Earthquake economic losses in moment-resisting steel frames equipped with fluid viscous dampers

The implementation of fluid viscous dampers can improve the seismic performance of a structure, especially in terms of collapse capacity and inter-story drift reduction. However, little attention has been given to the acceleration demand on non-structural elements attached to viscously damped structures and how the different parameters (i.e. velocity exponent, level of added supplemental damping, damping constant distribution and brace stiffness) involved in the design of viscous dampers affect the acceleration demand. Recent earthquakes worldwide have demonstrated the great impact of acceleration-sensitive non-structural elements on the total economic losses, as these elements represent a large part of the total building investment. In order to assess the impact of implementing fluid viscous dampers on the expected annual losses of buildings, three steel moment-resisting frame archetypes of different heights and dynamic properties were equipped with linear and nonlinear viscous dampers incorporating six different velocity exponents, designed by two different approaches for three targeted added supplemental damping ratios (total of 111 archetype buildings). Incremental dynamic analyses were carried out with the FEMA P-695 far-field ground motion set scaled to ten different intensities. The collapse fragility functions, the median peak inter-story drifts, the median peak floor accelerations, and the median residual drifts were then calculated. Based on these results and furnishing the buildings with typical non-structural elements for office use, the FEMA P-58 loss estimation methodology was applied to estimate the expected annual losses for all building archetypes. The numerical results show that the different parameters involved in the design of fluid viscous dampers have an important impact on the acceleration demand of non-structural elements, and thereby, in the expected annual losses of the archetype buildings.