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In the aftermath of the WWII, many French cities faced a great need for reconstruction in response to the heavy destruction caused by the bombardments. Reconstruction plans were developed and implemented at relatively short notice in response to a critical and urgent situation. However, not all cities adopted the same approach: (a) some proposed and implemented a new layout; (b) others tried to recreate the old street layout but with some updates such as widening and alignment; and finally, (c) some have preferred to resort to more targeted interventions. The choice of approach was motivated by various factors associated with the level of destruction, the futuristic vision of the architect or urbanist in charge, or the historic value of the place destroyed. This article assesses the impact of these approaches on the urban tissue by measuring changes in the overall morphology and intelligibility of multiple city centres before and after the reconstruction based on their cadastral maps. Intelligibility is first measured as a configurational property of the street layout and then as a result of public participation in a navigation task using these maps and digital technology that records the speed of movement and trajectories. This allows a comparison between the original street layout and the new one, as well as across the different cities. Drawing on indicators of spatial cognition, this interdisciplinary research approach provides a means to measure and better understand the impact of the reconstruction on the intelligibility of urban environments. [ABSTRACT FROM AUTHOR]

Highlights • Prediction errors tend to decrease as the number of instruments increases. • Errors are much lower when more than a small number of floors are instrumented. • Errors may be highly dependent on the arrangement of instruments. • The optimum arrangement of instruments depends on the prediction of interest. Abstract Seismic instrumentation in a building is used to accurately capture its response during an earthquake, and so should enable enhanced rapid post-earthquake predictions of the event's consequences for the building (among other benefits). Such instrumentation is costly, however, thus it is useful to know the extent to which varying degrees of its implementation within a building affect the accuracy of these predictions. The purpose of this study is to develop a methodology for quantifying the errors in post-earthquake damage and loss consequence predictions calculated from the FEMA P-58 Seismic Performance Assessment procedure, when different numbers of building instruments are used to capture the response of a building in a given event. We use responses measured in instrumented buildings during the 1994 Northridge earthquake, and obtain consequence predictions via the FEMA P-58 methodology. The density of instrumentation examined ranges from the case in which all floors are instrumented to that in which no instrumentation is present and FEMA P-58 simplified procedures are used to predict response and corresponding consequences. We find that errors in consequence predictions decrease as the number of building instruments is increased and that the reduction in error is substantial as soon as more than a small number of floors are instrumented. This is valuable information for a building owner if they wish to use seismic instrumentation as a means of rapidly obtaining damage and loss information for post-earthquake decision-making. [ABSTRACT FROM AUTHOR]

Cladding systems are conventionally designed to provide buildings with environmental protection against wind, temperature, humidity, moisture, etc. Recently, researchers have proposed to leverage these systems to provide additional protection against manmade (e.g., blast) and natural (e.g., earthquakes, hurricanes) hazards. This can be achieved, for example, by redesigning the connection between the cladding and the structural system to provide energy dissipation via friction. While promising, the use of flexible cladding connection has only been considered for singular hazards. In this study, the authors propose a novel semi-active damping system to connect the cladding to the structure via a variable friction mechanism. By varying the normal force applied on friction plates through a system of adjustable toggles, it is possible to mitigate vibrations over a wide frequency range, therefore enabling mitigation of different types of hazards (i.e. to achieve multi-hazard resistance). In its passive in-situ mode, the device is designed to provide very high stiffness and friction resistance to mitigate the effects of blast. The objective of this paper is to enable a holistic integration of said device within the structural design process by developing a performance-based design procedure. The study will focus on the passive in-situ mode of the device, which will provide a stepping stone for the development of performance-based design procedures for its semi-active (i.e. actuated) capabilities. The proposed performance-based design procedure consists of the following: 1) determine the design performance criteria, including the blast properties and allowable connection gap between the cladding and structure; 2) select design properties for the cladding connection, including stiffness and damping; and 3) design a rubber impact bumper located between the structure and the cladding in order to mitigate slamming of the cladding into the structure for very high blast loads. [ABSTRACT FROM AUTHOR]

Vibration from blasting operations exert negative effects on the comfort of nearby buildings (structures) resulting in the dissatisfaction of and even complaints from nearby residents. This problem impacts both blasting activities and social stability. Therefore, establishing a method for reasonably evaluating blasting vibration (BV) comfort and a standard can significantly reduce the complaints and civil disputes caused by construction activities involving blasting. This paper systematically reviewed the factors influencing BV comfort as well as the current evaluation indexes and criteria, and analyzed the mechanism of BV comfort. Starting with the three elements of BV, this paper developed a human body linear-elastic vibration model, according to which the effect of BV on the human body is regarded as an energy transmission and conversion process. Consequently, a comfort evaluation index, the human body absorbed blasting vibration energy (ABVE) index, was proposed. ABVE was used to determine the magnitude of human body ABVE in various bands, so as to quantitatively analyze the magnitude and frequency composition of ABVE. After a thorough investigation of the differences among BV energies produced by different blasting sources in terms of frequency composition, it was found that the main frequency bands of surface BV waves were closer to the natural frequency of vibration of the human body and thus exerted the greatest discomfort to humans. [ABSTRACT FROM AUTHOR]

This paper examines physical vulnerability of District No. 6 of Tehran to blast damages and blast loads. The main objectives are to enhance planners and decision makers' awareness of the extent of vulnerability of buildings in the study area (under different risk scenarios) and to provide guidance on how to enhance preparedness against potential risks. Physical vulnerability of District No. 6 of Tehran was evaluated under three different blast loading scenarios. An expert survey, involving specialists with expertise in urban development, passive defense, construction, and architecture was carried out to extract fourteen vulnerability criteria. Fuzzy criteria maps corresponding to each of these criteria were produced in Geospatial Information Systems (GIS) environment. Fuzzy analytic hierarchy processing was used to weigh the criteria. Criterion maps were combined using the fuzzy weighted linear combination operator. Finally, Ordered Weighted Averaging (OWA) operator was applied to generate final vulnerability maps. Results show that, for all scenarios, almost 70% of the buildings in the district are of high vulnerability. Sensitivity analysis confirms the reliability of the model. [ABSTRACT FROM AUTHOR]

In the event of a bomb blast taking place outside a building at the ground level, a hemispherical pressure wave travels in all directions and impacts the buildings and other structures in its path. The exterior walls, windows, doors and the structural system are impacted. The pressure wave enters the building through broken glass at doors and windows, blast damaged exterior cladding and any other openings in the exterior of the building. The increase in ambient pressure experienced inside the building depends upon the area of openings in the exterior walls and the roof, the air pressure due to the blast at the exterior wall and roof surface, the duration of the blast and the volume of the interior space. Depending upon these factors, the interior pressure can increase above the threshold of human tolerance, thereby causing injuries to the occupants in the form of damage to lungs and eardrums, in addition to injuries caused by broken glass and other damaged building components. This paper will present a simple method of estimating pressure buildup near the exterior walls and other locations subject to leakage of blast pressure from the outside. The threshold of human tolerance to high air pressure will also be indicated. [ABSTRACT FROM AUTHOR]

Explosive attacks on constructed facilities are a significant threat worldwide, producing devastating consequences including loss of life, property damages, and economic losses. This paper presents the development a blast effects assessment model (BEAM) capable of efficiently quantifying and visualizing blast effects on constructed facilities behind blast walls. The model provides novel and unique capabilities that enable designers to: (1) efficiently predict the blast damage level on facilities for a wide range of feasible design alternatives of blast charge weight, blast wall type, building material, and facility location; (2) quantify the effectiveness of feasible frangible blast wall types in reducing blast loading on facilities; and (3) generate visualizations of the anticipated facility damage areas based upon the blast charge weight, blast wall type, and building material combinations. These distinctive capabilities enable designers to accurately and efficiently evaluate all feasible design alternatives in order to select an optimal design solution that minimizes the risks to site personnel and facilities from the threat of explosive attacks. [ABSTRACT FROM AUTHOR]

Effects of different structural configurations, member orientations and standoff distances on blast-induced failure of steel frame buildings are investigated through development of fragility curves. Three steel frame buildings with different geometric configurations- square plan with rectangular shape in elevation, square plan with pyramidal shape in elevation, and semicircular plan with equal area at each floor level-are analyzed under blast load. The steel frame buildings are modeled, analyzed, and designed for dead load (DL), live load (LL) and seismic load (SL) for the National Capital Region (NCR), India. Force-controlled static nonlinear pushover analyses are performed to develop the fragility curves for the buildings under blast load. Different orientations of the columns (I-section) are considered to investigate the effect on building fragility under blast load. The results indicate significant effects of the structural configurations and column orientations on the blast resistance of the building. The pyramidal structure is found to be the most effective configuration in reducing the blast load effect on the structure among the considered configurations. It is also observed that the corner of a building is less critical in terms of blast load mitigation. [ABSTRACT FROM AUTHOR]

The increasing number of terrorist attacks brings the need to research on the blast resistance of buildings and transportation systems. Most of these attacks are lastly concentrated on the so called “soft targets” as railways stations, airports, bus stations, shopping centers, etc. In them, high vulnerability is frequently given by fenestrations or novel glass façade systems in general. In this regard, the paper is focused on the analysis of the dynamic behavior of blast loaded glazing windows. Given a reference specimen geometry and wood or plastic frame representative of traditional or new fenestrations respectively, the blast performance of such system is assessed via analytical SDOF calculations. Refined Finite Element (FE) numerical simulations are then presented and discussed, as a preliminary outcome of further exploratory investigations. Following the actual research study, experimental tests will be in fact carried out on the same fenestration systems. [ABSTRACT FROM AUTHOR]

The use of vehicle bombs to attack city centers has been a feature of campaigns by terrorist organizations around the world. A bomb explosion within or immediately nearby a building can cause catastrophic damage on the building's external and internal structural frames. The objective of this study is to shed light on blastresistant building design theories, the enhancement of building security against the effects of explosives in both architectural and structural design process and the design techniques that should be carried out. To analyze high-rise steel structure for blast loading, we have to generate a model of high-rise steel structure using E-tabs software which can resist all types of loading such as dead load, live load, seismic load using IS: 800 (2000) and IS: 1893 (part-1). The same structure is again analyzed for blast loading, due to which partial collapse or total collapse may occur which can be studied. The finite element software ETABS-2015, and a 3-dimensional model consisting of 20 stories of steel structures are first created, then blast loading is calculated and assigned using time history function. Blast loading at various standoff distance is calculated using IS: 4991 (1968). This blast load is assigned to structure and its behavior is analyzed. The parameters checked after analysis of blast loading on structure are demand capacity ratio, bending moments, shear force, deflection and story drift. [ABSTRACT FROM AUTHOR]

Among the lateral loads that a building structure may experience is that produced by blast from an explosion. The analysis of the response of building structure to blast loads is traditionally carried out on a member-by-member basis. The magnitude and variation of blast load with time depends on the position of the member being considered in the building. The nature of such loads is different for the front face, the side faces, the roof, and the rear face of the building. In particular, loads for the roof and side face members that span in a direction perpendicular to the shock front vary both spatially and temporally in a complicated manner. In the current practice, such loads are represented by an equivalent load that is spatially uniform but varies with time. The roof or the side face member along with the load acting on it is then converted to a single-degree-of-freedom system, whose analysis provides the desired response parameters, such as deflections and stresses. It is shown in this paper that the current methodologies provide widely differing results whose accuracy is suspect. A method that provides a better representation of the load variations and a more accurate procedure of analysis is presented. The implementation of the method is carried out through a computer program developed for the purpose and it is demonstrated that the entire process is as simple as the present techniques based on a single-degree-of-freedom representation. [ABSTRACT FROM AUTHOR]

The air blast that is generated by the explosion of bombs or fuel tankers on or adjacent to a bridge can cause severe structural damage, and may result in partial or full collapse of the bridge. The dynamic response and structural performance of buildings under blast has been the subject of several studies, with considerably less attention being paid to the assessment of bridges under extreme blast loading scenarios. To reduce the computational expense of conducting blast analyses on large or complex bridges, the numerical sub-structuring technique is used in current practice. However, the simplifying assumptions adopted in these sub-structuring methods can lead to erroneous results. Accordingly, this study attempts to simulate numerically the dynamic response of an entire cable-stayed bridge subjected to blast loading using the LS-DYNA explicit finite element code. Based on best practice available in the literature, the blast load estimation, material modelling and detailed numerical simulation are carried out and the response of a cable-stayed steel bridge (designed according to minimum requirements of the Australian Bridge Standard) under blast loads ranging from a small to large detonation at different positions above the deck and near pylon are obtained. Furthermore, the potential effects of blast loads on different structural components with a focus on the cross-sectional geometry of the pylons are investigated. [ABSTRACT FROM AUTHOR]

Computational tools and numerical strategies for the determination of the response of masonry walls under blast overpressure often rely on oversimplifying and conservative assumptions, which, although justifiable for design purposes, are not as warranted when fragility analysis and risk assessment are the objectives. In addition, due to the composite nature of reinforced masonry construction, the evaluation of multivariate fragility functions may likely require significant computational effort, owing to the multiplicity of variables describing the constituent materials and their associated uncertainty. The problem is further compounded by the effects of the high strain rates typically induced by blast loading, which make the understanding of masonry behaviour even more challenging; although efforts are being made in order to account for strain rate effects at the macro-scale, no well established models are available for reinforced masonry walls. Therefore, in order to perform accurate yet expedient fragility analyses that can effectively capture rate dependent phenomena, a dynamic model based on single-degree-of-freedom (SDOF) approach is developed. The SDOF model accounts for the nonlinear stress–strain behaviour obtained from standard prism tests and integrates strain rate dependent formulations provided in the open literature. The model predictions are corroborated using data—including pressure and displacement histories—from field testing of six scaled concrete block walls subjected to the detonation of live explosives. Within the scope of the current study, the proposed model is found to be a reasonable trade-off between computational efficiency and numerical accuracy and is an improvement upon a basic SDOF approach, which is typically based on the fixed dynamic increase factors recommended by modern design standards and technical manuals for blast protection. The results presented in this study are expected to contribute to the ongoing development of a comprehensive framework for the probabilistic risk assessment of structures subjected to explosive loading. [ABSTRACT FROM AUTHOR]

This paper details the development of a generalised damage identification procedure for reinforced concrete columns subjected to internal building detonations. With the successful application of advanced computational fluid dynamics and structural response modelling techniques, we have conducted a set of comprehensive parametric studies on reinforced concrete column failure when subjected to high-rate, coupled uplift and shear typically induced by internal explosive blast. The outputs of the parametric studies have been analysed using a multi-variable, non-linear curve fitting technique to develop the generalised damage identification procedure for columns, separately for two main internal blast conditions. The paper also presents a number of worked examples illustrating its application and significance in practice. [ABSTRACT FROM AUTHOR]

This paper presents experimental investigations and finite element (FE) analyses of sandwich beams with thin-walled tubes as core that were subjected to transverse blast loads. Three types of cores were studied, namely, closely arranged identical circular tubes, spaced circular tubes, and spaced square tubes. Different masses of TNT with various standoff distances were applied to the sandwich beams. The blast loads were large enough to cause permanent local deformation of the thin-walled tubes and significant global flexural deformation of the entire beams. The FE simulations using Ls-Dyna were compared to the experimental profiles, and an insight into the energy absorption of the local and global deformations as a result of impulsive loading was observed. From the FE analyses, influence of the diameter, the thickness and the number of the circular tubes on the final displacement was investigated. [ABSTRACT FROM AUTHOR]

This paper describes measurement and interpretation of strains induced in two, multiple story, older, urban structures by ultra-high frequency rock blast excitation from contiguous excavation. These strains are obtained from relative displacements found by integrating time correlated velocity time histories from multiple positions on the structures and foundation rock. Observations are based on ten instrumented positions on the structures and in the foundation rock during eight blast events, which provided over 70 time histories for analysis. The case study and measurements allowed the following conclusions: despite particle velocities in the rock that greatly exceed regulatory limits, strains in external walls are similar to or lower than those necessary to crack masonry structures and weak wall covering materials. These strains are also lower than those sustained by single story residential structures when excited by low frequency motions with particle velocities below regulatory limits. Expected relative displacements calculated with pseudo velocity single degree of freedom response spectra of excitation motions measured in the rock are similar to those measured. [ABSTRACT FROM AUTHOR]

In recent years, there has been a considerable increase in perceived risks of blast loading attacks or similar incidents on structures. Blast design is therefore a necessary aspect of the design for building structures globally and as such building design must adapt accordingly. Presented herein is an attempt to determine the numerical response of a seismically designed single-degree-of-freedom (SDOF) structure to blast loading. The SDOF model in the form of a portal frame was designed to withstand a typical seismic occurrence in Northern Trinidad. Blast loads caused by applying a 500 kg charge weight of TNT at standoff distances of 45 m, 33 m, and 20 m were then applied to the model. The blast loading on the frame was determined using empirical methods. The analytical study showed that the seismically designed SDOF plane frame model entered the plastic region during the application of the blast load occurring up to the critical standoff distance. [ABSTRACT FROM AUTHOR]

A centrifuge test was carried out to investigate the response of transit tunnels in saturated soils under internal blast loading. A similar test with dry soil was conducted beforehand as a comparison. The tests were carried out with a centrifugal acceleration of 50 g to simulate the effect of blast loading from 150-kg trinitrotoluene (TNT) inside a transit tunnel of 5-m diameter. Exploded bridgewire (EBW) charges were employed as the model explosives, and the model tunnel was simulated by thin-wall aluminum tube. The model tunnels were significantly damaged by the projectiles that were part of the EBW charges. Soil liquefaction occurred in saturated soil with 150 kg of TNT exploded at approximately the center of the tunnel. [ABSTRACT FROM AUTHOR]

Due to the increasing use of vehicle bombs on attacking important buildings by terrorist organizations around the world, it is necessary to design buildings with more resistance against blast loads. In this research, numerical studies have been done for threedimensional structural models of special moment frames, concentrically braced frames, and eccentrically braced frames with 3, 5, and 10 stories. The nonlinear dynamic method is applied for analyzing the models under two different levels of straight and oblique blast loadings based on the UFC 3-340-02. The plastic hinge rotations, ductility ratios, performance levels, and flexural moments in the models are obtained from the analysis and compared with each other. According to the results, it can be said that the eccentrically braced frame systems generally show better performances than other systems under blast loadings. Also due to different shock directions, the values of column plastic rotations and bending moments under oblique blast loadings are less than straight ones. [ABSTRACT FROM AUTHOR]

In recent years, improvised explosive devices has been an aspect of crusades by terrorist or movements around the world. The blast wave propagation of an explosive detonation can cause disastrous damage on the buildings, vehicles and also injuries to vehicle occupants. Full scale blast tests are expensive and time consuming but by using computational based numerical simulations can virtually predict these wave propagations and minimize the need of experimental testing. Computational fluid dynamics (CFD) is a common tool to do an analysis of free-field blast wave and against structure. This paper presents two different blast analyses; free field air blast and blast loading towards a structure using ANSYS FLUENT software. A high explosive of 1 kg blast peak overpressure data from an experiment has been patched at the specific domain of the symmetry plane. The computed results were found to be in agreement with theoretical and additional experimental data. The verified free field air blast model was expanded to study the blast loading response towards a structure. It was found that developed CFD can be further used to predict the blast wave propagation subjected to the vehicle structures or buildings. [ABSTRACT FROM AUTHOR]

This paper seeks to explore the vulnerability of a typical reinforced concrete (RC) building against progressive collapse as a consequence of internal blast. The emphasis has been on the local model analysis for which two approaches - one involving the use of CONWEP and another using fluid-structure interaction through Alternate Lagrangian Eulerian (ALE) element formulation - have been employed. The finite element model of the structure was created using LS-DYNA, which uses explicit time integration algorithms for solution. The results of the study are proposed to be used to control or prevent progressive collapse of the building. In order to validate the employed numerical models, blast test results of a RC column available in literature were validated using LS-DYNA modeling of the RC column. The deformation response of the column was compared which showed acceptable prediction. [ABSTRACT FROM AUTHOR]

The response of a blast mitigation cladding consisting of a face sheet and metal foam core subjected to a close-range blast is predicted. Whereas the cladding is sufficiently wide compared to the standoff distance between the explosion center and the cladding, the boundary of the blast induced bulge is released. The face sheet is considered as a rigid perfectly plastic membrane as the deformation of the sheet always exceeds half its thickness. A procedure predicting the depth and extent of the bulge is proposed with energy method. Subsequently, the minimum thickness of the foam layer is calculated based on the bulge depth. This design-oriented approach, in a ready-to-use manner, can be straightforwardly applied, facilitating the preliminary design of blast mitigation claddings with metal foam core. [ABSTRACT FROM AUTHOR]

The response of dam structures subjected to explosion shock loading is a key element in assessments for the dam antiknock safety and antiterrorism applications. The physical processes during an explosive detonated in underwater/air and the subsequent response of structures are extremely complex, involving many complex issues such as the explosion, shock wave propagation, shock wave-structure interaction, and structural response. In addition, there exists a significant contrast in wave propagation phenomena in the water and the air medium due to their different physical properties and interface phenomena. In this paper, a fully coupled numerical approach with combined Lagrangian and Eulerian methods is used to simulate the dynamic responses of a concrete gravity dam subjected to underwater and air explosions. The shock wave propagation characteristics from explosions in water and air are simulated and compared. The damage profiles of concrete gravity dams subjected to underwater and air explosions are discussed. The influence of the blast loading from explosions in water and air on the dynamic response and the damage of the dam is also investigated. The analysis results show that a submerged explosion causes significantly more damage to the dam in water than the same mass of explosive in air. [ABSTRACT FROM AUTHOR]

Breaching in light obstacles consists in making openings in the non-structural elements of a building with the view to enabling quick access in emergency cases. The light barriers under scrutiny throughout the current paper stand for walls of brick or concrete masonry units, reinforced concrete walls with thicknesses up to 12.5 cm and metal doors. To create breaches, two different kinds of special explosive devices were used, according to the obstacle: cutting and pushing charges. The subject is looked into from two complementary perspectives, that is, the first approach regards the technical solutions of breaching in light obstacles, whereas the latter is concerned with the protection of the emergency team and people to be rescued. The paper under consideration addresses the overall findings of the experimental research regarding breaching in light obstacles based on the above-mentioned perspectives. [ABSTRACT FROM AUTHOR]

The recent terrorist attacks all around the world and the evidence of the threats found especially in the Kingdom of Saudi Arabia have prompted the concerned authorities to address the risks to the critical infrastructure of the Kingdom. Understanding of the progressive collapse mechanism is an essential step to protect buildings against blast attacks. Buildings are very vulnerable to progressive collapse if one or more columns are lost due to extreme loadings. It is also important to study the likelihood of progressive collapse of buildings in Riyadh to avoid catastrophic events. The paper presents progressive collapse analysis of a typical multi-storey steel framed building in Riyadh to establish its vulnerability when subjected to accidental or terrorist attack blast scenarios. A commercial finite element (FE) package (LS-DYNA) was used to simulate the building response under blast generated waves. The numerical modeling was validated using the results of a published example of tubular steel beam subjected to blast load. Based on the FE analysis results, recommendations are given to mitigate (or control) the progressive collapse potential of steel buildings. [ABSTRACT FROM AUTHOR]

Gas dispersion and explosion dynamics can be very complex. Blast effects in the far field are less sensitive to the local dynamics of an explosion event, and simplified techniques have been developed to roughly estimate the amount of fuel involved (i.e., energy released) in an explosion based on the observed damage in the far field. However, these simple techniques are not suitable to predict the complex explosion dynamics that occur in the near field. The phenomena that drive explosions and resulting damage in the near field are complex in nature, as they depend on non-linear interactions between multiple variables (e.g., ignition location, flame accelerations due to object interaction, fuel reactivity, geometry of the facility regarding confinement and interconnected rooms, vent areas, etc.). Furthermore, the damage created in the near field by overpressure development, blast wave reflections and focusing, pressure impulse, pressure piling, blast wind and ensuing drag forces, may be difficult to interpret using simple methods. The origin of an explosion may, in fact, differ from the intuitive epicenter determined from oversimplified assumptions and may lead to incorrect conclusions regarding the cause and origin or initiating events of the accident. State-of-the-art 3D modeling tools, such as FLACS, are typically required to understand and evaluate complex explosions. FLACS was specifically developed to predict the consequences associated with complex explosions, especially in the near field, and has been extensively validated against hundreds of full-scale experiments. Therefore, FLACS simulations can be used to investigate the chain of events of the explosion and provide a more complete understanding of the evidence, including near-field blast damage. This paper presents the findings of how FLACS was used to help determine the explosion origin in the explosion that occurred at an ink and paint manufacturing facility in Danvers, Massachusetts, on November 22, 2006. This paper is not intended to provide complete investigation findings and will only provide the necessary background material to follow the explosion origin analysis. [ABSTRACT FROM AUTHOR]

Attacking city centers with pack portable bombs has become one of the regular terrorist attacks around the world. In these situations, life losses and injuries can be caused from various sources such as direct blast effects, structural collapse, debris impact, fire, and smoke. Casualties could increase when indirect effects are combined with closed exits or timely evacuation. So, calculating the annual risk of the structural collapses resulting from extreme loading conditions is subjected to many efforts. In this paper, the annual risk of blast-induced progressive structural collapse is calculated. The blast fragility is also calculated by a simulation procedure which generate possible blast configuration, and finally kinematic plastic limit analysis is used to verify the structural stability under gravity loading. As a case study, the blast fragility and the annual risk of collapse of a four-storey steel building are calculated. [ABSTRACT FROM PUBLISHER]

Abstract: The design of all spatial scales in a manufactured environment is part of the architectural skills and knowledge. Therefore, an architectural design should be drafted to reduce the vulnerability of humans and buildings against unexpected events, such as terrorist attacks and bombardments. Human casualties and equipment destruction inside the buildings could be prevented by designing a suitable architectural space. This study addresses the absence of a codified and detailed criterion to evaluate architectural spaces and their design. Hence, all proposed indices for architectural spaces have been extracted using the ideas of experts in the field of architecture and explosives. Questionnaires were presented to 25 experts to weigh the effective indices using the analytic hierarchy process method. The human-oriented (ergonomic) characteristics of the building space is found to be the most important factor in facilitating crisis management, followed by the location of critical spaces. [Copyright &y& Elsevier]

Impulsive blast sound from activity at DoD facilities, generated by artillery firing or ordnance, or demolition explosions, can cause structural blast damage or adverse community impact. This paper provides a detailed model, not widely available, for the probability of such damage starting with models for blast pressure loading and blast duration as a function of distance and TNTequivalent weight of the blast charge. This is followed by summaries of statistical models for blast propagation and diffraction and reflection effects on blast loading on buildings. Then, analytical models for the velocity response of building structures to the blast loads and key evaluation of the stress response to this structural velocity are provided. All of this is supported by data on critical configuration and physical parameters of the various types of responding structure to the blast loads and a summary of the failure data for these structures to the blast loads. Emphasis is placed on blast damage to windows. The paper ends with a useful and extensive development of the Probability of Damage (POD) for structure to blast loading. A comparison is also made between predicted and actual window damage observed from an accidental explosion near an apartment complex. Two Appendices are provided for: (A), the TNT-equivalent weight for a wide range of explosives and ordnance and (B), a definition of the Step-by-Step procedures used to carry out computation of the POD from blast from military training operations for a wide range of structures but mostly windows. [ABSTRACT FROM AUTHOR]

Purpose – Limitations in space and city planning constraints have led to the search for alternative shock mitigation devices that are architecturally appealing. The purpose of this paper is to consider a compromise solution which consists of partially open, thick, bending-resistant shapes made of acrylic material that may be Kevlar- or steel-reinforced. Seven different configurations were analyzed numerically. Design/methodology/approach – For the flow solver, the FEM-FCT scheme as implemented in FEFLO is used. The flowfields are initialized from the output of highly detailed 1-D (spherically symmetric) runs. Peak pressure and impulse are stored and compared. In total, seven different configurations were analyzed numerically. Findings – It is found that for some of these, the maximum pressure is comparable to usual, closed walls, and the maximum impulse approximately 50 percent higher. This would indicate that such designs offer a blast mitigation device eminently suitable for built-up city environments. Research limitations/implications – Future work will consider fully coupled fluid-structure runs for the more appealing designs, in order to assess whether such devices can be manufactured from commonly available materials such as acrylics or other poly-carbonates. Practical implications – This would indicate that such designs offer a blast mitigation device eminently suitable for built-up city environments. Originality/value – This is the first time such a semi-open blastwall approach has been tried and analyzed. [ABSTRACT FROM AUTHOR]

method of determining zones of characteristic explosion-induced deformations of tower equipment is proposed in this paper. The fact that a tower experiencing the effect of an external blast-induced pressure uniformly distributed over the lateral surface is assumed to be a cylindrical shell is a characteristic feature of the method. The dimensions of the zones of characteristic explosion-induced transformations, within the limits of which elastic and plastic deformations occur in the tower, are compared with the dimensions of zones of various degrees of explosion-induced destruction of buildings. [ABSTRACT FROM AUTHOR]

The combined manual TM 5-1300/NAVFAC P-397/AFR 88-22, Structures to Resist the Effects of Accidental Explosions, published by the joint departments of the Army, the Navy, and the Air Force, has been used in all NATO countries for the past 50 years for protective design applications. The manual was recently reformatted to meet the Department of Defense Unified Facility Criteria (UFC). As a first step, the current production of the new document, UFC 3-340-02, focused on making the original TM 5-1300 available in a more functional format so that future technical updates can be facilitated. In this study, a single-degree-of-freedom (SDOF) model, based on the guidelines of the UFC 3-340-02, was used to formulate a FORTRAN code to predict the response of SDOF systems under blast. The code was used to generate pressure-impulse (P-I) diagrams for a series of two-way reinforced concrete (RC) panels with different dimensions, aspect and reinforcement ratios, and support conditions. The P-I diagram predictions were compared to the results of experimentally validated nonlinear explicit finite-element (FE) analyses and significant differences in deflection and shear predictions were observed. The general trend of results and the major characteristics of the P-I diagrams were discussed in terms of the discrepancies between the SDOF and the FE predictions. The work presented in this paper is expected to contribute to improving the modeling provisions of the two-way RC panels in the future edition of the UFC 3-340-02 by understanding the limitations of SDOF models using advanced FE analysis techniques. [ABSTRACT FROM AUTHOR]

A ball powder production facility recently experienced two subsequent explosions which occurred due to the detonation of 2,800 kg and 17,000 kg ball powder components in the mixer building and the temporary storage building, respectively. Consequently, three persons were killed; and these two structures were damaged heavily. In this study, the outline of the mixer building is explained as well as the details of explosion and the behavior of the structural system of the mixer building against explosion. The observed damage mechanism of the mixer building is explained through a nonlinear dynamic blast load analysis as well as the evaluation of the original design, in situ material characteristics, and construction details. Furthermore, the potential reasons of the second explosion in the temporary storage building and the effects of this explosion are discussed considering the separation and public route distances given in related standards. [ABSTRACT FROM AUTHOR]

Abstract: Seismic protection of buildings under risk can be achieved by increasing the knowledge about the behaviour of existing structures. Operational Modal Analysis is a powerful tool used for this purpose all over the world. It provides the dynamic characteristics of structures under operational conditions or some particular environmental issues such as blasts and earthquakes. The main objective of this study is to evaluate blast effects on a reinforced concrete (RC) building considering experimentally determined dynamic characteristics. The study consists of three phases: the measurement of vibration characteristics of blasting, the theoretical modal analysis of the inspected building, and experimental verification of dynamic characteristics using modal testing. The vibration characteristics of blasting are measured around the inspected building on hard soil using a geophone set. The initial analytical model of the building is constructed according to the in-situ investigation on building. The theoretical modal analysis results are verified by carrying out modal testing on the RC building. The Operational Modal Analysis method is used for the extraction of the dynamic characteristics of the building, and blast vibrations are taken into account as environmental vibrations. The effects of blasting on the reinforced concrete building are introduced by assessing the vibration of blasting with the dynamic characteristics of the building. [Copyright &y& Elsevier]

Abstract: The RESRAD-RDD methodology was applied to model the short- and long-term radiation exposures after a hypothetical radiological dispersal device (RDD) event in an urban environment. It was assumed that an RDD event would result in outside surface contamination of the exterior walls and roofs of surrounding buildings, as well as associated paved areas and lawns. The contaminants also might move inside the buildings and deposit on floors and interior walls. Some important input parameters include occupancy factors, building characteristics, and weathering of surface contamination. The modeling results include predicted external dose rates, relative contributions from important surfaces, annual and cumulative doses, and radionuclide concentrations. Potential countermeasures evaluated include grass removal, soil removal, and washing of paved areas. [Copyright &y& Elsevier]

Because of changes in functional or security requirements, many new or existing buildings are now required to resist blast loads. New buildings can be designed and constructed to resist defined blast loads. Existing buildings, on the other hand, would have to rely on a risk assessment to determine both its vulnerability to blast effects and the necessary measures to mitigate the unacceptable blast effects. A rapid screening methodology has been developed for conducting a preliminary assessment of buildings against external blast effects. The methodology accounts for the threat, the vulnerability of the building, the consequence of an event and the risk, which is the product of the threat and the consequence. The rapid screening methodology has been applied to several buildings and the results are reasonable. This paper presents the rapid screening methodology and its application to two federal buildings in Canada. [ABSTRACT FROM AUTHOR]

Structural retrofits to buildings can be implemented to increase the protection level to occupants from potential terrorist bombing attacks. Retrofit strategies discussed in this paper can be categorized into three groups: (i) strengthening concepts, (ii) shielding concepts, and (iii) concepts to control hazardous debris. Strengthening concepts such as span reduction and increasing member sections are considered in this paper for three common construction systems including steel, concrete, and masonry. Shielding concepts are intended to prevent structural members from being fully loaded by blast forces and range from local area applications to entire building coverage. Examples of shielding concepts include a new section of wall that shields a vulnerable portion of the building or a new structure built over an entire building. Examples of concepts to control hazardous debris include arresting or deflecting failed cladding away from critical areas with “catch systems” or internal shield systems. This paper is intended to discuss typical building retrofit strategies for primary structural members (load bearing) and secondary structural members (nonload bearing) through strengthening, shielding, or controlling hazardous debris. [ABSTRACT FROM AUTHOR]

Designers charged to develop blast-resistant structural designs must be able to address the technical aspects of the explosion process and provide structural components with sufficient strength and ductility to resist the applied pressures. The blast environment is different from those of other loads with which designers deal, and uncertainties about the actual response of structures often are higher. For these reasons, designers often have less confidence in their abilities to explain to their clients their expectations about the actual response of the building to a blast event. This paper identifies some elements of the conventional design process that do not translate directly to blast-resistant design, reasons why uncertainties in performance expectations differ from those encountered with other load sources, and the need to understand and acknowledge residual risks for the facade, the structure, and the safety of the occupants of blast resistant buildings. [ABSTRACT FROM AUTHOR]

This paper presents a unique approach that can be used for the analysis of a blast due to an internal detonation. The information in this paper focuses on understanding the blast effects in a confined environment, blast loads prediction, and response analysis using computer codes and finite element modeling methods. An example is included in which a partial segment of a steel box member is analyzed for its response to an internal blast using blast prediction tools and finite element code. [ABSTRACT FROM AUTHOR]

Accurate analysis of reinforced concrete (RC) structures under blast loading is very complicated due to the nonlinear behaviour of concrete and reinforcement and the various failure modes to be considered. Although blast loads can excite a large number of modes due to their high frequency content, practical computational tools are usually limited to single-degree-of-freedom (SDOF) models. In addition to oversimplification, SDOF models are known to give inaccurate prediction for shear forces and support reactions. This is because accurate shear force prediction typically requires accounting for modes higher than the fundamental mode. In this study, a multi-degree-of-freedom (MDOF) model is developed that takes into account the nonlinear behaviour of RC structures and the material strength and deformation dependency on the strain rate. Using this model, a series of dynamic analyses were carried out for two typical structural members, with different combination of blast pressure and impulse. The effect of varying the number of degrees of freedom (DOF) was investigated through increasing the number of nodes used to descretize each structural member. The results of the developed MDOF model were compared to the results of available SDOF models which demonstrated the deficiencies of the latter. The developed MDOF model, with few DOF, was found to be capable of accurately predicting the dynamic shear of the modeled structural members. The model was also compared to available experimental results and showed good agreement. Changing the number of DOF also affected the pressure-impulse (P-I) diagrams for the structural member significantly, especially in the impulsive regime. [ABSTRACT FROM AUTHOR]

There are many computational techniques to model the consequences to built infrastructure when subject to explosive blast loads; however, the majority of these do not account for the uncertainties associated with system response or blast loading. This paper describes a new computational model, called “Blast-RF” (Blast Risks for Facades), that incorporates existing (deterministic) blast-response models within an environment that considers threat and (or) vulnerability uncertainties and variability using probability and structural reliability theory. The structural reliability analysis uses stress limit states and the UK Glazing Hazard Guide's rating criteria to calculate probabilities of glazing damage and occupant safety hazards conditional on a given blast scenario. This allows the prediction of likelihood and extent of damage and (or) casualties, useful information for risk mitigation considerations, emergency service's contingency and response planning, collateral damage estimation, weaponeering, and post-blast forensic analysis. [ABSTRACT FROM AUTHOR]

The blast response and ultimate resistance of reinforced concrete slabs externally strengthened with carbon fibre reinforced polymer (CFRP) laminates were investigated. Five square slab specimens, 1 m on a side, were retrofitted with 500 mm wide CFRP laminates bonded to their top and bottom surfaces. Another four nominally identical unretrofitted slabs were used as control specimens. Four of the retrofitted and the four control slabs were first subjected to the detonation of either 22.4 or 33.4 kg of explosive at a stand-off distance of 3.0 m. For reference, the fifth retrofitted slab was only statically tested to failure. Blast pressures and impulses and slab deformations were measured. After exposure to the blast, the slabs that were not completely damaged were statically tested to failure. Overall the retrofitted slabs performed better than the control slabs, but one retrofitted slab completely failed under the blast load while none of the control slabs experienced complete failure under similar load. [ABSTRACT FROM AUTHOR]

This study critically discusses the fundamental concepts used for evaluating the flexural and axial resistance of structures under blast. Simplified methods based on single degree of freedom are emphasized. The paper begins with how to estimate the blast parameters for a given charge size and standoff distance. These parameters include side-on and reflected pressures, positive phase duration, and side-on and reflected impulses. Subsequently, blast damage criteria are defined in accordance with prevailing guidelines and some of their short comings are discussed. To assess the impact of blast on the flexural safety and performance of structures, some simple methods are presented. The methods are either empirical or are based on the principles of energy and momentum conservation. The analytical results are in closed-form or in the form of pressure-impulse (P-I) diagrams. The effect of strain rate on both blast-induced flexural deflection and strength of structures, with particular emphasis on reinforced concrete structures, is discussed. [ABSTRACT FROM AUTHOR]

During the past decade, significant research has been carried out on the strengthening of reinforced concrete (RC) slabs, beams, and columns using externally bonded carbon fibre reinforced polymer (CFRP) sheets. Steel reinforced polymer (SRP) sheets have recently been proposed as an alternative to CFRP to strengthen reinforced concrete beams. This paper reports experimental and numerical results of RC beams and beam-columns transversely wrapped with SRP and tested under blast load. A total of 10 scaled RC members were tested at a variety of blast wave intensities. Detailed observations are reported and validated against numerical models created in AUTODYN for the unstrengthened RC members. The SRP wraps were resilient in the near-field blast range and enhanced the ductility of the concrete likely through enhanced confinement. Member capacity could be increased by the wraps in failure modes dominated by concrete crushing. AUTODYN appears able to reasonably predict the behaviour of the RC members when loaded by blast. [ABSTRACT FROM AUTHOR]

Recent bomb attacks on buildings have raised awareness about the vulnerability of structures to blast effects. The resiliency of structures against blast-induced impulsive loads is affected by structural characteristics that are also important for seismic resistance. Deformability and continuity of structural elements, strength, stiffness, and stability of the structural framing system and resistance to progressive collapse are factors that play important roles on the survivability of buildings under both blast and seismic loads. The significance of these structural parameters on blast resistance of reinforced concrete buildings is assessed through structural analysis. Both local element performance and global structural response are considered while also assessing the progressive collapse potential. The buildings under investigation include 10-storey moment resisting frames with or without shear walls. The blast loads selected consist of different charge-weight and standoff distance combinations. The results are presented in terms of ductility and drift demands. They indicate improved performance of seismic-resistant buildings when subjected to blast loads, in terms of local column performance, overall structural response, and progressive collapse potential. [ABSTRACT FROM AUTHOR]