Shaking Table and Numerical Seismic Performance Evaluation of a Fluid Viscous-Dissipative Bracing System

A shaking table campaign was carried out on a 2:3-scale, two-story steel frame structure retrofitted by a dissipative bracing system incorporating pressurized fluid viscous spring-dampers. Up to 1.16 g peak ground accelerations were imposed in the most severe of the 33 tests developed. The response was always elastic, with maximum interstory drift ratios limited below 0.62%. The protection technology, in fact, features high dissipative capacities and produced equivalent linear viscous damping coefficients up to 37.5%. A numerical enquiry carried out on the test structure in its original unbraced configuration showed interstory drift reductions from about 80% to about 90% when passing to dissipative braced conditions. A final performance-based analysis developed in terms of interstory drifts and beam and column rotations, in compliance with the criteria formulated in ASCE/SEI 41-06 Standard, emphasized three through five enhancements of building performance in retrofitted conditions for the four earthquake levels examined.