Papers by Keyword: Blast Resistance

Abstract: The resistance of structures to the effects of explosions is very current issue in these days. During explosion structures are subjected to extreme dynamic local loads and it is necessary to the structure and its reinforcement for this type of loading. In UHPFRC the reinforcement is evenly distributed throughout the structure in the form of dispersed steel fibres. Based on the knowledges of excellent mechanical properties of both steel and UHPFRC, there is an assumption that an appropriate combination of these materials in the sense of composite constructions should result in significantly less damage to the structure in the case of explosion. The paper is focused on the process of production of testing specimens intended for blast resistance tests. The first part of the paper describes tests elements and goals of the experiment. In the next part of the paper the design and material properties of the used concrete mixtures are described. Then production in the sense of formwork preparation and casting is described. At the end of the article, there is a brief comparison of the results achieved for specimens from UHPFRC and reference NSC.

Abstract: This paper presents achievements in the field of the numerical simulation of the fibrere reinforced concrete (FRC) and ultra-high performance fibre reinforced concrete (UHPFRC). The numerical simulations were performed to verify results of two experimental programmes focused on the blast resistance of FRC and UHPFRC. The response of the FRC and UHPFRC slabs to the contact and near-field blast was studied in these two experiments. As the detail behaviour of specimens could not be observed because of the blast load, the numerical models were prepared. The accuracy of the numerical models was evaluated based on the comparison of numerical and experimental results. Different approaches for blast simulation were tested and compared. The results indicate that the various phenomena (e.g. overpressure propagation, stress cumulation, crack propagation and damage extend) can be successfully simulated. However, the comparison of the soffit velocity, measured with the PDV unit and numerical model showed shortcomings of the numerical model. These numerical model inaccuracies are discussed and their reasons presented.

Abstract: The dynamic responses of sandwich structures with MHS(metal hollow sphere)and closed cell aluminum foams under blast loading were simulated numerically by employing the finite element software ANSYS/LS-DYNA. Both sandwich panels and sandwich spheres were modeled. Some factors that determine the blast resistance of the sandwich structures were investigated. According to the parametric studies, the sandwich structures with thin inner face sheet and thick outer face sheet have stronger blast resistance than others. Also the results show that sandwich structures with interlaced hollow spheres have a better performance than those with paratactic hollow spheres. Moreover, it's inferred that the density graded core with the biggest density as the first impact layer and the least density as the last layer has more benefits in energy absorption. The comparison between sandwich structures with metal hollow spheres and those with aluminum foams was studied experimentally and numerically and the results demonstrate that structures with aluminum foam have advantage in energy absorption but structures with MHS are stronger and can undertake more TNT.

Abstract: With the increase in acts of terrorism, the effects of the explosion on structures has become highly topical. The aim of the paper is an analysis of various approaches to determine the response of blast loaded reinforced concrete pillar. Homemade ANFO (Ammonium nitrate + fuel oil) explosive will be a reference explosive. Such type of explosives is the most used one in terroristic attacks. The paper will be focused on the analysis of the blast wave, based on the experimental tests, and dynamic analysis of a structure under such load.

Abstract: The paper describes approach for the description of punching-shear resistance of concrete slab specimens subjected to close blast. The procedure is based on a combination of standardized approaches, a rich experimental program and numerical modeling. The approach aims to quantify the close blast behavior in the means of the velocity of the loading, strain-rate dependent material characteristics and simplify it to allow practical use.

Abstract: This article presents results of experimental validation of complex phenomenon of blast wave and fragment impact on protective panel. Protective panel was made of HTK900K steel and Dyneema HB50 polyethylene. Standard level 1 IED surrogate was used. Test was conducted with regards to NATO STANAG 4569 and NATO AEP 55 standardizations. Computational analysis was performed using LS-DYNA code using explicit time integration scheme. Properties of steel, polyethylene and glue were obtained during laboratory tests. Steel was modeled using simplified Johnson-Cook model whereas polyethylene was modeled as composite material. Both blast wave and fragment impact was implemented in simulation. Good agreement between experimental and numerical data was obtained.

Abstract: The paper summarizes the up to now results of the development of special concrete intended for the explosion resistance applications, the emphasis is put also on minimal secondary fragments formation at the explosion. The fine-grained concrete matrix has been reinforced by various types of dispersed fibers (metallic, mineral and polymer) of different sizes and by their combination, while the same volume content of fibres has been kept. The concrete prism samples have been subjected to the determination of mechanical parameters (compressive and flexural strength, modulus of elasticity). The concrete test elements of the same sizes as commercial products have been made and their explosion resistance was tested. The material characteristics and explosion test data have been used for modeling the adequate wall thickness of the concrete element which should resist the explosion defined by type, size, weight and placement of the blast. In the next step the test elements has been reinforced by additional outer layer of non-metallic tissue and subjected to explosion tests.

Abstract: In this study, a finite element model is developed for simulation of the structural behaviour of steel-reinforced concrete panels under blast loading using LS-DYNA. Pure Lagrangian formulation is applied in the finite element analysis, and the strain rate effect is taken into account in the material models of both concrete and steel. The finite element model is validated by comparing the computed results with experimental test results from the literature. Structural behaviour of concrete panel with different parameters under blast loading is also investigated. Keywords: Blast resistance; Finite element model; Reinforced concrete panel; Strain rate effect

Abstract: Blast-resistant structures, such as blast door panel, are designed and fabricated in a solid way to resist blast loads. This not only increases the material and construction costs, but also undermines the operational performance of the protective structures. To overcome these problems, many researchers try to use high-strength materials and different structural forms in structural design to resist the blast and impact loads. This study introduces a new configuration of sandwich door panel equipped with rotational friction hinge device with spring (RFHDS) to resist blast loading. The RFHDS can help the panel equipped with RFHDS to recover, at least partially its original configuration after blast loading and maintain its operational and blast-resistance capability after a blast event. The energy absorption and blast loading resistance capacities of this proposed sandwich panel are numerically investigated by using finite element code Ls-Dyna. It is found that the proposed sandwich door panel with RFHDS can improve the blast-resistant capacity significantly. This new configuration of sandwich door panel can be employed to mitigate blast loading effects in structural panel design.

Abstract: Recently, the damaged building and loss of life have been increasing by man-made disasters. In this study, the blast resistance performance of fiber reinforced concrete against explosion was evaluated by the emulsion explosive and AUTODYN. The concrete without fiber was penetrated by emulsion explosive of 4605 kJ/kg and its back side was fractured heavily. The concretes with PVA, PE and Steel fiber have a higher blast resistance than that of concrete without fiber. Consequentially, the blast resistance of concrete was analyzed from viewpoint of fracture mode by AUTODYN and it was concluded that the fiber content is a beneficial for the blast resistance performance of concrete.