The second frequency spectrum of timoshenko beams

This paper investigates the reported existence of a second spectrum of frequencies of vibration of Timoshenko beams. A concept of coupled vibration is introduced and is used to explain the behaviour of the Timoshenko beams with various end conditions. It is shown that except for the special case of a highed-hinged beam there is no separate second spectrum of frequencies. It is also shown how several previous investigators misinterpreted the frequencies obtained for the Timoshenko beam and hence introduced the notion of a second spectrum of frequencies.