Terrorist Bomb Attacks Research Articles

15.10: Probabilistic analysis of steel columns under blast induced loads

ABSTRACTA growing interest for the design of structures to sustain blast induced loads has been observed in recent years due to the worldwide rise of terrorist bombing attacks. The blast parameters that are essential for design can be located in various publically available blast design manuals, where the proposed graphs and equations are based on a large experimental database established several decades ago. The degree of uncertainty in the determination of these parameters is significant, as a result of the unstable nature of explosives, the efficiency of the measuring equipment and the large pressure and impulse values involved in the blast phenomena.These uncertainties have been identified in the current study which focuses on the response of steel open sections under blast induced loads and addresses the influence of such uncertainties on the flexural response of axially loaded structural members. The variation of structural and load parameters was considered in the design procedure by utilizing a reliability‐based assessment methodology. A probabilistic approach was followed and the reliability of the column was defined with respect to limit states proposed in various blast design manuals. Probability curves are constructed, by using single‐degree‐of‐freedom models, showing the cumulative probability distribution of reaching a certain capacity with respect to a selected limit state. This way instead of a deterministic safe‐unsafe criterion in design, the probability of damage is introduced in relation to the applied axial load, which provides a valuable insight to the behaviour of structural members subjected to an explosion.

Dynamics of an Underwater Explosion Bubble near a Rigid Wall: Effect of Slenderness Ratio, Installation, and Distance Parameter

ABSTRACT Zhang, Z.; Wang, L.; Yao, X., and Lang, J., 2017. Dynamics of an underwater explosion bubble near a rigid wall: Effect of slenderness ratio, installation, and distance parameter. Structural damage of maritime construction (e.g., dams, warships, etc.) has received considerable international attention in recent years because of underwater explosions from accidental events and terrorist bombing attacks. Therefore, research studies on underwater explosion load characteristics will have a great influence on the future of coastal and maritime engineering. Here, level set–direct ghost fluid–Runge Kutta discontinuous Galerkin method and boundary element method are combined to establish a model of underwater explosion near a rigid wall. First, the hybrid algorithm is used to simulate the process of underwater explosion in free field; the results agree well with experimental data, proving the effectiveness of the algorithm. Second, the process of underwater explosion near a rigid wall is simulated by the p...

Post-blast capacity of ultra-high performance concrete columns

Over the past several decades, iconic and public buildings have become targets of terrorist bomb attacks, but most of these buildings were built without consideration of blast loading scenarios. Key load-carrying elements such as concrete columns are probably the most critical structural components for structural protection against bomb threats. Failures of columns may trigger catastrophic progressive collapse if there is insufficient structural redundancy. In a recent study, novel ultra-high performance concrete (UHPC) material formulated based on reactive powder concrete (RPC) was developed. Field blast tests on columns made of this material were performed. Test results showed that UHPC columns had excellent blast resistant capability, only small mid-height deflection and minor concrete damage was observed after the blasting tests. In the present study, to quantify blast-induced damage and assess residual loading capacity of UHPC columns, static axial loading tests on post-blast UHPC columns were carried out. Undamaged control samples were tested to provide benchmarks. Damage index and residual loading capacity of UHPC columns after various blast loadings were obtained. It was found that column cast with micro steel fibre reinforced UHPC preserved more than 70% of its loading capacity after 35kg TNT detonation at 1.5m standoff distance, while high strength concrete column only maintained 40% loading capacity after 8kg TNT detonation at 1.5m standoff distance.

Study on an engineering measure to improve internal explosion resistance capacity of segmental tunnel lining structures

With the increase of terrorist bombing attacks on subway systems, few research results could be traced on the internal explosion capacity of segmental tunnel linings. This paper presented some full-scale test results of segmental tunnel linings under internal explosions, and the deformation and failure patterns of segmental tunnel lining were analyzed and outlined, wherein the key factors and positions that dominate the damage of a segmental lining were figured out. Then based on a conceptual idea, attempts were made, by adding flexible damping cushions on the joints, to relieve the damage degree of contact area of bolts. At last, numerical simulations were performed and it was shown that, the localized failures of joint areas of tunnel segments could be relieved effectively after introduction of this measure, so the internal explosion resistance performance of segmental lining structures could be optimized and hence improved.

Analysis of the blast wave decay coefficient using the Kingery–Bulmash data

A growing interest for the design of structures to sustain blast-induced loads has been observed in recent years as a result of the worldwide rise of terrorist bombing attacks. The blast loading is usually characterized by a sudden increase in the pressure followed by an exponential decay. The parameters of this pressure pulse are essential for design and can be found in various blast design manuals available in the open literature. One of the most widely used sources is a technical report by Kingery–Bulmash, which provides values for many blast parameters in diagrams and polynomial form. However, it does not include an equation for calculating the blast wave decay coefficient, necessary for constructing the pressure–time history of an explosion at a certain point. In this study, a review of the technical literature that contains expressions for the blast pressure decay coefficient is performed, and relevant comparisons have been made. New equations describing the decay coefficient of the Friedlander equation for both incident and reflected cases for free-air and surface bursts are proposed. These equations express the decay coefficient in terms of the scaled distance and are not valid for close-in detonations. They are entirely based on the Kingery–Bulmash data, and their accuracy is satisfactorily checked against new experimental results and their trends assessed through a sensitivity analysis. Accordingly, the positive phase of the pressure–time curve at a point can be reliably and efficiently generated.

Static and dynamic material properties of CFRP/epoxy laminates

Carbon fiber reinforced polymer (CFRP) has been extensively used to strengthen structures owing to its outstanding mechanical properties. With an increasing threat from terrorist bombing attacks and accidental explosions, the application of CFRP has been extended to mitigate the effect of blast loading on structures. A better understanding of the dynamic material properties of CFRP/epoxy laminates at high strain rates is therefore needed for more reliable analysis and design of CFRP strengthened structures under dynamic loadings. In this study, the unidirectional tensile properties of CFRP (SikaWrap®-230C) and epoxy resin (Sikadur®-330) laminates is investigated experimentally over a wide range of strain rates. Quasi-static and low-speed tensile tests are conducted at strain rates varying from 7×10−5s−1 to 0.07s−1. Then, high-speed tensile tests are performed using a high-speed servo-hydraulic testing machine at strain rate from about 10s−1 to 240s−1. The testing results show that both the tensile strength and the stiffness of the CFRP/epoxy laminates are insensitive to loading speed when the strain rate is less than 50s−1. However, when strain rate is over 50s−1, both the tensile strength and the coupon stiffness increase with the increase of strain rate. High-speed camera images are used to assist inspecting the failure modes of CFRP/epoxy laminates. It is found that under high-strain rate tension CFRP/epoxy laminates fail differently from that at low-strain rate. The different failure mode is believed to contribute to the increment of laminate strength. The testing data are analyzed together with available testing results on CFRP/epoxy laminates at various strain rates. Empirical formulas of dynamic increase factor for CFRP material are derived for better prediction of material strength at various strain rates.

Advances in the research of blast lung injury

In recent years, a variety of explosive weapons become increasingly common used in regional military conflicts and terrorist bomb attacks. Meanwhile, the incidence of accidental explosion also showed an increase in the industries and daily life. The lung is the most labile organ and it is used to be severely injured organ in blast injury although even no signs of external injury could be observed on chest. Blast injury can present the symptoms such as lung rupture, bleeding, edema and emphysema. Respiratory dysfunction can affect oxygen supply to organs and systemic tissue, resulting in rapid and sustained hypoxemia and high mortality rate. Blast lung injury is characterized by respiratory disturbance and hypoxia. This article summarizes the etiology, pathogenesis, pathophysiological changes, diagnosis, and treatment of blast lung injury, with a hope to provide some useful clinical information.

The response of glass window systems to blast loadings: An overview

The failure of glass windows in terrorist bombing attacks and accidental explosion incidents has been cited as one of the major causes to the vast casualties. Many studies have been carried out to investigate the response and vulnerability of glass windows against blast loadings. These include laboratory and field tests that have been carried out to experimentally study glass window performance under explosion scenarios and development of analytical and numerical models to analyze and predict glass window responses. This article reviews literatures on the studies of the response of glass window systems to blast loadings. Over 100 papers and documents that are available in the open literature are reviewed. The background and history of the studies on the topic are also briefed. Understandings about the dynamic material properties of glass and available material models are summarized. Popularly used analysis methods and design standards for monolithic and laminated glass windows are outlined, and their accuracies are discussed. Recent studies including analytical solution, numerical simulation, and experimental investigations on glass window systems are summarized. Mitigation measures for blast-resistant windows are also briefly discussed.

Residual Loading Capacity of Ultra-High Performance Concrete Columns After

Columns are essential load carrying structural components and may experience accidental loads such as terrorist bombing attacks during their service life. Damages to columns may trigger structural collapse and it is therefore very important to protect critical load-carrying columns. In recent studies, a novel ultra-high performance concrete (UHPC) material was developed and static loading test results revealed its outstanding mechanical strengths and ductility. The present study investigates the blast load-carrying capacities of columns made of UHPC. Concrete columns built with UHPC were blast tested in the field first; then brought back to laboratory and subjected to static load tests to determine their residual load-carrying capacities after experiencing varying levels of blast damage. The results from the field blast tests and laboratory static load tests for residual load-carrying capacities are presented and discussed in this paper. Numerical models for simulating responses and residual strengths of the UHPC columns after blast loadings are also developed in commercial hydro-code LS-DYNA and presented in the paper. Comparisons between the test data and numerical results are made and the accuracy of the numerical model is validated.

Assessment of dynamic mechanical behaviour of reinforced concrete beams using a blast simulator

Critical infrastructures may become the target of terrorist bombing attacks or may have to withstand explosive loads due to accidents. The impulsive load connected to explosions is delivered to the structure in a few milliseconds forcing it to respond or fail in a peculiar mode. With reference to the above scientific framework this work presents an innovative apparatus designed and developed at the European Laboratory for Structural Assessment to reproduce a blast pressure history without using explosives. This apparatus is practically a hybrid nitrogen-spring-driven actuator that accelerates masses of up to 100 kg to a maximum velocity of about 25 m/s that impact against the tested structure. The pressure-load history applied to the structure is modulated and reshaped using appropriate layers of elastic soft materials (such as polymeric foams) placed between the specimen and the impacting masses. Specific instrumentation has extensively been utilised to investigate the blast simulator performance and to precisely measure the pressure loads applied to the specimen. A series of tests on real scale reinforced concrete beams/columns (250 × 250 × 2200 mm) has been performed to efficiently assess the performance and potentiality of the new blast simulator. Results are under evaluation. In addition to the experimental work, a series of numerical simulations by means of the explicit FEM code EUROPLEXUS have been carried out to support and improve the equipment design.

A YEAR OF IMPORTANT ANNIVERSARIES

A YEAR OF IMPORTANT ANNIVERSARIES

Damage prediction of concrete gravity dams subjected to underwater explosion shock loading

The damage prediction of concrete gravity dams under blast loads has gained importance in recent years due to the great number of accidental events and terrorist bombing attacks that affected engineering safety. It has long been known that an underwater explosion can cause significantly more damage to the targets in water than the same amount of explosive in air. While the physical processes during an underwater explosion and the subsequent response of structures are extremely complex, which involve lots of complex issues such as the explosion, shock wave propagation, shock wave-structure interaction and structural response. Hence a sophisticated numerical model for the loading and material responses would be required to enable more realistic reproduction of the underlying physical processes. In this paper, a fully coupled numerical approach with combined Lagrangian and Eulerian methods, incorporating the explosion processes, is performed. The RHT (Riedel–Hiermaier–Thoma) model including the strain rate effect is employed to model the concrete material behavior subjected to blast loading. Detailed numerical simulation and analysis of a typical concrete gravity dam subjected to underwater explosion are presented in this study. In terms of different TNT charge weights, the structural response and damage characteristics of the dam at different standoff distances are investigated. Based on the numerical results, critical curves related to different damage levels are derived.

Narrative, text and time: Telling the same story twice in the oral narrative reporting of 7/7

The question of whether it is possible to ‘tell the same story twice’ has been explored in work on conversational narratives, which has set out to understand the existence of some kind of ‘underlying semantic structure’ and ‘script’ (Polanyi, 1981). In conversational narratives, ‘local occasioning’ and ‘recipient design’ (Sacks et al., 1974) are factors that determine the form and function of the story. Here, ongoing talk frames the narrative while other participants provide a ready made audience, all of which, form part of the storytelling process. What happens, however, when a survivor of 7/7 (the date in 2005 of the co-ordinated terrorist bomb attacks on the London transport system in the morning rush hour, which killed 52 and injured hundreds of people), whose personal narrative was reported globally on the day of the event, is again interviewed two and a half years later for their experience of that morning? Is the ‘same story’ retold? Specifically, how far does the latest story replicate the experience and events of the first and which of the prototypical features of a personal narrative – at the level of both the macrostructure and microstructure – remain constant? By comparing both interviews and using Labov and Waletzky’s (1967) narrative framework as the central model for analysis, it is possible to see whether events within the complicating action or features of evaluation remain the most memorable, that is, they are recalled in the second telling as important aspects of the experience, and may be seen to be core narrative categories. While findings show that both narratives are comparable in form, a closer investigation finds compelling differences as well as unexpected linguistic choices. Not only has the second narrative become informed by other, external narratives to become part of a broader, mediated narrative but various discourse strategies of ‘dissociation’ in both interviews have resulted in a retelling of a traumatic experience that appears to have features of an eye witness report rather than a personal narrative. Moreover, this blurring of two distinct genres of storytelling provides a true insight of how the narrator positions himself inside this terrible experience.

Protection of flying vehicles against blast loads

Aircraft safety and security is a very important problem of nowadays. Terrorist bomb attacks on transport are most dangerous and often result in numerous victims. Threat of terrorist attacks on air transport is a nagging problem. The goal of the present paper is to present results of developing efficient air bomb inhibitors that preserve aircraft safety in case of onboard detonation of explosive equal of 2kg TNT.Methods for protection developed within the present paper could be successfully used for developing effective and lightweight shield for a spacecraft against high velocity impact of space debris fragments, which could also induce blast loads.

Apparent intended lethality: Toward a model of intent to harm in terrorist bomb attacks

This article sets out the concept of Apparent Intended Lethality (AIL) with respect to terrorist bomb attacks and explores its measurement through objective behavioral indices. AIL is assessed for 120 bomb attacks carried out by animal rights and anti-abortion extremists in the United States. A wide range of AIL is observed, ranging from hoax attacks to highly lethal attacks. Multidimensional Scalogram Analysis (MSA) reveals that single-issue terrorist bombers' intended lethality can be modeled according to three independent dimensions: device strategy, targeting, and pre-event warnings. This model can be used to measure AIL for an individual terrorist attack or an entire terrorist campaign, and can identify cumulative and compensatory lethality strategies. Many have noted the difficulty of assessing terrorist motivations; AIL provides an empirically based assessment of a key facet of terrorist intentions.

Comms in a crisis [communications emergency services

The resilience of communications is constantly tested during and after a major disaster. For this reason companies are creating innovative ways to ensure communication is maintained between the emergency services. Mobile communications have become integral to how emergency services respond to major incidents. The aftermath of the 2005 7/7 London terrorist bomb attacks saw mobile phone networks overloaded and network operators forced to initiate Access Overload Control (ACCOLC) to prioritise emergency calls. Unfortunately many key emergency personnel did not have ACCOLC-enabled mobile phones, and paramedics using SMS as part of the service's basic communications strategy could not get their messages through either.

A Bruise upon a Bruise: Forms and Traces of Violence in Graham Swift’s 'Out of This World' and 'Waterland'

While lacking the physical explicitness of other contemporary British novels, Graham Swift’s texts are at least of equal interest in terms of the attention paid to the numerous face(t)s of violence, as well as to the deep if not always detectable marks imprinted on the victims. The centrality of the terrorist bomb attack to the plot of Out of This World singles out Swift’s fourth novel for special attention as regards the idea of violence and even a superficial reading yields ample material, from the historical background of war and the detailed presentation of major campaigns of the twentieth century to the personal history of its protagonists. This paper aims to trace the different reactions to and manifestations of violence across three generations, then focus on the frequent philosophical disquisitions on the main topic of the text, before moving on to Waterland and its intricate palimpsest of bruises upon bruises, hissing guillotines, revenge, murder, suicide, madness and guilt.

Blast Resistance of Double-Layered Reinforced Concrete Slabs Composed of Precast Thin Plates

When designing blast-resistant reinforced concrete (RC) structures, reducing spall damage due to reflected tensile stress waves is a major problem. Furthermore, for rapid construction of the blast-resistant structures against sudden terrorist bomb attacks, it is necessary to build it with precast concrete walls and reduce the weight of the precast elements by reducing their size for ease of transportation and construction.In this study, to propose an idea for rapid construction and better blast resistance of blast-resistant RC structures, double-layered RC slabs composed of precast thin plates, 50 mm thick, were fabricated and utilized for contact detonation tests. The tests were conducted under a condition that the amount of explosives and the dimensions of specimen were constant respectively, and two types of concrete, normal concrete and polyethylene fiber reinforced concrete (PEFRC), were employed as the slab materials. Our results showed that creating an air cavity between the two layers of PEFRC slab was effective in reducing spall damage, while the air space had no advantage in normal RC, under a condition that the thickness of the air space was fixed at 15 mm. Furthermore, the above difference between PEFRC and normal RC slabs was discussed, based on the numerical result on the fracture process of the air-sandwiched normal RC slab.

Posttraumatic Stress Disorder in Hospitalized Terrorist Bombing Attack Victims

Posttraumatic stress disorder (PTSD) is a psychiatric disorder that results from exposure to a traumatic event and consists of intrusive and unwanted recollections; avoidance followed by emotional withdrawal; and heightened physiologic arousal. Hospitalized victims of suicide bombing attacks (SBAs) are unique because of the circumstances and severity of their injuries, which could affect the occurrence and delay the recognition of PTSD. Our objectives were to evaluate the prevalence and severity of PTSD among hospitalized SBA victims and to assess variables of physical injury as risk factors for the development of PTSD. Forty-six hospitalized SBA victims were evaluated for PTSD using the PTSD symptom scale self-report questionnaire by phone. Demographic and medical data regarding the severity and type of injury and medical treatment were collected from medical files. Injury Severity Score was used to assess severity of physical injury. Twenty-four of 46 (52.2%) hospitalized SBA victims developed PTSD. Presence of blast lung injury was significantly higher in the PTSD group compared with the non-PTSD group (37.5% versus 9.1%, respectively; p < 0.04). There was no significant difference in Injury Severity Score between PTSD and non-PTSD groups. Blast lung injury and intracranial injury were found to be positive predictors of PTSD (odds ratio, 125 and 25, respectively). No correlation was found between the length of stay, length of intensive care unit stay, or severity of physical injuries and the severity of PTSD. Hospitalized victims of SBA are considerably vulnerable to develop PTSD. Victims should be monitored closely and treated in conjunction with their physical treatment. Blast lung injury and intracranial injury are predictors of PTSD.

Abdominal Trauma After Terrorist Bombing Attacks Exhibits a Unique Pattern of Injury

Abdominal Trauma After Terrorist Bombing Attacks Exhibits a Unique Pattern of Injury