Expected seismic response and annual seismic loss of viscously damped braced steel frames

The economic losses observed in the last decades following moderate and large seismic events have demonstrated the importance of considering structural and nonstructural responses to evaluate the seismic performance of a building. In this regard, the implementation of fluid viscous dampers can improve the seismic performance of buildings, however, the conventional seismic design procedures of viscously damped structures focus on reducing the induced structural displacement while neglecting the acceleration response, ignoring the influence of different design parameters on the overall seismic response. This study assesses the seismic performance of steel moment-resisting framed buildings retrofitted with fluid viscous dampers by comparing their expected annual loss. To achieve this, three archetype buildings were retrofitted with different configurations of fluid viscous dampers and were subjected to nonlinear time-history analysis using the FEMA P695 far-field ground motion set as seismic input, retaining their peak story drifts, residual drifts, and peak floor accelerations, and computing their probability of collapse. The archetype buildings were also equipped with nonstructural elements and contents typical of office use, and the expected annual loss was computed using the procedure and tools proposed by the FEMA P-58 methodology. The results show that the design parameters of fluid viscous dampers can have a significant effect on the expected annual loss, with some configurations showing expected losses larger than those of the archetype buildings without dampers. In addition, it was observed that the lower expected annual loss tends to be associated with fluid viscous dampers with high axial stiffness and mid-range values of the other design parameters, such as 20% of supplemental damping and velocity exponent values near 0.5.