Temporary scaffolds in Japan are typically covered with plastic sheets to prevent construction equipment from falling. However, when the cover sheets are subjected to strong winds, the scaffolds can collapse. In order to prevent or reduce the number of those accidents, it is necessary to understand the characteristics of wind pressures acting on the scaffolds. In this study, wind tunnel experiments with a building model in uniform flow were conducted to clarify the fundamental characteristics of wind pressures acting on the simplified scaffold models. The wind direction that caused the maximum pressure was identified. With the different sizes of the nearby scaffolds erected on the other side of the building, the wind pressures acting on the scaffolds can vary depending on the wind direction. The similarity of the experimental results from case to case was statistically discussed based on the coefficient of correlation. For different experiment cases, wind pressures acting on the exterior surface of the scaffolds that were erected at the same positions but in different sizes from the nearby scaffolds are more or less close to each other, while the pressures acting on the interior surface are different due to the wind entering the gap between the building and scaffolds. Thus, pressure acting on the interior surface of the scaffolds is a significant factor for the stability of the scaffolds.

抄録全体を表示

CFD simulation was done for wind around Tokyo Bay area. For the purpose of acquiring data to verify the result of simulation, wind measurement was done at the landfill at Tokyo Bay area. It was shown by the measurement that wind speed become slower at the inland measurement site. Pseudo-compressibility method and Spalart-Allmaras turbulent model was used for wind simulation, which used MM5 output as initial and boundary condition. The result of comparison between measurement and simulation has shown that the error of simulation was less than 5%.

抄録全体を表示

The detailed structure of a gustfront was revealed with Doppler radar, Doppler sodar, weather station and video cameras at Yokosuka observation site, Japan. The gustfront was accompanied with a downburst from bow echo of developing thunderstorm. Two gusts occurred at the passage of gustfront. First gust was observed about 2 km behind the gustfront. Second gust occurred about 5 km behind of the first gust and maximum wind speed of the second gust was larger than that of the first gust. The vertical circulation of the gustfront had about 5 km in horizontal scale and 500 m in vertical and made "arc cloud" , which had 200m of cloud base and 500m of cloud top in height. Strong wind cores (> 25 m/s) existed between 30 m and 500 m in height at the front of the circulation. Two gust winds, which were observed at the surface, were well corresponded with the strong wind core near the surface and updraft region of the circulations. Vertical distribution of the wind speed changed remarkably for 5 minutes in the vertical circulations.

抄録全体を表示

Wind environment around a tall building is evaluated by the cumulative frequency of mean wind speed in the assessment criteria by Wind Engineering Institute. In the assessment criteria, mean wind speeds with the cumulative frequencies of 55% (55% wind speed) and 95%(95% wind speed) are shown as one of the assessment indices and it is stated that the 55% wind speed and 95% wind speed are equivalent to the yearly mean wind speed and the yearly mean of the daily maximum wind speed, respectively as the commentary. In addition, it is shown about a method to be based on an gust wind speed being converted by a gust factor.
The authors calculate the yearly mean wind speed, the daily maximum wind speed, the yearly mean gust wind speed and the yearly mean of the daily maximum gust wind speed and compare them with the 55% wind speed and 95% wind speed. And the gust factors based on the mean wind speed and the gust wind speed are also examined. This paper reports the knowledge about the 55% wind velocity and the 95% wind velocity and also reports the wind environment assessment based on gust wind speed by the scale parameter ratio or the gust factor at the probability of exceedance of 36.8 %.

抄録全体を表示

This paper presents a summary of the strong wind disaster which occurred Mizunami City and Ena City of Gifu Prefecture on July 2, 2006. The evidences and meteorological records showed that it happened around eleven thirty in the morning. Damage was summarized according to the field investigation and the damage reports by city office and Gifu Local Meteorological Observatory. Roofing of houses was mainly damaged, and the blow off of carport' s roofs was observed in numbers. Plants were also damaged but there was no casualty.

抄録全体を表示