Performance of viscous damping in inelastic seismic analysis of moment‐frame buildings

Summary This paper investigates the performance of viscous damping in the inelastic seismic analysis of moment‐frame buildings using a detailed model of a 20‐story steel structure. Damping schemes included are Rayleigh, condensed Rayleigh, Wilson‐Penzien, tangent Rayleigh, elastic velocity Rayleigh, and capped damping. Caughey damping is found not to be computationally viable. Differences among the damping schemes, as quantified by plastic hinge rotations and story drifts, become noticeable once these quantities reach the 3% level. In order of least to greatest hinge rotations and story drifts that occur under lateral response to horizontal ground motion, the damping schemes rank as Rayleigh (most damping action), condensed Rayleigh, Wilson‐Penzien, tangent Rayleigh and capped damping, which are about the same, and elastic velocity Rayleigh (least damping action). Performance of Rayleigh damping under vertical ground motion is discussed, including the effect of soil‐structure interaction. The propensity of Rayleigh damping to generate excessive damping forces and moments during inelastic seismic analysis is explained, and a parameter is introduced that can predict the potential magnitude of the effect. A review of some literature on amplified Rayleigh damping moments is also presented.