Forced vibration and natural frequencies of tall building frames

A procedure is presented for determining the response of a tall building frame to a harmonic motion of the ground. The procedure takes account of the elastic effects of the horizontal beams and requires the use only of a desk computer. Normal modes and natural frequencies can be determined to any desired degree of accuracy by trial and error. Response to any arbitrary motion of the ground can be determined in terms of the responses of the normal modes or, alternatively, by superposing the responses of the complete frame to each harmonic of the motion.