The possibility of inconsistencies among reference wind speeds in national border areas has been discussed at Workshops on Regional Harmonization of Wind Loading and Wind Environmental Specifications in Asia-Pacific Economies (APEC-WW). To identify the details of this issue, this study explores a unified approach for reasonably comparing reference wind speeds. First, we review an approach applied to averaging time conversions of wind speeds, in which the statistical distribution of the maxima of a stationary random function is derived. Next, we examine turbulence spectra and scales in 176 codes and standards around the world. Then, we compute peak factors for obtaining wind speeds with various averaging times, applying 11 combinations of turbulence spectra and sampling lengths, and confirm reasonable results in comparisons with those obtained in previous studies. Finally, we discuss some practical considerations in conversions and comparisons of reference wind speeds through some practical application examples.
Typhoon Jebi (2018) caused severe damage to Kinki region. The wind-induced acceleration caused by the typhoon was observed at a high-rise building in Osaka. In the present paper, the measurement results were predicted based on the spectral modal analysis by using the wind velocity and wind direction obtained from the WRF simulation as well as the wind force coefficients obtained from the wind tunnel experiment which was carried out when the building was designed. The measurement results and the simulated results were compared to understand the accuracy and possibility of the prediction for the response analysis with WRF simulation. Although it is necessary to improve the accuracy of input data and to extend the range of application of the spectral modal analysis, the results implied that the maximum wind-induced acceleration is possibly predicted even without observed wind data at a target building.
Laws and/or regulations of 137 of 195 countries are discussed from the perspective of 3 types of provisions: wind-resistant design liability, wind load calculation methods, and reference wind speeds or pressures. Studies of legal and regulatory jurisdictions and requirements reveal that (1) 137 countries mention or imply wind-resistant design liability, and 120 and 114 countries define wind load calculation methods and reference wind speeds or pressures, respectively; (2) 110 and 27 countries mention or imply wind-resistant design liability at the national and subnational levels, respectively, (3) 17 countries mention or imply only wind-resistant design liability and (4) 15 countries accept multiple different wind load calculation methods. Analyses of economic damage from storms and economic developments of countries confirm that the establishment of laws and/or regulations (1) does not necessarily directly depend on economic damage and (2) requires at least the lower middle income level of economic development.
The relation between the distribution of roof damaged by Typhoon Jebi, 2018 and the maximum wind speed during passing this typhoon (Vmax) were investigated by Geographic Information System. The variation of the damage ratio given as the ratio of the number of blue tarps to the number of houses in a survey mesh was very wide and did not show the clarify relationship with Vmax. Therefore, the number of the damage mesh (survey mesh including at least one damage) was counted and the relation between the cumulative number of damage mesh for the squared Vmax was investigated based on the weakest link probability model. As the result of this investigation, it was clarified that distribution of cumulative number of damage mesh was fit very well to Weibull distribution which is the solution of the weakest link probability model, and Weibull parameters were controlled by the housing density.
This study aims to validate prediction of pollutant dispersion in urban area based on wind tunnel experiment. For this purpose, wind tunnel experiments and filed measurements of tracer gas dispersion were conducted in the campus of Tokyo Polytechnic University, and their results were compared. In addition, wind tunnel experiment was carried out under various conditions of experimental model scale, wind speed, and pollutant emission rates to confirm similarity law. The normalized concentration obtained by the wind tunnel experiments agreed well with the field measurement data. It was also confirmed that the normalized non-dimensional concentration was nearly independent of experimental model scale, wind speed, and pollutant emission rate.
In this study, we investigated the characteristics of the wake of a sphere with a uniaxial through-hole．The sphere diameter was 25.4 mm, and the through-hole diameter was 6 mm. The sphere was placed in a uniform flow so that the through-hole is perpendicular to the streamwise direction. The Reynolds number based on the sphere diameter and the uniform flow velocity was 12,000. The flow velocity was measured by a hot-wire anemometer. As a result, the velocity defect of the sphere was smaller than that of a sphere without such through-hole. However, the significant differences were hardly observed as the flow moves toward the downstream direction.
Predictions of atmospheric dispersion based on wind-tunnel experiments and numerical simulations are generally executed under the quasi-steady state of wind fields. They however fail to consider the fluctuations in realistic wind directions. Therefore, the dispersion of air pollutants is often underestimated leading to an overestimation of their maximum concentration. For accurate estimations of atmospheric dispersion, it is important to know the variations in wind fields. In this study, the characteristics of the hourly standard deviation of wind direction fluctuation (σ θ ) were investigated using elevated observational data along the coast of the Japan Sea. The conditions of meteorological fields and of terrains were similar to those around thermal or nuclea r power plants. The results suggested that σ θ was mainly dependent on wind speed and the atmospheric stability. However , σ θ varied widely even for the same meteorological conditions, indicating the influences of the surrounding terrain and long-period wind fluctuations.
The wind characteristics of downbursts are significantly different from those of turbulent boundary layers. The nonstationarity, especially caused by a severe moving downdraft and strong divergent outflow near the ground, causes serious damage to buildings. The present paper investigates the characteristics of downbursts and its effects on buildings, based on an experiment with three kinds of jets, i.e., a pulsed jet, a moving jet and a pulsed moving jet, using a moving jet simulator that we have developed. The effects of non-stationarity of downbursts on the wind pressures and forces acting on buildings with three different sizes and six different heights are discussed. Finally, an evaluation method of downburst-induced wind loads on buildings is proposed based on the experimental results.
The Hydro-VENUS is an energy harvester exploiting the flow-induced oscillation of a pendulum-like blade. In this study, the effects of the angular amplitude and non-dimensional flow velocity on the energy harvesting performance of the Hydro-VENUS are investigated through water channel tests. A semi-elliptical cross-section blade with the cross-sectional aspect ratio of 6 is employed in these tests. The experimental results revealed that the maximum power coefficient is obtained at specific angular amplitude and non-dimensional flow velocity. The approximate solution for the power coefficient is theoretically provided considering non-linearity of hydrodynamic forces acting on the blade. This theoretical approach revealed that the power coefficient is determined by tip speed ratio of the blade and the maximum power coefficient is obtained at specific tip speed ratio.
Typhoon Jebi (T1821) derived significant damages around Kansai area in Japan and recorded the highest fire insurance payment. Therefore, the accurate estimation of wind field for Jebi is quite important for the future ratemaking. In this study, several models, which are an engineering typhoon model, a meteorological model and combined/maximum of those models were used for the estimation and validated by using measurements at weather stations and compared with fire insurance payment database. Wind speeds obtained from the engineering typhoon model show better agreement with measurements at weather stations than the meteorological model. On the other hand, the wind speed distribution from the meteorological model shows best agreement with damage occurrences in the insurance payment database, and the wind speeds are higher than the engineering model in those area. It is also found that the relation between estimated wind speeds and damage occurrences are slightly improved by considering seismic intensity of the 2018 Osaka earthquake as regression parameters.
The building to be experimented is a cargo storage shed to be constructed in the airport island. Large eaves is seted up on both the carrying entrance on the southwest side to accept cargo from vehicles and the one on the northeast side from aircrafts, and the cargo is loaded and unloaded beneath the canopy. The southwest side carrying entrance is almost in the windward against the prevailing wind direction (west) in the construction area and also there is no obstacle interrupting on the windward side. Therefore, countermeasure by anti-wind fence is being discussed, because there occurs a concern that the excellent working environment cannot be maintained by the strong wind.
The characteristics of peak external wind pressures acting on single and multi-span roofs were studied by performing wind tunnel tests on scaled models with differentroof shapes (monosloped,gable), roof slopes (5o, 10o,20o,30o,45o)and the number of spans (1-5).Effect of each parameter on both positive and negative peak wind pressures was examined. It is clarified that codified values in Notification No.1458ofthe Ministry of Construction generally underestimatethe wind loads acting on multi-span roofs. Based on these results, new load zoning as well as the proposed designpressure coefficients for cladding andcomponents on multi-span roofs were suggested.
In this study, uncertainties of aerodynamic force, gravitational force, excessive centrifugal force and lateral vibration induced inertial force acting on the train cars are investigated based on the measured data. A performance function is then proposed based on the reliability theory and the safety indexes are assessed when the train operation regulations are performed. The code calibration is carried out to obtain an acceptable safety index and a formula with partial factors is proposed to calculate critical wind speeds of overturning. Finally, the safety indexes for several train operation conditions are assessed based on the critical wind speed of overturning predicted by three formulas. It is found that the safety indexes obtained by the proposed formula are nearly constant values, while those by the conventional formula show different values for different train operation conditions.
