A new conductor of low-wind drag type with an 18-polygonal cross-section for overhead transmission line has been developed. Aerodynamic characteristics of the conductor regarding the mean drag coefficient were studied by wind tunnel tests, including effects of wind speed and turbulence intensity. As a result, 50% reduction of drag coefficient has been achieved under designing wind speed condition. The mechanism of wind drag reduction of the conductor was also studied by flow visualization tests in a water tunnel based on Reynolds similarity law. The flow visualization test revealed that “drag crisis” arises in the flow around the new conductor by effects of polygonal cross-section at Reynolds number an order of magnitude lower than that of a smooth circular cylinder.
Wind loads on free-standing canopy roofs have been studied experimentally. Two series of wind tunnel experiments were carried out. In the first series, simultaneous pressure measurements were made for three types of roof geometries, i.e. gable, troughed and mono-sloped, with relatively low pitches (up to 15o). In the second series, the overall wind forces and moments were measured for gable and troughed roofs with medium pitches, 20o to 30o, using a force balance. Correlation between the wind force and moment coefficients is investigated, and appropriate wind force coefficients for the design of main force resisting systems are proposed. Axial forces in the columns supporting the roof are regarded as the most important load effect. Two loading patterns causing the maximum tension and compression of columns are considered. The effect of obstruction under the roof on the wind force coefficients is also investigated.
Characteristics of wind-induced response of cable-stayed bridges with two steel edge girders were studied experimentally, and the effects of the Separation Interference Method and its applicability regarding the structural rationality were discussed. Two types of edge girders, i.e., I section and box girders, were considered. The vertical wind-induced responses of two I section girders were suppressed by locating the girders at the inner position. However, this requires additional bracket beams that anchor the stay cables, and may not be economical. The wind-induced responses of two box girders were generally suppressed by applying the Separation Interference Method without additional aerodynamic appendages such as fairings. This case does not require additional bracket beams and can possibly be used as an economical choice.
The purpose of this research is to construct a database of a non-stratified airflow past a steep simple terrain under an imposition of a uniform flow, and, in addition, is to do the accuracy inspection of the numerical model under development at present. This numerical model is referred to as the RIAM-COMPACT (Research Institute for Applied Mechanics, Kyushu University, Computational Prediction of Airflow over Complex Terrain), and is for the purpose of the prediction of airflow over complex terrain with several m to several km. This paper describes the experimental and numerical study of a non-stratified airflow past a three-dimensional isolated-hill in a uniform flow as the second phase. The Reynolds number, based on the uniform flow and the height of the hill, is about 104. Airflows around the hill include the unsteady vortex shedding. Attention is focused on airflow characteristics in a wake region. For this purpose, the velocity components in the streamwise direction were measured with a SFP (Split-Film Probe) in the wind tunnel experiment. In addition, the flow visualization was performed by using the smoke-wire technique. Through comparison of the experimental and numerical results, they showed a good agreement. The accuracy of both of the wind tunnel experiment by the SFP and also numerical simulation by the RIAM-COMPACT were confirmed as the result.
This report presents damage to roofs of SPring-8, which is the world's largest third-generation synchrotron radiation facility at Harima Science Garden City in Hyogo Prefecture, caused by Typhoon No.0416 on August 30, 2004 and No.0418 on September 7, 2004. As the results of the field studies, it is considered that the damage to roofs was due to not the wind power by the typhoon but due to strength decrease of bolts which had fixed roof materials.