• Journal of the Korea institute for structural maintenance and inspection
• /
• v.20 no.2
• /
• pp.34-39
• /
• 2016

Structural behaviour of PSC box bridge, on which KTX train runs, is analysed up to 500 km/h speed considering 12 stages track irregularity and interaction between bridge and vehicle. To evaluate wheel forces and rotations of vehicle, lateral wheel forces, derail factor and offload factor calculated on the track combining the bridge and 170 m normal track are compared with existing allowed limits. Maximum longitudinal displacement and accumulated sliding distance of the brige bearings for simply supported and 2 span continuous PSC bridges are presented by each running speeds. Long-term friction tests based on EN-1337-2 are conducted between PTFE and DP-mate plates. Finally, the long-term friction tests are proposed to consider the increasing speed of next generation high-speed train.

• Korean Journal of Materials Research
• /
• v.4 no.6
• /
• pp.669-680
• /
• 1994

Oxidation behaviour of TiAl intermetallic compounds with the addition of Cr, V, Si, Mo, or Nb was investigated at 900~$1100^{\circ}C$ under the atmospheric environment. The reaction products were examined by XRD, SEM equipped with WDX. The weight gain by continuous oxidation increased with the addition of Cr or V, but there was less weight gain when Mo, Si or Nb was added individually. he oxidation rate of Cr- or V-added TiAl was always larger than that of TiAI. However, oxidation rate of Si-, Mo- or Nb-added TiAl was almost same or smaller than that of TiAI. Thus, it is concluded that the addition of Cr or V did not improve the oxidation resistance, whereas the addition of Si, Mo or Nb improved the oxidation resistance. Oxides formed on TiAl with Mo, Si, and Nb were found to be more protective, resulting from the decrease in diffusion rate of the alloying elements and oxygen. Nb strengthened the tendency to form $AI_{2}O_{3}$ in the early stage of oxidation, due to the continuous $AI_{2}O_{3}$ layer formation and dense $Tio_{2}+AI_{2}O_{3}$ layer. According to the Pt-marker test of TiAI- 5wt%Nb, oxygen diffused mainly inward while oxides were formed on the substrate surface. Upon thermal cyclic oxidation at $900^{\circ}C$, it is shown that the addition of Cr or Nb improved the adherence of oxide scale to the substrate.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.3
• /
• pp.293-301
• /
• 2005

We conducted several different leaching experiments for assessing the potential environmental risk when utilizing recycled concrete for stabilizing bridge pier. The methods include continuous batch leaching test (DIN 38414-S4), availability test (NEN 7341), pH-stat test (CEN/TC 292/WG6) and tank diffusion test (NEN 7345). The concentration ranges vary depending on the testing method. Nearly all the trace elements were low, some elements recording under detection limit. The maximum concentrations for trace elements leached throughout the whole tests are (as mg/L); Cd (0.029), Cu (0.437), Pb (0.14), Ni, Zn (0.95), Hg (0.005). Although the testing methods we used in this study are much more rigorous than other commonly adapted method including TCLP and domestic testing method for solid waste, the trace elemental concentrations are under the criteria for hazardous material set by the TCLP and domestic method. The result seems to suggest that applying the recycled concrete on stream water will be accepatable practice as for as trace elements are concerned. However, the influence of inorganics such as Ca, Mg, Ni and $SO_4^{2-}$ on aquatic ecology should be further examined.

• Journal of the Korean Geosynthetics Society
• /
• v.19 no.3
• /
• pp.9-21
• /
• 2020

In this study, the design method of the combined sheet pile was considered in the coastal landfill where sandy and clayey soils are mixed, and the behavior in excavation was analyzed. It was confirmed from the elasto-plastic analysis that the predicted behavior of the temporary facilities of earth retaining differs according to the type of the combined sheet pile method (Built up, Interlocking, Welding) and the analysis method (soldier pile method, continuous wall method). In the case of sheet pile member force, the results of the continuous wall analysis method predicted the most conservative results. When the stress ratio (calculation/allowance) of each member was analyzed based on the maximum member force of the combined sheet pile method, the maximum value was obtained for bending moment in the side pile and combined stress in the case of the strut. As a result of finite element analysis, the member force of the side pile was the largest in the short-term effective stress analysis condition, while the compressive force of the strut was large in the consolidation analysis. When comparing the results of the elasto-plastic analysis and the finite element analysis, the shear force of the side pile and the axial force of the strut were greatly evaluated in the elasto-plastic analysis, and the bending moment of the side pile was the largest in the short-term effective stress condition of the finite element analysis. In addition, the displacement of the side pile was predicted to be greater in the finite element analysis than in the elasto-plastic analysis.

• Steel and Composite Structures
• /
• v.6 no.6
• /
• pp.459-477
• /
• 2006

A theoretical research project is undertaken to develop integrated analysis and design tools for long span composite beams in modern high-rise buildings, and it aims to develop non-linear finite element models for practical design of composite beams. As the first paper in the series, this paper presents the development study as well as the calibration exercise of the proposed finite element models for simply supported composite beams. Other practical issues such as continuous composite beams, the provision of web openings for passage of building services, the partial continuity offered by the connections to columns as well as the behaviour of both unprotected and protected composite beams under fires will be reported separately. In this paper, details of the finite elements and the material models for both steel and reinforced concrete are first described, and finite element studies of composite beams with full details of test data are then presented. It should be noted that in the proposed finite element models, both steel beams and concrete slabs are modelled with two dimensional plane stress elements whose widths are assigned to be equal to the widths of concrete flanges, and the flange widths and the web thicknesses of steel beams as appropriate. Moreover, each shear connector is modelled with one horizontal spring and one vertical spring to simulate its longitudinal shear and pull-out actions based on measured load-slippage curves of push-out tests of shear connectors. The numerical results are then carefully analyzed and compared with the corresponding test results in terms of load mid-span deflection curves as well as load end-slippage curves. Other deformation characteristics of the composite beams such as stress and strain distributions across the composite cross-sections as well as distributions of shear forces and slippages in shear connectors along the beam spans are also examined in details. It is shown that the numerical results of the composite beams compare well with the test data in terms of various load-deformation characteristics along the entire deformation ranges. Hence, the proposed analysis and design tools are considered to be simple and yet effective for composite beams with practical geometrical dimensions and arrangements. Structural engineers are strongly encouraged to employ the models in their practical work to exploit the full advantages offered by composite construction.

• Journal of the Korea Concrete Institute
• /
• v.22 no.1
• /
• pp.123-130
• /
• 2010

In this study, mixed recycled coarse aggregate (RCA) was produced by mixing RCA from waste concrete in order to evaluate a new method of RCA production. Bond strength between reinforcing bars and RCA concrete was qualitatively evaluated as a part of continuous studies to establish design code of reinforced concrete structural members using recycled aggregate. For practical application, specimens were manufactured with the ready mix RCA concrete. Parameters investigated include: concrete compressive strength (i.e 21, 27 and 40 MPa), replacement levels (i.e 0, 30, 60 and 100%), bar position (i.e vertical and horizontal) and bar location (75 and 225 mm). For the pull-out test, each specimen was in the form of a cube, with each side of 150 mm in length and a deformed bar, 16 mm in diameter, was embedded in the center of each specimen. From the test results, the most of HT type specimen with compressive strength of 21 and 27 MPa showed lower bond strength than the ones provided in CEB-FIP and considered in reinforcement location factor ($\alpha\;=\;1.3$). It was reasoned that bonded area of top bar specimen was reduced at the soffit of reinforcement because of bleed water of fresh concrete. Therefore the reinforcement location factor in current KCI design code should be reviewed and modified.

• Journal of Service Research and Studies
• /
• v.13 no.4
• /
• pp.142-159
• /
• 2023

As the core technologies of the 4th Industrial Revolution are introduced into luxury hotels, they are taking off as cultural and experiential spaces that provide new products and services to hotel users and new experiences. Therefore, this study investigated the effect of hotel users' perception of the experience of using technological amenity services on their trust and satisfaction, focusing on luxury hotels as smart hotel to identify the essential factors of smart hotels that can lead to continuous competitive advantage and improvements in the future. In addition, the study aimed to find an effective hotel marketing strategy and plan to satisfaction the smart hotel by maximizing customer satisfaction. To verify the research hypothesis, a survey was conducted targeting hotel users with experience using technological amenities in smart hotels within the last two years. As a result of the study, it was confirmed that all hypotheses were adopted except for the relationship between personification, intention to use technical amenities, and perceived performance expectations and satisfaction with smart hotels. Based on these research results, this paper presents theoretical and practical implications. Smart hotels are rapidly changing by introducing various smart technologies. Therefore, it will be meaningful data for securing a sustainable competitive advantage and establishing differentiated hotel management and marketing strategies.

• Korean Journal of Soil Science and Fertilizer
• /
• v.43 no.3
• /
• pp.374-383
• /
• 2010

Microwave radar can penetrate cloud cover regardless of weather conditions and can be used day and night. Especially a ground-based polarimetric scatterometer has advantages of monitoring crop conditions continuously with full polarization and different frequencies. Kim et al. (2009) have measured backscattering coefficients of paddy rice using L-, C-, X-band scatterometer system with full polarization and various angles during the rice growth period and have revealed the necessity of near-continuous automatic measurement to eliminate the difficulties, inaccuracy and sparseness of data acquisitions arising from manual operation of the system. In this study, we constructed an X-band automatic scatterometer system, analyzed scattering characteristics of paddy rice from X-band scatterometer data and estimated rice growth parameter using backscattering coefficients in X-band. The system was installed inside a shelter in an experimental paddy field at the National Academy of Agricultural Science (NAAS) before rice transplanting. The scatterometer system consists of X-band antennas, HP8720D vector network analyzer, RF cables and personal computer that controls frequency, polarization and data storage. This system using automatically measures fully-polarimetric backscattering coefficients of rice crop every 10 minutes. The backscattering coefficients were calculated from the measured data at a fixed incidence angle of $45^{\circ}$ and with full polarization (HH, VV, HV, VH) by applying the radar equation and compared with rice growth data such as plant height, stem number, fresh dry weight and Leaf Area Index (LAI) that were collected at the same time of each rice growth parameter. We examined the temporal behaviour of the backscattering coefficients of the rice crop at X-band during rice growth period. The HH-, VV-polarization backscattering coefficients steadily increased toward panicle initiation stage, thereafter decreased and again increased in early-September. We analyzed the relationships between backscattering coefficients in X-band and plant parameters and predicted the rice growth parameters using backscattering coefficients. It was confirmed that X-band is sensitive to grain maturity at near harvesting season.