Stability of highly damped concrete beam-columns

Abstract

In an earlier paper, authors have investigated the static and dynamic stability of cracked concrete flanged conservative beam-columns. The cantilever column witha lumped mass at its free end is subjected to an axial compressive force and alateralforce. Two critical values each of the axial and lateral loads are defined. Loss of static stability is predicted to occur by excessive displacements or brittle buckling while dynamic instability called divergence is shown to occur by vanishing natural frequency. In this paper, the dynamic stability of highly damped concrete beams-columnsis investigated. Two measures-damping ratio and damping coefficient-of structural damping have been employed. Critical loads and displacements are not affected by level of structural damping. Application of inadmissible set of loads results in dynamic instability by divergence at all levels of damping. In particular cases, highe damping has been predicted to destabilize even these conservative structures. Effect of initial conditions and higher damping on the inelastic stability, passive stability controland creep buckling of concrete beamcolumns have been delineated. Theoretical significance and practical relevance of the paper are also discussed.