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Structural damage detection is a field that has attracted a great interest in the scientific community in recent years. Most of these studies use dynamic analysis data of the beams as a diagnostic tool for damage. In this paper, a massless rotational spring was used to represent the cracked sections of beams and the natural frequencies and mode shape were obtained. For calculation of rotational spring stiffness equivalent of uncracked and cracked sections, finite element models and experimental test were used. The damage identification problem was addressed with two optimization techniques of different philosophers: ECBO, PSO and SQP methods. The objective functions used in the optimization process are based on the dynamic analysis data such as natural frequencies and mode shapes. This data was obtained by developing a software that performs the dynamic analysis of structures using the Finite Element Method (FEM). Comparison between the detected cracks using optimization method and real beam shows an acceptable agreement.

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Among the different lateral force resisting systems, shear walls are of appropriate stiffness and hence are extensively employed in the design of high-rise structures. The architectural concerns regarding the safety of these structures have further widened the application of coupled shear walls. The present study investigated the optimal dimensional design of coupled shear walls based on the improved Big Bang-Big Crunch algorithm. This optimization method achieves unique solutions in a short period according to the defined objective function, design variables, and constraints. Moreover, the results of the present study indicated that the dimensions of the coupling beam in the shear wall significantly affect the wall behavior by maximizing its efficiency which implies on its practical application by considering the wall in the flexural model.

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The seismic resilience of existing reinforced concrete (RC) buildings can be improved by optimizing both energy dissipation and post-earthquake recovery. This study proposes a practical framework for upgrading RC moment-resisting frames using nonlinear fluid viscous dampers (NFVDs). Two typical frames, a four-story and an eight-story structure, were modeled and analyzed in OpenSees. Nonlinear time-history analyses with seven earthquake records were carried out to estimate the Park–Ang damage index, while incremental dynamic analyses (IDA) with 22 far-field records from FEMA P695 were used to evaluate fragility and collapse performance. The NFVDs were represented through a velocity-dependent Maxwell model, and the optimal damper parameters and locations were determined through a cost-based single-objective optimization scheme under predefined damage limits. The results show that the optimized damper configurations effectively reduced structural damage and improved post-event functionality recovery under seismic hazard levels corresponding to 10% and 2% probabilities of exceedance in 50 years. Overall, the proposed approach provides an efficient and economical solution for improving the seismic performance and resilience of existing RC frame buildings.