Abstract: Recycled rubber materials are one of cheap and suitable materials for energy absorbers in protective structures. Standard tests of elastomers in uniaxial or biaxial tension is not suitable and efficient for energy absorbers made of recycled car tires. Simple compression test and simple impact test are described material properties from those tests are determined and compared with simulation in ANSYS/AUTODYN.
Abstract: Mitigation of the blast risk associated with terrorist attacks and accidental explosions threatening critical infrastructure has become a topic of great interest in the civil engineering community, all over the world. One method of mitigating blast risk is to retrofit vulnerable structures to resist the impulsive effects of blast loading. Masonry is one of the most commonly used materials particular in heritage buildings. An effective way to enhance the ability of unreinforced masonry walls to withstand blast loads and consequently to limit the amount of wall damage is strengthening it with reinforced concrete wall. In this research, the assembly of masonry wall with RC wall jacket from one side is simulated using nonlinear finite element method and ANSYS WORKBENCH V14.5 program to study its behavior under blast loading. A parametric study is performed where the influence of variation of some design parameters on the wall performance under blast effect is studied. The design parameters include masonry wall and RC wall thickness, interface between the two wall layers, stand-off distance, boundary condition, and reinforced concrete compressive strength. The performance of the strengthened walls is evaluated in terms of wall damage, maximum lateral deflection, and end rotation at the support.
Abstract: The present paper aims to examine the potential of the Applied Element Method (AEM) in simulating the blast effects in RC panels. The numerical estimates are compared with the results obtained in an experimental campaign designed to investigate the effectiveness of fibre grout for strengthening full scale RC panels by comparing the effects that a similar blast load produces in a reference and the strengthened panel. First, a numerical model of the reference specimen was created in the software Extreme Loading for Structures and calibrated to match the experimental results. With no further calibration, the fibre reinforced grout strengthening was added and the resulting numerical model subjected to the same blast load. The experimental blast effects on both reference and strengthened panels, despite the lack of high speed measurement equipment (pressure, strains and displacements sensors), compare well with the numerical estimates in terms of residual and maximum displacements, showing that, once calibrated, the AEM numerical models can be successfully used to simulate blast effects in RC panels.
Abstract: The article deals with the provisional bridging systems that are being used in the Czech Republic area. The main and mostly deployed bridge sets owned by one of the Czech agencies are covered. Every bridging systems is described, along with the way of construction, deployment and a list of main advantages and disadvantages. An evaluation of contemporary usability of the bridging sets is conducted at the end of the article.
Abstract: The development of the new technologies has also brought new possibilities of the wood processing, wood shaping and wood materials tending. By reason of increased human need for wood products the industry has shifted from the production in the workshops throught manufactures up to fabrications. This fact also causes increasing of the wood dust amount in the spaces of the production shops or halls, and by that also increased danger of the explosion of the wood dust. At the adequate initiatory source, sufficient amount of flammable material, oxidant and essential pressure, the explosion can occur and last for several miliseconds, therefore people rescue in the endangered spaces in case of explosion is impossible. One of the parameters which influence properties of the flammable wood dust is its particle size. The article deals with the particle size influence of the wood dust at its minimal temperature of ignition in the stired state. On the basis of the experimental measures the influence of the minimal action of the thermal energy for the activation of the ignition process of the wood dust in the stired state at the reacting of pressure and variousness of grit size is assessed.
Abstract: Theoretical assessments are given for the use of the through-transition technique of broadband ultrasonic spectroscopy to determine porosity of heterogeneous materials. Experimental measurements of local porosity of composites using the through-transition technique are presented. Dependences of elastic moduli on the concentration of hardening particles and porosity of metal matrix isotropic composite found. Experimental relationship between the phase velocity of longitudinal acoustic waves and the power of structural noise in samples of graphite epoxy composites is obtained.
Abstract: This manuscript presents the experimental testing and assessment of the combustible material behavior with a focus on modification by fire retardant during the process of combustion. We experimentally tested the material of representative natural thermal insulation made of hempen fiber and we compared these specimens with the application of representative fire retardant. The testing was proceed in accordance with the experimental method created with the purpose of evaluating the material behavior when exposed to a direct mid-height flame for a longer time period under laboratory conditions. The main aim of the experimental testing was possible improvement of fire-technical characteristic of building material for improve the fire protection.
Abstract: In relation to extraction of coal seams at significant depths, the issue of protection of safety equipment against pressure exerted by rock becomes very important. In many surveys of the effects of pressure exerted by rock it was demonstrated that the intensity of stress around the mine works increases the greater the depth of the mine works. However, surveys of technological mine works have shown that the level of deformation of the mine bracing varies in various types of rock at identical depths and no precise rule was established between the increase in pressure exerted by rock and the increasing depth of the mine works.
Abstract: The aim of solved problem is a development of a new invasive means for improvised explosive devices deactivation. The idea is a quick and reliable disposal of improvised explosive device with construction system as a tube bombe. Such tube bomb has to be deactivated, dismantled and to do not explode. The development of shaped – cumulative charge was conceptually solved in a way to pushed down metal end caps of the tube bomb, to pick up explosive with a detonating fuse and to prevent from its explosion. Dismantled parts put to forensic test, for the improvised explosive device constructer revelation.