Kunio Fujii

Effectiveness of tuned liquid dampers under wind excitation

Abstract Full-scale measurements of the wind-induced responses of four buildings (two airport towers, an observatory tower and a highrise hotel) were conducted to prove the efficiency of tuned liquid dampers (TLDs). The damping ratios of the buildings with and without TLD were evaluated by both the run-down test technique and the random decrement technique. The wind-induced responses of the buildings were measured before and after installation of TLDs. The exceedance frequency of the response over the human perception thresholds was also examined. The results obtained in this study demonstrate that the TLDs could significantly improve the serviceability of the buildings.

Suppression of wind-induced vibration of a tall building using Tuned Liquid Damper

Abstract An optimum TLD design of a tall building required for comfort and serviceability was studied in this paper. In designing an optimum TLD, some design parameters which affected the TLD performance were investigated, and a new simulation method was developed to predict the effect of the TLD on vibration suppression of a tall building. From numerical simulations by using the proposed method, the TLD designed in this study effectively reduced the wind-induced response for improved serviceability.

Experimental evaluation of aerodynamic damping of tall buildings

Aerodynamic damping of tall buildings is evaluated by wind tunnel tests using a stick model. The model is a 1500 scale model of a building. The side ratio of the model is varied in the range 0.33–3, and the aspect ratio is varied from 4 to 6. The aerodynamic damping ratios are evaluated from the wind-induced responses of the model by using the random decrement technique.

Wind load and wind-induced response estimations in the Recommendations for Loads on Buildings, AIJ 1993

The Recommendations for Loads on Buildings of the Architectural Institute of Japan (AIJ) was updated in June 1993. Separate windload estimations are required for main resisting systems and components and cladding. Two different calculation formulae are prepared for wind loads of main resisting systems: one is for the horizontal along-wind load and the other for the roof load. Three procedures with different accuracy are able to be selected by designers: the simplified procedure for low-rise small buildings, the detailed procedure I for middle-height rigid buildings and detailed procedure II for high-rise flexible buildings. Additionally, estimation of the across-wind and torsional loads is necessary for wind-sensitive buildings. Special load estimations for aeroelastic instabilities are also required for particularly slender and flexible buildings. All provisions are expressed only in equations, without any diagrams.

Simultaneous measurements of wind speed profiles at two sites using Doppler sodars

In the wind-resistant design of buildings and structures, it is very important to accurately assess the design wind speed at a particular site, considering the variation in wind speed with terrain roughness. The authors attempt to find a reasonable method for estimating design wind speed for given terrain roughness, through simultaneous wind observations at altitudes up to 420 m at sites with different roughnesses using two sets of Doppler sodars. In this paper, the characteristics of the mean wind speed profiles evaluated for each distinguished wind speed in each wind direction were presented. The longitudinal mean wind speed profiles in the same storms were also compared for two pairs of sites to study the variation in longitudinal mean wind speed as it is affected by inland terrain roughness.

Multi-channel simultaneous fluctuating pressure measurement system and its applications

Abstract A multi-channel simultaneous fluctuating pressure measurement system using electronically scanning pressure transducers has been developed for wind tunnel tests in the wind engineering field. The fluctuating wind pressures acting on tall building models are measured simultaneously using the multi-channel pressure measurement system, and the fluctuating wind pressures are integrated into the resultant fluctuating wind forces. The spectra of the wind forces agree well with the results obtained by a force-balance system. The pressure measurement system has also been used to investigate the properties of the fluctuating wind forces acting on the beams supporting flat roofs, and the gust factors of the load effects on the beams are examined.

Full-scale measurements of wind-induced responses on the Hamamatsu ACT Tower

Abstract In Japan, most high-rise buildings are equipped with vibration control devices in order to improve their habitability by reducing wind-induced vibration. The Hamamatsu ACT Tower is also equipped with active type vibration control devices. For the purpose of confirming the vibration control effects of these devices, observations of winds and vibrations have been carried out. This paper reports on the vibration control effects of the devices on wind-induced vibration, as well as the results obtained from observations of vibration responses of the building during strong seasonal winds and a typhoon.

Turbulence characteristics of wind flow at ground level in built-up area

Abstract This paper describes the statistical characteristics of wind at ground level. Observations of wind flow at ground level were conducted over a period of 2 years around a high-rise apartment building in a built-up area in Tokyo. The mean and gust wind velocities at ground level are approximated on the basis of the Weibull distribution. The probability distributions of velocity-ratio, gust factor and turbulence intensity are obtained. The relationship between the exceedance probability and the number of storms per annum is derived. The characteristics of the long-term power spectrum of wind velocity are clarified.

Effects of structural damping and eccentricity on wind responses of high-rise buildings

Abstract This paper investigates the effects of structural damping and eccentricity on the wind responses of high-rise buildings. Wind tunnel experiments were conducted on a 6-mass-point aeroelastic model with a side span ratio of 2 and an aspect ratio of 5. The experimental results are compared with analytical results by modal spectrum analysis using the wind force obtained from a dynamic balance over the applicable range of the analytical method without the motion-induced wind force. The aerodynamic damping from the autocorrelation function of the response acceleration for the tertiary mode, where torsional vibration is dominant, is also obtained.

EFFECTS OF SIDE RATIO ON CHARACTERISTICS OF ACROSS-WIND AND TORSIONAL RESPONSES OF HIGH-RISE BUILDINGS

Abstract With regard to studies conducted using aeroelastic models with the torsional degree of freedom, self-excited vortex-induced vibration and torsional flutter occur during torsional vibrations in the case of a structure with a side ratio D / B ( D : depth, B : breadth) of 2 or more. These results suggested the necessity of investigating aerodynamic instability during torsional vibrations. The authors have been carrying out a detailed investigation by wind tunnel tests using 6-mass-point aeroelastic models into the effects of density ratio, structural damping and eccentricity in the across-wind and torsional response characteristics of a high-rise building with a side ratio of 2 (Katagiri et al., Paper for Ninth International Conference on Wind Engineering, 1995, pp. 1408–1419). In this study, the effects of the side ratio on wind response characteristics are investigated.