Torsional wave propagation in reinforced concrete columns

Using a semi-analytical finite element (FE) method, the torsional phase velocity spectra of elastic waves were investigated for reinforced concrete (RC) columns with and without exterior composite layers. An examination of the spectra of these two types of columns shows that the retrofitted columns have a slightly smaller phase velocity in their first mode. In addition, the first mode shapes exhibit marked warping induced by the vertical bars. Comparisons of the exact phase velocity of the first mode with those calculated from elementary theories indicate that the elementary theories give a poor prediction of the torsional wave speed even at the long wavelength limit. This inaccuracy, which comes from not including the effect of warping, can be overcome by computing the torsional rigidity utilizing Saint-Venanrs semi-inverse method for torsional warping. ( 1998 Elsevier Science Ltd. All rights reserved