Jayadipta Ghosh

Reinforced concrete (RC) frames with low ductility remain a significant concern, particularly in regions prone to moderate to high seismic activity. Their global popularity calls for robust seismic retrofitting strategies to mitigate potential economic, social, and environmental impacts. Among these strategies, buckling-restrained braces (BRBs) have emerged to be effective for enhancing seismic performance with extensive experimental and numerical studies. However, the critical influence of masonry infills on the seismic performance of BRB-retrofitted structures is often overlooked due to their brittle nature. This study investigates the efficacy of BRB retrofitting in reducing life-cycle costs and improving sustainability metrics for low-ductility RC frames. A three-story, three-bay, low-ductility RC frame was selected as the case study structure. State-of-the-art finite-element models were developed in OpenSees for infilled and non-infilled frames, with and without BRBs. The modeling explicitly incorporated masonry infills, accounting for their strength and stiffness. A cloud analysis–based approach was adopted to develop the probabilistic seismic demand models and fragility curves. A state-of-the-art methodology was subsequently used to estimate economic loss, carbon emissions, and embodied energy. These metrics were then compared across configurations, providing stakeholders and decision makers with valuable insights to support informed choices in seismic risk mitigation using retrofits and sustainable design.

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Reinforced concrete (RC) frames with masonry infills represent a prevalent construction typology across the globe, including moderate to high seismic regions. Such structures are often characterized by high seismic vulnerability, and consequently, there is an urgent need for retrofit solutions to effectively improve their seismic performance. Buckling‐restrained braces (BRBs) represent one such solution. They are a type of dissipative device that can be included within the frames of an existing structure to increase its strength, stiffness, and energy dissipation capacity. Although a substantial amount of research has already been performed to understand the effectiveness of BRBs as a retrofit strategy, these studies have often neglected the contribution of masonry infills and the interactions between the infills and the BRBs. While masonry infills are usually overlooked in the analysis and design stage (owing to their brittle nature), past studies indicated that their strength and stiffness may significantly alter the structure's seismic performance, leading to undesirable and unexpected results. This study presents a detailed investigation of the impact of masonry infills on the seismic response and fragility of BRB‐retrofitted RC frames. A three‐story, three‐bay, low‐ductile RC frame has been selected for case study purposes. High‐fidelity finite element models are developed in OpenSees for combinations of infilled and non‐infilled structures—with and without BRBs. Nonlinear static and dynamic analyses are performed to evaluate the seismic response of the different configurations at local and global levels. Successively, cloud analyses are conducted by considering a set of 150 ground motion records to account for the record‐to‐record variability and develop seismic fragility curves. The present study sheds some light on the mutual interaction between the infill panels and BRBs retrofit intervention and highlights the critical aspects that must be considered in the design.