Prof Mohd Ashraf Iqbal from IIT Roorkee, India, is the first person to discover these meaningful changes in the application of prestressed concrete.
Every country assures security to its people irrespective of the difference in constitution and ideology. Apart from army, navy, and air force, the Research and Development (R&D) sector plays a vital role in improving the security of a country.
Prof Iqbal was a doctoral scholar at the University of Adelaide in Australia, where he first studied about prestressed concrete and carried it forward until today. Working under the Department of Civil Engineering at IIT Roorkee in India, he has found some groundbreaking details about the ‘Ballistic Impact loading under Prestressed Technique’ for the first time.
He is the first scientist to discover these meaningful changes in the application of prestressed concrete for the first time in the world.
The project has already been awarded by the Department of Science and Technology (DSP). It might soon be backed by AERD, Atomic Energy Research Department.
Prestressing of concrete enables reducing sections and crack width in the structural elements by eliminating flexural tension, and thereby making concrete more suitable for the construction of large span and un-cracked structures.
“Ballistic Impact loading under Prestressed technique is not being studied earlier, ” says Prof Iqbal.
Concrete is widely being used for the construction of strategic and important structures, such as:
1. It is the second largest material which is being used by human beings after water. It is highly durable, fire, and corrosion resistant and nonporous.
2. Prestressed concrete is primarily employed to reduce the sections and the crack width in the structural elements.
3. The utmost characteristic of eliminating flexural tension from structural elements has facilitated the prestressed concrete to draw widespread applications in strategic and important structures.
Basically, prestressed concrete is used in the construction of nuclear containment structure, a lead structure enclosing a nuclear reactor inside a containment which acts as a final barrier to radioactive release.
Structure of Nuclear Containment
In India we have double layered-containments, the internal structure is constructed by the prestressed concrete structure and the outer one is the reinforcing structure.
“Nuclear industry has the major application of prestressed concrete structure,” Prof Iqbal said.
Negligence in the construction can lead to a leak in harmful radiations from the nuclear containment.
If an aircraft hit the containment structure or if there is a failure inside the containment due to some machine component, turbine blades, or any other element then chemicals and radiations may affect the environment.
However, the ballistic impact theory guarantees that the concrete structures would not get damaged.
As the thickness of the structure gets reduced, less concrete is being used in the construction. Hence, a lesser amount of fuel and other requisite material is used in the preparations.
Based on the present research, authors have published about five research papers in peer-reviewed international journals and also presented this research in many international conferences.
Damage and Energy Absorption Characteristics
In general, plain concrete targets underwent brittle failure.
Thick radial cracks, 3 – 7 mm wide, originating from the impact location, developed across the target thickness and traversed over entire span leading to brittle failure.
The number of cracks in almost all plain concrete targets was found to be four.
The reinforced and prestressed concrete targets, however, did not experience any visible cracking, Fig. 6.
Numerical simulations accurately reproduced the failure in reinforced and prestressed concrete targets but cracking in plain concrete could not be predicted.
It has been observed that the magnitude of damage at the front surface was low and its variation with respect to projectile velocity, target thickness and type of concrete was insignificant.
The rear surface crater, on the other hand, had a significant influence on incidence velocity.
For a given concrete type and target thickness, the diameter of the rear surface crater decreased with the increase in projectile velocity.
This is due to the fact that the localisation of damage increases with the increase in strain rate.
The rate of decrease in the size of the crater with increasing velocity was the most prominent in prestressed concrete and least prominent in plain concrete.
For a given concrete, the volume of the rear surface crater (scabbing) increased with the decrease in incidence velocity and increase in target thickness.
The influence of velocity was most dominant in plain concrete and least dominant in prestressed concrete.
For a given thickness, however, the volume of scabbing was highest in the plain concrete followed by reinforced and prestressed concrete, respectively.
The initial prestressing thus proved to be effective in minimising the damage and improving the ductility of concrete