Performance-Based Optimisation of Friction Energy Dissipation Devices in Sub-Standard Steel Structures

Energy dissipation devices are extensively implemented to improve the seismic resilience of both newly constructed and existing retrofitted structures in a cost-effective manner. The engineering of these devices is intricate due to their sophisticated and non-linear response to seismic activities. Present optimisation strategies for these non-linear systems are characterised by high costs and significant computational demands, underscoring the necessity for more efficient optimisation approaches. This research introduces for the first time a practicable multi-level performance-based optimisation design method for nonlinear friction-based dampers (e.g., Rotational Friction Dampers (RFDs) and Chevron Dampers) across various multi-storey structures (3,7 and 12-storey frames with 3 spans) and examines the efficiency of different patterns of slip load distribution under fifteen natural and six artificial spectrum-compatible earthquake records. A novel cost-effective, multi-criterion performance-based optimisation approach is employed for seismic retrofit of existing substandard steel frames, utilising the Uniform Distribution of Deformation (UDD) concept, achieving predefined performance objectives across varying earthquake intensities. This research identifies the optimal distribution of slip forces across dampers through a Uniform Damage Distribution approach, enhancing the structural response to seismic activities. To investigate the efficacy of friction dampers under unexpected seismic intensities, a Self-Adaptive Passive Optimisation Method (SAPOM) has been devised. This method adjusts the mechanical attributes of the dampers, like slip load, to align with the peak displacement requirements until the predetermined performance criteria are met. The results demonstrate the efficiency of the suggested design methodology in managing the uncertainties related to future seismic events. This is achieved through a comparative analysis of outcomes derived from both simulated and real earthquake data, including the results from a single simulated event, the mean of multiple simulated records, and the mean of several actual earthquake records. The performance-based UDD optimisation technique effectively minimises the quantity of friction dampers and the supplemental loads imposed on the primary structure, all while achieving specified performance criteria during design-level seismic events. The proposed self-adaptive passive design approach proves more efficient and applicable across a broad range of seismic records compared to conventional passive methods. The proposed method notably decreases the quantity of bracing components and the structural loads relative to conventional code-based braced frame designs. It accomplishes multiple performance targets during design-level seismic events, adhering to the performance-based design guidelines outlined in current seismic standards. This approach is not only practical for implementation but also offers a straightforward and efficient tool for the optimal seismic retrofitting of steel frames with friction-based dampers.