IIT Madras develops framework to shield key infrastructure from missile threats

Chennai: Researchers at the Indian Institute of Technology Madras have developed a framework that can boost the protection of critical infrastructure in the country against the threat of ballistic missiles. This framework will help designers develop innovative solutions for improving the ballistic resistance of reinforced concrete (RC) panels.

Using computational simulations, the researchers studied the impact of missiles on Reinforced Concrete (RC), which is the main material used to construct vital structures ranging from military bunkers, nuclear power buildings and bridges to runways.

Concrete structures face highly localised damage such as penetration, perforation, scabbing, spalling and crushing under projectile impact load. Due to the strategic importance of these structures, it is necessary to protect them against projectile and debris impact, which can result in localised damage or even the collapse of the entire structure.

What is ballistics?

Ballistics is a field of engineering that deals with the launching, flight behaviour and impact effects of projectiles such as bullets, bombs and rockets. This science is used not only for designing bunkers but also for designing the walls of nuclear power buildings, bridges and other protective structures.

A study by IIT Madras

IIT Madras researchers conducted the study during 'Finite Element’ (FE) Simulation, a computational technique used to simulate and analyse physical phenomena in engineering and science. FE simulation relies on the Finite Element Method (FEM), a numerical approach for solving complex problems involving partial differential equations. These problems often arise in fields like structural mechanics, among others.

In this study, Dr Alagappan Ponnalagu, assistant professor, Department of Civil Engineering, IIT Madras and Roouf Un Nabi Dar, research scholar at IIT Madras, focused on the development of the novel performance-based design framework based on ‘Depth of Penetration’ (DOP) and Crater Damage Area in the RC panels. In addition to that, a probabilistic formula for estimating the crater diameter in RC panels was proposed.

Elaborating on this research, Dr Alagappan Ponnalagu said, “Ballistic design is crucial for widely utilised concrete structures in today’s unpredictable world. Usually, extensive experimental and numerical studies have been done to investigate concrete panels, resulting in design guidelines for local damage parameters. However, with the advent of performance-based design, the ballistic design of concrete structures lacks a comprehensive design philosophy.”

Applications of study

Speaking about the next steps in this research, Dr Alagappan Ponnalagu said, “We hope to extend the study to develop much needed lightweight, cost-effective and sustainable blast and ballistic resistant modular panels that can be used in the construction of bunkers along the borders and highly inaccessible areas for the Indian army.”

Further, Roouf Un Nabi Dar said, “We have proposed a novel performance-based design framework for RC panels based on damage states, namely DOP and crater diameter. Each damage state has four damage levels and is effectively coupled. Hence, the framework is a novel design philosophy ensuring resiliency against projectile penetration and crater formation of RC panels.”

The probabilistic model proposed by IIT Madras researchers for estimating crater diameter in RC panels under projectile impact was validated with several experimental test results from the literature. The agreement of the predicted crater diameter with the experimental results ensures its reliability and accuracy.