Seismic Performance Assessment of Conventional and Retrofitted Buildings Considering Nonstructural Systems

Abstract eng:
Inadequate nonstructural seismic performance during recent earthquakes has led to extensive repair costs and lengthy functional disruptions. This study investigates the application of fluid viscous dampers (FVDs) to minimize nonstructural damage. Studies on damper placement have focused on structural parameters, however repair costs are a more appropriate measure. Damper placement and amount of supplemental damping are examined. A conventional 16-storey concentrically braced frame (CBF) building and six FVD retrofitted designs are created. Nonlinear time history analyses are performed in OpenSees and the FEMA P-58 performance assessment procedure is used to calculate repair costs. The conventional building sustained extensive damage to structural and nonstructural systems. The FVD retrofitted designs achieved reductions of approximately 50% in both the ultimate limit state (ULS) and serviceability limit state (SLS) repair costs. Negligible SLS structural damage occurred, which is critical for achieving immediate occupancy. Increasing the total damping from 20% to 35% reduced repair costs by an additional 5% to 7% for the ULS, in contrast to a previously suggested maximum damping of 20% to 25%. Stiffness proportional placement produced lower repair costs than uniform placement, supporting placement techniques that concentrate dampers near the bottom of the structure. Limitations of the Eurocode 8 damage mitigation methodology were exposed. It was found that an interstorey drift limit of 0.5% should be prescribed for CBF structural damage prevention rather than 1%. The 0.5% limit did not prevent nonstructural damage. Advanced placement techniques may further decrease repair costs and is the subject of ongoing research by the authors.

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