PVP2006-ICPVT11-93903 EXPERIMENTS ON THE PLANAR LATERAL VIBRATION OF A VERTICAL FLUID-CONVEYING PIPE WITH AN END MASS

ABSTRACT This paper experimentally examines lateral vibrations of a cantilevered pipe that is hung vertically with an end mass and conveys fluid with a flow velocity that is entirely constant. It is well known from linear stability theory that when the velocity of a fluid exceeds a certain value, a certain characteristic mode of pipe vibration becomes unstable. Moreover, higher modes of pipe vibration become unstable simultaneously with increasing flow velocities. We are interested in the case in which two-frequency oscillation occurs in the pipe involving the above two unstable modes at higher flow velocities. This phenomenon will be called mixed mode flutter. This phenomenon for a cantilevered pipe is essentially different from the cases of a pinedpined or clamped-clamped pipe with two marginal modes. In these cases, only the higher mode of the pipe vibration becomes unstable while the lower mode becomes stable at much higher flow velocities. Experiments were conducted with a silicon rubber pipe conveying water. The planar behaviors of the vertical fluid-conveying pipe with an end mass were observed using an image processing system that is based on the images captured by two CCD cameras. As a result, lower mode flutter, unstable mixed-mode flutter and also higher mode flutter were experimentally confirmed for the cantilevered pipe. Furthermore, the above phenomena are discussed using the basic equation of nonlinear planar lateral vibration of a vertical fluid-conveying pipe with an end mass from the viewpoint of nonlinear dynamics

The Stress Distribution of a Transmission Tower Affected by Unbalanced Tension of Conductors under Strong Winds

Unbalanced tension load is defined as a load directed along the conductor, and its load scale greatly varies according to the conductor\u27s supporting system, the span length between the towers, and the conductor\u27s horizontal and vertical angle against the tower. Unbalanced tension load is an important factor which should be considered when designing Japanese transmission towers, which are typically constructed in mountainous areas. We then carried out non-linear stress analysis for wind loads on a transmission tower, assembled a record of strong winds resulting from recent typhoons that passed through Kyushu. As a result, it was revealed that a large unbalanced tension load was applied to the line; therefore, we studied to find an appropriate countermeasure for it

2008年3月から5月にかけて鹿児島県で発生した竜巻等による被害について : いちき串木野市、垂水市、枕崎市および中種子町での被害

We know many tornadoes hit frequently Kagoshima Prefecture. Since March, 2008 when Japan Meteorological Agency has started release of information calling for attention on a tornado, several tornados have hit Kagoshima Prefecture. Two tornados hit lchiki-kushikino City and Tarumizu City, Kagoshima Prefecture, on March 27 and more than 80 residential houses and agricultural facilities were damaged. Fortunately, there was no human damage. Some green houses in Makurazaki City have suffered damage due to a tornado on April 9 and gusty winds blew in Nakatane City in Tanegashima Island on May 1. The authors report the outline of damage to buildings and residential houses at lchiki-kushikino City and Tarumizu City based on the authors' findings of a post disaster investigation

送電線支持部材の応力分布に及ぼす強風時電線不平均張力荷重の影響

Unbalanced tension load is defined as a load directed along the conductor, and its load scale greatly varies according to the conductor's supporting system, the span length between the towers, and the conductor's horizontal and vertical angle against the tower. Unbalanced tension load is an important factor which should be considered when designing Japanese transmission towers, which are typically constructed in mountainous areas. We then carried out non-linear stress analysis for wind loads on a transmission tower, assembled a record of strong winds resulting from recent typhoons that passed through Kyushu. As a result, it was revealed that a large unbalanced tension load was applied to the line; therefore, we studied to find an appropriate countermeasure for it

送電線吊架ジャンパ装置の揺動による鉄塔部材の発振特性に関する振動試験

A hanging jumper beam of a transmission tower is adopted as a countermeasure against a short fault of jumper conductors under strong winds. However it is thought that the hanging jumper beam may cause the vibration of transmission tower members due to its weight when the hanging jumper beam starts to vibrate under strong winds. The authors have conducted an excitation test of a strain transmission tower with the hanging jumper beam to comprehend the dynamic behaviors of the hanging jumper beam. As a result, it was found that a big pendulum vibration of the hanging jumper beam generates twice the natural frequencies of the normal and tangential components of the beam vibration which induce a vibration of the tower in the direction of conductors. Moreover, some results of our wind response measurement revealed that the interactions between the hanging jumper beam and the tower components were more complicated than under a light wind due to the effects of cross arms, tower, conductors and insulators