Calculation of Blast Loads for Application to Structural Components. Administrative Arrangement No JRC 32253-2011 with DG-HOME Activity A5 - Blast Simulation Technology Development

This technical report describes a procedure that can be followed for the calculation of the loads to be applied to a structure as a consequence of a blast. The report considers explosions taking place outside a building, which are not addressed directly at the relevant European Standards (Eurocode EN1991-1-7) dealing with accidental loading scenarios. The aim is the production of a simple, self-contained guide enabling the structural engineer to conduct a preliminary design of buildings for possible terrorist attacks. Aspects of the theory of blast waves have been included at an introductory level. The approach of the empirical methods for the prediction of blast loads has been chosen, which is more straightforward and has resulted from extensive experimental testing. For the determination of the main blast parameters, several graphs and diagrams have been included, which have been collected and properly adapted from several authoritative sources. This should make the load calculation procedure easier to grasp and less demanding in terms of mathematical complexity and computational capacity. Selected case studies are also presented in order to demonstrate through simplified examples the steps that must be followed for the calculation of blast pressures on the surfaces of a structure.JRC.G.4-European laboratory for structural assessmen

Development of a Hopkinson bar apparatus for testing soft materials: application to a closed-cell aluminum foam

An increasing interest in lightweight metallic foams for automotive, aerospace and other applications has been observed in recent years. This is mainly due to the weight reduction that can be achieved using foams and for their mechanical energy absorption and acoustic damping capabilities. An accurate knowledge of the mechanical behavior of these materials, especially under dynamic loadings, is thus necessary. Unfortunately, metal foams and in general “soft” materials exhibit a series of peculiarities that make difficult the adoption of standard testing techniques for their high strain-rate characterization. This paper presents an innovative apparatus, where high strain-rate tests of metal foams or other soft materials can be performed by exploiting the operating principle of the Hopkinson bar methods. Using the pre-stress method to generate directly a long compression pulse (compared with traditional SHPB), a displacement of about 20 mm can be applied to the specimen with a single propagating wave, suitable for evaluating the whole stress-strain curve of medium-sized cell foams (pores of about 1-2 mm). The potential of this testing rig is shown in the characterization of a closed-cell aluminum foam, where all the above features are amply demonstrated.JRC.G.4-European laboratory for structural assessmen

Review on vehicle barrier protection guidance

A search and review of publicly available documents with guidance on the security of designated spaces against vehicle-ramming attacks has been conducted. The current report provides a list of these sources, which focus on the protection of public spaces, such as pedestrian areas, tourist sites, city squares or other perimeter protected areas. The list aims at bringing to the interested security stakeholders information on measures to prevent potential attacks and/or mitigate their consequences by properly designed and tested barrier systems.JRC.E.4-Safety and Security of Building

Simulation of blast waves by using mapping technology in EUROPLEXUS

Finite element or finite volume simulations for the development of blast waves by using a model for the explosion of the solid itself need very fine meshes in the explosive and in the zone around the explosive. Structures may have a long distance to the source of the explosive. This leads often to very big meshes with many elements. The explosive is meshed often only coarse and therefore the results are not very accurate. There are several possibilities to deal with this problem. Large 3D calculations with a solid TNT model using a JWL-equation can be used but they are more effective when the results of one finer mesh could be mapped in a coarser mesh after some calculation steps. When the blast wave reaches a certain distance to the charge, the small elements inside the charge are not needed any more since the pressure ratio is decreased strongly. These small elements results in very small time steps for the full model. The report shows the implementation of the mapping algorithm in EUROPLEXUS and several validation tests of the method.JRC.G.4-European laboratory for structural assessmen

Progressive collapse risk analysis: literature survey, relevant construction standards and guidelines

A technical literature survey has been conducted concerning the problems of building robustness and progressive collapse. These issues gained special interest in construction after the partial collapse of the Ronan Point apartment building in London in 1968. Enhanced interest appeared again after the disproportionate collapse of the A.P. Murrah Federal Building in Oklahoma City in 1995, and the total collapse of the World Trade Center towers in 2001, both caused by terrorist attacks. This report, which is an updated version of the 2009 one, aims at summarising the state-of-the-art in the subject of progressive collapse risk of civil engineering structures. First, a list of main terms and definitions related to progressive collapse are presented. Then, a review of procedures and strategies for progressive collapse avoidance is provided, based on selected EU and US design codes, standards and guidelines. A review of research efforts and results in the field follows, as reported in international journals and conference papers. Different proposals of robustness measures of structures are also examined, and some characteristic cases of progressive collapses of real buildings are presented.JRC.G.5-European laboratory for structural assessmen

Numerical Simulations in Support of the Blast Actuator Development Part II

The development of the blast actuator experimental device is now entering the second phase, where reinforced concrete beams are used as specimens. This demanding phase needs a lot of support from numerical simulation to both predict and resolve possible failures and to validate the test results. The current report presents the comparison between the experimental and numerical results, focusing on the justification of the appearing discrepancies. Moreover, interesting information, that can ameliorate the final configuration of the apparatus, is extracted after the interpretation of the numerical results.JRC.G.4 - European laboratory for structural assessmen

Review on Soft target/Public space protection guidance

The current document provides a list of the available information sources focusing on the protection of soft targets against terrorist and other types of malicious extremist attacks. The list aims at bringing to the interested security stakeholder existing documents with information and practical guidance on measures to prevent a potential attack and to mitigate the consequences, should such an attack materializes. The collected documents do not address critical infrastructure, but they mainly focus on the so-called soft targets, the term being used to represent vulnerable material or human assets, which in principle should not be specifically protected. However, such targets are often selected by terrorists in their effort to maximize casualties, inflict fear to the population and attain media coverage. The documents are grouped according to the following broad domains relating to soft targets: public places, education/religious/health installations, transport, building facades, urban resilience, security planning & risk management, policy/regulation/finance, people involvement, and drones. The referenced information sources originate from various countries and bodies, such as UK, France, Sweden, Czech Republic, USA, Australia etc. The list is quite comprehensive but it is limited to the publicly available documents and practically to those found in English and French.JRC.E.4-Safety and Security of Building

A new apparatus for large scale dynamic tests on materials

The development of an innovative apparatus, based on Hopkinson bar techniques, for performing large scale dynamic tests is presented and discussed. The activity is centered at the recently upgraded HOPLAB facility, which is basically a split Hopkinson bar with a total length of approximately 200 m, with bar diameters of 72 mm and where force pulses up to 2 MN and 40 ms duration can be generated and strain rates up to 50 s −1 can be achieved. Several modifications in the basic configuration have been introduced: twin incident and transmitter bars have been installed with strong steel plates at their ends where large specimens can be placed. A series of calibration and quantification tests has been conducted in order to prove the reliability of the experimental technique proposed. Moreover, real tests on concrete cylindrical samples of 200 mm diameter and of up to 400 mm length have been performed. Analyses of recorded signals indicate proper Hopkinson bar testing conditions and reliable functioning of the facility.JRC.G.4 - European laboratory for structural assessmen

e-BLAST simulator: final design, setup improvements and demonstration tests

The Electrical Blast Simulator (e-BLAST) activity involves the development of an apparatus capable of reproducing the effects of a blast pressure wave on large-scale structural components (such as columns, walls, etc.) without the use of explosives but through the action of impacting masses. The work relates to the PROTECT project which deals with the protection and resilience of the built environment (critical buildings, transportation and energy infrastructure etc.) under catastrophic events such as blast and impacts. The e-BLAST facility has been conceived and designed with the expertise acquired in the previous project “Blast Simulation Technology Development”, supported through an Administrative Arrangement by DG HOME. Differently from the prototype developed in that project, the e-BLAST exploits a recent technology that appears to be very promising in this particular research field. Specifically, three synchronous electrical linear motors have been adopted for accelerating the impacting masses. This choice has led to the development of a more efficient, versatile and low-cost facility. The report presents in detail the final facility design, its components and their assembly, and a series of preliminary tests carried out in the ELSA laboratory in order to assess the performance of the enhanced e-BLAST. Finally, a brief description of further developments and feasible large-scale structural tests, planned to be performed with the new apparatus, are discussed.JRC.E.4-Safety and Security of Building

Numerical simulations in support of the blast actuator development

Nowadays there is a need to develop special techniques to protect the critical infrastructures from exposing events. The use of real explosive material on the experiments is very expensive and a lot of security measures should be taken. Especially in the case that the test should be repeated many times in order to obtain accurate results is almost impossible to perform the real explosive experiments. That for came up the idea of a blast simulator that can reproduce an explosive charge in a most economic and controllable way. The setup of such an apparatus is a very difficult task where many details should be studied. The most appropriate way to study the several parameters that influence the performance of the blast actuator is to use numerical simulation techniques. This report performs numerous numerical investigations and gives answers to many questions concerning the performance of the impacting mass of the blast actuator on the specimen. The numerical results have been generated with the fast explicit transient dynamic finite element code EUROPLEXUS.JRC.G.5-European laboratory for structural assessmen