• KIEAE Journal
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• v.16 no.1
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• pp.67-71
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• 2016

Purpose: There is a growing interest in rainwater runoff reduction effect of green roof, as flooding caused by increasing impervious surface is becoming more and more frequent in urban areas. This study was conducted to prove runoff reduction and runoff delay effect of the retentive green roof and to investigate its influencing factors to the rainfall events that occurred in the summer of 2013. Method: The experiment intended to monitor the runoff quantity of the retentive green roof($140m^2$) and normal roof($100m^2$) in #35 building in Seoul National University, Seoul, Korea for 75 days in 2013. Result: On analysis of 9 rainfall events, it showed that the retentive green roof has 24.8~100% of runoff reduction ratio, 21.2~100% of peak flow reduction ratio, 0.5~3.75 hours of peak delay, and $1.8{\sim}7.2m^3$ of retaining capacity in an area of $140m^2$. It shows different results depending on rainfall and antecedent dry days. The results show that runoff reduction effect is effective when the rainfall is less than 50 mm and antecedent dry day is longer than five days on average. By installing retentive green roofs on buildings, it can help mitigate urban floods and rehabilitate urban water cycle.

• Journal of Environmental Science International
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• v.24 no.7
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• pp.927-937
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• 2015

This study was performed to identify and quantify the asbestos fibers released from two types of asbestos-cement slate roofs. One is a plant roof installed in 1987 which contained 15% chrysotile, and the other is a residential roof installed before 1983 which contained 12% chrysotile. The concentrations of asbestos fibers in air surrounding asbestos-cement slate roofs and in the falling water harvested from the same roofs on rainy days ranged from 0.0012 to 0.0018 f/mL and from 1,764 f/L to 10,584 f/L, respectively. The concentration of inorganic fibers in the soil around asbestos-cement slate roofs was from 217 to 348 f/g. With the above results, the excess lifetime cancer risk (ELCR) for the risk assessment of the asbestos fibers released from asbestos-cement slate based on US EPA IRIS (Integrated risk information system) model is within 5.5E-06 ~ 6.5E-06 levels which indicates that the levels do not exceed "the acceptable risk(1.0E-05)" recommended by WHO. The asbestos concentration in air, drained rainfall and soil around the plant slate roof was higher than that around residential slate roof, but the excess lifetime cancer risk (ELCR) from residential slate was higher than that from plant slate. This suggested that the enclose and encapsulation of residential roofs have priority in removal policy to minimize the exposure risk.

• Journal of Korean Association for Spatial Structures
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• v.11 no.2
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• pp.63-70
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• 2011

Livestock buildings are rural facilities as vulnerable to natural disasters as vinyl houses. Many of livestock buildings have a roof but without side walls. The roof of such structures is easily blown away by a typhoon and this results in a heavy loss. Therefore, farmers install winch curtains on the sides to prevent damages caused by typhoons. This study purposed to examine the distribution of wind pressure coefficient among different positions of livestock shed roof according to the opening of side walls. It was found that according to the distribution of peak external pressure coefficient on the roof surface of livestock shed, the wind blowing at wind angle $0^{\circ}$ was disadvantageous to roof surface regardless of the presence of side walls. However, it was confirmed that the peak external pressure coefficient was affected by wind angle and the length of eave depending on the presence of side walls.

• Journal of the Korean housing association
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• v.21 no.1
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• pp.23-30
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• 2010

The purpose of this study is to analyze the elevations of standard rural house designs after the 1990's. Various types of analysis were carried out on a total of 18 different sizes and 50 types of designs with p'yong sizes ranging from 12 to 44. The objects of analysis are the various elevations & the roof types that were supplied in the standard rural house design according to each year 1995 (8 sizes 20 types), 1997 (8 sizes 8 types), 1998 (l size 8 types), 2000 (2 sizes 4 types), 2001 (2 sizes 4 types), and 2004 (3 sizes 6 types). Results from the analysis demonstrate that (1) The gable roof has been used as the roofing type for standard rural house design since 1990. However the roof types of the standard rural house design includes only a few different types of gable roofs and roof materials(most roof types use asphalt shingle). (2) While most front elevations have been altered from asymmetrical to symmetrical most rear elevations have evolved from symmetrical to asymmetrical proportions since the 1990's (3) While siding materials and red-brick were most commonly used the main outer-wall materials prior to 2000, environmentally-friendly materials have been used as outer-wall materials since 2000. (4) In terms of the analysis of outer-wall objects before 2000 the walls were even, yet after 2000 these outer-walls evolved to become concave-convex walls. In other words, the evolution of the outer-wall has included a variety of wall types.

• KIEAE Journal
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• v.14 no.1
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• pp.31-38
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• 2014

Recently, the coverage of urban forests has been rapidly decreasing as the cities are created and expanding. Consequently, there arise urban problems such as heat island effect, urban flooding, urban desertification and so on. In this context, green roof systems is considered to be an efficient alternative to deal with these problems. However, it is difficult to apply green roof to new buildings since the majority of the buildings in cities are already constructed and the demand for new building constructions is not high enough. Therefore, it should be considered to apply green roof system to existing buildings for resolving various problems. This study evaluates heating and cooling energy consumption based on the combination of passive design factors such as wall, roof, window insulation in addition to a green roof system applied to an existing house by using an energy simulation program. Total 8 potential improvement cases are developed. Each case is applied to the same house with different insulation standard for simulations. Through the analysis of the simulated cases with the chosen test house, it is confirmed that heating energy consumption decreases as improvement cases are applied, but cooling energy consumption is relatively not much affected by each improvement case. In addition, when each improvement case is applied to already highly insulated house, the effect of thermal energy improvement decreases while the same improvement that is applied to the case with low insulated house tends to yield higher improvement rate.

• KIEAE Journal
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• v.13 no.5
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• pp.89-96
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• 2013

Green roofs can reduce surface water runoff, provide a habitat for wildlife moderate the urban heat island effect, improve building insulation and energy efficiency, improve the air quality, create aesthetic and amenity value, and preserve the roof's waterproofing. Green roofs are mainly divided into three types : intensive, simple-intensive, and extensive. Especially, extensive roof environment is a harsh one for plant growth; limited water availability, wide temperature fluctuations, high exposure to wind and solar radiation create highly stressed environment. This study, aimed at extensive green roof, was carried out on the rooftop of the library at Seoul Women's Univ. from October to November, 2012 and from March to August, 2013. To suggest the most effective vegetation model for biodiversity and heat island mitigation, surface temperatures were monitored by each vegetation model. We found that herbaceous plants of Aster sphathulifolius, Aceriphyllum rossii and Belamcanda chinensis, shrub of Syringa patula 'Miss Kim', Thymus quinquecostatus var. japonica, Sedum species can mixing each other. Among them, the vegetation models including Sedum takesimense, Aster sphathulifolius, Thymus quinquecostatus var. japonica was more effective on the surface temperature mitigation, because the species have the tolerance and high ratio of covering, and also in water. Especially, in the treatment of bark mulching, they helped to increase the temperature of vegetation models. In the case of summer, temperature mitigation of vegetation models were no significant difference among vegetation types. Compared to surface temperature of June, July and August were apparent impact of temperature mitigation, it shows that temperature mitigation are strongly influenced by substrate water content.

• Journal of Korean Association for Spatial Structures
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• v.12 no.3
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• pp.47-54
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• 2012

The roof surface of spatial structures is often damaged or destroyed because of its light weight roof structure and materials. Many of large scale stadiums have roof structure framed with steel truss or stay cable and wrapped or covered with membrane material Teflon, and this membrane material is easily damaged and its loss is quite serious. Through such examples, it was found that the studies on wind proof design of roofs of large space structures were not sufficiently made. This study conducted wind pressure experiment and fluid analysis in order to examine the aerodynamic characteristic of the roof shape of hyperbolic paraboloid spatial structures. Although the biggest minimum peak wind pressure coefficient was shown in the edges of the roof in the wind origin direction, it decreases with the advancement to the longitudinal direction of the roof.

• Journal of Korean Association for Spatial Structures
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• v.9 no.2
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• pp.83-90
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• 2009

The previous studies for dynamic behavior of spatial structure have been zoomed in on roof structure by numerical analytic method. But the roof structure of real spatial structures is supported by lower structure as column and wall. So, when earthquake is occurred, it is predicted that dynamic behavior of roof structure is affected by lower structure. Therefore, on this study, natural period characteristics of arch structures are analyzed according to section, length and the modulus of elasticity of brass column and polycarbonate column and additional mass of roof structure by the scale-down model of arch structure as the most simple structure of spatial structures. The changes of natural periods are generally alike. But, when Polycarbonate column is connected to roof structure, the change of natural period for change of section is relatively large. That means that change of section and section and length of column and additional mass of roof structure have less influence on change of stiffness because the modulus of elasticity of brass is relatively large.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.5
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• pp.377-387
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• 2016

In recent, in case that the underpass is constructed by trenchless method, its stability increases by reinforcing steel pipe with re-bar and mortar after propulsion into the ground to form pipe-roof. Therefore, it can be predicted that the integrated pipe-roof decreases the stress acting on the underpass by sharing load. In this study, to analyze the effect of integrated pipe-roof and behavior of stress around underpass, experimental tests for the rectangular and arch cross section of the underpass are performed using soil chamber. As a result, stress and strain acting on the underpass decrease due to sharing load by integrated pipe-roof. This phenomenon is more pronounced by increasing the stiffness of pipe-roof. Furthermore it can be expected that cross-section of underpass can be economically designed.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.6_1
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• pp.507-516
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• 2007

Segmentation and organization of the LiDAR (Light Detection and Ranging) data of the Earth's surface are difficult tasks because the captured LiDAR data are composed of irregularly distributed point clouds with lack of semantic information. The reason for this difficulty in processing LiDAR data is that the data provide huge amount of the spatial coordinates without topological and/or relational information among the points. This study introduces LiDAR data segmentation technique by utilizing histograms of the LiDAR height image data and analyzing roof shape for 3D reconstruction and visualization of the buildings. One of the advantages in utilizing LiDAR height image data is no registration required because the LiDAR data are geo-referenced and ortho-projected data. In consequence, measurements on the image provide absolute reference coordinates. The LiDAR image allows measurement of the initial building boundaries to estimate locations of the side walls and to form the planar surfaces which represent approximate building footprints. LiDAR points close to each side wall were grouped together then the least-square planar surface fitting with the segmented point clouds was performed to determine precise location of each wall of an building. Finally, roof shape analysis was performed by accumulated slopes along the profiles of the roof top. However, simulated LiDAR data were used for analyzing roof shape because buildings with various shapes of the roof do not exist in the test area. The proposed approach has been tested on the heavily built-up urban residential area. 3D digital vector map produced by digitizing complied aerial photographs was used to evaluate accuracy of the results. Experimental results show efficiency of the proposed methodology for 3D building reconstruction and large scale digital mapping especially for the urban area.