Natural Periods of Vibration of Buildings

TLDR: In this article, the measured periods of vibrations of a large number of buildings are used to compare the merits of existing formulas and of equations derived using a rational approach, and it is concluded that no single, simple, empirical equation will give reasonably accurate estimates for the periods of buildings having shear wall characteristics.

Abstract: The measured periods of vibrations of a large number of buildings are used to compare the merits of existing formulas and of equations derived using a rational approach. It is concluded that no single, simple, empirical equation will give reasonably accurate estimates for the periods of buildings having shear wall characteristics. The calculated periods of steel frame buildings are found to be proportional to the square root of the number of stories rather than directly proportional as is usually assumed. However, observed periods of such buildings indicate that the steel frame alone would contribute only about 25% of the effective stiffness. The dependence of the period on the flexibility of the floor girders is also demonstrated using a digital computer. Calculations show that these buildings behave essentially as if they had rigid floor girders, although the girders of the steel frames themselves are very flexible, so far as the period of vibration is concerned. Additional studies of the natural periods of actual structures are recommended.