Shear-type failure of concrete structural elements under blast and impact
Time: Thu 2026-02-19 10.00
Location: F3 (Flodis), Lindstedtsvägen 26 & 28, Stockholm
Video link: https://kth-se.zoom.us/j/68178082207
Language: English
Subject area: Civil and Architectural Engineering, Concrete Structures
Doctoral student: Viktor Peterson , Betongbyggnad
Opponent: Professor Samuel Rigby, School of Mechanical, Aerospace and Civil Engineering, University of Sheffield
Supervisor: Professor Anders Ansell, Betongbyggnad; Docent Mikael Hallgren, Betongbyggnad, Tyréns; Dr. Andreas Sjölander, Betongbyggnad
QC 20250119
Abstract
Civilian structures and fortifications consist primarily of reinforced concrete. Reinforced concrete provides mass, robustness, and redundancy while remaining cost-effective. When appropriate reinforcement detailing is provided and flexure dominates, these elements exhibit a high energy absorption capacity. This capacity is necessary to withstand high-intensity dynamic loads, such as collisions, fragment impacts, and air blasts. Flexure-dominated damage results in numerous wide cracks, which absorb energy through plastic deformation of the reinforcement. Shear-type failures are instead characterised by localised energy absorption in a single dominant crack, where concrete fracture and friction absorb most of the energy. Avoiding shear-type failures is thus central to the design of concrete elements subjected to high-intensity dynamic loads.
This thesis investigates the parameters governing the energy absorption capacity of reinforced concrete elements and proposes strategies to increase it. Experimental and numerical studies address shear-failure modes, governing parameters, differences between static and dynamic shear failures, mitigation techniques, and prediction models. Drop-weight impact tests on beams were conducted in the laboratory and monitored with high-speed cameras to study the development of shear failure in detail. Shock tube tests on reinforced concrete wall panels were used to investigate the response to air-blast loading.
The research contributes new insights into dynamic shear failures of reinforced concrete elements. Different shear-failure types were deliberately triggered, and their mechanisms and governing parameters were characterised. A major focus was the comparison between static and dynamic shear failures. The results show that, under dynamic loading, compression strut forces dominate in an initial transient phase, producing higher support reactions than in comparable static tests. As deformations increase and the external load decays, the response enters a quasi-static phase in which dynamic and static tests exhibit similar failure forces and displacements. For failures occurring in this quasi-static phase, the findings support the use of static shear-capacity models under dynamic loading. Recommendations for response models and new methods based on the experimental results are also provided.