Yukio Tamura

Wind Load Combinations of Atypical Supertall Buildings

AbstractWind loads are generally divided into along-wind, across-wind, and torsional loads, but in reality they occur simultaneously in time and space. Furthermore, because they do not show their maximums at the same instant, they need to be combined appropriately. In this study, pressure measurements were conducted on atypical supertall buildings to investigate wind load combinations. Using a simplified reference model with four columns, analyses in the time domain were conducted, and this paper proposes combination rules based on the concept of combination factor that can be applied to atypical supertall buildings. The combination factor for a square model is approximately 0.5, and those for atypical models differ depending on building shape. Two methods are discussed in the determination of combination factors, and comparisons between peak normal stresses by analysis and combination factor show relatively good agreement, ranging mostly within ±5%.

Correlation Analysis of Aerodynamic Forces acting on Tall Buildings with Various Side Ratios

The objective of this study is to construct the TPU aerodynamic database with wind tunnel test data of overall wind loads and responses on tall buildings. In this study, wind tunnel tests were conducted to investigate characteristics of wind forces and the effect of wind load combination by cross-correlation analysis among along-wind overturning moment, across-wind overturning moment and torsional moment on a tall building with various side ratios(D/B

Pressure Fluctuations on Tapered and Setback Tall Buildings

Recent tall buildings tend to have unconventional shapes as a prevailing, which is effective for suppressing across-wind responses. Suppression of across-wind responses is a major factor in tall building projects, and the so called aerodynamic modification method is comprehensively used. The purpose of the present study is to investigate the pressure fluctuations on tapered and setback tall buildings, including peak pressures, power spectra and coherences through the synchronous multi-pressure sensing system techniques. And flow measurements around the models were conducted to investigate the condition of vortex shedding. The results show that by tapering and setback, different distributions of mean pressure coefficients at leeward surface were found, which is caused by the geometric characteristics of the models. And the power spectra of wind pressures at sideward surface become wideband and the peak frequencies are different depending on heights, which makes the correlation near the Strouhal component low or even negative. The differences in shedding frequencies were also confirmed by the flow fields around the models.

Characteristics of wind-Induced Coupled Motion of Tapered and Setback Tall Buildings

For most of recent tall buildings, one characteristic is that their building shapes vary with height such as taper and setback, and this implies that the distribution of their struct ural components may also vary with height. Because of these structural variations, although the sectional shapes of these buildings are symmetric, it is difficult to say whether or not they are structurally symmetric. The acceleration responses of structurally asymmetric tall buildings are larger than those of non-eccentric buildings, thus raising the possibility of problems during strong winds and typhoons. This paper describes wind tunnel tests carried out using building models with height variations and acceleration response analyses, and discusses the resulting response characteristics. For tapered and setback buildings, although the across-wind accelerations are larger than those of a square building, the total root-mean-square accelerations remain small because of smaller along-wind and torsional rms accelerations. And it was found that the effects of statistical couplings between along-wind force and other two forces are negligible.

Chapter 3 Air: Typhoon and Tornado Risk Management

Human beings spend their daily lives within the range of the atmospheric boundary layer, where airflow is affected by friction from Earths surface. The airflow in this area is generally called wind. Strong wind occasionally causes severe damage to infrastructures and people because of its aerodynamic effects, but even weak and moderate winds can have serious environmental impacts on human society such as those seen with air-pollution problems and thermal effects.

Wind Pressure Distributions on Buildings Using the Coherent Structure Smagorinsky Model for LES

A subgrid-scale model based on coherent structures, called the Coherent Structure Smagorinsky Model (CSM), has been applied to a large eddy simulation to assess its performance in the prediction of wind pressure distributions on buildings. The study cases were carried out for the assessment of an isolated rectangular high-rise building and a building with a setback (both in a uniform flow) and an actual high-rise building in an urban city with turbulent boundary layer flow. For the isolated rectangular high-rise building in uniform flow, the CSM showed good agreement with both the traditional Smagorinsky Model (SM) and the experiments (values within 20%). For the building with a setback as well as the actual high-rise building in an urban city, both of which have a distinctive wind pressure distribution with large negative pressure caused by the complicated flow due to the strong influence of neighboring buildings, the CSM effectively gives more accurate results with less variation than the SM in comparison with the experimental results (within 20%). The CSM also yielded consistent peak pressure coefficients for all wind directions, within 20% of experimental values in a relatively high-pressure region of the case study of the actual high-rise building in an urban city.

Interference effects of an adjacent tall building with various sizes on local wind forces acting on a tall building

This article focuses on variations of local wind forces along height levels of a tall building due to an adjacent tall building with various height and breadth ratios through huge wind tunnel experiments. It deals with the characteristics of local wind forces including root mean square local wind force coefficients, non-dimensional power spectra, and root coherences along height levels of a tall building with an adjacent tall building in critical locations. It is shown that increases of over 20% in interference factors (MIFMD, RIFMD, and RIFML) for maximum mean and root mean square base overturning moment coefficients in along- and across-wind directions occur when the adjacent building is close to the principal building. Higher and wider adjacent buildings can cause not only higher mean wind loads but also higher dynamic wind loads in along- and across-wind directions, but the critical locations of an adjacent building with various height and breadth ratios are somewhat different. However, most critical locations of an adjacent building for wind-induced wind loads are within the region (X/B, Y/B)u2009=u2009(1.5, 0–1.5).

Experimental investigation of aerodynamic vibrations of solar wing system

The general characteristics of aerodynamic vibrations of a solar wing system were investigated through wind tunnel tests using an aeroelastic model under four oncoming flows. In total, 12 solar panels were suspended by cables and orientated horizontally. Distances between panels were set constant. Tests showed that the fluctuating displacement increases proportionally to the square of the mean wind speed for all wind directions in boundary-layer flows. Larger fluctuating displacements were found for boundary-layer flows with larger power-law indices. Under low-turbulence flow, the fluctuating displacement increased proportionally to the square of the mean wind speed for wind directions between 0° and 30°, but an instability vibration was observed at high mean wind speed for wind directions larger than 40°. And when the wind direction was larger than 60°, a limited vibration was observed at low mean wind speed and the instability vibration was also observed at high mean wind speed. Fluctuating displacements under grid-generated flow showed a similar trend to that of the boundary-layer flows, although the values became much smaller.

From Load Estimation to Performance Estimation—From Model-Scale Test to Full-Scale Test: With Special Interest in Asian Region

This paper first discusses the current status of natural-hazard-induced disasters, with special focus on devastating wind-related disasters in the Asian region. The importance of the combined effects of wind and water hazards, the importance of performance of cladding and components in wind resistant design of buildings, and deterioration of metal roofing systems of long-span structures mainly caused by fatigue of fixing joints due to daily solar heating effects are demonstrated. Some human errors caused by lack of attention to aerodynamic and structural behaviors are also indicated. Then, psychological impacts and social impacts are discussed, and common underestimation of social impacts of wind-induced disasters on society is pointed out. The main reason for repeated wind-induced damage is lack of information on the real performance of claddings, components and main frames under wind actions. The demand and necessity for full-scale tests are emphasized, aiming to check the performance of building and structural systems under realistic and controlled conditions of extremely strong actions of wind, rain, snow, fire, solar heating and so on. Finally, the academic and social significance of the full-scale storm simulator is discussed.

Application of remote sensing images for natural disaster mitigation using wavelet based pattern recognition analysis

During the past few decades there has been a tremendous increase in natural disasters and its effect on population and economy. Adverse events, such as cyclones, tornadoes, floods, volcanic eruptions, earthquakes, tsunamis, etc., turns into a disaster when it strikes in an area of vulnerable population. Immediate tracking of the damaged location provides near-instant help to the injured and also facilitates appropriate maintenance to damaged structures. The recent advances in the remote sensing area have accelerated the availability of satellite/aerial image data worldwide with ease. Advancement in the remote sensing area, especially after the rapid availability of satellite/aerial image data supplemented with the development in the computational field has been utilized in this paper to achieve the goal of faster automatic natural disaster location identification. Satellite/aerial imageries are used to acquire the data of the damaged location from an eagle-eye perspective and the application of the wavelet based pattern recognition and latest image processing techniques are used for identifying locations of major natural disasters like cyclones, tornadoes and floods.