ANALYSIS OF FREE-VIBRATIONS OF TALL BUILDINGS

An analysis Of free vibrations Of tall buildings. such as frame, shear -wall, and frame-shear-wall structures, is proposed and discussed in t his paper. Frame buildings are treated as shear beams with varying cro ss sections, the solutions of mode shapes of such buildings are expres sed in Bessel's functions, and the parameter of determining the fundam ental period can be found from a figure provided in the paper. Based o n the fact that the shear deformation and bending deformation are all considered for shear wall and frame-shear-wall structures. the formula s for calculating free vibrations of such structures are presented. It is very simple and convenient to apply these formulas to dynamic anal ysis of tall buildings. The measurement results and statistical analys is of frame, shear-wall, and frame-shear-wall structures in sites, and three examples of determining free vibrations of structures are also given in this paper. The examples show that the effect of shear deform ation on the first natural frequency is not significant. but the effec t of that on higher natural frequencies may not be neglected.