Peak Incident Pressure Research Articles

Blast resistance of RC tubular structure under internal ANFO explosion

The degree of structural damage is significantly more severe when a blast occurs inside than outside of a structure. However, existing designs for RC structures such as reinforced concrete containment vessels (RCCV) do not include design features to protect the structure for internal blast. Therefore, the internal blast resistance capacity of RC structures is evaluated by performing internal blast tests on RC tubular structures. The main objective of the study was to observe and document the basic structural behavior data obtained from internal detonation tests. ANFO explosive charge weights of 15.88, 20.41, 22.68 and 24.95 kg were selected for a charge detonating at a cross section center of the mid-span of the specimen, giving a standoff distance to the inner wall surface of 1000 mm. The data acquisitions include blast pressure, deflection, strain, and crack pattern. When the explosive charge weight increased from 15.88 to 24.95 kg, the peak incident pressure and time duration increased from 0.1718 to 0.3394 MPa and from 5.856 to 5.981 ms, respectively. Then, the test data were used to predict the internal charge weight required to fail a real scale RCCV using simple assumptions and the test data. The results of the study are discussed in detail in the paper.

Shock Wave Physics as Related to Primary Non-Impact Blast-Induced Traumatic Brain Injury.

Blast overpressure exposure, an important cause of traumatic brain injury (TBI), may occur during combat or military training. TBI, most commonly mild TBI, is considered a signature injury of recent combat in Iraq and Afghanistan. Low intensity primary blast-induced TBI (bTBI), caused by exposure to an explosive shock wave, commonly leaves no obvious physical external signs. Numerous studies have been conducted to understand its biological effects; however, the role of shock wave energy as related to bTBI remains poorly understood. This report combines shock wave analysis with established biological effects on the mouse brain to provide insights into the effects of shock wave physics as related to low intensity bTBI outcomes from both open-air and shock tube environments. Shock wave peak pressure, rise time, positive phase duration, impulse, shock velocity, and particle velocity were measured using the Missouri open-air blast model from 16 blast experiments totaling 122 mice to quantify physical shock wave properties. Open-air shock waves were generated by detonating 350-g 1-m suspended Composition C-4 charges with targets on 1-m elevated stands at 2.15, 3, 4, and 7 m from the source. All mice sustained brain injury with no observable head movement, because of mice experiencing lower dynamic pressures than calculated in shock tubes. Impulse, pressure loading over time, was found to be directly related to bTBI severity and is a primary shock physics variable that relates to bTBI. The physical blast properties including shock wave peak pressure, rise time, positive phase duration, impulse, shock velocity, and particle velocity were examined using the Missouri open-air blast model in mice with associated neurobehavioral deficits. The blast-exposed mice sustained ultrastructural abnormalities in mitochondria, myelinated axons, and synapses, implicating that primary low intensity blast leads to nanoscale brain damage by providing the link to its pathogenesis. The velocity of the shock wave reflected back from the target stand was calculated from high-speed video and compared with that of the incident shock wave velocity. Peak incident pressure measured from high sample rate sensors was found to be within 1% of the velocity recorded by the high-speed camera, concluding that using sensors in or close to an animal brain can provide useful information regarding shock velocity within the brain, leading to more advanced knowledge between shock wave physics and tissue damage that leads to bTBIs.

A rational bubble screen design approach for mitigation of underwater explosion near waterborne infrastructure

Underwater explosions pose a significant threat to waterborne infrastructure. The potential for damage to nearby infrastructure is dependent on parameters such as the peak incident pressure, energy flux density, radial standoff distance, and dynamic material strength and structural response. Bubble screens have been shown to be an effective means to attenuate specific shock wave characteristics such as the peak incident pressure and energy flux density to safe levels. This paper presents a comprehensive, rational design approach for protecting waterborne infrastructure using bubble screens. The paper presents an improved methodology to predict peak incident pressure and energy flux density produced by shock waves, which includes depth effects. In addition, the damage potential to various structural materials is established based on the equivalent dynamic loads and dynamic material strength. The results are compiled to form a step-by-step procedure for the design and implementation of a bubble screen system.

Observed airblast variability and model error from repeatable explosive field trials

Explosive field trials have been conducted to measure the peak incident pressure, impulse and time of positive phase duration following the detonation of 15 different masses of the Plastic Explosive No #4. A novel aspect of these field trials was the repeatability of tests. Eight pressure gauges collected data during each blast, and at each scaled distance. In all, 4 blasts were conducted for each scaled distance (i.e. up to 32 measurements recorded for each scaled distance) – 60 blasts were fired in total. Consequently, this repeatability of testing allowed the mean and variance of blast pressure–time histories to be quantified, with a view to better characterise the variability of a blast itself and model error variability. This article describes the explosive field trials, and the statistical analysis of blast load variability and model error for peak incident pressure, impulse and time of positive phase duration. It was found that the mean model error is close to unity with a coefficient of variation of up to 0.15 for pressure and 0.21 for impulse. The lognormal probability distribution best fits the model error data. The probabilistic models derived from these tests can be used for a variety of structural engineering applications, such as calculating reliability-based design load or partial safety factors for explosive blast loading, and estimating the probability of damage and casualties for infrastructure subject to explosive blast loading. This is illustrated for a terrorist explosive scenario involving a spherical free-air burst, where the damage modes of interest are breaching and spalling of a concrete slab. It was found that the variability of charge mass, range and model error have a significant effect on reliability-based design.

Parametric analysis of the biomechanical response of head subjected to the primary blast loading – a data mining approach

Traumatic brain injury due to primary blast loading has become a signature injury in recent military conflicts and terrorist activities. Extensive experimental and computational investigations have been conducted to study the interrelationships between intracranial pressure response and intrinsic or ‘input’ parameters such as the head geometry and loading conditions. However, these relationships are very complicated and are usually implicit and ‘hidden’ in a large amount of simulation/test data. In this study, a data mining method is proposed to explore such underlying information from the numerical simulation results. The heads of different species are described as a highly simplified two-part (skull and brain) finite element model with varying geometric parameters. The parameters considered include peak incident pressure, skull thickness, brain radius and snout length. Their interrelationship and coupling effect are discovered by developing a decision tree based on the large simulation data-set. The results show that the proposed data-driven method is superior to the conventional linear regression method and is comparable to the nonlinear regression method. Considering its capability of exploring implicit information and the relatively simple relationships between response and input variables, the data mining method is considered to be a good tool for an in-depth understanding of the mechanisms of blast-induced brain injury. As a general method, this approach can also be applied to other nonlinear complex biomechanical systems.

Reliability-Based Design Load Factors for Explosive Blast Loading

AbstractReliability-based design allows the decision maker to select the level of reliability for a specific blast loading scenario and key to this is an understanding of airblast uncertainty. Hence, explosive field trials have been conducted in Australia that measured the variability of free-field blast loading caused by military standard plastic explosives. The results have revealed a high level of variability of peak incident pressure, impulse, and time of positive phase duration for repeatable tests where variability would be expected to be a minimum. The accuracy of predictive blast load models (model error) was also assessed. A probabilistic blast load computer model is revised to capture these observed variabilities. The effect of a 20% mass-increase safety factor typically applied to explosive mass on the probability of exceeding a design blast load is assessed. Reliability-based load factors are calculated where the nominal load is multiplied by the load factor to ensure that the actual load is e...

A theoretical analysis of stress wave propagation in the head under primary blast loading

Traumatic brain injury due to primary blast loading has become a signature injury in recent military conflicts. Efforts have been made to study the stress wave propagation in the head. However, the relationship of incident pressure, reflected pressure and intracranial pressure is still not clear, and the experimental findings reported in the literature are contradictory. In this article, an analytical model is developed to calculate the stress wave transfer through a multiple-layered structure which is used to mimic the head. The model predicts stress at the scalp-skull and skull-brain interfaces as the functions of reflected pressure, which is further dependent on incident pressure. A numerical model is used to corroborate the theoretical predictions. It is concluded that scalp has an amplification effect on intracranial pressure. If scalp is absent, there exists a critical incident pressure, defined as P cr at approximately 16 kPa. When peak incident pressure σ in is higher than 16 kPa, the pressure at the skull-brain interface is greater than σ in; otherwise, it is lower than σ in.

Experimental Investigation of Aluminum Foam Lined Suppressive Shield Containment Vessels

Manufacture, transport, and storage of dangerous goods, especially energetic materials, in Canada and around the world pose serious challenges to explosives regulators and inspectors. Currently siting of manufacturing and storage facilities are in accordance with quantity-distance principles designed to mitigate effects of accidental explosions. The land requirements to satisfy these principles are imposing financial burdens on the explosives sector. This paper presents an experimental program designed to investigate the effectiveness of suppressive shield containers in reducing the blast pressure outside of the container while eliminating fragments thus reducing the distance requirement for the stored amount of explosives. Several suppressive shield panels including aluminium foam-lined panels were tested to study their effect on blast pressure and impulse. In addition computational fluid dynamics techniques were used to study suppressive shields effects on blast environment. The results show reduction of the incident peak blast pressure by 60% and the incident impulse by 58%. The aluminium foam-lined suppressive shield panels attenuated the peak incident pressure and impulse by 80%.

Aluminum Foam-Lined Suppressive Shields for Safe Transport of Explosives

The manufacture, transportation, and storage of explosives in Canada and around the world pose serious challenges to explosives regulators and inspectors tasked with ensuring the safety of nearby populations. Explosives are routinely transported through, and manufacturing and storage facilities are often located close to, populated areas and traffic routes. This proximity increases the risk of severe casualties and infrastructure damage if there is an accidental or deliberate explosion. Even though an explosion is unlikely, the consequences can be severe. Several accidents that have involved explosives are discussed in the literature. These accidents highlight the devastation likely to result from an explosion and underscore the importance of finding cost-effective solutions to mitigate the effects on the population and infrastructure. This paper presents a research program designed to investigate the effectiveness of suppressive shield containers in reducing the blast pressure outside the container and eliminating fragment hazards from an explosion. Several types of suppressive shield panels, including panels lined with aluminum foam, were tested in a blast chamber. The results show reduced peak blast pressure outside the container by as much as 60% and in the incident impulse by about 58%. When the suppressive shield was lined with aluminum foam, a further reduction in peak incident pressure (up to 80%) was achieved.

Analytical and experimental study on the fluid structure interaction during air blast loading

A new fluid-structure interaction model that considers high gas compressibility is developed using the Rankine–Hugoniot relations. The impulse conservation between the gas and structure is utilized to determine the reflected pressure profile from the known incident pressure profile. The physical parameters of the gas such as the shock front velocity, gas density, local sound velocity, and gas particle velocity as well as the impulse transmitted onto the structure are also evaluated. A series of one-dimensional shock loading experiments on free standing monolithic aluminum plates were conducted using a shock tube to validate the proposed model. The momentum was evaluated using high speed digital imagery. The experimental peak reflected pressure, the reflected pressure profile, and the momentum transmitted onto the plate were compared with the predicted results. The comparisons show that the gas’s compressibility significantly affects the fluid structure interaction behavior, and the new model can predict more accurate results than existing models. The effect of factors, such as the areal density of a plate and the peak incident pressure on momentum transfer are also discussed using the present model. Moreover, the maximum achievable momentum and the fluid structure interaction time are defined and calculated.

Blast Performance of Sandwich Composites with In-Plane Compressive Loading

An experimental investigation was conducted to evaluate the dynamic performance of E-glass Vinyl Ester composite face sheet / foam core sandwich panels when subjected to pre-compression and subsequent blast loading. The sandwich panels were subjected to 0 kN, 15 kN and 25 kN of in plane compression respectively, prior to transverse blast wave loading with peak incident pressure of 1 MPa and velocity of 3 Mach. The blast loading was generated using a shock tube facility. During the experiments, a high-speed photographic system utilizing three digital cameras was used to acquire the real-time 3-D deformation of the sandwich panels. The 3D Digital Image Correlation (DIC) technique was used to quantify the back face out-of-plane deflection and in-plane strain. The results showed that in-plane compressive loading facilitated buckling and failure in the front face sheet. This mechanism greatly reduced the blast resistance of sandwich composites.

Shock loading and drop weight impact response of glass reinforced polymer composites

Abstract Response of E-glass reinforced vinyl ester and urethane panels of varying structures subjected to shock loading and drop weight impact loading have been studied. Shock waves are created using a shock tube with a testing range of 3.08–7.53 MPa peak incident pressure. The materials performance under shock loading was evaluated by post-mortem visual damage assessment, residual compressive strength, and permanent deformation mapping of the panels. Drop weight impact performance was measured by energy absorbed by the samples, depth of penetration, and extent of internal damage. Glass preforms having total areal weights 144 and 216 oz / yd 2 (4.88 and 7.32 kg / m 2 ) were infused with either one of three separate types of vinyl ester and one urethane resin. The results show that urethane panels having total glass preform areal weight of 216 oz / yd 2 ( 7.32 kg / m 2 ) performed better than similar vinyl ester resin panels. It was also found that of two materials with identical vinyl ester resins having total preform areal weight of 144 oz / yd 2 ( 4.88 kg / m 2 ) , the one with a finer glass structure consistently performed better in all evaluation criteria for shock wave and drop weight impact testing.

Evaluation and rehabilitation of a building affected by a gas explosion

AbstractThe paper deals with efficient solutions for rehabilitation of a block of flats affected by a gas explosion in December 2002. The first part of the paper is devoted to general aspects of the effects of explosions on buildings and personnel. The characteristic of the peak incident pressure as well as maximum reflected pressure are presented. The design procedures and rehabilitation solutions of the buildings subjected to blast loads are described. Rehabilitation solutions for general structural vulnerabilities as well as specific solutions for rehabilitation are presented for RC structures, steel structures and masonry structures. These solutions have been adopted from those already used to develop seismic retrofits. Special attention has been paid to carbon‐fibre‐reinforced plastic (CFRP) materials.The second part presents a case study analysis and rehabilitation of a block of flats. The damage due to the explosion is presented for the different structural elements: those in direct contact with blast pressure and the surrounding structural members. Structural analysis comprises two important aspects: the behaviour of the structural members subjected to direct blast pressure and the analysis of the state stresses in the entire building.The rehabilitation solutions were chosen in accordance with the actual stage of the building. New elements have been used instead of the completely destroyed structural members. RC coatings and columns were necessary to assure continuity and stability of vertical members with serious damage after explosion. Longitudinal beams have the role of connecting the new vertical members. Utilization of CFRP for strengthening of slightly damaged elements has the advantages of easy technology and short time of erection. The other technical and economical advantages of the rehabilitation solutions are: safe behaviour under seismic action; slight change of general stiffness of the structure; small cost of rehabilitation. The consolidation and finishing works were completed by the middle of 2003.