This paper presents a numerical study on the resistance of windows with Anti-Shatter Film (ASF) against explosive loading. The evolving terrorism threat, particularly the increased use of drone-borne explosives, put an emphasis on appropriate window protection. This calls for a specific focus on blast load scenarios against glass facades. In this paper, attention is given to the blast response of traditional monolithic glass windows, and a reference system with 6 mm thickness (1590 mm × 1190 mm the dimensions) is taken into account. Introducing a 0.15 mm thick ASF. Initially, the effects of the ASF properties are assessed under standard far-field blast load conditions (R= 40 m the explosive-to-window distance and W= 100 kg the charge of equivalent TNT). The analysis shows a significant sensitivity of the performance of the ASF to its properties, and thus its benefits in terms of safety level of the target window as a whole. Additionally, focusing on a drone-related threat scenario, two near-field blast conditions are analysed, with the explosive-to-window distance reduced to R= 2 m and R= 1 m respectively. Parametric results are critically discussed, by comparing the blast responses in qualitative and quantitative terms.

In recent years, large-scale numerical simulations played an essential role in estimating the effects of explosion events in urban environments, for the purpose of ensuring the security and safety of cities. Such simulations are computationally expensive and, often, the time taken for one single computation is large and does not permit parametric studies. The aim of this work is therefore to facilitate real-time and multi-query calculations by employing a non-intrusive Reduced Order Method (ROM). We propose a deep learning-based (DL) ROM scheme able to deal with fast transient dynamics. In the case of blast waves, the parametrised PDEs are time-dependent and non-linear. For such problems, the Proper Orthogonal Decomposition (POD), which relies on a linear superposition of modes, cannot approximate the solutions efficiently. The piecewise POD-DL scheme developed here is a local ROM based on time-domain partitioning and a first dimensionality reduction obtained through the POD. Autoencoders are used as a second and non-linear dimensionality reduction. The latent space obtained is then reconstructed from the time and parameter space through deep forward neural networks. The proposed scheme is applied to an example consisting of a blast wave propagating in air and impacting on the outside of a building. The efficiency of the deep learning-based ROM in approximating the time-dependent pressure field is shown.

Far-field blast loading has been studied extensively for decades. Close-in, confined, and semi-confined detonations less so, partly because it is difficult to obtain good experimental data. The increase in computational power in recent years has made it possible to conduct studies of this kind numerically, but the results of such simulations ultimately depend on experimental validation and verification. This work thus aims at using reliable experiments to validate and verify numerical models developed to represent blast loading in general. Test rigs consisting of massive steel cylinders with pressure sensors were used to measure the pressure profiles of semi-confined detonations with different charge sizes. The experimental data set was then used to assess numerical models appropriate for simulating blast loading. In general, the numerical results were in excellent agreement with the experimental data, in both qualitative and quantitative terms. These results may in turn be used to analyse structures exposed to internal blast loads, which constitutes the next phase of this research project.

The threat stemming from the use of vehicles as a weapon in urban environments may be mitigated by employing properly designed protective structures such as bollards, street furniture or landscaping options. In order to assess the performance of a barrier resistance to a vehicle impact, the initial step involves characterizing the load on the barrier. To this aim, two recently developed generic vehicle models are utilized to conduct numerical simulations of vehicle impacts on a security barrier. Various impact configurations are examined and compared based on force-time functions. In addition to comparing the impact loadings in terms of peak forces, comparisons are also done in terms of equivalent static loads, determined by computing the dynamic load factors (DLF). The study provides new insights into the characterization of vehicle impact loads on security barriers, which could improve current engineering practices in the field.

The determination of the blast protection level and the corresponding minimum load-bearing capacity for a laminated glass (LG) window is of crucial importance for safety and security design purposes. In this paper, the focus is given to the window response under near-field blast loading, i.e., where relatively small explosives would be activated close to the target, representative of attack scenarios using small commercial drones. In general, the assessment of the load-bearing capacity of a window is based on complex and expensive experiments, which can be conducted for a small number of configurations. On the other hand, nowadays, validated numerical simulations tools based on the Finite Element Method (FEM) are available to partially substitute the physical tests for the assessment of the performance of various LG systems, especially for the far-field blast loading. However, very little literature is available on the LG window performance under near-field blast loads, which differs from far-field situations in two points: i) the duration of the load is very short, since the blast wavelength tends to increase with the distance and ii) the load distribution is not uniform over the window surface, as opposed to the almost plane wave configuration for far-field configurations. Therefore, the current study focuses on the performance assessment and structural behaviour of LG windows under near-field blasts. Typical behavioural trends are investigated, by taking into account possible relevant damage mechanisms in the LG window components, while size effects for target LG windows are also addressed under a multitude of blast loading configurations.

The analysis of load-bearing capacity and the determination of blast protection levels for ordinary glass windows and façade components in buildings is known to represent a design and research issue of crucial importance. In the same way, reliable methods to address this issue are mostly based on cost and management expensive experimental investigations on full-size samples. According to the tendency of recent years, this paper presents some of major outcomes of Finite Element (FE) numerical methods and simulations that have been explored in the framework of the GLASS-SHARD research project for glass windows and facades under explosion or soft-body impact. The attention is focused on the analysis of a Triple Glass Unit (TGU), so as to address the blast performance of a rather ordinary glass window for buildings characterized by the presence of multiple laminated glass (LG) layers, on one side, and by the presence of two interposed gas cavities. The TGU blast performance is investigated in terms of load-bearing capacity of single components, with respect to variations in the input blast loads (stand-off distance R, charge W, etc).

The protection of masonry walls against blast-induced loads by using textile-reinforced mortar (TRM) is investigated herein.Typically the consequences to a structure from explosions (either intentional or accidental) may range from total or partial building collapse due to the direct release of energy to injuries and fatalities due to the created debris.Masonry elements are of stiff and brittle nature and demonstrate considerable resistance in mediumsized compressive loads but degrade dramatically for stronger loads and impacts under tensile stresses.TRM constitutes a novel composite, using open-mesh textiles made from fibre rovings, which has been proven effective as strengthening material to carry the tensile stresses of outof-plane inertial loading, while satisfying the necessary compatibility, reversibility and durability requirements for masonry buildings.Retrofitting of existing structures with the use of TRM can substantially increase their strength and deformation capacity, providing a sufficient protection to the occupants from blast loads.It should be noted that improving the deformation capacity of masonry can increase the gravitational load bearing capacity of the structure and minimise second order phenomena during a blast event.In this work, we propose a numerical method to accurately predict the various structural effects of explosions on masonry.The focus is to evaluate the developed damage due to impulsive loads and investigate the enhancement of the global dynamic response of a masonry wall before and after retrofitting.Masonry consists of brick units surrounded by mortar joints.The brittle behaviour of this two-phase material is modelled in the EUROPLEXUS explicit finite element code for fast transient phenomena, in complex three-dimensional fluid-structure systems.The performance of masonry is described using plasticity laws for the constituent elements and damage for softening.Geometric nonlinearity effects accounting for large displacements and large rotations are also considered.The numerical response is validated using out-of-plane experiments of masonry walletes.

In facade construction the glazed elements have always been considered the most critical components for the minimization of hazards during a blast event. In today’s blast events, terrorists have changed their mode of action and targets where the glass performance is weak have become even more of a concern. Therefore counter-terrorism offices (such as in the UK) have been introducing design guidelines for crowded places, making a compromise between safety and sustainability. This paper describes how it is possible to achieve a resilient urban environment, where glass is still the dominant element of the architectural scope making use of glazed facade systems with excellent blast protection performances. Novel façade systems have recently been developed by means of effective simulation techniques. The numerical tools recognize, enhance and balance the already existing façade capacity to resist the blast loads and take into account the fundamental dynamic interactions between all façade elements. In this way, innovative façade components (such as curtain walling brackets) have been developed which have the ability to upgrade conventional or lightly enhanced glass facade systems to higher blast protection levels.

The work presents a numerical approach for the determination of the risk of injuries due to explosion events in large closed spaces, such as metro and railway stations, airport terminals, malls. The study is based on the numerical simulation of blast loading scenarios via fluid-structure interaction techniques. Such severe loading conditions induce large motion and significant deformation of the structure and this complicates the definition of a single discretization scheme for both the structural and the fluid domains. Therefore, a special methodology is used in order to de-couple the structure from the fluid at the topological level. The numerical results are generated with the fast transient dynamics explicit finite element code EUROPLEXUS. Investigations focus in particular on the glass parts of the structure due to their fragility and the consequent fragment generation. The numerical results are properly processed in order to calculate the fatal and non-fatal injuries risk. For the fatal injuries, special attention is also paid to the assessment of risk due to the impact of flying debris on the human body.

• We provide a new computational framework for transient fluid-structure interaction. • Complex phenomena such as structural failure and fluid interfaces are accounted for. • High-accuracy is achieved via a multi-purpose adaptive strategy for fluid & structure. • Advanced experiments for tanks under impact are simulated with very accurate results.

In response to the heightened terror threat in recent years, there is an increasing interest in the introduction of access control zones at sites that are characterized by an increased likelihood of being the target of a terrorist attack, as latest data reveal that unprotected areas of mass congregation of people have become attractive to terrorist groups. Such control zones could be located within the building that has to be protected or attached to it. The elevated security needs for these areas call for a design that will consider the risk of internal explosive events. The purpose of this article is to outline a strategy for limiting the consequences of an internal blast, while guaranteeing that the produced blast wave does not propagate into vulnerable areas. In particular, the focus is on the introduction of a protective wall system in the form of a meander that allows unobstructed access of the public and at the same time reduces the possible blast inflow to the building's interior. The performed numerical simulations show that the proposed strategy yields much smaller injury risk areas compared to a design without the addition of protective walls and is recommended for upgrading the security of buildings.

This study uses experimental data to evaluate the capabilities of a numerical model in EUROPLEXUS (EPX) to predict ductile failure in thin aluminium plates subjected to blast loading. The loading was generated using a shock tube facility designed to expose structures to extreme loading conditions. The plates had an exposed area of 0.3 m × 0.3 m and experienced large deformations including failure at the supports at the largest blast intensities. Pressure measurements were synchronized with two high-speed cameras in a stereoscopic setup to capture the dynamic response using three-dimensional digital image correlation. The experimental results were used as basis for comparison to finite element (FE) simulations in EPX. Failure was introduced in the FE simulations using element erosion. Adaptive mesh refinement was applied in an attempt to describe the crack propagation observed in the experiments. The mesh refinement was driven by the damage parameter in the material model and occurred at user-defined levels. The numerical results were in good agreement with the experimental data, and were able to predict both the global deformation and the crack growth in the plates with good accuracy. The numerical model was also used to investigate the influence of FSI effects on the dynamic response of the plates. It was found that FSI may significantly mitigate the blast load acting on the plate, resulting in reduced deformations.

The determination of the blast protection level of civil engineering buildings components against explosive effects represents a design topic of crucial importance, in current practice. However, some key aspects of blast resistant structures design have been only marginally considered in the last decade, and currently still require appropriate regulations. This is especially true in the case of glass windows and facades, where the intrinsic material brittleness is the major influencing parameter for blast-resistant assemblies. While blast assessment of buildings and systems is usually achieved by means of experimental investigations, as well as Finite-Element numerical simulations, general regulations and guidelines are currently missing. In this regard, the European Reference Network for Critical Infrastructure Protection - Task Group (ERNCIP-TG) “Resistance of Structures to Explosion Effects” attempts to develop guidelines and recommendations aimed to harmonise test procedures in experimental testing of glass windows under blast, as well as standardized approaches for their vulnerability assessment via Finite Element numerical modelling. In this paper, major ERNCIP-TG outcomes and next challenges are briefly summarized.

AbstractOpen‐cell metal foams are a new class of cellular materials with structural features resembling those of lightweight load‐bearing materials such as cancellous bones and wood. Their high stiffness‐to‐weight ratio coupled with their typical long, flat stress‐strain response make them ideal candidates as cost‐effective shock energy absorbers in crashworthiness, impact loading and blast mitigation strategies. The macroscopic mechanical properties of foams are strongly influenced by both the mechanical behaviour of single pores at the mesoscopic level and the struts and their structure at the microscopic length‐scale, based on a strong structure‐property relationship. This is shown in the present contribution where an experimental‐numerical investigation has been conducted demonstrating the existence of strain‐rate effects at different hierarchical scales. Micro inertia effects arising due to the pore geometry as well as further strain‐rate effects stemming from the rate‐sensitivity of the Ni coating in Ni/Al hybrid foams are also outlined. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Over the last decades improvised explosive devices (IEDs) have been used by terrorist groups that aim at producing infrastructure damage, victims and disruption in the community. The outcome of such attacks vary depending on a number of factors, such as the amount and type of the explosive, the distance of the detonation centre, the target etc. For the design of structural elements to resist blast-induced loads, the calculation of the blast parameters is essential and is commonly performed with the use of the KingeryBulmash technical manual. Even though the proposed parameters have proven adequate for medium and large scaled distances, there exist serious doubts concerning their validity for close-in explosions. As the supporting experimental data are scarce, numerical simulations will be employed, with the FE code EUROPLEXUS, for simulating the evolution of the spherical blast wave through the air. The analysis reveals that the widely utilized Friedlander equation cannot capture adequately the pressure-time history at small scaled distances due to the effect of the expanding detonation products. A new set of equations and corresponding diagrams in terms of scaled distance is proposed that update the Kingery-Bulmash relationships providing enhanced parameter accuracy for points located close to the detonation centre.