Damping Formulae for Reinforced and Partially Prestressed Concrete Beams

Abstract

A full-size test program was carried out on 26 simply-supported and continuous reinforced and partially prestressed concrete beams to study the cracking behaviour and damping characteristics of concrete beams. The beams were subjected to free vibration tests and logarithmic decrement values corresponding to each load level were measured. Separate regression analyses on the reinforced and the partially prestressed beams were undertaken. These analyses resulted in two separate empirical formulae for predicting the logarithmic decrement of damping in reinforced and in partially prestressed beams. Comparison with test results from all 26 beams indicates that the predictions are accurate. It is also found that the damping formula for reinforced beams is applicable to both single and continuous spans. The proposed damping formulae predict damping from the residual crack widths of the beams. As such, formulae developed for predicting residual crack widths from given variables defining the beams and their deflection-span ratios are also reported.