• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.53-56
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• 2008

This paper is to investigate the change of the period of hot weather concrete with elapse of age based on climate data. Climate data for 30 years and 5 years are used respectively. Determination of the period of hot weather concreting on architectural execution in Korea according to the specifications of AIJ, KSCE, and ACI are discussed. According to the research, the period of hot weather concreting with each specification in most regions lasts over 35 days. Compared with the period of cold weather concreting in hillside and inland area, coastal areas have shorter period in the same latitude. The period of hot weather concreting tends to decrease with high latitude. As expected, with the elapse of age, the period of hot weather concrete exhibited to decrease, especially, big city like Seoul, Busan etc had remarkably increased period by as much as a week. This is due to the global warming and industrialization effect with the elapse of age.

• Atmosphere
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• v.29 no.4
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• pp.451-461
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• 2019

Medium-range forecast is highly dependent on ensemble forecast data. However, operational weather forecasters have not enough time to digest all of detailed features revealed in ensemble forecast data. To utilize the ensemble data effectively in medium-range forecasting, representative weather patterns in East Asia in this study are defined. The k-means clustering analysis is applied for the objectivity of weather patterns. Input data used daily Mean Sea Level Pressure (MSLP) anomaly of the ECMWF ReAnalysis-Interim (ERA-Interim) during 1981~2010 (30 years) provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). Using the Explained Variance (EV), the optimal study area is defined by 20~60°N, 100~150°E. The number of clusters defined by Explained Cluster Variance (ECV) is thirty (k = 30). 30 representative weather patterns with their frequencies are summarized. Weather pattern #1 occurred all seasons, but it was about 56% in summer (June~September). The relatively rare occurrence of weather pattern (#30) occurred mainly in winter. Additionally, we investigate the relationship between weather patterns and extreme weather events such as heat wave, cold wave, and heavy rainfall as well as snowfall. The weather patterns associated with heavy rainfall exceeding 110 mm day^-1 were #1, #4, and #9 with days (%) of more than 10%. Heavy snowfall events exceeding 24 cm day^-1 mainly occurred in weather pattern #28 (4%) and #29 (6%). High and low temperature events (> 34℃ and < -14℃) were associated with weather pattern #1~4 (14~18%) and #28~29 (27~29%), respectively. These results suggest that the classification of various weather patterns will be used as a reference for grouping all ensemble forecast data, which will be useful for the scenario-based medium-range ensemble forecast in the future.

• Journal of Physiology & Pathology in Korean Medicine
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• v.21 no.2
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• pp.571-577
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• 2007

The purpose of this study was to investigate the relationship between the pain and the weather. One hundred ninety three patients treated for pain were recruited for this study. All subjects completed a 8-item weather and pain questionnaire to find out whether the pain are related to change in the weather, Of all subjects, 126 patients(65.3%) believed that change in the weather affected their pain. Of theses 126 patients, 85 patients(67.5%) reported that their pain was affected before weather changes, 44 patients(34.9%) stated that their pain was affected during weather changes. Damp/Rainy(n=91, 72.2%) and cold(n=60, 47.6%) conditions were mostly considered to have influence on pain. Of all subjects, 125 patients(64.8%) believed that change in the weather affected their mood. In the female group, a tendency to have pain or mood sensitivity to change in the weather was significantly higher than the male group(p=0.006, p=0.003) In the non-religious group, a tendency to have pain or mood sensitivity to change in the weather was significantly higher than the religious group(p=0.006, p=0.004). Of the pain sensitive group to change in the weather, 97 patients(77.0%) reported that they also have mood sensitivity to change in the weather(p=0.000). In the pain or mood sensitive group to change in the weather, their pain intensity(VAS) was significantly higher than the other group(p=0.000, p=0.021). The results of this survey give support to the idea that most patients with pain believe that weather has an important impact on their pain. Further investigations are needed to identify the mechanisms involved in the effects of weather changes on pain.

• Advances in concrete construction
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• v.5 no.6
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• pp.659-669
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• 2017

Grouts compared to other material sources, could be highly sensitive to cold weather conditions, especially when the compressive strength is the matter of concern. Grout as one the substantial residential building material used in retaining walls, rebar fixation, sidewalks is in need of deeper investigation, especially in extreme weather condition. In this article, compressive strength development of four different commercial grouts at three temperatures and two humidity rates are evaluated. This experiment is aimed to assess the grout strength development over time and overall compressive strength when the material is cast at low temperatures. Results represent that reducing the curing temperature about 15 degrees could result in 20% reduction in ultimate strength; however, decreasing the humidity percentage by 50% could lead to 10% reduction in ultimate strength. The maturity test results represented the effect of various temperatures and humidity rates on maturity of the grouts. Additionally, the freeze-thaw cycle's effect on the grouts is conducted to investigate the durability factor. The results show that the lower temperatures could be significantly influential on the behavior of grouts compared to lower humidity rates. It is indicated that the maturity test could not be valid and precise in harsh temperature conditions.

• Atmosphere
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• v.28 no.2
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• pp.187-200
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• 2018

The heavy snowfall phenomenon with thunder and lightning occurred in Yeongdong coastal region on 20 January 2017. Amount of snow on that day was a maximum of 47 cm and was concentrated in a short time (2 hours) at the Yeongdong coastal area. The mechanism of thundersnow was investigated to describe in detail using observational data and numerical simulation (Weather Research and Forecast, WRF) applied lightning option. The results show that a convective cloud occurred at the Yeongdong coastal area. The east wind flow was generated and the pressure gradient force was maximized by the rapidly developed cyclone. The cold and dry air in the upper atmosphere has descended (so called tropopause folding) atmospheric lower layer at precipitation peak time (1200 LST). In addition, latent heat in the lower atmosphere layer and warm sea surface temperature caused thermal instability. The convective cloud caused by the strong thermal instability was developed up to 6 km at that time. And the backdoor cold front was determined by the change characteristics of meteorological elements and shear line in the east sea. Instability indexes such as Total totals Index (TT) and Lightning Potential Index (LPI) are also confirmed as one of good predictability indicates for the explosive precipitation of convective rainfall.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.33-38
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• 2002

Concrete placed under cold weather has some defects such as the decrease of initial strength by hydration delay, strength unrecovery at unhardened concrete freezing, and structural failure and crack by expansion pressure. So, in this study, we tried to evaluate the JIS mortar which was made under cold weather using de-icing agency. In mortar test, the do-icing agency increased compressive strength under standard curing, and the de-icing agency made by NaNO$_2$ gave the highest strength. However, as pre-curing time under 21$^{\circ}C$ was short, the de-icing agency made by NaNO$_2$ and Ca[NO$_3$]$_2$ had the highest strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.769-774
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• 2001

The purpose of this study is to analyze the curing effect of heating cable for concreting in cold weather. An experiment was conducted to evaluate the temperature history of concrete structures cured with embedded heating cables. Results are as follows : In comparison with the non-heating case, applying of heating cable resulted in the rise of temperature in the range of $10^{\circ}C$. In order to get successful results, the optimal pitch length for the embedded heating cables ranged from 20cm to 25cm. When working with the existing curing methods, applying this heating cable would be more effective in concrete curing. Finally, a formula and process was suggested to predict the Internal temperature history of concrete structures under the various curing conditions.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.617-622
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• 2001

This paper presents the effectiveness of cold weather concreting by applying both anti-freeze agent and insulating forms developed through previous study investigating insulating effects on the concrete and the strength gain. According to test results, in $-10^{\circ}C$ of air temperature, when euroforms are applied, the temperature of plain concrete drops below $0^{\circ}C$ and maintains its temperature during early 24 hours. However, when insulating forms are applied, the temperature of concrete keeps 8~$13^{\circ}C$ during first 24 hours. Insulating forms has better performance on insulating effects than existing euroforms. Concrete containing anti-freeze agent shows temperature rising effects about $1^{\circ}C$ compared to plain concrete. Strength gain of core concrete shows higher when insulating forms is applied.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.05a
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• pp.21-26
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• 2002

This paper is intended to verify the efficiency of anti-freeze agent and insulating form by analyzing the temperature history and the property of strength-increase about the concrete that is placed in the insulating form and normal form, using new type anti-freeze agent in batcher plant According to the results about the temperature history, while the lowest temperature shows 3$^{\circ}C$ in case of normal concrete + euroform, 4$^{\circ}C$ in case of normal concrete + insulating form, it shows 6$^{\circ}C$ in anti-freeze agent + the insulating form, so the effect is most favorable. The compressive strength with mixing anti-freeze agent or not, shows high in order of standard curing, structure-managing and open air-placed specimen and the concrete mixing anti-freeze agent shows the highest compressive strength-increase.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.143-148
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• 2002

Recently, to consider economical and constructive aspect, Usage of Admixture, like Blast-Furnace Slag and Fly-Ash, are increased. Blast-Furnace Slag, a by-product of steel industry, have many advantage, to reduce the heat of hydration, increase in ultimate strength and etc. But it also reduces early-age strength, it is prevented from using of Blast-Furnace Slag at cold-weather-concrete. In this study, for the purpose of increasing usage of Blast-Furnace Slag at cold-weather-concrete, it is investigated the strength properties of concrete subjected to time and period of frost damage for early age curing. According to this study, if early age curing is carried out before having frost damage, the strength of concrete, subjected to frost damage, is recovered. And that properties is not connected with the frost cause.