Chennai: Researchers at the Indian Institute of Technology (IIT), Madras, have developed a framework that can boost protection of critical infrastructure in the country against the threat of ballistic missiles, according to officials.
The framework will help designers develop innovative solutions for improving the ballistic resistance of reinforced concrete (RC) panels, they said.
The findings of the research were published in the reputed peer-reviewed journal “Reliability Engineering & System Safety”.
According to a press release by the premier institute, 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.
The release says concrete structures face highly localized damage like 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 localized damage or even the collapse of the entire structure.
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.
The 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 the study, Dr Alagappan Ponnalagu, Assistant Professor of the Department of Civil Engineering, and Roouf Un Nabi Dar, a research scholar, zeroed in 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, a probabilistic formula for estimating the crater diameter in RC panels is proposed.
“Ballistic design is crucial for widely utilized concrete structures in today’s unpredictable world. Usually, extensive experimental and numerical studies have been conducted 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,” Ponnalagu said.
“Moreover, while quantifying damage parameters, incorrect and inconsistent results are obtained by using deterministic empirical formulations. We have now provided a reliable design formula for estimating crater diameter in addition to the development of a novel performance-based ballistic design framework for RC panels. This study is helpful not only in terms of providing the ballistic design framework and probabilistic crater quantifications formula but also in understanding the ballistic behaviour of RC panels,” he added.
Speaking about the next steps of the research, Ponnalagu said, “Our future work is to extend this 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 Army.”
“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 levels and is effectively coupled. Hence, the framework is a novel design philosophy ensuring resiliency against projectile penetration and crater formation of RC panels,” Dar said.
“On the other hand, the local damage response in terms of crater formation in RC panels was studied under projectile impact. A probabilistic approach is taken to formulate a reliable formula for quantifying unexplored crater damage based on the well-established Bayesian methodology for RC panels that takes into account uncertainty. This caters to the need to take care of uncertainties that deterministic models do not. The probabilistic model proposed by the 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,” he added.
