Viscous and hysteretic damping

Impact of capacity design violation in augmented structural systems


Capacity design, while protecting a structure against undesirable energy dissipations, has major implications on member sizes and overall cost. Furthermore, in some situations where protected elements possess some inelastic deformation capacity, it may be unwarranted. One of these situations is when the forces applied to the protected elements result from viscous dampers. This is because when viscous forces cause yielding in an element, the element deforms, so no deformation in the viscous damper is required. If no deformation is required, the velocity is zero, so there is no force. This implies that very little inelastic yielding is likely to occur in protected elements.

In order to investigate whether or not this is so, a single storey structure was designed and fitted with braces to reduce its response. Both hysteretic and viscous braces were used to obtain the same peak displacement response. The column strength was decreased by a fixed percentage and inelastic dynamic time history analysis was conducted. The amount of energy dissipated in the columns was then compared to determine whether hysteretic braces or viscous braces caused more column yielding so that appropriate over strength values could be developed for different brace types. It was found that the amount of energy absorbed by the column depends on the period but also on the brace design ductility. However, irrespective of the period or design ductility, the column hysteretic energy dissipated by a viscous brace was lower than that dissipated by a hysteretic brace. It follows that column yielding may be significantly less critical for viscous, rather than for hysteresis, braced structures.


Bradley, B. A., Dhakal, R. P., Mander, J. B., Li, L. (2008). "Experimental multi-level seismic performance assessment of 3D RC frame designed for damage avoidance." Earthquake Engineering & Structural Dynamics 37(1): 1-20. Doi: 10.1002/eqe.741 DOI:

Rodgers, G. W., Solberg, K. M., Chase, J. G., Mander, J. B., Bradley, B. A., Dhakal, R. P., Li, L.. (2008). "Performance of a damage-protected beam–column subassembly utilizing external HF2V energy dissipation devices." Earthquake Engineering & Structural Dynamics 37(13): 1549-1564 Doi: 10.1002/eqe.830 DOI:

Somerville, P., Smith, N., Punyamurthula, S., and Sun, J. (1997). "Development of Ground Motion Time Histories For Phase II Of The FEMA/SAC Steel Project, SAC Background Document Report SAC/BD-97/04."

How to Cite
Labise, C. C., Rodgers, G. W., MacRae, G. A., & Chase, J. G. (2012). Viscous and hysteretic damping. Bulletin of the New Zealand Society for Earthquake Engineering, 45(1), 23-30.

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