In this paper, the reproducibility of Typhoon FAXAI (T1915) using a meso-scale model WRF-ARW with 1-km horizontal resolution was discussed. Additionally, we tried to evaluate the results using meteorological observations which were available immediately after the typhoon passed. Our WRF simulation has the capability of reproducing well the position of typhoon center as well as the temporal change of surface pressure during the passage of typhoon. Especially, the pressure drop observed at the Yokohama Local Meteorological Observatory was well simulated. The intensification of wind speed and the change of wind direction associated with the approach and the passage of typhoon were found in areas located the right-hand side of the typhoon path, and the simulation has good accuracy of reproduction of strong winds in the comparison with the time-series at Kisarazu AMeDAS station. The result indicated the non-axisymmetry of low-level wind, precipitation and cloud fields, which was suggested from satellite, Doppler radar, and wind profiler observations.

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For effective use of the sea breeze as a countermeasure against urban warming, it is important to analyze the wind field within the atmospheric boundary layer over the city and clarify the relationships between the sea breeze above the city and the temperature near the ground, in summer. In this study, a concurrent measurement of wind velocities using two Doppler lidars in the city center, and the air temperature at multiple observation points was conducted in coastal city Sendai, Japan. The characteristics of vertical and horizontal wind velocity fluctuations of sea breezes were analyzed quantitatively by spectrum analysis, and the effects on temperature were analyzed.

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We have analyzed the wind conditions of a couple of sites in Japan and foreign countries, particularly paying attentions to the fluctuation in wind directions. We have proposed an evaluation formula for the fluctuation intensity in the wind direction. In recent years, we have built wind poles and small wind turbines at several locations in Japan and abroad, mainly in Kyushu, and have been performing daily wind condition and power generation data acquisition and analysis. We compared wind turbulence, i.e., wind speed and wind direction variability, between mountainous and coastal winds in Japan and those in other countries (e.g., seaside), and reported the differences. We have found a large difference in turbulence between the complex terrain and seaside areas.

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The reduction of the power generation cost is a major factor in the main power generation of renewable energy, and the frequency distribution of the average wind speed greatly influences the power generation in the environmental conditions surrounding wind power generation. It has been pointed out that in offshore wind power generation, which is currently attracting attention in Japan, the effects of the topography are not small, as practical use is advanced from coastal areas with shallow depths. Therefore, in this study, we compared the wind observation record at a lighthouse in the coastal and its wind turbines with hub height of more than 60 m, and examined the influence of the topography based on the wind conditions simulation results by MASCOT. By applying these results, we will contribute to the examination of offshore wind candidate sites in the future.

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The constructions of the offshore wind turbine in Japan are in the stage of designing the bottom-mounted ones near the coast line. Numerical weather prediction models provide information of the detailed wind profiles, however, the effect of the land adjacent to the site may not be well captured because of the horizontal resolution with the order of kilometer. Recent improvement in the physics schemes on the models have enabled the usage of the model with sub-kilometer scale, and hence, it may be applicable for the above objective. Targeting Choshi site in Japan, we performed 200m horizontal resolution simulations for two individual two-weeks, which are selected by the reason that the wind directions were categorized within a small number of the sector. The simulated wind speed was consistent to the observations in terms of the probability distribution function of the scalar velocity. The two seasons showed a contrastive thermal stratification conditions, and this effect on the wind profiles are analyzed in detail.

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A tornado occurred in Nobeoka, Miyazaki on the morning of September 22, 2019, when the typhoon No.17 was approaching. About 500 houses were broken and 18 peoples were injured by the tornado. The present study aims to clarify the characteristics of the tornado. Its funnel cloud was wide bowl shape and it was difficult to identify the tornado. But its moving velocity was found to be 96 m/s. And the maximum velocity, 43 ? 52 m/s, was estimated by the drop level of cloud bottom. Furthermore, we will report the result of the trial identifying the tornado with the rotating motion of the cloud.

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Accidents caused by strong winds during outdoor use of air playground equipment, which are often seen in amusement parks, event venues, indoor play facilities, etc., have occurred in recent years. Since the weight of the air playground equipment is light and easily blown away by the wind, it is necessary to fix it with a pile or weight when installing.Currently, in Japan, Japan Inflatable Products Safety Association(JIPSA) has established a provision for safety management, but has not yet reduced the damage. In this study, we proposed a calculation formula for calculating the degree to which additional load (sandbag, weight such as polytanks, and pegs) to be installed auxiliary in the air playground equipment is necessary. In addition, the pulling test was also performed to examine the strength of the batting pile required for the calculation formula.

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These measurements were conducted to define the characteristics of air flow in climate chamber 1 of the IEQ Laboratory at the University of Sydney under natural cross ventilation condition in summer season. Thermal anemometers recorded two different heights (600mm and 1100mm) horizontal, two directions (N-S and E-W) vertical distributions and time history of air velocity in this report. The outdoor wind conditions were predominantly easterly during the period of study. The indoor air velocity close to window was higher than near-wall and middle of chamber. It was increased with height in case of near windows, and decreased with height in case of middle of chamber.

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The authors have been developing a method to estimate the airflow distribution in urban area with limited observation information by combining POD (Proper Orthogonal Decomposition) with LSE (Linear Stochastic Estimation). In this paper, the effectiveness of this method was verified by reconstructing and predicting instantaneous airflow distribution obtained from LES (Large-Eddy Simulation) for cubic building group model. We validated the reconstructed and predicted values with POD-LSE by comparing with the LES data as the true value and investigated the sensitivity of the accuracy to the size of analysis area and the number of observation points.

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This paper presents the identification of the dynamic system for the K?rm?n-type vortex shedding, based on the mode analysis results of the turbulent structure around a rectangular prism building model. First, proper orthogonal decomposition (POD) was performed on the turbulent velocity data. In this case, the 2nd dominant POD mode (mode 2) was found to be controlled by the inflow fluctuation, and the 1st, 3rd and 4th dominant POD mode (mode 1, 3 and 4) depicted the main periodic vortex shedding phenomenon on the wake of the building. Then, the dynamics system of modes 1, 3 and 4 were fitted into a polynomial regression model, which showed an average trend of the trajectory of the state. The two limit cycles of the regression model were found to depict the two rotation directions of the K?rm?n-type vortex, which were the final states if the system is free of perturbations. Additionally, two characteristic periods were recognized from the trajectory generated from the regression model, which indicates a fast motion and a slow motion of the wake vortex.

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A rectangular cylinder with an aspect ratio of B/D smaller than 0.6 requires three-dimensional unsteady computational fluid dynamics (CFD) simulation since a three-dimensional flow is generated in the span-wise direction in the wake of this cross section. And it is known from previous studies that CFD simulation of two-dimensional section causes a large difference in the results of existing wind tunnel experiments. In this study, large eddy simulation (LES) is conducted in case of the aspect ratio B/D equals 0.4 and we verified two points, the span-wise length and the mesh size in the span-wise direction. These were examined by comparing the aerodynamic coefficients obtained in this study with the results of existing wind tunnel experiments. As a result, it was found that the mesh size in span-wise direction should be smaller than D/10 and the span-wise length should be longer than 4D when performing a three-dimensional CFD analysis on a rectangular cylinder with an aspect ratio of B/D smaller than 0.6.

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Large amplitude aerodynamic vibrations of bluff bodies with three degrees of freedom (DOF), in which horizontal, vertical and torsional directions, are perhaps explained by the unsteady aerodynamic forces determined by the relative angle of attack and the time derivative of it in comparatively higher reduced wind velocity region. For the first step, to verify this idea, these unsteady aerodynamic forces were applied to explain the large-amplitude responses in torsional 1DOF using a rectangular cylinder with a side ratio of five, where the torsional flutter appears. The unsteady aerodynamic forces of the continuously rotating body were measured and tried to define by the relative angles of attack and their time derivatives. These unsteady aerodynamic forces were able to reproduce the unsteady aerodynamic forces under torsional 1DOF forced vibrations. Furthermore, the response amplitudes obtained from the time domain response analyses using these unsteady aerodynamic forces were in good agreement with the results of wind tunnel experiments with the elastically supported body.

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When wind pressure acting on a structure and flow around the structure have fluctuating components, characteristics of the dominant frequency components are important for wind resistant design. In this research, spatial correlation characteristics for the rectangular cross-section with wind speed and angle of attack are clarified using not only power spectrum, correlation coefficient, and coherence but the indices focusing on the dominant frequency components proposed in this research. Furthermore, the effect on the spatial correlation when a splitter plate was installed in the wake region orthogonal to the cylinder axis was examined. The results such that the correlation decreased at the angle of attack after periodical reattachment were obtained.

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Range of angle of attacks is specified in the wind-resistant design of long-span bridges. It is understood that the angle of attack is caused by a constant wind inclination due to neighboring topography, fluctuating inclination angle due to wind speed fluctuations and static deformation due to wind load. The fluctuating inclination angle due to wind speed fluctuations was studied based on theoretical backgrounds, which concluded that ±3 degrees of the angle of attack is enough for a 1,500m suspension bridge on a flat terrain. In this study, based on filed measurements of wind and a wind-tunnel test, the theoretical backgrounds for the setting of the fluctuating inclination angle is verified and a more reasonable method is presented.

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Modern structures are more susceptible to larger dynamic excitation brought about by stronger wind forces. For this reason, accurate estimation of the actual wind loads acting on the structure has become greatly necessary. Also, important dynamic parameters of the building, particularly natural period and damping ratio are considered to be highly uncertain and may contribute additional errors in the estimation of wind forces. Hence, the effect of uncertainty in the evaluation of these dynamic parameters to the estimated wind forces must also be given more careful consideration. This paper investigates the accuracy of modal analysis in estimating the wind forces acting upon a 10 degree-of-freedom model and determines the sensitivity of these estimated wind forces when errors in the natural period and damping ratio are introduced.

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In recent years, seismic isolation structures have been adopted for high-rise buildings. In accordance with its highness, the wind load becomes larger than seismic load relatively. So, wind force increases the amount of isolation-layer deformation. Therefore, there is concern that the response of isolation-layer may extend to the plastic range. However, the current wind load design in Japan is based on only elastic response of structure. In addition, it is difficult and impractical to estimate the response by time history response analysis for elastic-plastic response. That’s why it is necessary to develop a stochastic method to predict elastic-plastic wind induced response. This paper proposes a simplified prediction method of the elastic-plastic wind-induced response for a high-rise isolated building with steel dampers by using ““Recommendations for Loads on Buildings””, and its accuracy is verified by comparison with results of time history response analysis.

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In recent years, not only the seismic but also wind-resistant design of the high-rise building is considered, for safety along with the comfortability to the residents. The passive control system is widely used in the high-rise building to dissipate energy from vibration. Among all kinds of passive control systems, the viscoelastic (VE) damper, which is accompanied by the frequency-sensitivity, needs to consider the efficiency of the energy dissipation subjected to the external force (Kasai et al.,2002), including the seismic of massive amplitude with high-frequency and wind excitation of the minor amplitude with low-frequency. In the paper, the fractional derivative (FD) material (Kasai et al.,1993) is adopted as the exact solution of the VE material, which needs to consider the temperature factor along with the frequency-sensitivity factor, is much more complicated than that of a simplified VE damper system when doing the simulation in dynamic analysis. On the other hand, the simplified VE damper system, such as the Kelvin system and the Maxwell system, is commonly used in seismic control with high reliability, but no evidence approved whose in the wind control. Comparing with features of the earthquake, the strong wind excitation which directly applies to the upper structure of the building, has a wide-band frequency content. It leads to a significant difference in the structural response between the simplified VE damper systems and the FD system. To improve the reliability of the simplified VE damper system subjected to strong wind excitation, this research evaluated the wind-induced response along with the energy dissipation of the simplified VE damper systems considering the influence of frequency-sensitivity.

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In case of high-rise buildings, it is important to take measures to avoid vibration caused by wind. One of the measures is setting up the dampers in the buildings. Among them, the viscoelastic damper is effective for vibration caused by wind because it has effects against a small deformation. However, there is concern about changing the performance of it caused by long duration vibration. The purpose of this research is constructing a design method of vibration control buildings considered that the stud-type viscoelastic damper declines performance caused by long duration vibration. We propose the method for assessing the response of vibration control buildings considered that it declines performance by reducing its performance from the initial value.

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Viscoelastic (VE) dampers are widely installed in tall buildings to mitigate structural vibrations induced by earthquake and strong wind. They dissipate the kinetic energy through shear deformation of the steel-sandwiched VE material, and in the process, heat is generated within the damper. Since the VE dampers properties (i.e., damping and stiffness) are temperature and frequency dependent, significant damper temperature increase from long-duration loading (e.g., wind loading) can greatly affect their performance. Customarily, their properties are easily evaluated from the hysteretic relationship of force and deformation obtained from harmonic loading. However, wind-induced vibrations of tall buildings are random by nature. Hence, the authors propose an evaluation method by considering equivalent sinusoidal waves of the long-duration random deformation based on the random vibration or spectral approach which is fundamentally used in wind engineering. Taking into account the frequency dependency of VE dampers, low-frequency and high-frequency components of the random deformation are separated, thus, two equivalent sinusoidal waves are considered in the dynamic analysis considering heat generation and transfer analysis. Combined results from these equivalent sinusoidal waves agree well those from the original random deformation.

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Research interest in viscoelastic (VE) dampers as passive control device for high-rise buildings has been increasing due to the effectiveness of such dampers in dissipating not only the seismic vibration but also of the wind-induced vibrations.Evaluating the dynamic characteristics of VE dampers requires computationally-demanding analysis due to the complexity of the VE material properties.There has been proposed simplified method to predict the dynamic characteristics of VE dampers, but it was only applied and verified for harmonic loadings.Its accuracy for random loadings must be investigated since actual wind response of viscoelastically-damped high-rise building is random.In this paper, the authors propose a simplified method to predict the dynamic characteristics of VE dampers under long-duration random excitation such as wind.

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The number of passive-base-isolation (PBI) structures increased rapidly in Japan after the Great Hanshin earthquake of 1995. In recent years, PBIs has also been installed in high-rise buildings, and the combination of a PBI and active structural control (ASC) has been employed in many buildings globally to improve control performance. However, conventional approaches need numerical simulations to calculate the maximum response, thereby making complicate the design of control systems that satisfy design limitations. This paper presents a new method that theoretically estimates the mean control force and mean displacement response under along-wind force using only the static equilibrium. Moreover, the gust factors for PBI buildings with ASC, which estimate the maximum displacement and control force are devised. Our method makes it possible to estimate the mean and maximum control force and the displacement of the structure without using simulation.

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The current wind-resistant design of structures is performed under the assumption that the main structure is kept to an elastic state and mainly relies on design guidelines for load recommendations on buildings. However, as the building’s height increases, it becomes subjected to stronger external wind forces. In this circumstance, if a hysteretic damper is installed in a high-rise building, there is a possibility that the damper may behave plastically due to larger external wind forces. Therefore, understanding the plasticity behavior of hysteretic dampers installed in high-rise buildings under the load recommendations on buildings will pave the way to easily evaluate the elasto-plastic behavior of these passively controlled buildings. For this reason, the authors propose a method to determine the hysteretic damper plasticity based on the load recommendations on buildings and examine the effect of using an equivalent model with reduced degree of freedom.

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Recently, seismic isolation structures are becoming widely adopted for high-rise buildings but there are only few studies on the wind response of such buildings. The authors aim to address this matter by studying the actual behavior of two conjoined seismically isolated high-rise buildings(J2-3) based on wind response observation records. This complex-shaped conjoined buildings were constructed in two phases: (1) the flat-shaped J2 building was completed earlier, and (2) later followed by the construction of the conjoining J3 building. The wind response record for the J2 building alone in phase (1) has been reported in the past. However, actual wind response of the completed J2-3 building is not yet well investigated. this study aims to grasp the influences of conjoining buildings and the change of the building shape on wind response behavior. In this paper, as the preliminary stage, the authors report the detailed response analysis of the conjoined buildings during typhoon.

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In recent years, the base-isolated system has been applied to more and more tall buildings. However, as the building gets taller, wind force may increase, which may lead to the residual deformation occurred in the isolation layer because of the plasticized steel dampers. When evaluating the residual deformation of the isolation layer, it is not enough to use the 10-minute wind force with no change in wind speed and wind direction as introduced in the existing wind-resistant design. In the case of a typhoon considering wind speed and wind direction change, because of the wind force against the isolation layer deformation, overestimation on the residual deformation may occur if the 10-minute wind force is used. Therefore, by numerical studies on a MODF model, this paper focuses on the residual deformation of the isolation layer in typhoon simulation to provide useful information for practical design.

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Vertical fins on walls of building are required wind resistant design because these components are exposed to outer air. Recently, buildings tend to high-rise and long-life. High-rise buildings are predicted to be exposed to strong wind, long-life buildings are predicted to be longer time of action of fluctuating wind. Therefore, the evaluation of the wind resistant design for fatigue safety on cyclic wind load in-service period is necessary for a building. This study performs to evaluation of fatigue damage of vertical fins on walls of high-rise building as the wind force coefficient range by wind tunnel experiment. As a result, the tendency of the wind force coefficient range is similar to the tendency of the fluctuating value of wind force coefficients. On the other hand, it is confirmed that these tendencies are locally different.

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For bridge wind-resistance design, the aerodynamic stability of a long-span bridge is sensitive to bridge attachments such as handrails, but the effect of handrail configuration on aerodynamic stability have not been studied in detail. As the full reproducing of handrail shape in numerical simulation need extremely fine grid generation and large calculation cost, how to reproduce or model the handrail configuration for mesh simplification in numerical simulation draws a large concern. In this study. 1 DOF Spring-supported free-vibration wind tunnel tests were conducted to investigate the effect of handrail configuration on vortex-induced vibration of a single box girder. Without changing porosity as well as the height and shape of the top horizontal bar, as the number of horizontal bars between the top bar and the foundation increases, the maximum heaving VIV amplitude decreases. On the other hand, increasing the side ratio of middle horizontal bars reduces the maximum amplitude of heaving VIV. Moreover, the possibility and limitation of simplifying the handrail model in experiment or in CFD were discussed based on the experimental results.

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In this study, measurement tests were performed using rotary devices with arbitrary input waveforms to investigate the unsteady aerodynamic force characteristics of four-bundled conductors. Aerodynamic coefficients, which are defined as functions of the angle of attack and non-dimensional angular velocity, were measured from tests performed at a constant angular velocity. Subsequently, the validity of the aerodynamic force formulation using these two variables was confirmed by comparing the unsteady aerodynamic coefficients obtained from two different measurement tests: one performed at constant angular velocity, and the other that used sinusoidal waves as the input. Furthermore, results of the time history analysis, in which the aerodynamic forces were calculated by using the relative angle of attack and relative angular velocity at each time step, showed good agreement with the test results for large-amplitude galloping.

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The dry gauze method, which uses gauze embedded in a wooden frame, is often used to evaluate the amount of airborne salt. However, the scattering behavior of particles around the collection device and the deposition mechanism to the gauze fibers has not been studied in detail. In this study, to study the relationship between the collected salinity by this method and the actual atmospheric salinity, the particle collection efficiency of single gauze fiber was investigated based on the flow fields around the circular cylinders by CFD. The result shows that the particle collection efficiency of circular cylinders depends on the Reynolds number, particle size, and the distance between the cylinders.

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It is appropriate to evaluate thermal comfort and heatstroke risk in urban street area based on the accumulated heat stress of walking pedestrians and their human physiological responses. Additionally, since the wind environment to which pedestrians are exposed differs according to the direction of walking even in the same urban street, it is considered to change the human physiological responses, the thermal comfort and heatstroke risk of walking pedestrians. In this study, the influence of the wind environment to which pedestrians are exposed on the human physiological responses and the thermal comfort of walking pedestrians was quantitatively evaluated by the results of simultaneous measurement of the physical environment to which pedestrians are exposed and the amount of human physiological responses of walking pedestrians and numerically simulated by CFD analyses coupled with calculations of radiation and conduction. Moreover, the effects of countermeasures against urban warming introduced in the urban street were evaluated based on the accumulated heat stress of walking pedestrians.

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Predictions of pedestrian wind environment and planning of countermeasures against strong winds are required in an environmental impact assessment for urban developments. It has been difficult to conduct assessment of the wind environment for each design modification because of the high cost of wind tunnel experiments or numerical simulations for predicting wind environments in complex urban areas. In this study, the author has developed a wind environment simulator using three-dimensional convolutional neural network (3D-CNN) that enables predictions of wind environment in complex urban areas to be made with speed and ease. This paper describes the methodology for prediction of the wind environment by 3D-CNN, the learning method, and the validation results.

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The authors developed an innovative small-size and low-cost Coherent Doppler Lidar (CDL) to obtain three-dimensional wind field with a good temporal and spatial resolution, aiming at the safe and stable operation of Un-maned Aerial Vehicle). In order to obtain the 3D-wind field in the urban area, it is necessary to construct a dense network of high-performance CDL with a maximum observation range of 30 km. We will discuss the overview of observational experiment and the verification results.

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