Blast Wall Shielding Effectiveness

2017 ◽  
Author(s):  
Jihui Geng ◽  
J. Kelly Thomas
Keyword(s):  
Blast Wave ◽  
High Explosive ◽  
Blast Loading ◽  
Blast Waves ◽  
Shielding Effectiveness ◽  
Wave Shape ◽  
Mitigation Option ◽  
Blast Damage ◽  
Wave Parameters ◽  
Vapor Cloud

Blast walls are frequently considered as a potential mitigation option to reduce the applied blast loading on a building or structure in cases where unacceptably high levels of blast damage are predicted. There are three general explosion types of interest with respect to blast loading: High Explosive (HE), Pressure Vessel Burst (PVB), and Vapor Cloud Explosion (VCE). The blast waves resulting from these explosion types can differ significantly in terms of blast wave shape and duration. The effectiveness of a blast wall depends on these blast wave parameters (shape and duration), as well as the blast wall parameters (e.g., height, width and standoff distance from the protected structure). The effectiveness of a blast wall in terms of mitigating the blast loading on a protected structure depends on the combination of the blast wave and blast wall parameters. However, little guidance is available on the effectiveness of blast walls as a mitigation option for non-HE explosion sources. The purpose of this paper is to characterize the effect of blast wave parameters on the effectiveness of a blast wall and to provide guidance on how to determine whether a blast wall is an effective and practical blast damage mitigation option for a given blast loading.

Effect of Explosion Source Type on Blast Wave Shielding

2013 ◽  
Author(s):  
Jihui Geng ◽  
J. Kelly Thomas
Keyword(s):  
Blast Wave ◽  
Target Location ◽  
Blast Waves ◽  
Explosion Hazard ◽  
Shape Parameters ◽  
Wave Shape ◽  
Blast Overpressure ◽  
Screening Study ◽  
Vapor Cloud ◽  
The Uk

A key component of explosion hazard evaluations is the determination of standoffs to given blast overpressure values. Many such evaluations use a simplified methodology that assumes that the blast wave propagates from the explosion source to the target location without interacting with intervening buildings or structures (i.e., without blast wave shielding). This is obviously a perfectly acceptable approach for a screening study, but blast wave shielding effects can be significant in certain circumstances (e.g., within a building group). A methodology was proposed by the UK Health & Safety Laboratory (HSL) in 2001 to account for blast shielding due to buildings/structures between the explosion source and target location. The HSL methodology is based on the blast waves generated by high explosives (HE). This paper extends the blast shielding evaluation to blast waves generated from pressure vessel bursts (PVB) and vapor cloud explosions (VCE). The influences of blast wave shape parameters (overpressure, duration and rise time) on blast wave shielding are examined. The results indicate that the degree of blast shielding is strongly dependent on the source of the blast wave (i.e., on the blast wave shape parameters) and that the shielding factors obtained with HE blast waves are not always directly applicable for PVB and VCE blast waves.

scholarly journals Clearing of Blast Waves on Finite-Sized Targets – an Overlooked Approach

2011 ◽  
Vol 82 ◽  
pp. 669-674 ◽  
Author(s):  
Andrew Tyas ◽  
Terry Bennett ◽  
James A. Warren ◽  
Stephen D. Fay ◽  
Sam E. Rigby
Keyword(s):  
Blast Wave ◽  
Experimental Testing ◽  
Experimental Studies ◽  
Blast Loading ◽  
Blast Waves ◽  
Total Impulse ◽  
Cast Doubt ◽  
The Face ◽  
Loading Parameter ◽  
Semi Empirical

The total impulse imparted to a target by an impinging blast wave is a key loading parameter for the design of blast-resistant structures and façades. Simple, semi-empirical approaches for the prediction of blast impulse on a structure are well established and are accurate in cases where the lateral dimensions of the structure are sufficiently large. However, if the lateral dimensions of the target are relatively small in comparison to the length of the incoming blast wave, air flow around the edges of the structure will lead to the propagation of rarefaction or clearing waves across the face of the target, resulting in a premature reduction of load and hence, a reduction in the total impulse imparted to the structure. This effect is well-known; semi-empirical models for the prediction of clearing exist, but several recent numerical and experimental studies have cast doubt on their accuracy and physical basis. In fact, this issue was addressed over half a century ago in a little known technical report at the Sandia Laboratory, USA. This paper presents the basis of this overlooked method along with predictions of the clearing effect. These predictions, which are very simple to incorporate in predictions of blast loading, have been carefully validated by the current authors, by experimental testing and numerical modelling. The paper presents a discussion of the limits of the method, concluding that it is accurate for relatively long stand-off blast loading events, and giving some indication of improvements that are necessary if the method is to be applicable to shorter stand-off cases.

Modeling Articulated Human Body Dynamics Under a Representative Blast Loading

2011 ◽  
Author(s):  
X. G. Tan ◽  
Andrzej J. Przekwas ◽  
Gregory Rule ◽  
Kaushik Iyer ◽  
Kyle Ott ◽  
...  
Keyword(s):  
Blast Wave ◽  
Human Body ◽  
Fluid Dynamic ◽  
Free Field ◽  
Time History ◽  
Blast Loading ◽  
Blast Waves ◽  
Time Step ◽  
Time Step Size ◽  
Body Dynamics

Blast waves resulting from both industrial explosions and terrorist attacks cause devastating effects to exposed humans and structures. Blast related injuries are frequently reported in the international news and are of great interest to agencies involved in military and civilian protection. Mathematical models of explosion blast interaction with structures and humans can provide valuable input in the design of protective structures and practices, in injury diagnostics and forensics. Accurate simulation of blast wave interaction with a human body and the human body biodynamic response to the blast loading is very challenging and to the best of our knowledge has not been reported yet. A high-fidelity computational fluid dynamic (CFD) model is required to capture the reflections, diffractions, areas of stagnation, and other effects when the shock and blast waves respond to an object placed in the field. In this effort we simulated a representative free field blast event with a standing human exposed to the threat using the Second Order Hydrodynamic Automatic Mesh Refinement Code (SHAMRC). During the CFD analysis the pressure time history around the human body is calculated, along with the fragment loads. Subsequently these blast loads are applied to a fully articulated human body using the multi-physics code CoBi. In CoBi we developed a novel computational model for the articulated human body dynamics by utilizing the anatomical geometry of human body. The articulated human body dynamics are computed by an implicit multi-body solver which ensures the unconditional stability and guarantees the quadratic rate of convergence. The developed solver enforces the kinematic constraints well while imposing no limitation on the time step size. The main advantage of the model is the anatomical surface representation of a human body which can accurately account for both the surface loading and the surface interaction. The inertial properties are calculated using a finite element method. We also developed an efficient interface to apply the blast wave loading on the human body surface. The numerical results show that the developed model is capable of reasonably predicting the human body dynamics and can be used to study the primary injury mechanism. We also demonstrate that the human body response is affected by many factors such as human inertia properties, contact damping and the coefficient of friction between the human body and the environment. By comparing the computational results with the real scenario, we can calibrate these input parameters to improve the accuracy of articulated human body model.

Enhancement of blast wave parameters due to shock focusing from multiple simultaneously detonated charges

2021 ◽  
pp. 204141962110333
Author(s):  
Amir Zaghloul ◽  
Alex Remennikov ◽  
Brian Uy
Keyword(s):  
Blast Wave ◽  
Blast Waves ◽  
Terrorist Attacks ◽  
Blast Loads ◽  
Single Charge ◽  
Shock Focusing ◽  
Approximate Methods ◽  
The Past ◽  
Wave Parameters ◽  
Blast Parameters

With the increase of terrorist attacks over the past decades, many engineering societies have started issuing design guides to calculate blast loads on structures. While such guides can be successfully used to assess blast loads due to single detonations, the effects of multiple detonations are often overlooked. In this research, the enhancement in blast parameters resulting from simultaneously detonating multiple charges is investigated, emphasising the interaction of blast waves with narrow targets. A parametric CFD study using the finite volume code Viper::Blast was performed where the number of charges, their arrangement, and the scaled stand-off distances were changed. It is found that, when detonated simultaneously, multiple charges return much higher pressure and impulse values compared to an equivalent single charge. Moreover, an arced arrangement of multiple charges is more efficient than a flat arrangement in enhancing blast wave parameters. Such enhancement is beneficial in scenarios involving demolition. Approximate methods to compute blast wave parameters from multiple simultaneously detonated spherical charges are presented in this study, where pressure and impulse from multiple charges can be computed by only knowing the parameters resulting from an equivalent single charge.

scholarly journals Review of Blast Loading Models, Masonry Response, and Mitigation

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Eid Badshah ◽  
Amjad Naseer ◽  
Muhammad Ashraf ◽  
Feroz Shah ◽  
Kareem Akhtar
Keyword(s):  
Boundary Conditions ◽  
Urban Environment ◽  
Blast Wave ◽  
Material Properties ◽  
Free Field ◽  
Blast Loading ◽  
Masonry Structure ◽  
Mitigation Strategies ◽  
Masonry Buildings ◽  
Wave Parameters

Different models for prediction of blast loading, response of masonry structure against blast load, and various mitigation strategies are discussed. Variation of peak positive incident pressure with scale distance in free field spherical burst and surface burst scenarios, proposed by different researchers, is presented and compared. The variation is found significant in the region of small scaled distances. Blast wave parameters in urban environment have been found different from the free field scenario. Effects of geometry, boundary conditions, and material properties on response of masonry buildings were found significant. Different mitigation strategies such as blast wall, landscaping, architecture, and retrofitting techniques are presented.

scholarly journals Guidelines to inform the generation of clinically relevant and realistic blast loading conditions for primary blast injury research

2021 ◽  
pp. bmjmilitary-2021-001796
Author(s):  
J W Denny ◽  
A S Dickinson ◽  
G S Langdon
Keyword(s):  
Blast Wave ◽  
Blast Loading ◽  
Wave Interaction ◽  
Blast Waves ◽  
Experimental Investigations ◽  
Loading Conditions ◽  
Primary Blast ◽  
Blast Overpressure ◽  
Engineering Theory ◽  
Blast Traumatic Brain Injury

‘Primary’ blast injuries (PBIs) are caused by direct blast wave interaction with the human body, particularly affecting air-containing organs. With continued experimental focus on PBI mechanisms, recently on blast traumatic brain injury, meaningful test outcomes rely on appropriate simulated conditions. Selected PBI predictive criteria (grouped into those affecting the auditory system, pulmonary injuries and brain trauma) are combined and plotted to provide rationale for generating clinically relevant loading conditions. Using blast engineering theory, explosion characteristics including blast wave parameters and fireball dimensions were calculated for a range of charge masses assuming hemispherical surface detonations and compared with PBI criteria. While many experimental loading conditions are achievable, this analysis demonstrated limits that should be observed to ensure loading is clinically relevant, realistic and practical. For PBI outcomes sensitive only to blast overpressure, blast scaled distance was demonstrated to be a useful parameter for guiding experimental design as it permits flexibility for different experimental set-ups. This analysis revealed that blast waves should correspond to blast scaled distances of 1.75<Z<6.0 to generate loading conditions found outside the fireball and of clinical relevance to a range of PBIs. Blast waves with positive phase durations (2–10 ms) are more practical to achieve through experimental approaches, while representing realistic threats such as improvised explosive devices (ie, 1–50 kg trinitrotoluene equivalent). These guidelines can be used by researchers to inform the design of appropriate blast loading conditions in PBI experimental investigations.

The Reaction of the Head and Neck to Blast Waves: Comparison to Blunt Impact

2008 ◽  
Author(s):  
Timothy P. Harrigan
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Blast Wave ◽  
Closed Head Injury ◽  
Blast Loading ◽  
Element Model ◽  
Blast Waves ◽  
Sudden Increase ◽  
Fluid Structure ◽  
Ale Formulation

Due to the relatively large number of exposures to IED blasts in Iraq and Afghanistan, the mechanical effects of blast waves impinging on the head have become an area of high interest. The ways in which the physical aspects of blast loading can cause injury are controversial in some respects but a general consensus is forming that much of the knowledge from closed head injury due to blunt trauma can be applied to injury mechanisms in blast loading [2]. In particular, sudden head rotations are known to be significant, as these are connected to high strains in brain tissue, in much the same way that rotations applied to a jar full of gelatin can induce deformations in the gelatin. High strains induced by sudden rotations of the head are known to be significant in developing injuries to the white matter of the brain [3, 4]. This study used a coupled fluid-structure finite element model to assess the effects of blast over pressure on translation and rotation of the head due to blast wave exposure. A finite element model of a 5th percentile Hybrid-III dummy was used which was supplied by Livermore Scientific Technlogy Corp. (LSTC) as part of a license for LS-Dyna. The ALE formulation for fluid-structure coupling was used [1]. The sudden increase in head velocity is significant, but the sudden increases in rotation rates are small compared to those for some impacts. The increases in velocity and rotation rate due to the passage of the blast wave on the head of the dummy occur over a few milliseconds, and rotation becomes significant only after the neck loads become active, 15 to 20 milliseconds after blast wave impingement. These results indicate that efforts to modify the rotational velocity of the head in the reaction to a blast wave should act within 15 to 20 milliseconds of the blast.

scholarly journals In silico investigation of biomechanical response of a human subjected to primary blast

2021 ◽  
Author(s):  
Sunil Sutar ◽  
Shailesh Ganpule
Keyword(s):  
White Matter ◽  
Blast Wave ◽  
Rotational Motion ◽  
Blast Waves ◽  
Primary Blast ◽  
Body Model ◽  
The Past ◽  
Biomechanical Response ◽  
The Brain ◽  
Full Body

The response of the brain to the explosion induced primary blast waves is actively sought. Over the past decade, reasonable progress has been made in the fundamental understanding of bTBI using head surrogates and animal models. Yet, the current understanding of how blast waves interact with the human is in nascent stages, primarily due to lack of data in humans. The biomechanical response in human is critically required so that connection to the aforementioned bTBI models can be faithfully established. Here, using a detailed, full-body human model, we elucidate the biomechanical cascade of the brain under a primary blast. The input to the model is incident overpressure as achieved by specifying charge mass and standoff distance through ConWep. The full-body model allows to holistically probe short- (<5 ms) and long-term (200 ms) brain biomechanical responses. The full-body model has been extensively validated against impact loading in the past. In this work, we validate the head model against blast loading. We also incorporate structural anisotropy of the brain white matter. Blast wave human interaction is modeled using a conventional weapon modeling approach. We demonstrate that the blast wave transmission, linear and rotational motion of the head are dominant pathways for the biomechanical loading of the brain, and these loading paradigms generate distinct biomechanical fields within the brain. Blast transmission and linear motion of the head govern the volumetric response, whereas the rotational motion of the head governs the deviatoric response. We also observe that blast induced head rotation alone produces a diffuse injury pattern in white matter fiber tracts. Lastly, we find that the biomechanical response under blast is comparable to the impact event. These insights will augment laboratory and clinical investigations of bTBI and help devise better blast mitigation strategies.

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