Multi-level performance-based design optimisation of steel frames with nonlinear viscous dampers

Abstract This paper presents a practical multi-level performance-based optimisation method of nonlinear viscous dampers (NVDs) for seismic retrofit existing substandard steel frames. A Maxwell model is adopted to simulate the behaviour combined damper-supporting brace system, with fractional power-law force–velocity relationship NVDs, while distributed-plasticity fibre-based section approach used beam-column members thus incorporating nonlinearity parent frame in design process. The optimum height-wise distribution damping coefficients NVDs satisfying given performance requirements identified via uniform damage (UDD) philosophy. efficiency proposed illustrated through time-history analysis 3-, 7- and 12-storey frames under both artificial natural spectrum-compatible earthquakes. Sensitivity performed investigate effects initial distribution, convergence factor uncertainty ground-motion prediction on strategy. final solution also investigated by using drift-based, velocity-based, energy-based UDD approaches identify most efficient index parameter purposes. It found that regardless selected parameter, methodology leads exhibiting lower maximum inter-storey drift, local (maximum plastic rotation) global compared an equal-cost distribution. However, drift-based generally results better performance. shown can be efficiently satisfy multiple objectives at different intensity levels earthquake excitation, line recommendations current codes. easy implement purposes represents simple yet tool NVDs.