• Structural Engineering and Mechanics
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• v.44 no.4
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• pp.449-463
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• 2012

For buildings subjected to blast loading, structural failure can be categorized into local failure (direct blast effects) and progressive collapse (consequential effects). In direct blast effects, the intensive blast pressures create localized failure of structural elements such as exterior columns and walls. Columns, and their behaviour, play a key role in these situations. Therefore investigating the behaviour of columns under blast loading is very important to estimate the strength, safety and reliability of the whole structure. When a building is subjected to blast loading, it experiences huge loading pressures and undergoes great displacement and plastic behaviour. In order to study the behaviour of an element under blast loading, in addition to elastic properties of materials, plastic and elastic-plastic properties of materials and sections are needed. In this paper, using analytical studies and nonlinear time-history analysis by Ansys software, the effects of shape of column sections and boundary conditions, on behaviour and local failure of steel columns under blast load are studied. This study identifies the importance of elastic-plastic properties of sections and proposes criteria for choosing the best section and boundary conditions for columns to resist blast loading.

• Geomechanics and Engineering
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• v.11 no.3
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• pp.421-438
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• 2016

Explosions inside transportation tunnels might result in failure of tunnel structures. This study investigated the failure mechanisms of circular cast-iron tunnels in saturated soil subjected to medium internal blast loading. This issue is crucial to tunnel safety as many transportation tunnels run through saturated soils. At the same time blast loading on saturated soils may induce residual excess pore pressure, which may result in soil liquefaction. A series of numerical simulations were carried out using Finite Element program LS-DYNA. The effect of soil liquefaction was simulated by the Federal Highway soil model. It was found that the failure modes of tunnel lining were differed with different levels of blast loading. The damage and failure of the tunnel lining was progressive in nature and they occurred mainly during lining vibration when the main event of blast loading was over. Soil liquefaction may lead to more severe failure of tunnel lining. Soil deformation and soil liquefaction were determined by the coupling effects of lining damage, lining vibration, and blast loading. The damage of tunnel lining was a result of internal blast loading as well as dynamic interaction between tunnel lining and saturated soil, and stress concentration induced by a ventilation shaft connected to the tunnel might result in more severe lining damage.

• Structural Engineering and Mechanics
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• v.32 no.2
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• pp.337-350
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• 2009

Finite element simulations are increasingly used in structural analysis and design, especially in cases where complex structural and loading conditions are involved. Due to considerable progresses in computer technology as well as nonlinear finite-element analysis techniques in past years, it has become possible to pursue an accurate analysis of the complex blast-induced structural effects by means of numerical simulations. This paper aims to develop a better understanding of the behavior of steel-concrete composite beams (SCCB) under localized blast loading through a numerical parametric study. A finite element model is set up to simulate the blast-resistant features of SCCB using the transient dynamic analysis software LS-DYNA. It is demonstrated that there are three dominant failure modes for SCCB subjected to localized blast loading. The effect of loading position on the behavior of SCCB is also investigated. Finally, a simplified model is proposed for assessing the overall response of SCCB subjected to localized blast loading.

• International Journal of Concrete Structures and Materials
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• v.1 no.1
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• pp.19-28
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• 2007

A dynamic constitutive damage model for reinforced concrete (RC) structures and formulations of blast loading for contact or near-contact charges are considered and adapted from literatures. The model and the formulations are applied to the input parameters needed in commercial finite element method (FEM) codes which is validated by the laboratory blast tests of RC slabs from literature. The results indicate that the dynamic constitutive damage model based on the damage mechanics and the blast loading formulations work well. The framework on the dynamic constitutive damage model and the blast loading equations can therefore be used for the simulation of failure of bridge components in engineering applications.

• Structural Engineering and Mechanics
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• v.65 no.5
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• pp.587-600
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• 2018

Infill panel is the first element of a building subjected to blast loading activating its out-of-plane behavior. If the infill panel does not have enough ductility against the loading, it breaks and gets damaged before load transfer and energy dissipation. As steel infill panel has appropriate ductility before fracture, it can be used as an alternative to typical infill panels under blast loading. Also, it plays a pivotal role in maintaining sensitive main parts against blast loading. Concerning enough ductility of the infill panel out-of-plane behavior, the impact force enters the horizontal diaphragm and is distributed among the lateral elements. This article investigates the behavior of steel infill panels with different thicknesses and stiffeners. In order to precisely study steel infill panels, different ranges of blast loading are used and maximum displacement of steel infill under such various blast loading is studied. In this research, finite element analyses including geometric and material nonlinearities are used for optimization of the steel plate thickness and stiffener arrangement to obtain more efficient design for its better out-of-plane behavior. The results indicate that this type of infill with out-of-plane behavior shows a proper ductility especially in severe blast loadings. In the blasts with high intensity, maximum displacement of infill is more sensitive to change in the thickness of plate rather the change in number of stiffeners such that increasing the number of stiffeners and the plate thickness of infill panel would decrease energy dissipation by 20 and 77% respectively. The ductile behavior of steel infill panels shows that using infill panels with less thickness has more effect on energy dissipation. According to this study, the infill panel with 5 mm thickness works better if the criterion of steel infill panel design is the reduction of transmitted impulse to main structure. For example in steel infill panels with 5 stiffeners and blast loading with the reflected pressure of 375 kPa and duration of 50 milliseconds, the transmitted impulse has decreased from 41206 N.Sec in 20 mm infill to 37898 N.Sec in 5 mm infill panel.

• Steel and Composite Structures
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• v.10 no.5
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• pp.429-455
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• 2010

The current research presents a detailed methodology for generating air blast loading for use within a finite element context. Parameters describing blast overpressure loading on a structure are drawn from open literature sources and incorporated within a blast load generation computer code developed for this research. This open literature approach lends transparency to the details of the blast load modeling, as compared with many commonly used approaches to blast load generation, for which the details are not publicly available. As a demonstration, the load generation code is used with the finite element software LS-DYNA to simulate the response of a steel plate and girder subjected to explosions modeled using these parameters as well as blast parameters from other sources.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.3
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• pp.369-380
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• 2019

When a extreme loading such as blast is applied to prestressed concrete (PSC) structures and infrastructures for an instantaneous time, serious property damages and human casualties occur. However, a existing design procedure for PSC structures such as prestressed containment vessel (PCCV) and gas storage tank do not consider a protective design for extreme internal blast scenario. Particularly, an internal blast is much more dangerous than that of external blast. Therefore, verification of the internal blast loading is required. In this paper, the internal blast resistance capacity of PSC member is evaluated by performing internal blast tests on RC and bi-directional PSC scaled down specimens. The applied internal blast loads were 22.68, 27.22, and 31.75 kg (50, 60, and 70 lbs) ANFO explosive charge at 1,000 mm standoff distance. The data acquisitions include blast pressure, deflection, strain, crack patterns, and prestressing force. The test results showed that it is possible to predict the damage area to the structure when internal blast loading occurs in PCCV structures.

• Structural Engineering and Mechanics
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• v.31 no.1
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• pp.25-38
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• 2009

Local failure of a primary structural component induced by direct air-blast loading may be itself a critical damage and lead to the partial or full collapse of the building. As an extensive research to mitigate blast-induced hazards in steel frame structure, a state-of-art analytical approach or high-fidelity computational nonlinear continuum modeling using computational fluid dynamics was described in this paper. The capability of the approach to produce reasonable blast pressures on a steel wide-flange section column was first evaluated. Parametric studies were conducted to observe the effects of section sizes and boundary conditions on behavior and failure of columns in steel frame structures. This study shows that the analytical approach is reasonable and effective to understand the nature of blast wave and complex interaction between blast loading and steel column behavior.

• Structural Engineering and Mechanics
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• v.36 no.6
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• pp.729-744
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• 2010

There is world wide concern for safety of nuclear power installations after the terrorist attack on World Trade Center in 2001 and several other civilian structures in the last decade. The nuclear containment structure in many countries is a double shell structure (outer shell a RCC and inner a prestressed concrete). The outer reinforced concrete shell protects the inner shell and is designed for external loading like impact and blast. A comparative study of non-linear response of reinforced concrete nuclear containment cylindrical shell subjected to impact of an aircraft (Phantom) and explosion of different amounts of blast charges have been presented here. A material model which takes into account the strain rate sensitivity in dynamic loading situations, plastic and visco-plastic behavior in three dimensional stress state and cracking in tension has been developed earlier and implemented into a finite element code which has been validated with published literature. The analysis has been made using the developed software. Significant conclusions have been drawn for dissimilarity in response (deflections, stresses, cracks etc.) of the shell for impact and blast loading.

• Structural Engineering and Mechanics
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• v.38 no.4
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• pp.479-501
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• 2011

Even though fiber reinforced polymer (FRP) has been widely used as a retrofitting material, the FRP behavior and effect in FRP retrofitted structure under blast loading, impulsive loading with instantaneous time duration, has not been accurately examined. The past studies have focused on the performance of FRP retrofitted structures by making simplifications in modeling, without incorporating accurate failure mechanisms of FRP. Therefore, it is critical to establish an analytical model that can properly consider the specific features of FRP material in evaluating the response of retrofitted concrete structures under blast loading. In this study, debonding failure analysis technique for FRP retrofitted concrete structure under blast loading is suggested by considering FRP material characteristics and debonding failure mechanisms as well as rate dependent failure mechanism based on a blast resisting design concept. In addition, blast simulation of FRP retrofitted RC panel is performed to validate the proposed model and analysis method. For validation of the proposed model and analysis method, the reported experimental results are compared with the debonding failure analysis results. From the comparative verification, it is confirmed that the proposed analytical model considering debonding failure of FRP is able to reasonably predict the behavior of FRP retrofitted concrete panel under blast loading.