The criterion for wind environment assessment proposed by Wind Engineering Institute Co., Ltd. has often been used for the wind environment assessments around high-rise buildings. This criterion is based on the relation between the mean wind speeds at cumulative frequencies of 55% and 95% measured by 3 cup anemometers and the surrounding terrain condition. The relation between this criterion and the human sensation for wind strength hadn’t been clarified. In our previous research, we investigated the relation between the mean wind speed at a cumulative frequency of 95% and the cumulative frequency of the human sensation for wind strength. In order to use this relation for the actual investigation of wind environment, it should be presented easier for a general public to understand. In this paper, we discuss the relation between this criterion and the percentage of people dissatisfied for wind strength. In addition, this paper shows the influence of a temperature on the percentage of people dissatisfied for wind strength and the relation between the percentage of people dissatisfied and the danger of pedestrian blown down.

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Probability density distributions of each velocity component at pedestrian levels are required to predict extremely rare and strong wind events. Therefore, in this study, the PDFs were compared between the Gaussian and modified Gaussian distributions with the third-order and fourth-order statistics, as known as the Gram-Charlier Series (GCS), for the velocity components around a simplified urban array determined by a large-eddy simulation. The GCS with the third-order and fourth-order moments could predict the PDFs and percentile values of each velocity component more accurately than those determined by the Gaussian distributions. In addition, the comparison shows that it can be judged whether the PDFs are represented by the Gaussian distributions or not by confirming the third and fourth order statistics.

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This study examined the applicability of a plant canopy model in large-eddy simulation (LES) with a 0-equation subgrid scale (SGS) model considering only drag force term for pedestrian wind environment (PWE) by comparing with a 1-equation model reproducing the increase in SGS kinetic energy k_SGS within the tree crown. The two simulations for the flows around a two-dimensional row of trees provided in the benchmark case by Architectural Institute of Japan and actual homestead trees were conducted. In the benchmark case, the 1-equation model reproduced similar results to the 0-equation model due to the small increase in k_SGS In addition, the 0-equation model still reproduced the results of field observation in an actual homestead trees case. The effect of increasing k_SGS on the mean wind speed, grid scale turbulent kinetic energy, and probability density function of wind velocity fluctuation became small under the spatial resolutions generally used for the simulation for PWE.

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This study compared the accuracies of the Weibull distribution method (two-parameter Weibull and three-parameter Weibull methods, i.e., 2W and 3W methods) and Gram.Charlier series (GCS) method for estimating the low-occurrence wind speed at the pedestrian level around an isolated building. The wind speed data analyzed in this study is taken from an LES database. For the advantage of the models to predict the probability density function (PDF) of the wind speed data, the 2W, 3W and GCS methods more accurately modelled the unimodal distribution than the bimodal distribution. In addition, the highest-order GCS method in this study (i.e., GCS-6th method) exhibited better flexibility in modelling PDFs than the 2W and 3W. For estimating the low-occurrence wind speed, the 2W, 3W and i-th-order GCS methods require the mean and standard deviation, these two statistics plus the skewness, and the first-order to i-th-order statistics, respectively. For the estimation accuracy, the 2W method is better than the second-order GCS method and the 3W method is better than the third-order GCS method although the GCS-6th method is regarded as the most accuracy method in this study owing to incorporating the higher-order statistics.

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The wind and temperature fields around a cubic array in unstable boundary layer were simulated by large-eddy simulation. This study aimed to evaluate the performance of polyhedral meshes with local mesh refinement andthe effect of boundarylayer meshes on the characteristics of wind velocity and temperature fields within a focused area. A precursor simulation was conducted to obtain wind and temperature fluctuations for the inflow boundary conditionin the unstable boundary layer. After validation,four cases with differentpolyhedral mesh arrangements were compared. The polyhedral cases with local meshrefinement showed comparable accuracy with the orthogonal case. The boundarylayer meshes on the groundand surfaces of cubic building models improved the accuracy of the wind and temperature fields near the surfaces.

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In this study, we conducted a field observation of drifting snow in the snowfield of Teshikaga in Hokkaido for two months and used the regional meteorological model WRF in order to reveal fluctuation of visibility distribution for increased snow-drift flux due to turbulent fluctuation under blowing snow without snowfall. The estimated 10-minute mean visibilities were agreed fairy well with the measured value with the transmissometer at the observation site. It was indicated that the visibility decreased especially near the outlet of the valley in Teshikaga, and the minimum of 1-minute mean visibility decreased by 70% compared to the 10-minute mean visibilities due to turbulence fluctuation.

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This study describes the difference of design method for low-rise buildings in Japanese Building Law, JBL, and the one for horticulture facilities in Horticulture Design Standard, HDS. Although the exceedance probability of design wind speed for buildings during their lifetime is relatively high in JBL, the safety of such buildings is secured mainly due to the strength of materials utilized in allowance stress design method. On one hand, HDS has the advanced safety index of design wind speed. On the other hand, HDS uses unsuitable wind coefficients for wind resistant design, and careful attentions have not been paid to the internal pressure. This may be a cause of damage to horticulture facilities due to strong wind.

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This paper investigates the dynamic behavior and collapse of a mechanically-attached membrane roofing system with metal substrate under wind loading, based on pressure loading tests using full-scale assembly specimens. The specimens were subjected to wind pressures varying both temporary and spatially, which were generated by using the time histories of wind pressure coefficients obtained at different points on the roof of a flat-roof building model in a wind tunnel. A step-wise pressure test was also carried out for a comparative purpose. The results indicated that the fixing points were subjected to not only vertical forces but also horizontal forces, the magnitude of which was nearly equal to the vertical ones. The horizontal forces reduced the failure loads and changed the failure modes of the roofing system. The failure load under step-wise pressure was generally smaller in magnitude than that under wind pressures. Therefore, the step-wise pressure loading test can be used for evaluating the wind resistant performance of the roofing system on the safer side.

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In the wind-resistant design of cladding, existing estimation methods approximate to space-averaged peak loading by temporally filtering the time series measured from a pressure tap. This study applied the machine learning method to reconstruct the pressure distribution on a panel with non-linearity and high spatial resolution (i.e., super-resolution field), which allows the estimation of peak pressure by direct space averaging. The top corner tile of high-rise buildings was focused on, and the super- resolution pressure fields were reconstructed from low-resolution measurements under both windward and leeward conditions. The reproduced time-averaged pressures agree well with experiments. The super-resolution method has higher precision in the prediction of extreme pressure than traditional single-point time-filtered method, and has strong robustness which is independent of selection of individual measurement tap.

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Design wind speeds for a low-rise building below Zb are provided as a constant value in Japanese codes and specifications. The wind loads for a low-rise building are usually safer but impractical structural design are sometimes required when the building height is lower than Zb. In the present study, wind speed near the ground with roughness blocks are measured with a wind tunnel experiment and computational fluid dynamics with large eddy simulation (LES). The characteristics of the mean and fluctuating wind speeds are compared to the results of the previous studies, and the previous equation for estimating turbulence intensity is extended from the result of the present study. Finally, the proper orthogonal decomposition analysis was performed on the wind speeds obtained from the LES simulation to understand the spatial characteristics of wind fluctuation near the ground.

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This study investigates the pressure acting on a low-rise building roof and its surrounding wind speed, based on the full-scale measurement during the passage of TY202116. The pressure was measured with a new measurement system developed by the author’s research team. The analysis of the pressure acting on the roof together with the wind speed nearby shows strong non-stationarity; negative peak of the pressure as well as gusty wind occur in clusters, illustrating difference in characteristics compared to the inflow wind and wind pressure commonly assumed in wind tunnel experiments and wind resistant design for tall buildings. This observation calls for further investigation of wind load acting on low-rise buildings, in order to better understand the mechanism of their damages and to evaluate wind induced risk for such buildings.

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Building shape polygons were adopted to improve the accuracy of the building damage probability model applying the weakest link model. The building area ratio(ε), which is the ratio of building area to evaluation mesh area, was used as an indicator of building density. Additionally the damage or non-damage was determined for each mesh using the damaged building shape polygons. As results of investigation for building damage by Typhoon Jebi in 2018, it was found that the damage probability estimated from the damage probability model using the ε and the maximum wind speed squared as explanatory variables show good match with the actual values. Moreover, comparison of the estimated values by the constructed model with the actual damage mesh distribution showed that they generally corresponded to each other. In addition, the results of damage probability estimation of building damage by Typhoon Faxai in 2019 with the probability model constructed based on the building damages by Typhoon Jebi suggested that the proposed model was applicable to the other typhoons as well.

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After the typhoon hit, if we could quickly carry out damage assessment for residents, repair of the house and apply of disaster insurance could also be provided sooner than now. Based on the deep learning method, the drone photos of the Kyonan Town, which were taken one year after Typhoon Faxai, were used to detect and evaluate the roof and wall damage of houses, in this paper. This paper is mainly divided into four parts: taking photo using drone, outputting the texture of the roof and wall, detecting damage from the texture and classify the level of damage of the houses. The average F value of the detection was more than 0.80 and classification of that was about 0.65.

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This study investigated the wind speed with a reproduction period of 50 years, that of 500 years and typhoon characteristics at landfall for each area in Japan for each experiment using current climate experiment (HPB), +2℃ experiment (HFB_2K), +4℃ experiment (HFB_4K) data of global model of database for Policy Decision making for Future climate change (d4PDF). The results revealed that the wind speed with a reproduction period of 50 years and that of 500 years of HFB_4K on land in Japan were 1.05 to 1.10 and 1.05 to 1.15 times higher than those of HPB, therefore buildings may be subjected to stronger wind loads than at present if global warming continues. In addition, this study revealed that typhoons at landfall in Japan in HFB_2K and HFB_4K were more developed than HPBs, and in some landfall areas they traveled slower. This showed that duration of strong winds may be longer and winds on the left side of near the center of the typhoon may be stronger. On the other hand, it is thus possible that winds may weak on the right side of near the center of the typhoon.

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When the Typhoon Trami (2018) moved northeastward in the Pacific Ocean south of the Kyushu Island at 6:30JST on 30 September 2018, a tornado occurred and caused damages in Kochi city. A funnel cloud also appeared two hour later. Their parent clouds were one of wavy clouds formed more than 500 km apart from the typhoon center. The present study aims to clarify the characteristics and environment of the parent clouds. The results of radar analysis show that the wavy clouds of about 30km in length are arranged parallel to the radial axis of the typhoon and move north-northwestward. The parent clouds have a mesocyclone at its southwest end, but their arrangement is different from the ordinary mini supercells. Then, the mesocyclone repeats alteration of generation. The environment indices, MUCAPE and SREH of in this case are found to be larger and smaller than those of a mini supercell in outer rainband, respectively.

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Approximately 150 POTEKA weather observation equipments are installed and compose a high density ground surface observation network (POTEKA network) with the spatial resolution of approximately 1~2 km on the plain of Gunma and Saitama prefectures in Japan. Downburst gust prediction algorithm with POTEKA network can detect the occurrence of downburst gust of temperature drop type in advance on this plain. Moreover, this algorithm can precisely predict the gust damaged area and the gust occurrence time for the 3 eminent downbursts of the F1/JEF1 category. As the result of the accuracy verification of the gust prediction algorithm, the threshold of 2 ℃ drop in 1 minute is precise. Also, it is confirmed that the resolution of approximately 1~2 km assures the lead time of approximately 30 minutes before the gust occurrence and the precise narrowing function of prediction area.

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In this study, the numerical simulation of Typhoon Hagibis (2019) considering sea surface temperature warming was conducted to investigate the impact of the future change in sea surface temperature on the development and attenuation process of the typhoon. The sea surface temperature for the future climate was created by adding the difference between monthly mean sea surface temperature in 2090s and 2010s, which were predicted by MRI-CGCM3, to that for the current climate. Under the future climate condition, the typhoon continued to develop up to a higher latitude and the typhoon intensity at landfalling time increased significantly compared with that under the current climate condition. This was because the sea surface temperature at a higher latitude under the future climate condition was much higher than that under the current climate condition and a large amount of water vapor was supplied from the sea surface. It was also shown that, under the future climate condition, not only the typhoon intensity but also the typhoon size increased and the strong wind can occur over a wider area.

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We examined the applicability of the gradient wind model newly proposed by Wang et al. (2017) by evaluating vector correlation between observed high-altitude wind velocities and the gradient wind model velocities. As for the observed high-altitude wind velocities, we used the observation results obtained by Japan Meteorological Agency at six wind profiler stations in the central region of the main island of Japan, during the Typhoon Jebi 2018. The classical gradient wind models of Yoshizumi and Georgiou were similarly examined for benchmarking. As the results, the modeled winds of Wang model have exhibited the highest correlation with the observed winds, while those of the Georgiou model have exhibited the lowest correlation. The performance of the three gradient wind models was found consistent with our previous studies for Typhoons Faxai 2019 and Haishen 2020.

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A multi-span cable-stayed bridge is planned for the Osaka Wangan Expressway Western Extension. The main girders of a multi-spam cable-stayed bridge have a low deflection frequency. And it makes wind resistance to vortex-induced vibration a problem. In addition, the separated two-box girder cross section make wind resistance to vortex-induced vibration a problem. Therefore, spring support tests using a partial model with different fairing shapes of the box girders and wind-resisting additives were conducted on the separated two-box girder cross section of this bridge to investigate a main girder cross-sectional shape with high wind stability.

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A long-span one-tower cable-stayed bridge is planned in the section between Port Island and Wada Cape (Kobe-Nishi sea route) on the Osaka Wangan Expressway Western Extension. This bridge is one of the world's longest one-tower cable-stayed bridges. The resistance to the vortex-induced oscillation becomes the problem due to the low frequency of the main girders of a long-span cable-stayed bridge. Therefore, wind tunnel test with spring supported sectional model of the box girder with different fairing shapes was conducted. As a result, a trapezoidal fairing shape with better aerodynamic resistance was found. In this paper, the outline of wind tunnel tests are described.

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Magnitude and loading patterns of wind loads must be set properly to secure horizontal stability of a bridge structure. Details of wind loads and its loading patterns are stipulated in the Design Specification of Highway Bridges and the Design Manual of Steel Highway Bridges where a upper and lower chord of sway bracings share the wind load equally. Since background of wind loading pattern in the specification is not known, rationalization of bridge structures encounters difficulties. In this study, aiming at obtaining fundamental data of wind load distribution on a plate-girder bridge structure for structural rationalization, wind loads on bridge parts are investigated by a wind-tunnel test. The study revealed quantitative results which are almost identical to the current design specification.

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This research intends to experimentally investigate the effects of the wind barrier on the aerodynamic response of the bridge, the crosswind environment, and the aerodynamic forces of the vehicle on the bridge. The discussion focuses on the wind-barrier section configuration, i.e., Straight-line Type (ST) and Curved-line Type (CT), and the Opening-area Ratio (OR) of the wind barrier, which is the ratio of the area of its total openings to its windward-surface area. A streamline box girder model of side ratio B/D = 9 (B: girder width; D: girder height) with different wind barriers is applied in a series of wind tunnel tests, i.e., the vertical and torsional one-degree-of-freedom (1DOF) free vibration tests, and wind velocity measurement on the girder. The wind barrier of OR = 0% resulted in the vortex-induced vibration and torsional flutter of the girder because it promoted the detachment of the separated flow from the girder, however increasing OR stabilized these aerodynamic instabilities because increasing OR resulted in increasingly strong turbulent flow on the girder. The wind velocity below the vehicle height on the girder was significantly decreased by decreasing OR, while the wind barrier of OR = 50% still reduced the wind velocity by about 50% compared with that without the wind barrier. As a result, based on the measurement of the aerodynamic forces on a simplified vehicle on the girder, enlarging OR increased the drag force coefficient (Cs) of the vehicle, whereas the wind barrier of OR = 50% still reduced Cs by about 50% compared with that without wind barrier.

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Understanding the characteristics of strong crosswinds on bridges is important for taking more effective countermeasures against vehicle running safety. The crosswinds on the bridge have been partly evaluated through wind tunnel test or CFD, while little study has been conducted on along-bridge evaluation by field measurement. Therefore, we investigated the characteristics of the crosswind on the Trans-Tokyo Bay Highway Bridge which has variable-depth box girder based on the field measurement by using a vehicle crossing the bridge. On the measurement day, the inflow wind speed was as high as about 13m/s, and the wind direction was perpendicular to the bridge axis. The measurement results on the most windward lane showed that the effects of the larger bridge girder height were significant in decreasing the wind speed. Still, some intermittent high wind speed was observed, too. The cause was the difference in the height of shear flow separated from the leading edge of the bridge girder. In the measurement result on the most leeward lane, the effects of girder height were less observed due to entrainment．

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This study investigates the method of wind speed estimation from rain drop trajectories by using Particle Tracking Velocimetry technique. In our previous report, it is confirmed that the average wind speed estimated from the trajectories of water drops in uniform flow, which is made in wind tunnel, has an accuracy of less than 5%. However, the instantaneous wind speeds estimated from the trajectory of an individual water drop varies and its cause is not investigated. Therefore, this study further investigates the process of wind speed estimation from water drop trajectories and aims to determine the causes of estimated wind speed fluctuation, with the intention to suggest a new method of wind speed estimation. Estimated wind speeds with the new method have a less deviation, compared to the wind speeds estimated with the previous method.

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To reduce the cost of training data collection in the data-driven calibration of cup anemometer, this study proposes a novel strategy using the transfer learning based on domain adaptation to apply existing data appropriately to model training of new prediction. The proposed calibration framework performs an unsupervised step with relevant features-based clustering analysis and a supervised step with several artificial neural network models. Two field measurements were taken at two locations around a building, about a year apart, in which the former was set as the train datasets and the latter was set as the test datasets. The prediction accuracy of the models trained by the existing train datasets to the new test datasets was evaluated. The comparative study between k-means clustering and agglomerative clustering was also discussed. Overall, by comparing with the evaluation metrics on the error evaluation, and the relative error of wind speed statistics of calibrated measurements, it was verified that the calibration effect of the proposed strategy outperformed conventional machine learning method which utilized the train datasets directly.

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Efficient estimation of energy harvesting performance in the pendulum-based galloping energy harvester is proposed and its validity is examined. In this estimation method, the power coefficient of the oscillating pendulum of the harvester is predicted based on measured torques of the steadily rotating pendulums. The predicted power coefficients were close to the power coefficients measured in oscillating pendulums. However, this estimation method does not perform properly in relatively low nondimensional flow velocities where the quasi-steady theory does not hold true.

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In order to develop a vibrational power generator using the magnetostrictive material and the flow- induced vibration of a cantilevered rectangular prism, the experiments were performed in a wind tunnel. We focus on the low-speed galloping vibration for rectangular prisms with side ratio of D/H = 0.2, 0.3, 0.4, 0.5 (where D is the depth of the prism in the flow direction and H is the height of the prism) and the high-speed galloping vibration for a rectangular prism with side ratio of D/H = 1.0. The effect of a gap G between a prism and a splitter plate on the transverse vibration characteristic of prisms and the performance of vibrational power generator were investigated. In the case of a rectangular prism with D/H = 0.2, 0.3, 0.4, 0.5 without a splitter plate, the onset reduced velocity of vibration is lower than that of a rectangular prism with D/H = 1.0 because the low-speed galloping occurs. In the case of a rectangular prism with a splitter plate, the power of a rectangular prism with D/H = 0.2 with a splitter plate of a gap ratio G/H = 0.2 was highest. However, the amplitude increases as wind speed increases because the high-speed galloping occurs. The high-speed galloping leads to damage to the power generator. On the other hand, the rectangular prism with a splitter plate of G/H = 1.2 is better for the power generation than that with the other gap ratio.

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Finite element analyses of galloping of four-bundled conductors observed in the Tsuruga test line were conducted using the three-dimensional nonlinear finite element analysis code “CAFSS”. The maximum tension fluctuations obtained through the simulations of the several blowing angle conditions were almost the same if the wide range of the ice accretion angle was considered. Additionally, the maximum tension fluctuations obtained through the observations and simulations were consistent under the wind speed of 16m/s. However, over the wind speed of 16m/s, the maximum tension fluctuation in simulation increased when the wind speed increased, although that in the observations decreased. It is necessary to investigate the mechanism of decrement of the maximum tension fluctuation in the observation and consider the mechanism in the method of galloping simulations.

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Galloping is occasionally observed in overhead transmission lines owing to ice accretion. Galloping characteristics and effects of countermeasures against it might vary depending on the ice accretion type, namely, freezing rain, wet snow accretion, and in-cloud icing, because the shape of ice accretions can vary based on the type. In Japan, galloping is often caused by wet snow accretion in plain areas. To investigate the galloping effect on overhead transmission lines owing to wet snow accretion, field observations of four-bundled conductors have been carried out at the Kushiro test line since 2014. On January 12, 2022, large galloping was finally observed at this site. The conductors mainly vibrated in the vertical two-loops/span mode coupled with the horizontal and torsional modes, where the maximum total amplitude reached approximately 5.8 m in the vertical direction. Contrarily, in the line that was installed loose spacers as a countermeasure, the galloping amplitude was significantly reduced compared with that observed in the line with normal spacers.

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In Japan, many chimneys for thermal power plants over 100m high have been built. Such super-high chimneys have a more slender shape than normal structures, often having aspect ratios of 20 or more. In such cases, "tower-supported chimneys," in which the horizontal forces acting on the exhaust cylinder are supported by a truss-type steel tower, are often adopted in Japan. Chimneys are one of the important facilities for operating thermal power plants, but these are considered old since they were built more than 30 years ago. Therefore, it is important not only to design for maximum wind loads, but also to avoid damage due to cumulative loads. In this study, we attempted to model the spatial correlation characteristics of layer wind force based on wind tunnel test.

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It is known that the weather conditions have a great influence on logistics in the construction of offshore wind power plants. Specifically, it is necessary that the wind speed and wave height do not continuously exceed the threshold value for the time required for work at sea. In this report, a multi-agent simulation was applied based on the meteorological reanalysis data ERA5 in estimating the process in consideration of these conditions. Issues were also extracted by comparing the meteorological and oceanographic data obtained by reanalysis with the observed data. Trial calculations were performed assuming the construction of offshore wind turbines on the Sea of Japan side of northern Japan. In particular, it was found that the process was delayed due to the strong winds and high wave heights in winter. Furthermore, the possibility of expanding the application of multiple projects to logistics that uses multiple ports in a network, and the use at the maintenance stage are also expected.

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Previously, we demonstrated that the wind speed of the downwind turbine decreased and it could be influenced by the wind wake of the upwind turbine by numerical simulation targeting two wind turbines in complicated terrain. In order to examine the effect of wind wake more thoroughly, we used observed data from two turbines to compare of wind speed ratio and turbulence intensity between two cases, with and without effects of wind wake. It revealed that the wind speed of the downwind turbine by 24% reduced and turbulence intensity by 27% increased in the target wind direction decreased when upwind turbine operates compared with when it stopped. In addition, it found that wake caused generated power of the downwind turbine to drop.

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Large scale wind turbines can sometimes cause noise annoyance problems, which are thought to result from the spread of aerial vibration. The strength of aerial vibration decreases exponentially with distance, whereas ground vibration attenuation with distance is relatively small; therefore, low-frequency ground vibration should be considered. In this study, xyz-direction ground vibration amplitude was investigated using the fast Fourier transform. First, the data point was found to be distributed over two of the coordinate axial directions in the coordinate space of the xyz-direction frequency amplitude at a location with annoyance problem. Next, the horizontal-to-vertical (H/V) ratio of each frequency was analyzed to determine the characteristics of the ground that indicate such a property. Finally, it was found that the H/V ratio increases in the range of over 3 Hz in a place where an annoyance has been detected. This result suggests that, if annoyances are detected, the boundary surface of the geological structure is located at a shallow depth.

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