• Journal of the Korean Institute of Landscape Architecture
• /
• v.30 no.3
• /
• pp.25-34
• /
• 2002

The purpose of this paper is to discuss the function of microclimate amelioration of urban trees regarding the environmental benefits of street trees in summer, focusing on the heat pollution-urban heat island, tropical climate day's phenomenon and air pollution. We measured the diurnal variation of air/ground temperatures and humidity within the vegetation canopy with the meteorological tower observation system. Summertime air temperatures within the vegetation canopy layer were 1-2$^{\circ}C$ cooler than in places with no vegetation. Due to lack of evaporation, the ground surface temperatures of footpaths were, at a midafternoon maximum, 8$^{\circ}C$ hotter than those under trees. This means that heat flows from a place with no vegetation to a vegetation canopy layer during the daytime. The heat is consumed as a evaporation latent heat. These results suggest that the extension of vegetation canopy bring about a more pleasant urban climate. Diurnal variation of air/ground temperatures and humidity within the vegetation canopy were measured with the meteorological tower observation system. According to the findings, summertime air temperatures under a vegetation canopy layer were 1-2$^{\circ}C$ cooler than places with no vegetation. Due mainly to lack of evaporation the ground surface temperature of footpaths were up to 8$^{\circ}C$ hotter than under trees during mid-afternoon. This means that heat flows from a place where there is no vegetation to another place where there is a vegetation canopy layer during the daytime. Through the energy redistribution analysis, we ascertain that the major part of solar radiation reaching the vegetation cover is consumed as a evaporation latent heat. This result suggests that the expansion of vegetation cover creates a more pleasant urban climate through the cooling effect in summer. Vegetation plays an important role because of its special properties with energy balance. Depended on their evapotranspiration, vegetation cover and water surfaces diminish the peaks of temperature during the day. The skill to make the best use of the vegetation effect in urban areas is a very important planning device to optimize urban climate. Numerical simulation study to examine the vegetation effects on urban climate will be published in our next research paper.

• Journal of the Korean Geotechnical Society
• /
• v.29 no.10
• /
• pp.5-18
• /
• 2013

The differential settlement between the foundations causes the critical damage on the transmission tower constructed in soft ground. Connected-pile foundation for transmission tower structures is an option to prevent the differential settlement. It consists of main foundations and connection beams that are placed between the individual foundations at each corner of tower. In this study, 24 model pile load tests were conducted at a construction site in jeonlabuk-do to investigate the effects of the connection beams on transmission tower foundation. In model tests, various load conditions and connection beam conditions were considered. As the test results, the displacements of connected-pile foundation differed in accordance with load directions. The settlements of connected-pile foundation decreased with the increased stiffness of connection beams, lateral load capacity decreased in accordance with load height, and the lateral load capacity on the failure criteria was similar regardless of load direction.

• Journal of the Korean Geotechnical Society
• /
• v.28 no.8
• /
• pp.31-41
• /
• 2012

Pile foundation for transmission tower constructed in weak ground can cause the damage of the tower due to the different settlement between the foundations. In Japan and USA, connected-pile foundations whose 4 foundations are connected each other by beams were used for transmission tower (TEPCO 1988, IEEE 2001). Resistance increasing factors for connected-pile foundation signify increasing amount of resistance due to the effect of connected-pile material. In this study, we performed model lateral load tests of connected-pile foundations for transmission tower and found the resistance increasing factors for connected-pile foundation. The tests were performed in silty clay, and the resistance increasing factors were founded in various conditions that lateral load directions and height, the stiffness of beams in the connected-pile foundations were changed. The resistance increasing factors from our research were presented as a function of normal lateral loading height and normal stiffness of the connected-pile material. The resistances which were estimated from the resistance increasing factors were similar to measured values.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.9
• /
• pp.369-374
• /
• 2016

Cooling towers have been installed on rooftops or outside of buildings and widely applied to control the indoor temperature in residential areas and buildings. However, the noise and vibration resulting from their operation may cause problems in adjacent buildings. The purpose of this study is to measure the noise and vibration of an industrial cooling tower located adjacent to industrial plants and to investigate its influence on the surroundings according to an authorized evaluation standard. Further, in order to measure the effect of the vibration of the tower on the precision equipment inside the plant, an experiment is conducted to measure the vibration of the ground in the plant and the targeted precision equipment. The measurement results indicate that the noise in the cooling tower is 4 to 9 dB(A) higher than the maximum level defined in the standard of 68dB(A). The effect of the vibration of the tower on the precision equipment is comparatively minimal, because that in the supporting frame of the building is weaker than that on the floor where the precision equipment is located. The vibration of the floor on.

• Journal of the Korea Institute of Building Construction
• /
• v.9 no.2
• /
• pp.31-38
• /
• 2009

In today's construction industry, buildings have been more complicated and higher, the demands of steel works have been increasingly concerned, which makes the schedule planning and management more significant. However, in actual construction sites, management is more based on a manager's construction experience than productivity data accumulated in previous projects. Moreover, most of the existing studies also featured a theoretical approach rather than an analysis of data straightforwardly collected in sites. In this study, a steel-erection site was visited to collect productivity data. The study found that there were significant disparities between aboveground work productivity and underground work; one tower crane operated work and two tower crane operated; and work productivity conducted in clear weather condition, cloud and rainy. However, the productivities of 'first node on ground' and 'second node on ground' were estimated similar. The productivity data collected and factors affecting the productivity will help managers to plan and control their similar steel-erection works. This study will also be beneficial for those performing related studies.

• Journal of Environmental Science International
• /
• v.27 no.11
• /
• pp.1155-1167
• /
• 2018

We developed a small sensor observation system (SSOS) at a relatively low cost to observe the atmospheric boundary layer. The accuracy of the SSOS sensor was compared with that of the automatic weather system (AWS) and meteorological tower at the Korea Meteorological Administration (KMA). Comparisons between SSOS sensors and KMA sensors were carried out by dividing into ground and lower atmosphere. As a result of comparing the raw data of the SSOS sensor with the raw data of AWS and the observation tower by applying the root-mean-square-error to the error, the corresponding values were within the error tolerance range (KMA meteorological reference point: humidity ${\pm}5%$, atmospheric pressure ${\pm}0.5hPa$, temperature ${\pm}0.5^{\circ}C$. In the case of humidity, even if the altitude changed, it tends to be underestimated. In the case of temperature, when the altitude rose to 40 m above the ground, the value changed from underestimation to overestimation. However, it can be confirmed that the errors are within the KMA's permissible range after correction.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.11a
• /
• pp.387-390
• /
• 2007

Recently the diameter of the 5MW wind turbine reaches 126m, and the tower height is nearly the same with the wind turbine diameter. The blade will experience periodic inflow oscillation due to blade rotation inside the ground shear flow region, that is, the inflow velocity is maximum at uppermost position and minimum at lowermost position. In this study we compare the aerodynamic data between two inflow conditions, i.e, uniform flow and normal wind profile. From the computed results all of the relative errors for oscillating amplitudes increased due to the ground shear flow effect. Especially My at hub and $F_x$, $M_y$, $M_z$ at LSS increased enormously. It turns out that the aerodynamic analysis including the ground shear flow effect must be considered for fatigue load analysis.

• Journal of the Korean Society of Mechanical Technology
• /
• v.20 no.6
• /
• pp.894-900
• /
• 2018

Among the soft ground improvement methods, PBD is the most common construction method because it is cheap and construction is fast. However, if the ground is rigid, additional work is required. In this study, the structural safety, natural vibration, and safety angle of the steel vertical tower structure were evaluated in the development of the PBD composite perforator which can be combined with drilling work and PBD construction. Structural safety was assessed when the wind load of 20 m/s was simultaneously applied to the PBD construction load of 20 tons, the perforating operation of 25 tons, and the wind speed of 50 m/s was applied only to the wind load. The natural frequencies were evaluated up to the sixth mode, and the safety angle was evaluated for static and dynamic safety angles.

• Transactions of the KSME C: Technology and Education
• /
• v.4 no.1
• /
• pp.19-26
• /
• 2016

This paper presents the measurement and analysis results for the performance of HGCHP system using a cooling tower as a supplemental heat rejector. In order to demonstrate the performance of the hybrid approach, we installed the monitoring equipments including sensors for measuring temperature and power consumption, and measured operation parameters from February 1, 2014 to February 28, 2015. Leaving load temperatures to building showed an average value of $11.7^{\circ}C$ for cooling and $39.5^{\circ}C$ for heating, respectively. From the analysis, the daily PF of hybrid GCHP system varied from 2.6 to 6.6 over the measurement period.

• Earthquakes and Structures
• /
• v.6 no.5
• /
• pp.495-514
• /
• 2014

The performance of passive control system for the seismic protection of a multi-tower cable-stayed bridge with the application of partially longitudinal constraint system is investigated. The seismic responses of the Jiashao Bridge, a six-tower cable-stayed bridge using the partially longitudinal constraint system are studied under real earthquake ground motions. The effects of the passive control devices including the viscous fluid dampers and elastic cables on the seismic responses of the bridge are examined by taking different values of parameters of the devices. Further, the optimization design principle of passive control system using viscous fluid dampers is presented to determine the optimized parameters of the viscous fluid dampers. The results of the investigations show that the control objective of the multi-tower cable-stayed bridge with the partially longitudinal constraint system is to reduce the base shears and moments of bridge towers longitudinally restricted with the bridge deck. The viscous fluid dampers are found to be more effective than elastic cables in controlling the seismic responses. The optimized parameters for the viscous fluid dampers are determined following the principle that the peak displacement at the end of bridge deck reaches to the maximum value, which can yield maximum reductions in the base shears and moments of bridge towers longitudinally restricted with the bridge deck, with slight increases in the base shears and moments of bridge towers longitudinally unrestricted with the bridge deck.