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Title: Performance-based optimisation of friction energy dissipation devices in RC structures
Author: Nabid, Neda
ISNI:       0000 0004 7655 4181
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2019
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Energy dissipation devices are widely utilised as a viable cost-effective solution to enhance the seismic performance of existing/newly designed structures. Optimum design of control devices is a challenging task due to complexity and high nonlinearity of these systems under earthquake excitations. The existing optimisation techniques for non-linear problems are computationally expensive. This highlights the need for more efficient optimisation methods for the design of non-linear structures with supplemental damping devices. In this study, a practical design method is proposed for more efficient design of friction dampers for different multi-storey buildings (3, 5, 10, 15 and 20-storey frames with 3 and 5 spans), friction damper designs (different slip load distribution patterns) and seismic design excitations (a set of twelve natural and synthetic earthquakes as well as twenty far- and nearfield earthquakes). A low computational cost multi-criteria performance-based optimisation methodology is then developed for optimum design of friction dampers in RC structures (using a concept of Uniform Distribution of Deformation; UDD). In the proposed method, two or more predefined performance objectives are simultaneously satisfied under different earthquake levels. The reliability of the method is assessed through sensitivity analyses using different initial damper slip loads, convergence parameters and earthquake records. To accelerate the speed of the optimisation, a novel adaptive UDD optimisation method is also established for optimal arrangement of the friction dampers. The efficiency of the suggested approach is then evaluated against a Genetic Algorithm (GA) as a global evolutionary optimisation method. Using the same concept, a three-phase optimum design method is proposed for simultaneous discrete optimisation of bracing elements and continuous optimisation of friction devices in RC structures under strong earthquakes. The results indicate that, irrespective of slipload distribution, the optimum range of slip loads leading to maximum energy dissipation efficiency is a function of the number of storeys and earthquake PGV level. The proposed performance-based UDD optimisation method can efficiently decrease the number of required friction dampers and additional imposed loads to the main structure while satisfying the predefined performance levels under the design earthquakes. The design solutions obtained from the adaptive UDD after a few nonlinear dynamic simulations are very close to those achieved from the GA approach after thousands of analyses. Compared to code-based design braced frames, using the proposed method leads to considerably lower number of bracing elements and reduced imposed loads to the structure, while satisfying multiple performance objectives under design earthquakes.
Supervisor: Hajirasouliha, Iman ; Petkovski, Mihail Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available