Papers by Keyword: Blast Load

Abstract: The present study investigates the response of precast concrete sandwich wall panels under blast load incorporating varying degrees of composite action. The percentage of composite action quantifies a panel’s composite behavior relative to a fully composite assumption, with 0% indicating a fully non-composite panel and 100% indicating a fully composite panel. For this study, the precast panel is modeled as an equivalent single degree of freedom (SDOF) system using the transformation factors. The panel is subjected to a range of blast load while the degree of composite action is varied from 0% to 100%. The response of the panels is evaluated in terms of support rotation, ductility, and support reactions. The effect of degree of composite action on the response of the panel is investigated for a range of blast impulses. The threshold blast impulse value is determined for each partial composite panel considering the moderate level of damage of the panel as per ASCE 59-11 and plastic response of the panel. Further, a range of optimum degree of composite action is identified while trading-off between support rotation and support reaction. The effect of panel span and section moment capacity on the optimum degree of composite action is investigated. It is observed that span length affects the optimum degree of composite action although moment capacity is not influential.

Abstract: The Cowper-Symonds relationship is the most common empirical equation used to model the influence of strain rates in steel structures subjected to blast loads. The simplicity of this relationship makes it as the preferred choice due to the minimum number of coefficients used in the equation. However, different coefficients were reported from experimental results where it was found that the coefficients could be influenced by the thickness of the specimens, types of materials and method of testing. Even so, the actual coefficients even for the same type of material such as for mild steel could be differ. It is known that strain rates effect increases the yield strength of steel, and this could reduce the maximum displacement of steel structures such as steel plates subjected to blast loads. This influence could be more significant if the steel plate was stiffened. Therefore, this study investigated the influence of Cowper-Symonds coefficients for steel plates with stiffeners subjected to close-in blast loads. The numerical investigations were performed using finite element software, Abaqus. The target plate was a 0.4 m x 0.4 m plate with 0.002 m of thickness subjected to a 0.012 kg of Plastic Explosive No. 4 (PE4) at 0.04 m stand-off distance. The influenced of stiffeners were investigate first where five stiffeners’ configurations were used and, in each configuration, the stiffeners come with different geometry ratios. Two best stiffened steel plates have been chosen to study the influence of different Cowper-Symonds coefficients. Different coefficient values of dominator, D and hardening coefficients, q was used. The results shows that any possible coefficient combinations of Cowper-Symonds relation are possible to use in predicting response of steel plates subjected to blast loads. From this study, the most ideal stiffened square steel plates for offshore platform could be identified.

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: 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: A method of numerical analysis of the phenomenon of the air shock wave propagation is presented. The paper describes an explicit own solution. It uses Finite Volume Method (FVM). It also takes into account energy losses due to a heat transfer. For validation, the results of numerical analysis were compared with the literature reports. Both one-dimensional (an explosion in the pipe) and three-dimensional (explosion within the compartment) flow of a shock wave were analysed. Values of impulse, pressure, and its duration were studied. Finally, an overall good convergence of numerical results with experiments was achieved. Also the most important parameters were well reflected.

Abstract: In the past few years, the increase in the number of terrorist attacks has shown that the effect of blast loads on buildings is a serious matter that should be taken into design consideration. These man-made disasters have created a challenge to structural engineers world over about the deficiency in the design process. Blast loads are extreme, instaneous, unpredictive impulses acting over milliseconds. Due to this nature of blast loads, it is complicated to analyse the dynamic responses of the structures. Usage of advanced engineering materials for construction can solve these structural problems to an extent. This paper presents the analysis and design of an underground blast resistant shelter made up of high performance fiber reinforced cementitious composites (HPFRCC). This research focuses on an alternative section of cylindrical module of the shelter. The dynamic behavior of module under blast load is studied in finite element software Abaqus CAE 6.12. It is observed that the material stress-strain behavior is greatly influenced by strain rates of loadings. Shelter manually designed using codes in working stress method is verified with the analytical analysis

Abstract: Guidelines of blast resistant design for AASHTO girder bridges have not taken up much importance on researches. As the transportation infrastructure mainly bridges are highly vulnerable for bomb attack, they must be designed to resist it. The analysis and design of bridges subjected to blast load requires a detailed understanding of blast propagation and its dynamic effects on various structural elements. The response of bridge components subjected to blast load is carried out using Abaqus explicit finite element software. The bridge is modeled on the basis of AASHTO-LRFD bridge design specification for highway bridges. Blast load has been introduced on different critical location of the bridge to understand their effects on various structural elements and extent of damage. A thorough parametric study varying standoff distance and TNT mass is done to understand their importance in developing a blast resistant design for AASHTO Girder Bridge. The study concludes that the value of maximum displacement decreases with the increase in standoff distance.

Abstract: The paper deals with the response analysis of interaction of a gaseous shock wave and a glass plate structure with particular reference to the character of excitation wave and material characteristics of structure. The goal of this analysis is the determination of a hypothesis of failure of window glass plate on the basis of the actual plate rotation during extreme plate displacement. Pressures greater than the ultimate stress or plate rotation bring to the collapse of the glass plate structure. The assumptions and results of theoretical - numerical solution are compared with experiments in situ and in laboratory conditions.

Abstract: With the rapid development of transportation, the vulnerability of bridge under blast loading has more and more attracted people's attention. To ensure the safety of the bridge under the impact of blast loading is very important. This article describes the current situation of bridge structure antiknock research in China and other countries. What’s more, pointed out the shortcomings of existing research and presented that the antiknock research of bridge structure should combine numerical simulation with model test at the same time. This article researches the stress, strain and bridge damage rule of 1: 5 model of T-beam Bridge under explosion effect of small doses explosive.

Abstract: The terrorism and regional conflicts posed a threat to the world peace. Some terrorist explosions caused collapse of the buildings, which brought heavy tragedies to the human components. Therefore research on damage of structural components and resistance to damage have become the focus of our attention. Finite element software LS-DYNA was applied to simulating the response of reinforced concrete columns under blast loading. And analysis on dynamic response under different loading period was carried out. By studying on the stress and strain of reinforced concrete columns subjected to blast loading, the possible failure modes were obtained. In addition, the bearing capacities of concrete columns that are reinforced with carbon fiber and steel panel were analyzed, and the reinforcement effects were compared to provide reasonable reinforcement schemes for structures blast-resistant design.