Research Projects

A significant portion of India’s urban building stock, particularly in high seismic zones such as the Himalayan belt, the North-Eastern region, and the NCR region, comprises reinforced concrete (RC) frame structures with open ground stories (OGS). While the OGS configuration offers functional and architectural advantages, it introduces abrupt discontinuity in lateral stiffness and strength, making these buildings highly susceptible to soft-story collapse during earthquakes. The risk becomes more severe when these buildings are also non-ductile, constructed without compliance to modern seismic and detailing codes. Strengthening such vulnerable buildings is an urgent priority; however, existing retrofitting methods often face challenges related to cost, constructability, and architectural constraints. This proposal aims to develop and validate a low-cost Hybrid Yielding Damping Device (HYDD) specifically designed to retrofit non-ductile RC OGS frames. The proposed HYDD integrates both shear and flexural yielding mechanisms in a compact and modular configuration, enabling enhanced energy dissipation capacity, stable hysteretic behavior, and improved ductility. Its replaceable design ensures ease of installation without major structural alterations, making it suitable for widespread adoption. The project proposes using a collar beam system to address the limitations posed by aged, weak concrete in non-ductile RC members, particularly their inability to sustain high lateral forces. This intermediary connection strategy enables secure anchorage of the HYDD without directly transferring forces into vulnerable existing columns or beams, thereby ensuring a safe and reliable load path for energy dissipation. The project will begin with component-level experimental testing of HYDD prototypes under reversed cyclic loading to characterize strength, stiffness, ductility, and energy dissipation behavior. Numerical simulations using ABAQUS will support this phase by modeling the damper's inelastic deformation and buckling behavior and validating the test results. Following this, full-scale system-level testing will be conducted on RC OGS frame specimens first in the unretrofitted condition, and then with HYDD retrofitting using collar beams. Frame-level performance assessment, including nonlinear pushover and incremental dynamic analyses, will be carried out using OpenSees. To broaden the applicability of the findings, a set of Machine Learning-based fragility models will be developed. Simulation data from OpenSees will be used to train predictive models that quantify damage states and seismic vulnerability of RC OGS buildings with and without HYDD retrofitting. These models will enable rapid and scalable assessment of retrofit effectiveness across a range of building types and seismic intensities. The integrated research framework combines innovative damper mechanics and practical retrofitting solutions like the collar beam system, large-scale validation, and AI-based fragility modeling to fill a critical gap in India’s seismic risk reduction efforts. Expected outcomes include validated HYDD prototypes, system performance data, numerical models, and an open-source tool for vulnerability assessment. The findings will be disseminated through scientific publications, technical manuals, and collaboration with agencies such as CPWD, PWD, and NDMA for potential field-level implementation.