Abstract 1. 1. The fact of E t ≠ E c , obtained by the tension and compression tests of a concrete bar, has given us an interesting suggestion that in a concrete bar the longitudinal vibration shows a kind of asymmetric vibration, and consequently, the time-displacement curve of any element of it, by which the amplitude and frequency for the two types of vibration —namely those of the tension and compression sides-can be calculated, has been obtained. 2. 2. By the practical method of Fourier's analysis, the harmonic expression of the above time-displacement curve has been obtained, and its close coincidence with the original time-displacement curve has been obtained.