Wind Deflections of Tall Concrete Frame Buildings

Compact and inexpensive seismographs and tiltmeters have been developed during this project to measure the large displacement, low frequency oscillations of tall buildings due to wind. They were used to record the motion and tilt of a 55-story concrete frame building in Chicago for a period of 30 days. Simultaneous recordings were made of (1) displacement in orthogonal horizontal directions at diagonal corners of the top floor; (2) tilt in two orthogonal directions at diagonal corners of the top floor, the center of the 42nd floor, and the center of the 3rd floor; and (3) wind direction and velocity above top of building. At a recorded wind velocity of 70 mph it was found that the top of the building leans over 1.5 in. and oscillates through a peak-to-peak displacement of 1.0 in. with a fundamental period of 4.0 sec. Fundamental and third mode vibrations were observed.