The following is an excerpt.
The truck pulled up by the concrete lab early one morning and dumped the grey mass into forms and wheelbarrows. As you can see in this time-lapse video*, it kept students and staff very busy getting the moulding done.
The reason for all this effort is one of this spring’s master theses at SIMLab and SFI CASA. Students Vetle Solheim Gjesdal and Øystein Eirik Kvist Jacobsen have put up on the task of examining «Projectile impact on plain and reinforced concrete slabs».
Frequently used in protective structures
Concrete is everywhere. It’s underfoot as we walk pavements and streets and it keeps our houses off the ground. It’s the stuff cities are made of. However, Gjesdal and Jacobsen’s MSc thesis’s backdrop is the frequent use of the material in protective structures where weight and space limitations are no issues. This makes concrete of particular interest in fortification installations for defence purposes.
Due to its widespread use in critical infrastructure, many studies on the behaviour of concrete components exposed to extreme loadings such as ballistic impact can be found in the open literature. However, the results are somewhat inconsistent, and further research is required.
Aim to reveal the ballistic capacity
The student´s cast slabs are 100 mm thick, and together with appurtenant material specimens, they are now stored for curing. When hardened and ready, they will subject them to impact from ogive-nose steel projectiles in SIMLab’s ballistic range. The aim is to reveal their ballistic capacity.
Vetle Solheim Gjesdal and Øystein Eirik Kvist Jacobsen will examine the perforation resistance of plain and reinforced concrete, both experimentally and numerically. In these tests, the effect of rebars on the perforation resistance is of particular interest. All component tests will be done in combination with relevant material tests instrumented with digital image correlation (DIC), which is an optical technique for measuring strain and displacement.
Close cooperation with the Norwegian Defence Estates Agency
The material test data will be used to calibrate proper concrete material models. Finally, numerical simulations of the component tests will be carried out using a suitable finite element solver. The data generated will be used to validate and verify some frequently used numerical methods involving impact loading of concrete structures.
The project runs in close cooperation with SFI CASA partner the Norwegian Defence Estates Agency. Supervisors are Professor Tore Børvik and Researcher Martin Kristoffersen, together with NDEA research engineers Sumita Dey and Oda L. Toreskås. Post doc Andria Antoniou at SFI CASA is also involved.
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The work is a continuation of a previous project from 2019. Back then, Guri Lillehaug and Marte Vestermo Nesje studied combined impact and blast loading on concrete plates. They did tests in both the ballistic range and the shock tube. The aim was to explore a shockwave effect when the material is already damaged by a missile impact.
READ MORE: Students Preparing to Attack Concrete
In all, 17 students are now set out to work on master’s theses at SIMLab and SFI CASA. The thesis requires 20 full-time weeks of work. For SIMLab and SFI CASA, the master’s students are essential contributors from research and testing to transferring and implementing technology in the industry. The MSc theses should be submitted to the Department of Structural Engineering, NTNU, no later than 11 June.
Here is the full list:
*The time-lapse video is made by staff engineer Steinar Seehus.