Hisao Marukawa

Analytical study on wind-induced vibration of power transmission towers

Abstract This paper describes a method for analyzing wind-induced vibrations of power transmission towers coupled with power lines and the results of two case studies. It also discusses the influence on response characteristics of differences in transmission support systems and differences between peak factors, computed from a time -series and from power spectrum density. The results of this study show that differences in the way power transmission towers support power lines have an influence on response characteristics, and peak factors computed from a time-series response are greater than those computed from power spectrum density.

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.

Full scale measurements of wind velocity in two urban areas using an ultrasonic anemometer

Abstract This paper describes the results obtained from the measurements of the characteristics of wind turbulence in urban areas through the use of ultrasonic anemometers. The data used in this paper is what which was gained from the year long observation extending from January 1990 through December 1990 and during two typhoons No. 8922 and No. 9011. The values of the turbulence intensity at a height of less than 100m were approximately 10%–15% larger than those recommended for corresponding urban areas by the AIJ standard, in which the specified power index of the wind profile is set at 0.3. The shape of the power spectral density for the u component agrees fairly well with the shape of the Karman type spectrum. The power spectral density of the v component is quite similar to the karman type spectrum for the u component.

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.

Full-scale measurements of wind-induced vibration of a transmission line system in a mountainous area

This paper clarifies the characteristics of wind and wind-induced vibration of an electrical transmission tower installed on a mountainous area, based on full-scale data obtained at wind speed of less than 25 m/s. The data was collected between 1991 and 1993. As a result, it can clearly be seen that difference of wind direction has a strong influence on wind characteristics. The vibration characteristics of the tower with conductors are strongly influenced by the behavior of the conductors. The aerodynamic damping of the conductors plays an important role in their total damping. The response values for acceleration, strain of the tower with conductors, and tensile forces of conductors increase in proportion to the power of the wind speed. In general, the value of each power index is less than 2.

Full-scale measurement of wind pressures and response accelerations of a high-rise building

Abstract This paper describes the results of full-scale measurements of wind pressure and wind-induced response acceleration for an 18 storey building 68 m high. It also gives estimates of the response acceleration of this building in accordance with the AIJ Standard for Loads and External Forces on Buildings and Structures, the National Building Code of Canada, and the method suggested by Ohkuma and co-workers. The values of estimated response acceleration correspond to the values of the full-scale measurements.

Across-wind and torsional acceleration of prismatic high rise buildings

Abstract A simple empirical formula for the estimation of across-wind and torsional acceleration of prismatic high rise buildings is examined through a wind tunnel test. In the wind tunnel test, the side ratios (D/B, D:depth, B:breath) of the models are between 0.3 and 5, and the aspect ratio H/√A H:buildings height, A:plan area) are between 4 and 8. As to the approaching flows, two kind of boundary layers representing open and urban flow conditions are applied. In the formula the response acceleration is expressed in proportion to the power of the mean wind velocity. The characteristics values derived from the formula are compared with the values from the test, the codes and other studies. Furthermore an expression for the power spectral density of the across-wind overturning moment is suggested for better estimation of the across-wind acceleration. There is a difference of less than 10% between the estimated value obtained through the use of the proposed equation and the value from the wind tunnel test.

Study of wind-induced response of long-span structure

Abstract In this study, a wind tunnel test was conducted for an actually designed long-span structure whose roof consisted of two different shapes. Based on the data obtained from this experiment, we simulated a multi-point fluctuating wind pressure time series by the Monte Carlo method. Then, a modal time series response analysis was carried out using the wind pressure time series, in order to investigate the effect of higher mode vibrations on estimation of member displacement and stress.

Numerical analysis of overhead transmission line galloping considering wind turbulence

This study aims at clarifying the factors that cause transmission line galloping and the conditions influencing it, and at determining response evaluation indices of gallopings in turbulent flows. This is done using a three-dimensional analytical method considering a large deformation. The analysis is based on four-bundle transmission lines. Obtained results are as follows: 1 The occurrence of galloping in the smooth flow is limited by the combination of the following parameters: the initial angle of wind attack, the initial icing angle, and the wind speed. The galloping predominates mainly with one or two of the lowest in-plane, out-of-plane, and torsional modes for the free vibration under the conditions that the transmission line is subject to dead load as well as static wind force. However, the galloping always occurs with torsional vibration. 2 The shape of the Lissajous figure for displacement depends on the initial angle of wind attack and the initial icing angle, as well as wind speed. The main shapes are vertically elliptic, horizontally elliptic, and a configuration having the shape of a horizontally rotated figure of eight. 3 The predominant frequency components of gallopings in turbulent flows are amplified and controlled by the turbulence intensity. Vibration frequency components unrelated to galloping increase linearly with rise in turbulence intensity. 4 There is a time lag of 30 s between galloping vibration and the fluctuating wind speed. The relationships between mean wind speeds and both trend components and standard deviations of galloping in turbulent flows closely correspond to those relationships during the smooth flow, and they can be obtained using the average time of 10 times the shortest vibration period of the transmission line. That is, the response values of transmission lines in the smooth flow can be utilized to estimate gallopings in turbulent flows. To estimate the maximum amplitude of a galloping, a peak factor of approximately 2.5 can be used.

Wind-induced vibration of transmission line system

Abstract This paper describes results of a full-scale measurements and a time series analysis for the wind-induced vibration of a transmission line system. The time series analysis is based on a quasi-static assumption. The study is mainly discussed as in terms of the effects of the coupling motion between a steel tower and conductors. This is accomplished through comparing the results of measurement with calculated ones. As for the analytical response value of the coupled steel tower, the power spectrum of the response displacement has many peaks at the points that correspond to the natural frequencies of the tower, conductors and their coupling motion. Furthermore, in the frequency range which coincide with the natural frequencies of the conductors, are recognized on an interaction response between different vibration modes. Those coupling response characteristics are prominent in a longitudinal direction and are affected by the modeling manner of the supporting condition of the end of the conductors. As is explained above, the qualitative tendencies for the analytical value are in good agreement with the measured ones. However, quantitatively there were differences between their values.