Wind Tunnel Investigations of Torsional Wind Loads Acting on Rectangular Prisms

• Main Authors: Fu, Chung Lin, 傅仲麟
• Other Authors: Cheng Chii-Ming
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/42956006373303696659

碩士 === 淡江大學 === 土木工程學系 === 85 === Due to slenderness and less rigidity of modern building, wind loads become the dominate lateral force for highrise building design . The fluctuating wind loads acting on hig-rise building consist of drag force , periodic acrosswind force due to vortex shedding and torsional force due to load asymmetry. The paper studies torsional force on a rectangular prism with various cross sectional length -to-width ratio in two simulated atmospheric boundary layer flows .The experiments were performed by a new pressure-measured system. Through this system ,pressures at four side of rectangular prisms can be measured simultaneously, and then relationship between torsion and drag force ,lift force can be obtained. The results indicate that torsion will increase with length -to- width ratio .when length - to-width ratio less then critical value , 70%~90% of torque comes from asymmetries pressure distributions on the leeward side . If length -to-width ratio greater then critical value ,50%~90% of torque comes from the side face ,,the contributions increase with length -to-width ratio. The contributions to the torque from the two half forces of each side are opposite to each other and tend to cancel out .Therefore , the vortex shedding peak in the pressure spectrum on side face doesn''t appear in the torque spectrum .However , the contributions to the torque from the two leeward half faces are the same , the effects tend to add up .So the vortex shedding peak will appear in the torque spectrum .