Drop Weight Testing of Samples Made of Different Building Materials Designed for the Protection of Classified Information.

Classified information is information of vital importance to the State, which must be protected against disclosure, misuse, damage, unauthorized reproduction, destruction, loss or theft in the interest of the State. At present, there are four levels of classification. For each classification level, precise requirements are laid down for the material of the walls, partitions and ceilings of the rooms in which classified information is stored. Several types of materials are defined for each classification level. The objective of this study was to test and determine whether the different types of materials proposed for the Confidential level meet the same level of resistance. A drop weight test via pendulum was used to determine the resistance. A 50 kg weight was used to break through a 60 × 100 cm sample. The impact of the weight was on the exact center of the sample. The result of the tests was that to break through samples of different materials, large differences in the drop height of the weight were required. The most resistant was the specimen made of reinforced concrete, which required 3 impacts from a height of 80 cm to break through. On the contrary, the least resistant were the specimens made of masonry of autoclaved aerated concrete, where after 2 falls from a height of 5 cm, the sample broke into 2 parts.

Laminated Glass Plates Subjected to High-Velocity Projectile Impact and Their Residual Post-Impact Performance.

This study aims to analyze the performance of laminated glass against ballistic loading and investigates its residual load-bearing capacity. Two groups of specimens were used in quasi-static four-point bending experiments, first without prior ballistic damage and then with it. The main objective was to compare the load-bearing capacity of these two groups to see the effect of ballistic damage. Three different layer compositions were used. The ballistic loading was conducted using an in-service 9 mm bullet fired from a semiautomatic carbine with the glass specimens hanging on steel ropes in a free boundary setup. Numerical simulation and analytical methods were used and validated against the measured response of the undamaged specimens. The simulations were in good agreement with the experimental results. All of the glass specimens were able to withstand the ballistic loading, and the subsequent performance during the quasi-static bending loading was similar to that of the undamaged specimens. The quality of the glass edges seemed to be more important than ballistic damage. The front-plate damage played a negligible role, and the back-plate damage needed to be extensive to influence subsequent performance. Provided that ballistic damage is mainly localized only to the centers of the plates, it did not affect the post-impact loading capacity.

Experimental Investigation of Cohesion between UHPC and NSC Utilising Interface Protrusions.

The interaction of ultrahigh-performance concrete (UHPC) and normal-strength concrete (NSC) is one of the main issues for strengthening conventional concrete structures or other applications where NSC and UHPC are interrelated. UHPC stands out for its strength and durability, while NSC is significantly inexpensive and easier to work with. Efficiently designed structures can exploit the advantages of both mixtures. At the interface of these materials in newly designed structures, the formwork can be modified at the interface to give the concrete surface sufficient roughness and thus cohesion as required. This improves both the tensile and shear strength of the contact resulting in the enhanced capacity of the composite structure. In this study, a button foil was inserted into the formwork for the UHPC and then a part of NSC was made. The shear strength of the interface without any stress component in the transverse direction was measured on small-scale samples. It was to justify the possibility of the use of this interface in real constructions such as beams and columns. The main objective of further research is to design a composite beam using a UHPC shell as formwork for NSC and protrusions at the interface. It is expected that the U-shaped shell made of the UHPC could significantly contribute to the load-bearing capacity of the resulting composite NSC−UHPC structure and also to its enhanced durability. In addition, if the NSC is enclosed in a shell of UHPC, it can be made from various secondary materials, therefore it can decrease cement consumption by more than 50%.

Electromagnetic Properties of Steel Fibres for Use in Cementitious Composites, Fibre Detection and Non-Destructive Testing.

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.

Simulations of the Behaviour of Steel Ferromagnetic Fibres Commonly Used in Concrete in a Magnetic Field.

The efficiency of fibre reinforcement in concrete can be drastically increased by orienting the fibres using a magnetic field. This orientation occurs immediately after pouring fresh concrete when the fibres can still move. The technique is most relevant for manufacturing prefabricated elements such as beams or columns. However, the parameters of such a field are not immediately apparent, as they depend on the specific fibre reaction to the magnetic field. In this study, a numerical model was created in ANSYS Maxwell to examine the mechanical torque acting on fibres placed in a magnetic field with varying parameters. The model consists of a single fibre placed between two Helmholtz coils. The simulations were verified with an experimental setup as well as theoretical relationships. Ten different fibre types, both straight and hook-ended, were examined. The developed model can be successfully used to study the behaviour of fibres in a magnetic field. The fibre size plays the most important role together with the magnetic saturation of the fibre material. Multiple fibres show significant interactions.