About the lab
Experimental Centre (EC) is an accredited department of the Faculty of Civil Engineering at the Czech Technical University in Prague. EC provides experimental works in the civil engineering field regarding mainly static and dynamic testing of structural building elements and materials. Experimental works are performed in the specialized laboratories as well as in-situ.
Featured research (14)
This paper aims to determine the resistance of a wide range of building materials against projectile penetration using the depth-of-penetration (DOP) test and several well-established ballistic factors. Within the DOP test, the residual penetration into a backing aluminum alloy cylinder after passing through a sample with a defined thickness and bulk density was measured. The materials investigated here were plasters, mortars, autoclaved aerated concretes (AAC), normal-strength concretes (NSC), ultrahigh-performance concrete (UHPC), full fired-clay brick (FCB), granite, basalt, laminated glass, and ice. The findings show that the ballistic efficiency factors depend substantially on the material used, allowing one to identify materials with different levels of penetration resistance. Inferences drawn from this study can be used by engineers, architects, and contractors to assess the perforation resistance of various building materials to optimize their use against high-speed projectile impact. In addition, it is demonstrated that the uniaxial compressive strength of the building material might be misleading as the identifier of a material resistance against projectile impact because a significant difference in penetration resistance between materials with comparable compressive strength was found.
This paper deals with the description, measurement, and use of electromagnetic properties of ferromagnetic fibres used as dispersed fibre reinforcement in composite mixtures. Firstly, the fibres’ magnetic properties are shown, and a method of measuring the hysteresis loop of fibres is proposed. The results from the measurements are presented and a discussion of the influence of measured parameters on the fibres’ orientation in a magnetic field is performed. Furthermore, methods of non-destructive estimation, of their amount and orientation in the composite specimens, are discussed. The main experimental goal of this paper is to show the relationship between this non-destructive method’s results and the destructive flexural strength measurements. The method is sensitive enough to provide information related to fibre reinforcement.
The article presents a mobile anti-vehicle barrier created from a high-performance fibre-reinforced concrete, which resembles a historical design of the Czech Hedgehog barrier. The performance of this design when subjected to a moderate velocity vehicle impact was evaluated. A preliminary crash test provided basic data to perform an optimisation of the design using numerical simulations conducted in LS-DYNA. Several key observations were made regarding the crucial role of the barrier-surface interactions and overall barrier behaviour. Based on the simulations, improved geometry of the barrier was proposed and subjected to more full-scale crash tests with various barrier placements. The improved barrier design was able to stop an ordinary road vehicle weighing 1300 kg moving with a velocity of 48 km/h while retaining beneficial characteristics, most importantly low weight.
The static response of ballistic panels and also its resistance to blast and ballistic impact is investigated in the framework of this study. By connecting individual ballistic panels together, the protective barrier can be constructed. The protective barrier can be featured as a system with high mobility and versatility that is achieved by linking basic interlocking plate elements together. The resulting protective barrier can be shaped according to many possible scenarios in a wall with various possible opening angles and a small post with the tetragonal base or a larger post with the hexagonal ground plan. The material solution of the protective barrier benefits from the application of ultra-high-performance fibre-reinforced cement-based composites (UHPFRCC), which meets the requirements for enhanced resistance against extreme loads such as blast or impact. Besides, by using UHPFRCC, thin and slender design can be adopted, which is advantageous in many ways. Slender design results in a lower weight, allowing for easy manipulation and replacement. To verify the behavior of the panels, the proposed barrier was subjected to various loadings at different strain rates. The experimental campaign demonstrated that the protective barrier has a reasonable load-bearing capacity and also sufficient resistance against projectile impact and blast effects.
This paper summarizes recent achievements in shotcrete utilizing ternary binder. Ternary binder is composed mainly from fly ashes and, during hydration, produces large volumes of ettringite beneficial for early-strength gain in shotcrete. Savings in mineral resources, utilization of by-products and reduction in clinker consumption are seen as key benefits for the implemented solution. Design of ternary binder is discussed, including thermodynamical modelling and evolution of volume fractions in the binder. Ternary binder showed high stability with regards to input oxide variations, naturally occurring in heterogeneous fly ash production. Based on the results, a mock-up experiment was performed to verify the effectiveness of ternary binder in shotcrete with excellent results. Approximately 20 tons of the ternary binder is weekly consumed in the pilot project of metro D in Prague. Shotcrete serves as a temporary primary lining in the new Austrian tunnelling method. Substitute for cement in the form of ternary binder reached 50% for concrete strength class C25/30, following J2 curve strength gain.
- Faculty of Civil Engineering (FSV)
About Petr Konvalinka
- Petr Konvalinka currently works as a professor at the Faculty of Civil Engineering (FCE), Czech Technical University in Prague (CTU). Petr does research in Static a Dynamic Analysis of Structures and their parts, Materials Engineering, Mechanical Engineering and Engineering Physics. His most recent publications are in the field of impact loading and temperature loading of the cement composites.