This contribution presents a multi-level optimization procedure of nonlinear viscous dampers (NVDs) for the seismic retrofit of existing substandard steel frames. The procedure is based on the concept of uniform damage distribution (UDD) and aims to identify the best characteristics of NVDs to satisfy pre-assigned design requirements. The damper-brace elements are simulated with a Maxwell model comprising a dashpot with power law force-velocity behavior in series with a linear spring simulating the stiffness of the brace-damper system. The beam and column members of the steel frames are modelled with a distributed-plasticity fiber-based section approach. The optimization procedure is based on iterative nonlinear time-history analyses performed in OpenSees interfaced with an external subroutine written in MATLAB that governs the adjustment of the damper properties. The method is developed with reference to a set of synthetic and natural earthquakes compatible with the Eurocode 8 response spectrum. The effectiveness of the design procedure is illustrated through examples on 3-, 7- and 12-storey substandard steel frames. It is demonstrated that the proposed procedure leads to frames with reduced maximum inter-story drift, maximum plastic rotation and global damage index compared to an equal-cost uniform damping distribution. A slight variant of the procedure is also capable to comply with multiple performance objectives at different intensity levels of the earthquake excitation, thus realizing a multi-level optimization of the nonlinear viscous dampers. This is of practical importance in view of current performance-based design guidelines of seismic standards.

Multi-level optimisation of nonlinear viscous dampers for seismic retrofit of substandard steel frames

De Domenico D.
Primo
;
2021-01-01

Abstract

This contribution presents a multi-level optimization procedure of nonlinear viscous dampers (NVDs) for the seismic retrofit of existing substandard steel frames. The procedure is based on the concept of uniform damage distribution (UDD) and aims to identify the best characteristics of NVDs to satisfy pre-assigned design requirements. The damper-brace elements are simulated with a Maxwell model comprising a dashpot with power law force-velocity behavior in series with a linear spring simulating the stiffness of the brace-damper system. The beam and column members of the steel frames are modelled with a distributed-plasticity fiber-based section approach. The optimization procedure is based on iterative nonlinear time-history analyses performed in OpenSees interfaced with an external subroutine written in MATLAB that governs the adjustment of the damper properties. The method is developed with reference to a set of synthetic and natural earthquakes compatible with the Eurocode 8 response spectrum. The effectiveness of the design procedure is illustrated through examples on 3-, 7- and 12-storey substandard steel frames. It is demonstrated that the proposed procedure leads to frames with reduced maximum inter-story drift, maximum plastic rotation and global damage index compared to an equal-cost uniform damping distribution. A slight variant of the procedure is also capable to comply with multiple performance objectives at different intensity levels of the earthquake excitation, thus realizing a multi-level optimization of the nonlinear viscous dampers. This is of practical importance in view of current performance-based design guidelines of seismic standards.
2021
978-618-85072-5-8
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11570/3219018
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