Jiří Štoller

Field Tests of Cementitious Composites Suitable for Protective Structures and Critical Infrastructure

The paper deals with field tests of cementitious composites suitable for protective structures and critical infrastructure. The tests of ballistic resistance against contact and distant explosions are performed according to the NATO standards. The results of tests of plain concrete, steel fibre reinforced concrete and high performance fibre reinforced concrete are analysed.

Design and Assessment of Shape of Protective Structure by Usage of CFD Software Environment Ansys Fluent

The purpose of the study was to design and assess the shape of the construction of the protective structure with regard to its building materials and technical possibilities for its production. Another indispensable limiting condition was the requirement for its easy transportability, assembly and modularity. The optimal shape solution was sought out by using CFD simulation carried out in the software environment of ANSYS Fluent. Appropriateness of different variants of the protective structure, differing form each other by parameterized shape, was assessed on the basis of a drag coefficient. After obtaining a representative number of measured values of the frag coefficient for each variant, results were processed using optimization methods built in the software environment Ansys Workbench, which has found its minimum value. On the basis of this value the most suitable candidate for the optimal variant of the shape of protective structure was chosen. This candidate was subsequently evaluated using the simulation for verification of forecasted value of its drag coefficient.

The Application of Fibre Reinforced Concrete for Protective Shelter from Auxiliary Material

The article deals with the application of fibre reinforced concrete for protective shelter from auxiliary material. It describes a basic structure element, a structure of the shelter, and a process of building.

Research of Prospective Materials for Military Protective Structures

Different types of composite materials with potential application in ballistic protection of static objects are discussed and compared in present study. The studied solutions include: 1) the concretes with or without reinforcement, 2) the metallic boxes with internal gap filled with different materials and 3) the ceramics-metallic composite armours. Besides the ballistic resistance, the areal weight and the price are taken into account. The weight of solutions is important in case of static objects mainly from logistic point of view. The proposals of ballistic compositions presented in the study can facilitate the choice of solutions according to specific requests.

The Basic Properties of Materials Suitable for Protective Structures and Critical Infrastructure

The deals with the basic properties of cement-based materials that are appropriate for protective structures and critical infrastructure. The basic properties of materials were tested on the material samples. The samples were tested before loading by the distant explosion, by the penetration and by the puncture. During the material testing were measured the compressive strength, the tensile strength and the dynamic modulus of elasticity. The article discusses only the compressive strength and the tensile strength.

Experimental Ballistic Loading of Steel Fiber Reinforced Concrete Slabs and Unreinforced Concrete Slabs by Plastic Explosives

The article presents the results of experimental tests carried out on steel fiber reinforced concrete slabs and on unreinforced concrete slabs. The aim of the experimental tests was to determine its suitability for anti-spalling layer by using effects of plastic explosive PlHx 30 explosion. Slabs of steel fiber reinforced concrete and of plain concrete were made according to the same recipe. For this experiment, high-strength concrete with strength class C70/85 was used. In the mixture of steel fiber reinforced concrete, it was added 30 kg of fibers per 1 m3, type Dramix RC-65/50-BN. The interior surface of shelters walls must be protected against the concrete spalling, which are caused by detonations on the outside surface. The results of the tests proved that steel fiber reinforced concrete is not a suitable material for the anti-spalling layer.

Assessment of Protective Structures on the Basis of Their Acceleration Caused by Blast Wave

The purpose this study was to assess the protective structures of different shapes on the basis of their acceleration caused by blast wave. Six variants of models was assessed in the software environment Ansys Autodyn, an explicit tool for modelling the nonlinear dynamics of solids, fluids, gases and their interactions, where the compared parameter was the value of the acceleration of the structures loaded with blast wave. This study represent the second step in the search for optimal shape of protective structure with regard to limitations such as building materials on the base of concrete, low manufacturing cost, modularity and easy transportability and follows the conclusions from the study [11].

Reinforced Concrete Frames under Distant Blast

The article deals with the field tests of UHPFRC frames loaded by distant detonation of 50 kg of TNT and also by direct explosion of 120mm mortar shell. The paper analyses the results obtained from ultrasound diagnostics that was made before and after the explosion.

Protective Structure Design against Airblast Effect

In the Army of the Czech Republic, the protective structure design is currently regulated by a military standard Žen 2-1/1, mainly for buried structures and against nuclear loads. As the nature of current armed conflicts suggests, it would be more appropriate to design above-ground protective structures exposed to the effects of direct or indirect fire weapons. The paper describes a search for an ideal above-ground structural shape exposed to an airblast. Several shapes were designed and their behavior under a typical airblast loading was tested using ANSYS software. As a result of the analysis, the most suitable shape of a protection structure was designed.

Non-Destructive Examination of Cement Based Materials before and after Explosion Tests

The article describes the use of ultrasonic testing methods for examining slabs made from cement based materials. For the detection of cracks, in full-scale slabs before and after the explosion, ultrasonic pulse method was used. Data obtained before the explosion confirm the high quality of the cement based material. Another set of data taken after the explosion shows the scale of cracks in the slabs. The article compares material characteristics of the unreinforced concrete, steel fibre concrete and high performance fibre reinforced concrete on the basis of materials tested by using the passage ultrasonic method after the explosion.