Research Projects

The proposed research addresses a pressing challenge in structural engineering: the seismic vulnerability of aging, corroded reinforced concrete (RC) buildings, which are widespread in urban infrastructure across India and other developing countries. Many of these buildings were constructed prior to the implementation of modern seismic design codes and now suffer from inherent structural deficiencies, including low-ductility, poor detailing, and inadequate lateral load capacity. Their vulnerability is further exacerbated by corrosion due to environmental exposure (particularly in coastal regions) which degrades the mechanical properties of concrete and steel, reduces rebar cross-sections, and weakens critical components such as beam-column joints and columns. These factors together heighten the risk of brittle failures under seismic loading. Although several localized retrofitting techniques have been explored in the past such as steel jacketing, concrete encasement, and FRP wrapping, these methods may not provide sufficient global lateral stiffness or energy dissipation capacity, especially during strong seismic events. In this context, Buckling Restrained Braces (BRBs) offer a promising global retrofit strategy due to their stable hysteretic behavior, ability to dissipate large amounts of energy in both tension and compression, and ease of installation in existing frames. However, current research on BRBs largely focuses on uncorroded structures, with little attention given to their application in corrosion-damaged RC buildings. The interaction between deteriorated components and added braces, as well as the effect of varying corrosion levels on BRB performance, remains poorly understood. This project proposes a comprehensive investigation combining experimental and numerical methods to enhance the seismic performance of corroded low-ductility RC frames using BRBs. The central hypothesis is that BRBs can significantly improve the strength, ductility, and seismic resilience of corroded frames. To test this hypothesis, the study will first simulate corrosion deterioration and characterize its effect on structural components. Subsequently, cyclic tests on corroded and BRB-retrofitted specimens will be performed to capture damage progression, energy dissipation, and failure modes. These experimental results will be used to calibrate detailed nonlinear finite element models of as-built, corroded, and retrofitted RC frames. Using these models, nonlinear dynamic analyses will be performed with region-specific ground motion records to develop seismic fragility curves for various damage states. These fragility curves will enable a probabilistic assessment of the effectiveness of BRBs in reducing vulnerability across different corrosion scenarios. The research outcomes are expected to fill critical knowledge gaps in seismic retrofitting practice. The key innovations include: (i) application of BRBs to compensate for corrosion-induced deficiencies in RC frame, (ii) experimental validation of BRB performance in corroded frames, and (iii) seismic fragility analysis using calibrated numerical model and region-specific ground motions. The anticipated impact of the project is twofold. First, in terms of fundamental understanding through experimental testing, it will advance the knowledge of BRB retrofit in improving seismic performance of corroded RC frames. Second, in terms of application, it will support the development of sustainable retrofit strategies that extend the life of aging structures while minimizing post-earthquake damage. These findings may be directly applicable to large inventories of aging buildings in seismically active, corrosion-prone regions of India and beyond, and can inform national seismic risk mitigation programs and retrofit guidelines.