• Smart Structures and Systems
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• v.25 no.1
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• pp.81-96
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• 2020

Wind measurements were made on the Canton Tower at a height of 461 m above ground during the Typhoon Vincente, the wind-induced accelerations and displacements of the tower were recorded as well. Comparisons of measured wind parameters at upper level of atmospheric boundary layer with those adopted in wind tunnel testing were presented. The measured turbulence intensity can be smaller than the design value, indicating that the wind tunnel testing may underestimate the crosswind structural responses for certain lock-in velocity range of vortex shedding. Analyses of peak factors and power spectral density for acceleration response shows that the crosswind responses are a combination of gust-induced buffeting and vortex-induced vibrations in the certain range of wind directions. The identified modal frequencies and mode shapes from acceleration data are found to be in good agreement with existing experimental results and the prediction from the finite element model. The damping ratios increase with amplitude of vibration or equivalently wind velocity which may be attributed to aerodynamic damping. In addition, the natural frequencies determined from the measured displacement are very close to those determined from the acceleration data for the first two modes. Finally, the relation between displacement responses and wind speed/direction was investigated.

• Journal of Korea Water Resources Association
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• v.38 no.10 s.159
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• pp.825-839
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• 2005

Application of the EST approach for the simulation of the risk-based typhoon hazard potential is described in this paper. For six selected cities In the Korean peninsula, EST simulations for one hundred years were performed one hundred times using historical typhoon data as a training data set. The analytical results of EST simulations were then post-processed to estimate the means, standard deviations, and ranges of variation for the maximum wind velocities and the daily rainfalls. From the comparison of the averages of the wind velocities for the 100 year recurrence interval typhoons, the wind hazard potential of them was revealed to be highest for Mokpo among the six cities, followed by Busan, Cheju, Inchun, Taegu, and Seoul in descending order For the flood hazard potential associated with a typhoon, Busan was ranked to be the highest hazard potential area, followed by Mokpo, Cheju, Seoul, Inckun, and Taegu. In terms of the overall typhoon hazard potential, cities in the southern coastal regions were identified as being exposed to the most severe typhoon hazard.

• Wind and Structures
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• v.25 no.1
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• pp.1-24
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• 2017

This paper presents a 1:25 multi-freedom aero-elastic model for a high lighting pole at the Zhoushan stadium. To validate the similarity characteristics of the model, a free vibration test was performed before the formal test. Beat phenomenon was found and eliminated by synthesis of vibration in the X and Y directions, and the damping ratio of the model was identified by the free decay method. The dynamic characteristics of the model were examined and compared with the real structure; the similarity results were favorable. From the test results, the major along-wind dynamic response was the first vibration component. The along-wind wind vibration coefficient was calculated by the China code and Eurocode. When the peak factor equaled 3.5, the coefficient calculated by the China code was close to the experimental result while Eurocode had a slight overestimation of the coefficient. The wind vibration coefficient during typhoon flow was analyzed, and a magnification factor was suggested in typhoon-prone areas. By analyzing the power spectrum of the dynamic cross-wind base shear force, it was found that a second-order vortex-excited resonance existed. The cross-wind response in the test was smaller than Eurocode estimation. The aerodynamic damping ratio was calculated by random decrement technique and the results showed that aerodynamic damping ratios were mostly positive at the design wind speed, which means that the wind-induced galloping phenomenon is predicted not to occur at design wind speeds.

• Journal of Environmental Science International
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• v.27 no.3
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• pp.203-217
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• 2018

For this study, WRF numerical modeling was performed, using RDAPS information for input data on typhoons affecting the Korean peninsula to produce wind data of 700hPa. RAM numerical modeling was also used to calculate 3-second gusts as the extreme wind speed. After comparing wind speeds at an altitude of 10 m to evaluate the feasibility of WRF numerical modeling, modeled values were found to be similar with measured ones, reflecting change tendencies well. Therefore, the WRF numerical modeling results were verified. As a result of comparing and analyzing these wind speeds, as calculated through RAM numerical modeling, to evaluate applicability for disaster preparedness, change tendencies were observed to be similar between modeled and measured values. In particular, modeled values were slightly higher than measured ones, indicating applicability for the prevention of possible damage due to gales. Our analysis of 3-second gusts during the study period showed a high distribution of 3-second gusts in the southeast region of the Korean peninsula from 2002-2006. The frequency of 3-second gusts increased in the central north region of Korea as time progressed. Our analysis on the characteristics of 3-second gusts during years characterized by El $Ni{\tilde{n}}o$ or La Nina showed greater strength during hurricanes that affected the Korean peninsula in El $Ni{\tilde{n}}o$ years.

• Structural Engineering and Mechanics
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• v.89 no.5
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• pp.479-489
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• 2024

The cracking mechanism in ceramsite aerated concrete block (CACB) infill walls were studied in low seismic fortification intensity coastal areas with frequent occurrence of typhoons. The inter-story drifts of an eight-story residential building under wind loads and a seismic fortification intensity of six degrees were analyzed by using the PKPM software. The maximum inter-story drift ratio of the structure in wind load was found to be comparable to that under the seismic fortification intensity of six degrees. However, when accounting for the large gust wind speed of typhoon, the maximum inter-story drift ratio was much larger than that obtained under reference wind load. In addition, the finite element models of RC frames were employed by displacement loading to simulate two scenarios with and without window hole in the CACB infill walls, respectively. The simulation results show no signs of cracking in both the infill walls with window hole and those without window for the inter-story drift caused by seismic loads and the reference wind load. However, both types of infill walls experienced structural creaking when assessing the gust wind pressure recorded from previous typhoon monitoring. It is concluded that an underestimate of wind loads may contribute substantially to the cracking of frame CACB infill walls in low seismic fortification intensity coastal areas. Consequently, it is imperative to adopt wind pressure values derived from gust wind speeds in the design of CACB infill walls within frame structures. Finally, the future research directions of avoiding cracks in CACB filled walls were proposed. They were the material performance improving and building structure optimizing.

• Spatial Information Research
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• v.19 no.5
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• pp.47-52
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• 2011

Recently damage scale by local winds and typhoon has dramatically increased. Korea has the terrain over 70% of the land and the planning of the wind load is necessary to estimate reflecting appropriately the change of the wind-speed according to the characteristic of the terrain and in the Korean Building Code(2009), this is stated and it reflects to the design process. However, in order to estimate the topographic factor of the wind speed considering the topographic characteristics in the structure design actually, it has many difficult points including the local topographic survey, etc. In this paper, the Digital Elevation Model(DEM) is created using TIN interpolation method in the form of the digital map and then the interface was designed and implemented which can automatically estimate the topographic factor of wind speed by using ESRI(R)ArcObjectTM and the Visual Basic programing language. By applying it to the terrain which positioned in the downtown area, the practicality of the topographic factor of wind speed estimation interface was checked.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.6
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• pp.545-554
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• 1998

The diurnal variation of O3 concentration shows two peaks, the first peak at noontime and the secondary peak at night. In order to show why the secondary peak, high nocturnal O3 concentration, occurs without sunlight which is a essential factor of a photochemical response, the O3 concentration, several weather elements and synoptic weather map were used for June∼September at 1995, 1996. The mean concentration of high nocturnal O3 concentration days is higher by 5.4 ppb than that of low nocturnal O3 concentration days. The nocturnal O3 concentration is higher than that of diurnal O3 concentration during high nocturnal O3 concentration days, at July, 1995 and June, 1996. The high nocturnal O3 concentration is related to low air pressure, high cloud cover and high wind speed. The correlation coefficient, r. between nocturnal O3 concentration and wind speed, pressure and cloud cover is 0.387, -0.218, and 0.194, respeftiviely. It is interesting that the O3 concentration increases at Pusan when the typhoon passes by. The same result showed at Taegu when the typhoon FAYE passed by. According to the analysis of nocturnal O3 concentration for June∼September at 1995 and 1996, it seems that the high nocturnal O3 concentration relates to the trough and cyclones passing by Pusan.

• Journal of Environmental Science International
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• v.30 no.9
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• pp.753-762
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• 2021

This study analyzed the characteristics of strong winds accompanying typhoons for a period of 116 years, from 1904 to 2019, when modern weather observations began in Korea. Analysis shows that the average wind speed and high wind rate caused by typhoons were higher over the sea and in the coastal areas than in the inland areas. The average wind speed was higher over the West Sea than over the South Sea, but the rate of strong wind was greater over the South Sea than over the West Sea. The average wind speed decreased by 1980 and recently increased, while the rate of strong winds decreased by 1985 and has subsequently increased. By season, the strong winds in autumn (september and october) were stronger than those in summer (june, july, and august). Strong winds were also more frequent in autumn than in summer. The analysis of the changes in strong winds caused by typhoons since the 1960s shows that the speed of strong winds in august, september, and october has increased more recently than in the past four cycles. In particular, the increase in wind speed was evident in fall (september and october). Analysis of the results suggests that the stronger wind is due to the effects of autumn typhoons, and the increased possibility of strong winds.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.2
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• pp.135-144
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• 2023

In order to provide basic data to increase the efficiency and stability of seamanship at anchoring, the characteristics of the hull motion including dragging anchor due to external forces were observed at Mokpo and Jinhae anchorage for the avoidance of the typhoon. As a result, it is necessary to check the embedding motion and holding power of the anchor according to at initial position to decrease dragging anchor. Dragging anchor at anchorage seems to have been easily caused according to discrepancy between embedded anchor flukes and the towing direction due to the change in wind direction, rather than the wind speed. This discrepancy, thus, should be considered when anchoring. This test vessel with a small radius of curvature of the stem is relatively vulnerable to the influence of wind direction and wind speed, so it is easy to cause a decrease in the holding power due to an increase in the rate of turn. When the current speed is greater than or equal to 1 knot, the range of the rate of turn is reduced resulting in a relatively increased holding power. In addition, during the swing, the tension of the chain was high according to the angular velocity change of heading at three-quarters of the swing length rather than the left and right ends.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.6
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• pp.325-334
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• 2022

It has been more than 30 years since the term climate change began to become popular, but recently, rapid accelerated phenomena are appearing in the form of extreme weather all over the world. It is showing a distinctly different phenomenon from previous years, with heavy rain falling in the Death Valley desert in the U.S., and temperatures rising more than 40 degrees in Europe. In the Korean Peninsula, super typhoons with very strong wind speeds have become a major disaster risk for many years, and the supply of more energy due to the rise in sea temperature increases the possibility of super typhoons, requiring a proactive response. Unlike the method using numerical analysis, this study analyzed past typhoon data to study changes in typhoon characteristics for coastal disaster prevention. Existing studies have targeted all typhoons that have occurred, but in this study, a specific area was set up in the southern ocean of the Korean Peninsula and then a study was conducted. The subjects of the study were typhoons that occurred over the past 40 years from 1980 to the present, and it was confirmed that the maximum wind speed of typhoons affecting the Korean Peninsula increased slightly. The wind speed of typhoons in the specific area is about 80% of the maximum wind speed in their lifetime, and a correlation with ENSO could not be confirmed.