The Earthquake Engineering Online Archive

Dynamic behavior of a multistory pyramid-shaped building

Stephen, Roy M.; Hollings, Jeffrey P.; Bouwkamp, Jack G.

UCB/EERC-73/17, Earthquake Engineering Research Center, University of California, Berkeley, 1973, 99 pages (545.1/S73/1974)

This report describes the experimental and analytical studies of the dynamic behavior of the Transamerica Building, a multistory pyramid-shaped steel structure, sixty stories in height, located in San Francisco, California. The 853 ft high building has a square plan, 174 ft by 174 ft and consists of a two-story high ground floor, a triangularly shaped tubular space truss around the perimeter between the 2nd and 5th floor levels and above this level, a moment resistant frame with the exterior walls sloping inward at an approximate ratio of 1 to 11. The upper 10 stories consist of an open-framed pyramid-shaped structure which is not occupied. On the east and west sides of the building, starting just below the 30th floor, shafts project from the building which contain elevators on the east side and a stairwell and duct shaft on the west side. The experimental work consisted of both forced vibration and ambient studies in which the natural frequencies, mode shapes and damping values were determined. These experimental values are compared to the analytical model results. The natural frequencies determined by all these methods agree very closely for the translational motion. However, the agreement for the torsional motion does not seem to be as good. The first four mode shapes are compared for the three methods. The first and second modes seem to agree very well; however, at higher modes discrepancies are noted. The damping capacities determined experimentally from the frequency response curves range from .7 to 2.8 percent.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-73-17.pdf (9 MB)