by the application of the inner surface attachment rib, due to the resulting increase in the strength of the CFT column. Therefore, it is considered that the CFT method using the corrugated rib structure reinforcement developed through this study satisfies the structural and fire resistance performance criteria without the need for a refractory coating. Future studies will be needed to make the process efficient and economical for factory production.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.7 no.5
• /
• pp.129-137
• /
• 2007

It is very urgent to research the proper recycling method of marine dredged soil as construction material for environmental conservation. Couple of developed countries have been lots of related researches on recycling of marine dredged soil for marine environmental conservation. This is highly imperative in our country. A small-scaled model test for underground pipe has been conducted on the use of controlled low strength materials with marine dredged soil. The flexible pipe, which is called PVC, was used. Four different testing materials, such as natural sand, insitu-soil, sand-CLSM with marine dredged soil and insitu-soil CLSM with marine dredged soil, were used. The vertical and lateral displacement of pipe with CLSM is one tenth of common granular materials. Also, the use of CSLM showed lower lateral and vertical pressure than that of common granular materials. The main reason is the effect of cement hardening of CLSM. This could increase of the stiffness of pipe with backfill materials. In this study, the data presented show that marine dredged soil and in-situ soil can be successfully used in CLSM and reduce the deformation and earth pressure on flexible pipe.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.7
• /
• pp.380-388
• /
• 2016

Using the magnet gear, it is possible to transmit power without mechanical contact. As the drive shaft in a magnet gear-based speed reducer system is isolated from the drive shaft, the system is a two-inertia resonance system that should cope with an external load with the limited air-gap stiffness. On the other hand, the drive shaft or low-speed side is controlled only by the torque of the drive shaft through an air-gap, and the excessive oscillation or the slip can then be generated because of an abrupt disturbance that is different from the general mechanical gear system. Therefore, the disturbance loaded at the low speed side should be measured or estimated, and considered in the control of the driving shaft. This paper proposes a novel full-state feedback controller with a reduced-order observer for the speed reducer system using a magnet gear with a unified harmonic modulator. The control method was verified by simulation and experiment. To estimate the load at the low speed side, a novel observer was designed, in which the new state variable is introduced and the new state equation is formulated. Using a full-state feedback controller including the observer, the test result against disturbance was compared with two D.O.F PI speed controllers. The pole slip was compensated within relatively a short time, and the simulation result about the estimated variable shows a similar tendency to the test result. The test results showed that the magnet gear-based reducer can be applied to an accurate servo system.

• Geotechnical Engineering
• /
• v.12 no.4
• /
• pp.5-20
• /
• 1996

In this study it was analyzed by 2-D FEM and 3-D FEM to evaluate the ground reinforceing effect of steel pipe reinforced multi -step grouting (SPRG) technique and the behavior of ground in the vicinity using the nonlinear FEM program for the ground condition of alluvium located on the top of tunnel applied by SPRG technique. It was found that the nonlinear 3-D analysis performed better than 2-D analysis in evaluating the usefulness of the SPRG technique, and it was also found that the safety was relatively secured by the stiffness of steel pipe to distribute the concentrated stress in the tunnel faceing. It was reported that the change of settlement on the top of tunnel becomes about 40% of the total expected settlement before tunnel faceing reaches tunnel gauging point, and 60% of the total expected settlement while tunnel facing passes tunnel gauging point and takes a distance about tunnel diameter. With the aid of the SPRG technique the control range of displacement and stress of the ground in the vicinity could be reached up to tunnel top, namely depth ratio from 0.38 to 0.83 or 2D(D : tunnel diameter) before the tunnel facing, and about 20% of settlement control in this particular case was possible.